Not enough people have mentioned the god-tier move of making this video exactly how long it needed to be and that’s it. If any other creator covered this topic, this would’ve been a 14 min video at least. Bless you, sir. Subscribed.
@nintardo2231 you can check my other comments to see the explanation, but here's a hint, it has to do with the conservation of energy 😉. This guys great at programming, but he's not so great at physics.
a lot of new things are possible on old hardware, just because of how much more we know about stuff like 3D rendering and programming now! back then stuff like this was POSSIBLE, but probably would've never happened
What would happen if you: - Incrementally change how far down the moving portal moves, will the cube be "sucked" up and out the other portal? - Both portals are moving in opposite directions, will the cube get the sum of the portals speed? - Move the portals toward each other, having the object in the middle?
Just interjecting with my own thoughts: 1. Yes, the cube would be sucked up a bit. I think about it as a person that were standing and the orange portal slamming into me from the top. All the air above me has exited the blue portal at a high velocity, then comes my head, which has just entered another end of the world at a high velocity (this would be the same if the orange portal were stationary and I ran/fell head-first into it), so my head would definitely get tugged into the other end. Now if the portal stops midway, my head will retain the inertia and in the worst case, I'll be decapitated. Again, I think of it as jumping out of a moving train and the train immediately stopping to 0 when only my head is out of the door. 2. Logically, yes. 3. Depends entirely on how the atoms are recreated/phased on the other end. Ideally, they would either phase into each other or be in superposition. But logically, the atoms would layer/intertwine and you would end up with a fine Chell paste.
So the first question you had can be answered two ways, the previous commenter included velocity which is one of the ways to interpret it. I think you meant in a slower way as in how far would the portal need to go before it was sucked out. If the portals are both on a surface that faces the direction of gravity then it’s just when the center of gravity of the cube goes through that or would be “sucked” up and out. The second question is actually demonstrated in the video when he puts a portal through a surface and essentially it is the answer to your question. Its basically like if you were to drop a hula hoop over yourself, one side is moving (relatively) exactly at an opposite velocity of the other side. The third question is a bit harder to answer but I’d imagine it would be like trying to stuff the cube into a place with zero volume. In a real life scenario where we magically have portals to test this, I’d imagine that any object you put between the portals would make contact with itself and begin resisting whatever is pushing the portals together until it yields to the pressure.
This is the logical set of answers based on what the math is trying to simulate. What would actually happen in the N64 physics engine depends entirely on how James is simulating the "teleport." 1. Half the cube should appear on each portal face, at first. Gravitational forces on the Portal B side will immediately take effect on only the mass that is present on that side, and effect the whole cube as a calculation of the opposing forces on the other side, Portal A. 2. Yes, both logically, and according to the math. 3. It would look exactly the same as if there were no portals at all, and it was just two panels sandwiching the cube. Logically, the portals (or more accurately, the objects the portals are moving on) would either be forced to stop with the cube in the middle, or the opposing sides of the cube would crush the cube itself, depending on the force objects that the portals are painted on are exerting on the cube. It would be ultimately the cube crushing itself, but the force applied to the cube would be equal to the objects that the portal are moving on.
If we talk about just physic and not how he simulate the portal. 1. Think of it like the portal is grabing part of the box and throwing it like how you lift a box. So the answer is yes. 2. Since we are dealling with portal, we are dealing with relative position and velocity we have to take that into account. If you are talking opposite here as in from your POV in a room one go left and one go right with the direction facing the place they are heading. What would happen would be the velocity of the cube = the velocity of red portal + the velocity of blue portal. Imagine the slam experiment but the stationary one also moving forward. But opposite here mean how the portal is moved base on it orientation like one is going forward and one is going backwards then it will stay still like the hoola hoop example in the video. 3. The box will be destroy as it will try to exist in the same space. Imagine it more like slamming the middle box with 2 other box exactly the same down to the attom and the imperfection toward the middle one.
@@VarunGupta3009Yeah that phase/superposition answer doesn't really make sense, it's not like the portal instantly teleports an item into a different point in space, it lets the item "enter" that position from a specific direction, so the cube wouldn't have to phase into anything. The correct answer is what herewegoagain wrote: the cube would simply find itself in the middle of its own two sides crushing itself with the same force as the moving panels. If you assume the portals to magically be unstoppable then sure, they would push until the cube disintegrates into atoms but you're just asking what would happen if you put the cube in an infinitely strong press.
“I could make you wait for it, but I value your time more than retention rate.” Mad respect for that. I just told my friend about this project and his first question was if the ch_createairboat command will be in the de-make. 😂
I see no reason for this, unless he first made a de-make of half life 2 and was building his current project on top of it. But that would be... fuckin weird my dude
Test idea: what happens when you halt the piston mid-way through the box? If the box is being treated as a point (with a 3D hit box built around it), I imagine the box won't "jump" out of the exit portal until the entrance portal has crossed the box's reference point. If you treat the box as a bunch of infinitesimal boxes rigidly bound to each other, perhaps more interesting stuff can occur, like having only half as much momentum when it leaves, or being dragged by gravity due to half of the box being affected by it in different directions.
That's actually a great question. My guess is that he will simplify the problem and make the mass point like somewhere at the centre of the object rather than having it distributed. It sounds to me that having a distributed mass might be computationally a bit too much for a 64. But as you point out that would lead to some edge cases not behaving with the correct Physics while for the majority (where that simplification works well) he's got it spot on.
if the portal stopped halfway through the box you'd simply have half the momentum and so half(i cant remember physics its either this or a fourth) the velocity it would have had if the portal went all the way
While the engine would likely require changes to account for this, I also think it would logically exit at half the velocity: If the matter inherits the relative velocity of the portals, and only half of it exits the portal, half of its matter inherits the velocity. The affected matter would continue to shoot forward and either pull the rest of the object along - and as the rest of the mass has no relative velocity, the object would equalize to about half velocity - or it would tear itself in half. This would be entirely based on the structural integrity of the object. If the bonds are strong (like a block of metal) they will stay as a whole object, but if they are extremely weak (like jello) it would be torn apart.
There is no momentum on the box as the box never moves, it is the universe that is moving ... Its a stationary box on a moving universe... If the universe stops relatively to the box mid way the box will appear to stop... That would mean interestingly that if the portal would stop at any time in the period the box is in the air after "Jumping" out it woul lose its aperent lateral velocity. Now another way to look at it is... It's more of an information teletransportation. In that case every particle on the box gets deleted and recreated in its state including relative velocity vector. In this case the box would probably be shred apart as an instantaneous stoppage of the portal would produce an infinite acceleration capable of riping the box at the bond level that separate a moving particle from a non moving one..
In "reality" I think the object would be crushed, and if the force moving the portals isn't enough to crush the object then the portals would just stop moving.
THIS is the question. Using the box as the example, I agree with the others - it would collide with itself. But what is hard to answer is if the portal act as a window, with no physical connection with the box, will it be able to meet the other portal and create infinite force? Surely that's impossible? But so are portals, probably... In game world I'm sure the box would just go flying or teleport to a random coordinate, probably out of any feasible range and crash the game. OP can you try this with a long pole, but the pole is on an angle, if at the right angle, surely the portals could meet since the pole would never collide with itself. This is as fascinating as playing Portal was for the first time, thank you to all cause that's all I've ever wanted to feel again. Edit: After thinking about it, it wouldn't be infinite force, but just a lot of force, or enough to collapse any object down to what I would assume to be a micro black hole? Too much mass in a certain space - which actually happens with stars etc... That seems reasonable if we allow portals to exist. I'm content with this theory.
@@EldeNova So.... The EASY answer to that paradox is to realize that the cube doesn't have infinite rigidity. If it can exert force on itself through the portals, then that means it's under compression. It will immediately begin to heat up. Depending on the material properties of the cube, it could crumble, crack, deform, or crush. If it crumbles, then parts of the cube will be expelled from between the portals. If it cracks, the parts of the cube will slip relative to each other, again possibly being expelled as a result. If it deforms, then mass will squeeze out the sides, again being expelled. And if it crushes, it'll get hotter. If the cube melts or vaporizes, see "deforms". If something somehow prevents the mass of the cube from escaping, then eventually you're going to trigger nuclear reactions and the mass will turn into energy, escaping from the trap. And yes: if somehow THAT'S prevented from happening, welcome to Black Hole City, population Cube, though the moment the portals move apart again it'll instantly vaporize via Hawking radiation and kill everyone around. The COMPLICATED answer to that paradox is that you have to figure out where the energy to push the cube into itself comes from. The answer to that gets into some... pretty complicated physics. The short version is that moving the portals relative to each other must necessarily require the input of energy because it changes the geodesics of spacetime. (That is, there's potential energy bound up between the portals just like there's potential energy bound up in a ball at the top of a hill.) A realistic implementation of the physics would mean that a surface without a portal would be easier to move than a surface with a portal attached to it. And where does the energy to move the portal come from? From the piston attached to the surface, of course! So that means that trying to push a cube into itself would cause it to become harder to move the portal by AT LEAST as much as it would take to crush the cube if the portals weren't there. If the piston isn't strong enough to crush the cube, it'll stop moving. Welcome to the Hydraulic Press Portal! Today we are going to crush... cubes.
If the object could fit side by side with itself, it would push itself out of the way and sit next to itself, and the portals would get closer and closer until the object couldn’t repeatedly push itself out of the way anymore. once the object is balanced on itself or cannot fit anymore next to itself, then it would lay against itself and the side of the portal. The portals would be forced a certain distance apart but could be shifted together after overcoming friction to pass over the object infinitely. To bring the portals together would compact the object, causing pieces to fall from between the portals. If you smack the portals together really hard, I bet the air would begin nuclear fusion and blast the portals apart. This brings the question of what would be made if an atom fused with itself? Would nuclear fission be forced to take place if the portals were separated? Strange stuff.
I want to thank you. 1) giving the answer early, its why i stuck around for the rest of it, a sign of respect for a genuinely interesting video that gave a little more information and context to cement the findings presented 2) exactly how long it needed to be, tests, findings, results repeated tests with different settings and end. This earned a sub, if everything else on this channel is presented like this im going to be watching a lot
gosh, I remember this project when you were just testing out how much "depth" the N64 could render when looking at portals through a portal. this is amazing
There ARE moving portal in Portal 2. They're being used specifically in one scene in which you need to use a laser and a moving surface to cut through pipes. Although I think I've heard there more of a hack and don't really work find with actual objects.
@@dopi3220 so true, god everyone’s dumb it’s like they don’t even consider the movement of the solar system relative to the Milky Way or the movement of the milky way relative to… ? on a daily basis lmao
valuing the viewers time and immediately grabbing my attention by briefly explaining its an N64 demake was such a good way to start the video to keep me hooked, well written and well done.
Isn't long form media also valuing the viewers time? I feel like my time was just wasted by a guy saying "my engine proves I'm right now complain in the comments"
@@pappi8338 To be honest, somebody could make a perfect video that has no loopholes in the explanation and somebody will still want to be the underdog and go "yeah, but" and get 1K likes.
So, are you expecting him to debate himself to save you the time of doing it? He has an opinion and a logical argument to back that opinion, and he doesn’t hide the fact that he created an engine to do what cannot be done with the original engine, based on physics and relative motion. Your argument is more of a “because I said” than anything in the video.
You tear the fabric of space-time and the universe implodes, only to create a super mass that explodes in a big bang that starts this whole reality all over again.
portal 2 contains moving portals. you have to cut the lines to the neurotoxin and you do it using lasers through moving portals. it's the only implementation of moving portals in the series.
They're only enabled in that one room, far away from the player or any physics objects, because the developers were never able to get them to work properly. Moving portals in the Source engine are very buggy, and will fling things around that aren't even touching them.
True. This is achieved by changing the config settings when the map loads. You can always allow this using the command “ch_allowmobileportals 1”. However, portals cannot slam down on stationary objects, as the game hasn’t been coded to do so
you just gave me the biggest mindf**k of the day. cause until this time I just thought that the in game universe doesn't allow moving portals for some reason. now it all doesn't make sense
in game, idk Using real world physics, my guess is the top/front half of the cube will have velocity, because it's already through the portal, but the bottom/back half won't, so it's just about whether that velocity is enough to overcome the cube's inertia and pull the rest of it through. I'm not sure of the exact numbers, but it should definitely move at least a little... probably. A good guess would be it goes half as far, but I suppose it'd need a test, to be sure.
@@Bluhbearyou are 100% correct. Let’s say the piston stops half way through the cube, it depends on how much the cube weighs obviously and how fast the piston is moving. Just like you said if the top half overcomes the inertia of the bottom half then the cube will go through. If the piston stop 1/4th of the way at the top leaving the other 3/4th on the bottom, you’ll probably get the cube to do a little “hop” but not go all the way through the portal.
I'm going to say that all of the replies explanations so far are wrong, though the results may be similar. Imagine not the orange portal moving, but the floor instead. What happens if you stop the cube halfway through the orange portal is almost exactly the same as if you move it all the way through (minus the bottom half of the cube still being in a different gravity zone for longer without being pushed, if you push it halfway through). So if you slam the floor with cube onto the orange portal, the speed is the same as when you slam the orange portal onto the floor as explained in the video, and if you stop the slamming halfway through the cube (minus the small correction as written) because the "slam" speed was the same. Ofcourse this correction is going to have a bigger and bigger effect as you go to an infinitesimal part of the cube.
@@woud3404I'll point out a small potential flaw in your logic; (but props! I wouldn't have thought this through all the way without reading your post) just that slamming the portal down from above and the floor (with cube) up from below aren't quite equivalent. When the portal is moving down the floor and cube are stationary with one another. When the floor moves the cube up it imparts momentum to it, which is all fine and well until the floor stops moving up, which from the point if view of the cube is like it accelerating downwards away from it. If we look at the portal-stops-halfway-down case one would lead the to top half of the cube having velocity relative to portal, and converting that velocity to momentum upon exciting. This would impart half the momentum of a full portal drop, it would pop out the exit portal at half speed as the top half yanked the bottom half through. Maybe slightly more, actually. Between the portal starting to clip the top of the cube and it's final position the cube should start moving as portions of it pull 'upward' on the rest, causing the relative velocity to increase. This would make a great word problem for calculus students. In the floor-stops-halfway-up case the cube would be entering the portal at the regular full speed, and as the floor stops gravity would act to deaccelerate it, but only the back half is still in a gravity-down zone, the front half is experiencing gravity as 45 degrees off from 'forward' (direction of travel). This would nearly cancel, impart some spin, and let the momentum carry the cube the rest of the way through at nearly full speed. Again, calculus for the exact answer.
Except his explanation makes no sense when you understand that momentum is conserved between portals. Think of it like a baseball in a car. If you remove air, a car driving over a baseball will not move the baseball. Because before the car drove over the baseball, its momentum was 0. Therefore, after it drives over the baseball, the momentum would be 0. In the first clip where the cube goes flying, the car drives over the baseball and stops, then causes the baseball to go flying in the opposite direction as fast as the car had been moving, having never touched the baseball. Somehow, the car imparted momentum to the baseball, having never touched it.
@@trmerc7635 Except that's not really how this works. Imagine it from the perspective of the exit portal. The moment the entrance portal touches the cube it starts coming out the other end. This happens regardless of whether it falls into the portal or if the portal moves towards it. Assuming the velocity of the cube falling is the same as the portal moving towards it the cube is coming up out of the other portal at the same speed in either situation. And this is where the momentum plays a role. The exit portal does not care how the cube is coming through, all that matters is how fast it's coming through. Momentum doesn't just stop as soon as it's come through and plop down, it's going to want to keep moving in the direction it was coming out of the portal at. If actually look at the exit portal you can see the cube come closer and come through the portal. From the exit portal's perspective the entrance portal may as well have been static and instead the platform the cube is on got pushed upwards. This is why relative velocity is key here. All that matters is the relative velocity of the cube compared to the portal.
@@RNeeko It really is how it works. Instead of a portal, imagine a car. If you throw a baseball at a moving car and it goes through the open windows, does the ball get faster or slower? No. Because the ball did not interact with a physical object to impart momentum. The portals are just points in space that are connected. So is a long tube. If you throw a ball through a tube that is moving, as long as the tube doesn't touch the ball, it doesn't affect the speed of the ball. For some reason, people seem to think because it is a wormhole and not a physical tube, it somehow changes the laws of physics.
@trmerc7635 the cube has to leave the exit portal with the same speed it has entered the portal... thus giving it momentum. Witch causes the box to accelerate upon exiting the stationary portal.
I think you are misunderstanding how the portals work in the game. The portals are not physical objects that can move and interact with other objects, they are just openings in space that connect two locations. The velocity of an object that passes through a portal is relative to the portal, not to any other reference frame. This means that if a portal is moving, it will affect the velocity of an object that exits the other portal, even if the object itself is stationary. To illustrate this, let’s use your analogy of a baseball and a car. Imagine you have a car with two open windows on opposite sides, and a baseball that is resting on the ground. Now, suppose you drive the car over the baseball, so that one window is above the baseball and the other window is on the other side of the car. If you ignore air resistance and friction, what will happen to the baseball? Will it stay on the ground, or will it fly through the car? The answer is that it depends on how you look at it. From the perspective of someone standing on the ground, the baseball will stay on the ground, because it has no horizontal velocity and nothing is pushing it. From the perspective of someone inside the car, however, the baseball will fly through the car, because it has a horizontal velocity equal to the speed of the car in the opposite direction. This is because motion is relative, and different observers can measure different velocities for the same object. Now, imagine that instead of windows, you have portals on opposite sides of the car. The portals are connected, so that anything that enters one portal will exit the other with the same velocity, relative to the portal. What will happen to the baseball now? Will it stay on the ground, or will it fly through the portals? The answer is that it will fly through the portals, regardless of how you look at it. This is because the portals are not physical objects that can move and interact with other objects, they are just openings in space that connect two locations. The velocity of an object that passes through a portal is relative to the portal, not to any other reference frame. This means that if a portal is moving, it will affect the velocity of an object that exits the other portal, even if the object itself is stationary. To see why this is true, let’s look at what happens to the baseball from different perspectives. From the perspective of someone standing on the ground, the baseball will enter one portal with zero horizontal velocity and exit the other portal with a horizontal velocity equal to the speed of the car in the same direction. This is because when an object enters a portal, it inherits its velocity relative to the portal. Since from this perspective, the portal above the baseball is moving with the speed of the car in one direction, the baseball will exit the other portal with the same speed in the same direction. From the perspective of someone inside the car, the baseball will enter one portal with a horizontal velocity equal to the speed of the car in the opposite direction and exit the other portal with zero horizontal velocity. This is because when an object exits a portal, it preserves its velocity relative to the portal. Since from this perspective, the portal below the baseball is moving with the speed of the car in the opposite direction, the baseball will enter the other portal with the same speed in the opposite direction. As you can see, both perspectives agree on what happens to the baseball, even though they measure different velocities for the same object. This is because the portals are not physical objects that can move and interact with other objects, they are just openings in space that connect two locations. The velocity of an object that passes through a portal is relative to the portal, not to any other reference frame. This means that if a portal is moving, it will affect the velocity of an object that exits the other portal, even if the object itself is stationary.
"So... why am I demaking Portal for the Nintendo 64?" BECAUSE IT'S FREAKING AWESOME!!!!!!!!!!!! I've been following that little project for a while now! Absolutely fantastic work!!!!!
So, lets say the portal lands on top of a human (really fast), but makes a sudden stop half way. Would then upper part of human (the part that has gone through the portal) be set in motion on other side of portal, and then pull lower part with it? If speed of portal slamming down was fast enough, subject could be ripped in half. #Spagettification
@@james.lambert but would you get ripped in half though? If you think about it, the moment the first hair on your head enters the portal it's already pulling on your body. When your head is through, its already pulling your torso. It's easier with "ticks" because you don't have to worry about individual atoms, but if you think about it an insanely fast portal might just rip you to shreds instead.
Yeah I always likened it to any changes in motion to a portal is like moving the entire universe on the other end of the portal. If you moved a portal (aka: accelerated a portal), you'd actually need to move/accelerate the whole universe along with it to match, unless the exit portal moved in a matching speed and direction to cancel it out. In "reality" you would be able to theoretically have a moving portal relative to its exit but it would have to continue moving in that direction and never change - absolutely no acceleration (no changes in direction or speed) would be possible as that would take infinite energy to do. Having the portal change direction or rotation would be akin to literally moving the entire universe on the other side of it. The reason is because of what you said, the person would get spaghettified if you went half way and then stopped. That's because the whole universe is suddenly 'stopping' (aka: instantly accelerating) on the other torso end of the portal relative to the other side of the portal that his legs are standing in. Rotation of a portal is especially impossible; When you rotate a portal, the outer edges of the universe would be accelerating relative to your viewpoint at a rate of speed approaching infinity the further out you observe. If the universe is infinite then the rotation speed at the far corners of the universe also becomes infinite, and it would require not only infinite energy but also an infinite speed limit in the universe to move the whole universe on a swivel at infinite accelerations, as it must happen in order to conserve momentum between the two portals. Also just to be technically correct, you can't have a moving portal anyway due to relativistic effects in spacetime. Spacetime is not uniform, so movements through it would not be a simple x universe moving relative to y universe, but rather you'd encounter shifting spacetime due to differing gravity at different points, and therefore even a totally uniform movement in one single direction relative to the exit portal would be varying all over the place, growing in differences the further out into the universe you look. For this same reason it would probably even disqualify a stationary portal just because of the immense energy required to reconcile the two reference frames - aka: the two 'universes' on either side of the portal.
Interestingly, the force between the two parts of the human would be directly caused by the portal's deceleration. The next question would then be: What's the consequence of that? Would a human/ an object that's halfway through a portal be able to hold the portal in place? Would a heavy object sticking halfway through the portal increase the inertia of the object that the portal is attached to? Would (as DeSinc conjectures) a moving portal have the inertia of the whole universe? I don't expect that: moving portals would not cause any effects, unless an object sticks through. But I would still not be 100% surprised if we figured out that portals that have objects sticking through would have infinite inertia while the object is sticking through; and in that case one _could_ argue that - since it's independent of the object - the cause isn't the object at all and all portals would have infinite inertia even when nothing is sticking through.
So if you throw a cube in a stationary portal while the other is travelling backwards at the same speed, you kill the momentum. It looks very consistent to me.
I don't get it, the portal is just a link between 2 different places, it doesn't matter at which speed the portal is moving you remain unaffected by that, the only difference is that you get through the portal faster
First of all, appreciate the video length. Secondly - test your solution with the piston stopping half-way through the cube. The way physics should work, the half that's already flying out of stationary portal should pull the still stationary half from the other end, losing a bit of energy. But would be interesting to see how it would actually work in the physics you coded.
it would depend on the vector of the exit portal and the speed of the piston. it would need to be enough force to pull the cube out of its state of rest and then overcome gravity. you could write this as a physics equation easily enough.
@@adultdeleted True. I was writing that assuming the rest of experiment is same (angles and the speed of the piston). Would be interesting to play around with different setups, though. Like what if exit portal is stationary on the ceiling, i.e. facing same direction as the entrance. Then depending on combination of speed and what chunk of it goes through the portal the cube would either remain stationary or get pulled through... This could be a fun toy like 4D Toys.
Logically, the entrance portal is rushing down and then stopping, so the cube should rush out partway but then suddenly stop when the entrance portal stops. I think the trick is that portals only conserve momentum relative to the portals, not relative to the room. So if the cube is going through the portal a force on the portal to make it stop moving is equivalent to a force on the cube to make it stop as well. The same would be true if the entrance portal is stationary halfway down the cube but you start moving the exit portal around, it should drag the cube with it.
Typically objects in physics engines don't have mass density fields, but rather are point objects with discrete momenta. So it will either jump or not jump, but not half jump.
Personally I'm not very into physics but I understand GLaDOS saying that the portals do not affect momentum to mean that my momentum will never be affected by the portals. Otherwise the forces acting on different parts of me might be so different as I pass through a portal, that I might conceivable be torn apart by a portal falling fast enough, as each part that enters the portal suddenly accelerates into the portal.
Thing is, momentum is relative to your reference frame. If the portal is moving towards the cube, from the perspective of an observer moving with the portal, the portal is stationary and the cube is moving, so the cube has momentum. Also in-game portals already change momentum. Momentum has magnitude and direction and the portals in the game change the direction no problem.
it's actually the opposite interpretation that has this problem. Say you have an orange portal that's stationary, and a blue portal travelling sideways at 1000 m/s. If you stick your head into the orange portal, this game dev's logic states that your head should poke out of the blue portal at 1000 m/s- you'd move along with it, so the most you'd feel is a strong wind whipping your hair. However, if you don't think your body should inherit the momentum of a moving portal, then sticking your head out of the moving blue portal would cause your head to emerge at 0 m/s, as the portal flies away- (low-speed head goes in, low-speed head comes out-) snapping your neck clean off.
@@NotaWalrus1If you have a drone flying stationary and put an open window on the back of a truck and drive at the drone will it pass through and not move or will it suddenly ping off into outer space
@@Xtv1234I feel if you came out the back end you'd be perfectly fine and would just drop but if you came out the front end it would just blow you back in. A lot of people's theories seem to forget air exists and is real and we aren't just surrounded by empty space void of atoms. The air would be going through too. You wouldn't just put your head through and have it suddenly be 100% different
What happens if you stop the moving orange portal while the cube is only halfway through? Would the momentum of the cube coming out the blue portal make it so the cube gets sucked inside the the orange portal and out the blue? If it doesn't go fully through, would it at least jump up a little?
I wanted to see this too! I think that the cube would stop moving when the portal stopped moving, that's almost entirely based on my own intuition though
here's my hypothesis (at least in a real-world physics sense, no idea about his engine): in the instant the orange portal stops, half of the cube has had the momentum transferred to it, while the other half hasn't. therefore, the cube will only receive half of the momentum! the non-moving part gets pulled along by the moving part, and the moving part gets slowed down by the non-moving part. so, it'll still be launched, but only half as far!
in-engine, it will probably either move or not depending on which side the origin position of the object stops at. in the real world or a physically accurate simulation, the momentum would be imparted in proportion to the weight of the object on either side of the portal
@Vaasref I mean your conclusion is kinda right because relative to a fixed point in space earth is accelerating and so am I but saying gravity is acceleration is a gross oversimplification and the way you worded it implies that I am accelerating downwards regardless of the normal force from my chair right now… TLDR all motion is relative, including acceleration.
Absolutely. I got about halfway through the video, sure that the answer was A, and spent about 30 minutes thinking about it, looking it up, and reading the comments before I understood why B makes more sense. Then I resumed the video and he answered it in 30 seconds lol.
Except it's wrong. We've actually demonstrated this as false as we've created "white holes" for qubits that instantly communicated information over distances and didn't impart any extra energy when doing so. All you're doing is taking the outside of a window and moving it somewhere else. Just as if you had stuck your hand through a window you would not get flung through it, the location of the exit is all that changes. If you drop a hula hoop over yourself you are not flung out the other side. Not only does he lack a basic understanding of inertial frames of reference and light cones, but he's asserting that the universe has an inherent "orientation", or an up and down locked to one position in the universe. This is a very stupid idea postulated by flat earthers, and has been debunked at every turn.
@@xelgodis80085 lmao, it must suck to be so conceited you can’t finish a video before rage commenting. You literally just used the hula hoop example that the video proves is different from the Portal Paradox.
@Scottish Cheese except both he and you don't understand inertial frames of reference. If his model held true, light itself would be accelerated through a portal, which is stupid to say the least. It's a white hole, and the laws of thermodynamics are conclusive about the effects of a white hole, and have been demonstrated in real lab settings. That you lack the fundamental knowledge to begin understanding *why* you're wrong isn't my problem. Grow up.
Realistically wouldn’t a cube be stationary as if on a flat surface and only be affected by gravity, normal, and friction forces once out the other portal. I mean if you did that same thing but stopped halfway through the cube it would be odd for it to fly off the ground and gain speed from nowhere. Unless there are some unique portal physics I don’t know about. It’s a pretty cool video either way.
Portals aren't just doorways, but that completely redirect momentum for no cost. The only truth is that any velocity vector going in, is equal going out. To the Portals, an object moving towards the portal vs a portal moving towards an object looks exactly the same. On the blue (exit) side, while the entrance side is halfway through, they see the Box emerging at speed. Once the entrance hits the ground, the box is still exiting at speed.
My theory is that a portal stopping half-way over a cube would cause it to partially fly off. Half the molecules of the cube would be stationary, half would be "moving", so the forces would balance out. In-game, it would probably only matter if the object's origin or Center of Mass made it through the portal plane.
@@Appletank8 They redirect momentum but they don't create it. A portal is like a doorway, connecting two spaces in otherwise impossible ways Portals do not thrust things out at specific velocities; they do to make the game work of course, but all they do is connect space I do not see how he cube would gain any sort of momentum from a portal falling over it. The space through the orange portal is dictated by where the blue portal is. And even if that space is rapidly changing, there is no force causing the cube to move
@@100Darkspine technically going from a low portal to a high portal creates potential energy outta nowhere. that's why you can make perpetual motion out of a floor/ceiling pair. Anyways, the only rule of portals is that if something enters the portal at speed, it will exit at speed. In order to exit a portal at all, you need some sort of velocity, otherwise nothing happens. From second 1 to second 2 of going through the blue portal, the box has a noticable change in position, therefore it now has a speed, Distance/time. There is no way for the blue portal to tell the difference between the entire room moving at constant speed towards the portal, vs the portal moving at constant speed towards the box, so the results will be identical regardless.
@@100Darkspine The portals are not creating the momentum. The cube already has momentum relative to the orange portal. Expecting it to stop once it leaves the blue portal is expecting its momentum to change for no reason.
Well, that's friggin cool. 😲 I'd also argue that in theory the orange portal should experience resistance when it hits the cube, such that it performs equivalent work to flinging the cube out of the blue portal. That conserves energy-though not momentum, because having portals facing different directions has already broken that permanently in this universe.
My position is that to properly use conservation laws through portals you must use the reference of the portal, in this case to conserve energy, velocity, relative to our reference, must remain constant at input and output (ignoring non conservative forces obviously) if we consider the portal as a system energy in must equal energy out… in any case energy is not conserved as potential energy can be increased with a portal eg perpetual motion machine using portal on floor and ceiling.
@@DracoTorment The object traversing the portals is ALWAYS the reference frame. Portals are only transformations of the vectors. If a person sat on the floor and the portal slammed down around them, they would feel acceleration and would fly out the exit. This is consistent with he person's interpretation; if they'd looked up, they would have observed the wall and ceiling careening toward them at speed, a sight consistent with them flying out the exit at speed. Further, we know the object's reference frame is the only view point we should examine because it is the object which possesses the momentum, velocity, and energy we are concerned with. The portals are just a boundary in space with an appropriate transformation that stitches space together at that boundary.
Iirc, that’s a matter of just changing a single value to allow for it, but the logic required for the portal paradox isn’t implemented, as it was never intended to be used outside of that set piece. So instead of either result happening, the box doesn’t go through. I may be wrong, this is just going off of what I remember.
I would say the issue with this discussion is the difference between momentum and velocity. If you're basing your coding on velocity, then the cube should move at the same relative speed as the slamming portal, but if you're basing on momentum, as the orange portal can't impart any energy to the cube, the cube should just fall out, based on the possible position of the blue portal.
Agreed, and I feel that the velocity is also a bit of a red herring, since it assumes both sides of the portal are the same frame of reference, which I don't think is a simple answer.
My thoughts exactly. His setup violates conservation of momentum. I reasoned it out slightly differently though. If we assume that slamming the portal down on the cube launches it through the other portal, then there must be some force applied by the portal to the cube. If this force is proportional to the speed of the portal and points through the portal in the opposite direction of its motion, then the hula hoop example will actually launch the cube into the air!
@@1925683 not quite, as I could be reasoned that in the same way the orange (down) portal imparts energy to the cube, it could be argued that the blue (up) portal could rob it of the energy, and that addition/subtraction of energy could be based relative of the two portals position in space/ velocity/momentum.
@@1925683 even stationary portals violate conservation of momentum. if you throw a cube down into a portal and it shoots out horizontally from a portal on the wall then momentum wasn't conserved the hula hoop example is fine because you still have the cancellation of the motion of the exit portal and the cube being pushed through
Nope. e=mc² applies in both scenarios. Speedy thing goes in, speedy thing goes out. It does not matter how the relative speed came about. In fact, the portal paradox is nothing more than people arguing against relativity. It does not matter if it's the cube moving towards the portal or the entire planet being lifted up to the portal by a piston. The difference in speed remains the same. The only argument there is room for is whether the game is programmed with realistic physics or inconsistent and arbitrary ones. And in my opinion, any portal mechanic that doesn't impart momentum in such a scenario has sloppy programming if momentum is supposed to be preserved between portals.
bro the texture of the paint on the wall and his skin as well as his shirt and arms are literally so similar that I thought there was a static filter applied to the entire video. watching this was trippy as all hell.
So this is basically the same as the "shooting a cannonball from a moving car" experiment from Mythbusters. Id love to see a video on "shooting the cube in to a portal where the exit is moving the same speed as the shot cube but in the other direction (maybe for when you imolement the bouncy pads (if you haven't done that already))
Right when you talked about the "hula-hoop" analogy, it made sense. Everyone proposes the paradox when only taking in consideration the entrance portal, never the exit. While they make a womehole while in tandem with one another they have their own unique positions in space, be it speed, or direction. Which does make a lot of sense. My next portal paradox, is what if you do this across lateral direction, while moving?
So, imagine the portals are like the window of a car. but, because the portals exist unconnected to two different inertial reference frames, then what occurs outside the blue portal, is not connected to what occurs outside the red portal. So lets imagine you have a stationary red portal. And a moving blue portal. If you stick your arm through the red portal then your scenario is best described like this. Everything inside the car, is the red portal. The car is stationary and not moving. Everything outside the blue portal is sticking out a car window. It is moving relative to the rest of the world. (Great - this explains that you will feel wind on your arm). But what happens now, when the "blue portal" car stops. Well, in a normal car your entire body would feel a decelerating force and would struggle against it. The parts of your body in "Red space" are in a stationary car, so those parts feel no decelerating force. The parts of your arm in "Blue Space" now want to keep moving forward, while the blue portal entrance slows down. But, the tube of your arm in red space is connected physically to the tube of your arm outside the window in blue space. So now, your arm in red space "Pulls" on your arm in blue space (in the direction of the deceleration the blue portal is undergoing). Your arm in blue space wants to keep going, but the blue portal is changing the acceleration, and applying that via the portal boundary. Assuming the deceleration the blue portal is undergoing is low enough that it doesn't tear your arm off, you would decelerate your arm to the same relative velocity of the blue portal. IE, in short, your arm in bluespace would "feel heavy" in the same way that your limbs feel heavy when you slow a car down. And your body (which is strapped in via seat belt or whatever) "pulls" your arms to the same relative velocity of the car. But in this instance, your body in redspace doesn't feel the deceleration, only the arm in bluespace does.
There's nothing applying force onto the cube itself... Portals are basically wormholes... You're treating the ends of the portals as two separate entities, when they're one and the same. If we're using the logic used for the angled portal, then it should have been shot out the top when it was in the hula-hoop orientation. Simply by adding rotation (180° rotation in the hula-hoop example), doesn't add velocity. IF ANYTHING, what would occur if the portals were theoretically wide enough, is that you'd be stuck in a constant state of free-fall, until you gained enough momentum from the gravity and/or air pressure on the "stationary" end of the portal, to reach the edge of the portal. Think of it like this. Assume you're floating in space. And both ends of the portal are 1km wide, and the orange end is moving at you at 100km/h. And the blue end is moving in the opposite direction at 100km/h as well. You'd be in a constant state of free-fall until you gained enough momentum to reach the edge of the portal. Remember, the portals are one and the same, the physical space between each end is arbitrary. In this, the portals act like a small scale black-hole, requiring you to increase your momentum beyond that of the wormhole in order to escape. The wormhole isn't imparting momentum onto you.
haha I love that all of my favorite niche projects wouldn't exist if talented people like you didn't just do it for no particular reason but to satisfy your passions/obsessions. And the world is a better place for it.
I'm actually really glad that you brought this question up because I decided to wrack my brain on this question as a serious question regarding what would really happen, suffice it to say that yeah, GLaDOS literally explained it, speedy thing goes in, speedy thing goes out, and that speedy thing is from the relative point of view of the portals which from their view are always stationary while everything else moves around or through them. A fun side piece I realised though is angular momentum and forces acting through a portal, as well as a very interesting scenario of "What happens if the portal stops half way? Does it stop like nothing happened or what?", and the answer is "moment of inertia still exists, however much mass passed the portal will have inertia, pulling on the rest of the mass of the object through the portal like a harsh yank but through the entire intersecting plain.", which leads to very weird potentials of indirect forces acting on portal surfaces. I don't remember everything on the matter off the top of my head as this was like a year and a half ago that I thought about this and logically approached it as, but there's a lot of weird and cool edge cases regarding physics and portals, I have the entire argument and logical set written down somewhere if anyone wants to chat about it as it's a very interesting extended problem.
I've also thought about these some time ago. iirc If you place the exit portal on a rail, facing a wall, and then start pushing a long stick into the entry portal, when the pole touches the wall, instead of stopping you from pushing further, the exit portal will start moving on the rail, even though it's not in contact with anything. super weird behaviour but that's what makes it interesting!
@@kantoros yeah, that leads into the whole "weird potentials of indirect forces" thing. On the one hand, in theory, there shouldn't be any effect on the portals as they are not being contacted. On the other hand, in theory, there _should_ be an effect on the portals due to their ability to impart moment of inertia. And while I don't remember my original conclusion, I'm actually leaning toward the latter thanks to some recent physics concepts I came to know about recently. The way it'd work would likely end up acting like an air spring or pneumatic piston with a pressure gradient leading to a "spooky force acting at a distance" to appropriately quote Einstein. You're still applying force to the wall on the other side of the portal, but with it acting as a stopping, stationary force, the force will instead start being imparted on the portal as it effectively acts as an inverted form of the same effect that causes imparting of moment of inertia.
@@RonWolfHowl dude I would _love_ to make a video on this but I do not have the means to do so on my own, and it's kind of sad given there is an absolute ton of amazingly fun nuance to the brain breaking physics of this that would be amazing video content. For example a visual representation of exactly what is going on with the other reply I just made would work wonders for explaining it better. It also just sucks in general because if I had the means to making a video on this subject I'd also absolutely be working on the two portal 2 mod campaigns I've been writing up every now and then when inspiration strikes. Moving portals and their properties was going to be a thing I was going to attempt after having thought about them and their physics.
Portal 2 actually has _two_ examples of a portal on a moving surface. When we shoot a portal at the moon at the end of the game, it's easy to forget that the moon is actually moving substantially fast relative to the Earth. The moon portal is moving like 4000 km/h relative to the Earth portal, and yet when Chel and Wheatley enter it they aren't suddenly launched off the moon's surface at mach 3.5. The portals preserved their relative speed, as in this video.
I've always wanted to know for sure what would happen if a person/object was between two moving walls, both with portals on the surface, as they move towards the person/object from either side. My belief is the person/object would make contact with itself on the sides facing the portals and then crush itself - though the physics are hard to imagine, because if the portals went perfectly over them/it, then in theory there'd be no resistance placed onto the walls to prevent them from fully closing and having the person/object perfectly pancake themselves imbetween. Others believe you'd somehow stumble into some kind of imbetween portal space, though I believe this doesn't add up, because they're portals and not wormholes - there is no space between one portal and the other which one has to traverse to reach the other side.
Generally in a case like this, any theory that violates physics is probably wrong. Sometimes a theory makes no sense but the math all checks out, and it turns out to be true. The mystery then is figuring out why it works that way. In this case, I feel like pancaking something between the portals is probably wrong, as is the in-between space, as neither seems consistent with what we know about physics. A more logical outcome is for the object to exert a force that prevents the walls from closing completely. How is anyone's guess, but it probably depends on how exactly portals work in the first place. Or something else might happen, which would lead to new discoveries in physics.
@@Greywander87 Perhaps some kind of force would be exerted on the walls when the two portals reach the edge of the person/object they're simultaneously closing in on - but that would rely on the portals themselves being receptive to resistance, and them then also transferring resistances onto the surface they're on - imo that doesn't add up logically. E.g. if you had a portal on one unstable and loose wall (say an office wall tile) which someone is primed to run and jump through, and a portal on another wall which is solid, and then you seal that portal off by placing another solid and immovable object infront of the portal the person would be exiting from, the person moving through the entrance portal would be meeting that object blocking the exit portal, exerting force on that - both the portals and the walls they're attached to encounter no resistance or force. Imo this is why a person stood between two portals moving towards them would simply be pancaked by themselves by a force that encounters no resistance from said pancaking - it would in theory work with infinite mass but relative velocity.
I feel like, it'd be the same as imagining that your left and right are copies of you, being pushed towards you, then my right shoulder gets pressed against the right copies left and vice versa. They keep pushing more, with deadly force and all 3 of us (tho we're all just 1) are squashed
I think the most intuitive way to answer these questions is to convert the problem into an equivalent one where the portals do not exist. If you were to instead have two people stuck between what is essentially a hydraulic press, then yes, they would be pancaked. This technique helps solve the subsequent question of whether the portals would need to exert additional force to pancake the person - they would, since the press would. This conclusion is supported by the requirement of energy conservation, as energy must be expended to deform an object.
@@the1necromancer I think you're overlooking the fact that the portals are the whole point of the thought experiment though - they don't obey any known laws of physics, hence why it's so interesting to speculate how a portal (as depicted in the game) would function in ways beyond what is demonstrated - it's more about intuiting the information about how the portals work that we already know - they're not wormholes, they're seemingly without a physical presence themselves, they're simply magical doorways which can be dynamically relocated. The moving walls with the portals on their surface would provide the velocity at which something is pancaked between them, but they don't tangibly interact with anything except the surface they're placed on (they stay relative to it) - the surface doesn't experience any resistance or impact or any sort of force from an object passing through a portal on it - therefore we have to assume if two portals simultaneously moved across either side of a person meeting in the middle of them, that the person would be crushed by themselves in a manner where no resistance is experienced by the walls (unless part of the person sticks out beyond the surface of the portal.)
I actually appreciate you using the logic of conservation of momentum to solve the portal paradox. The portal moving over the cube at, say, 60mph, is no different from the cube moving into the portal at 60mph. This is very logically sound and I appreciate your approach
It is different, by the same logic a cube going 60mph not losing any speed from going through portal proves that portals have no mass, thus a portal colliding with a cube shouldn't increase its speed
I tried explaining this to my dad, he disagrees because the box didn't have energy to begin with. I told him to watch this video later, so hopefully I can win the argument through this video.
@@lasadaf5336 Portals also create and destroy energy, so really they can behave however people want them to behave. But you can also think of it that in order for the box to actually come out of the blue portal at all, each part of the box that comes out must be pushed out of the way by the next part of the box coming out behind it, and this will happen at the same speed that the orange portal moves over the box.
@@kremitthetaco8725 the way I picture it is the same as if you took a hollow box with a hole in the bottom and dropped it onto the platform with the cube. The box’s momentum would be absorbed by the platform and the cube wouldn’t move. Here, because the portal transports the cube to the slanted surface, to me the cube would slide off. “Cube moving towards the portal is the same as the portal moving towards the cube” is valid as a way to explain conservation and is true given specific reference frames, but it disregards initial conditions. For example, depending on the reference frame me shoving you is the same as you shoving me, yet we both know there are more factors involved and in all likelihood the two actions would not yield equal results.
@@Scuuurbs Your analogy with the hollow box doesn't take into consideration that the cube already enters the portal before it touches the platform. What is absorbing the relative momentum of the cube from the moment it enters the portal to the moment the portal touches the platform? Let's say it takes 1 second to fully push the portal over the cube. That's 1 second of relative momentum basically pushing the cube through the portal until it stops. If the cube truly had no momentum when leaving the portal, then the same would apply to every single particle the cube is made of, right? If every particle of the cube is static relative to the portal, they would all try to materialize on the same location on the surface of the exit portal Do you know what happens when you force 2 particles to exist in the same location? I don't. I don't think anyone does. But it probably wouldn't leave the cube intact. The only thing which would stop that from happening is if the following particles push the preceding particles out of the portal, which would once again apply the relative momentum to the cube. So this also leads to the result shown in the video. I'm also really not sure what "initial conditions" you're talking about. The entire point of the Portal games is that you're in a test facility for portals which exists particularly to eliminate external factors.
@@kremitthetaco8725The particles of the cube are "pushed" by the same atomic forces that maintain the cube's shape, irrespective of any qualities the portal possesses. The only momentum that exists for the cube in this scenario is from the reference frame of the portal itself, which is unintuitive. Better to use the reference frame of an observer - in which case the momentum exists entirely in the piston/panel the portal is attached to, and its momentum is absorbed by the platform the cube was on, as well as whatever the piston is connected to.
@@Scuuurbs The laws of physics don't care much about what is perceived as "unintuitive" by some observer. If the camera was attached to the moving platform, your entire point of view on the experiment would change but the laws of physics remain the same. The cube and portal have relative momentum to each other and that's the only thing that matters. And if you're saying the particles of the cube are pushed through the portal, then they must have momentum when exiting the portal. And how fast would they be pushed? Is it some arbitrary number? Or is it simply the speed at which the cube is pushed into the portal?
Sounds right. reminds me of Tom Scott's video on that unconventional auger wherein the tube and its openings are spun, but the auger itself remains stationary yet still elevates grain. Also when you think about it, on a cosmic scale, all velocity is relative.
Just a nitpick, the physics of the rotating auger aren't the same as the physics of the stationary auger with rotating shaft, I believe the grains will move in distinguishable ways and have a different stress distribution. This is because in Newtonian mechanics rotating reference frames are non-inertial and so aren't related by such a simple transformation. Fictitious forces such as coriolis forces and centrifugal forces appear in them. Read about Mach's bucket experiment. In an idealized Newtonian (non-relativistic) universe, spinning the entire universe around a bucket won't cause the water to form a parabolic curve on its surface.
I love that you're just saucy enough for the people who are inevitably going to kludge together rebuttals to the really well-explained mechanisms you've posited.
actually the conservation of momentum stays true because relative to the space outside of the exit portal the the cube is actually moving so as its coming out it gains momentum making it fly off
@@MommysGoodPuppy Couldn't you also say that the space relative to the exit portal is moving towards the cube? The global velocity of the cube is still 0 and relative motion only describes motion from a particular frame of reference
I think it is introducing some dire consequences. If "cube" has some more traction with the surface (glued, welded, etc), there is potential to tear objects apart. Also, normally, objects are getting momentum in some natural ways based on their structure/joints, but if the portal is the thing that you are getting momentum from - momentum passing to some 2d slice of an object with is potentially can break it internally.
This would of course be true regardless if the weld/glue/bolts/fasteners by any other name were too weak. That by itself though wouldn't necessarily prove this unsound. Would just mean that if something was weak enough to be moved, it would be moved. Portals rarely care about fasteners anyway, see GLaDOS about all the cameras I knocked off her walls
The issue is not in the cube though. This comes from the portal suddenly stopping after it slammed down. If the cube were on a pillar the portal could continue downwards, with no damage to the cube. Only when the portal stops moving you introduce an acceleration between the two frames, potentially causing a break in the pillar. The real issue is thusly not relatively moving portals, but relatively *accelerating* ones
I feel like all you have to do is imagine the process frame-by-frame. The cube has to appear on the outside of the blue portal at the same instant that it passes through the orange one. The speed at which that happens has to be the same as the speed of the moving portal. So, when the box exits the moving portal, there's no reason it should lose the momentum it just gained.
Thank you for respecting our time. just for that you got my like, subscribe, and loyalty to finish watching the video. I am looking forward to your N64 Portal game. That sounds like lots of fun!! Great job keep it up! We love your work!
if you still have doubts, think about this: let’s say the cube is 1m long, and the orange portal is rushing towards it at 10 m/s. That means that in 0.1 seconds the cube will be through the orange portal. But think about the blue portal now, the cube should also exit the blue portal at the same speed it entered the orange one, obviously. So the cube will come out the blue portal in 0.1 seconds too. If a one meter cube moves through a hoop in 0.1 seconds then 1/0.1 = 10 m/s.
this is a big issue people are trying to solve about "how would a real wormhole act" as it is simply a tunnel from one point to another based on general assumptions and maths - and by that, moving the tunnel, if it were to serve for instantaneous traversal, would likely yield a similar result and the way a portal's function is described is not entirely dissimilar from a wormhole, and in fact, people study the idea that maybe portals if achieved like this in real life would actually be wormhole technology.
@@KingOfRedPlays I'm a bit curious. What is more realistic, a portal that is simply a hole and has an exit somewhere else? Or an actual tunnel with a bit of length to it?
@@amitbar5691 I don't know... For the cube to shoot out like that, it must have made a pretty big impact. And I mean, the impact doesn't have a limited range, after all, or does it? It has to be the entire universe colliding with itself, unless there's a logical error in my thinking. Maybe this is actually realistic given we accept the idea of portals, but it seems to give portals a ton of power that goes beyond traversal which doesn't seem to fit the use case they've been assigned in-universe Then I think it also gets even weirder... because if it works like this, then the entire gravitational force of the planet must have an effect through the portal onto itself, so frankly, I can't imagine that it could possibly physically work like the way he coded this
The other form of reasoning I use to come to the same conclusion is to try and think about the situation 1 frame at a time, for lack of a better term. When the Cube first has the moving portal coming down on top of it, then that portion of the cube is sticking out of the other portal. 1 Frame later the entrance portal has moved down slightly and thus more of the cube is now sticking out of the exit portal. But in order for that to happen, the portion that was already sticking out of the exit the previous frame had to have moved out of the way. It is essentially pushed by the previous portion of the cube trying to make room for itself. And the speed at which it was pushed would be equal to the speed that the entrance portal is falling down over the cube. So while the portal is falling over the cube, the cube must be moving in order to physically move through the exit portal. But maybe it doesn't move beyond that point? Well that doesn't make much sense either. When the entrance portal finishes hitting the floor, the cube will have still just been moving due to it pushing itself through the portal, and inertia would still apply. So it still needs to lose all the energy that it just gained. There's nothing stopping it from moving other than gravity and air resistance. So it would slow down accordingly to those properties. Thus if the portal was fast enough to launch the cube, the cube will naturally fly out the other portal. The other counter argument I've seen is that it doesn't make sense cause there's no clear source of the energy that propels the cube out of the other portal. but this is simply a fundamental property of portals as we see them. The simple act of placing one portal above another one creates energy from nothing. After all if you put a portal on a ceiling and floor and ran water through it, you could have a perpetual motion infinite energy device if you stuck a turbine in it. I mean you can do this in-game after all. So while I do argue that Newton's Laws still apply to the physics of portals, they do inherently break the fundamental law that energy cannot be created or destroyed. (similarly going from a higher elevation portal to a lower one effectively destroys energy as well)
Waitttttt that’s a really good explanation! I still didn’t get it after the video until I read this, but that makes sense to me! (Much more than some coding equation)
This is a fundamental misunderstanding of what a portal is. You assume that the cube is being moved through the portal, that it had to gain some energy to continue to push through threshold. This assumes that a portal is two separate objects. A portal is just a hole. For all intents and purposes, it's the exact same as dropping a hula hoop on a cube. The hula hoop represents a singular hole in space that is itself represented by two portals in this scenario. The entire hole is moving (which is NOT represented in the video, and why it only works when setting it up as a single moving hole in his engine). There is no force to overcome. When the moving portal has firmly stopped against the ground, the cube is still sitting on that ground. Any movement of an object that has a portal dropped on it is purely an illusion. The object has not moved. It is still sitting where it started. The only difference with an angled platform is that the axis on which gravity effects it would change and eventually drag it off the platform, provided the ground and cube themselves are not providing enough friction to counter that. You also never create energy from nothing in Portal, nor do you destroy energy. The terminal velocity example you mention is simply providing an infinite corridor in which something can fall to reach terminal velocity due to gravity. You aren't creating any energy with the portals. As far as destroying energy, we don't do that either in the game and I'm not entirely sure what example you were trying to give for that.
@ChaoticNature portal above portal. place a copper coil around this collumn and drop a magnet through. boom- infinite electricity. how is this not creating energy out of nothing?
@@sydssolanumsamsys You're mistaking the conversion of one type of energy into another with the generation of energy. You're converting kinetic energy (gravitational and magnetic) into electricity. The portals themselves are making no energy, they're simply removing the work needed to reset the magnet to the top of the coil. That's also not infinite as the coil would heat up, and beyond a certain point would melt and break down the system.
I’d love to see how your game engine handles the orange and blue portals both moving but at different velocities, i.e. the orange portal moves down onto the box while the blue portal is elsewhere moving at a different velocity than the orange portal (and perhaps even at different angles to see what affect gravity plays). Particularly if the blue portal is moving in the same direction as the orange portal, how does the cube handle going from one to the other when they’re different speeds?
He did it already! the first experiment that is shown is exactly that. as you can see, the angle of the blue portal is not the same as the orange, and both move at different speeds, all that will happen is the speed of the cube will vary in the exit following the equation he proposed
@@DWal32 Mathematically that is just a different speed though. Going by the equations shown in the video, only the relative velocity of the portal and object matters, so varying the speed of the blue portal only changes the resulting speed of the cube as it flies (or plops) out of the blue portal, maintaining the relative speed between the cube+portal system.
@@DWal32 In terms of the math involved that really isn't important. Combining the two velocities and changing their vector would work the same way, just with different magnitudes of velocity input and thus different magnitudes of velocity resulting.
Portals are basically kinetic energy / potential energy translations. If you have a velocity difference between them, it translates onto the object passing through. An object passing through a portal higher than another is just an object going through an instantaneous PE adjustment in the form of space displacement . A moving portal is basically a KE translation, which necessarily involves a velocity difference between frames of reference.
why do we imagine that a portal separates spaces and if the portal moves, then its space moves? It always seemed to me that the portal only teleports objects while maintaining their kinetic force, only in the case of the game Portal this force rotates at the angle of inclination of the portal itself
@@TheDEFCHER If you put the portal at a higher altitude, you already have a change in potential energy, and if you consider that velocity also varies according to how far away it is from the center of Earth's rotation (or when faced on a completely different orbital body like the moon), it will also necessarily need to have a change in velocity which also requires a change in kinetic energy. When you go out of the moon portal, you do not get flung at the speed difference between the orbital speed of the moon and the velocity of rotation of the Earth, which is a difference of several hundred kilometers per second. There's really no argument, just unwillingness to see that potal physics would just be too inconsistent otherwise.
I mean, it does. The test shown when it drops is accelerating at -9.81 m/s^2. The blue portal is also accelerating in the opposite direction, so it cancels. Like Portal itself, there's still probably a terminal velocity limit, so it isn't uncapped acceleration. Where this still isn't completely resolved is if there is a delay in rematerializing something after it enters the orange portal. If there is any delay, then the cube will have a slightly slower exit velocity than as it was derezzed. That would cause it to be compressed... I probably don't want to be the first living thing to pass through an accelerating portal.
It kinda doesn’t get weirder. In-game it’s just the center of the cube that counts as either being in or out of the portal. In real life, the cube would experience a “pulling” force (just like with the moving portal) but if the portal accelerates, the force just becomes bigger. As long as the structural integrity of the cube holds, it’s like picking it up with a vacuum hose around the cube.
I wasn't onboard until you did the "hula hoop slam" and it changed my mind the instant you pointed out that the exit portal was also moving. Nicely done
What bothers me about this problem and this solution is: what exactly gives the velocity to the cube? From the cube's perspective, what pushes it away from the floor? Does it suddenly feel a force upwards and away from the portals? How does the Orange Portal transfer it's velocity to the cube if it never even touches it?
Say you place a portal on a ceiling and another on the floor and you drop a cube into it, allowing it to fall infinitely. As it passes through the portals it keeps picking up speed and if it wasn't for air resistance it would in fact pick up speed forever. Where is the energy coming from in that process? You might say gravity but no amount of height would allow you to fall at speeds reaching the speed of light within earth's gravitational field. No the portals themselves convey energy to objects that pass through them simply by their very nature of being able to transport objects to disparate points in spacetime. But to give a more practical answer, the cube essentially pushes off of itself and the floor below it. Looking at purely the blue portal, what you would initially see in slow motion as the orange portal descends, is a small portion of the cube sticking out of the blue portal. Then a moment later more of the cube would be sticking out of the portal. But that would mean that the first portion of the cube would have to have moved out of the way in order for that to happen. Essentially the lower portion of the cube is pushing the higher portion forwards in order for it to exist the portal. And then the next portion does the same and so on and so on. By the time the cube fully exits, the entire cube is moving at the same velocity as the orange portal.
@@BlazeMakesGames No, it wouldn't keep picking up speed. The energy comes from gravity, that is a fact. You're in freefall, like jumping off a cliff, but you keep teleporting back up. The portals are doing absolutely nothing. The cube would reach terminal velocity and it would just keep falling at that same velocity. There is a limit to the speed. If we were in a vacuum, and you tossed a cube into portals that faced each other, the cube would keep the velocity you threw it at, because there are no other forces acting on it. If none moving portals did act on objects going into them, then everything would be shot out of stationary portals equal to the amount of force they exhibit. however, the portals do not interact in that way. They do not interact with objects going through them. Portals are more like doorways. If a moving wall with an open doorway came towards you, and you go through, are you inheriting the wall's velocity? The difference here being the space on the other side, and how the forces on the other side interact with you, not the portal.
@@BlazeMakesGames By your definition, if you even touched a portal, it should suck you through it. On your gravity example, if you had infinite height, with a constant acceleration due to gravity, an object would speed up to its terminal velocity. This is what is happening in your example. This just can't happen outside of portals because A: get too far from earth and gravity decreases, and B: get too close, and the ground stops you. The portals really just move one location in space to another, they don't pull objects through themselves (unless one is in space, sucking objects in because of the pressure difference).
its crazy how when i notice a video is gonna wait til the end to show results i just skip, see the results then leave the video, but here seeing the results first made me wanna watch the entire thing and i would have watched a whole 20 minute video going more in depth about these physics and complications. amazing video with out using predatory tactics 10/10
My issue is that the hula hoop analogy is always how the portals work. They're just holes, the ends just happen to not physically connect. There's no reason for the energy of the portal to be conferred to the cube. Momentum is conserved between portals as well as the lack thereof. All of this with the caveat that I flunked out of high school. Regardless, loving the progress on the project, can't wait to see more!
I think if one portal moves, the other would have to move, too. The energy transfer from the portal to the cube seems to be a trick that gets around the space/occupation constraint on the other side. Normally the entrance portal is static. This means forces acting on the cube have to push it through the portal. But if the portal moves, how is there going to be enough room on the other side, if the cube is not moving? I think the relativity trick is just a trick.
Portals convey energy to what passes through them all the time. If you simply place a portal above another portal and pass an object through it, then it has just magically gained energy via passing through the portal. After all think about the times when you place a portal on the floor and ceiling of a room and fall infinitely. You continuously build up speed because the portals are in effect conveying energy to you by granting you more potential energy than should be possible. Momentum is conserved through portals, but energy is not. Similarly if you go through a high portal to exit at a lower elevation, you will have effectively destroyed energy as well. Portals by their very nature allow you to create and destroy energy at will.
@@BlazeMakesGames In your example the energy isn't coming from the portals, it's coming from gravity. With nothing to slow an object down, gravity will cause it to accelerate through the portals until it's stopped. The energy is not magically gained. Momentum *is* energy, and is conserved through portals, but the portals themselves neither add nor take it away from the object.
@@Pop4484 well portal isn't a nintendo ip so I doubt they would care that much even if you used an emulator since they don't own the game so they can't really do anything about it
Nah, absolutely 100% spot on. Another way to show it is to pull the exit portal back the same velocity as the entry portal drops. The cube would then lose all velocity again.
You, sir get a instant like and subscribe for a) not waiting with the result towards the end of the video b) making the video as long, as it needs to be c) seeming like a good youtuber overall
Great work, I love it! I feel like the cube should not shoot out like that, because it rests still on the ground and the teleport just happens faster - I guess the ground would absorb the momentum here...
i always thought of it as the total momentum of all three objects remaining consistent, so i figured the cube should stop, but admittedly i struggle to keep track of everything
I have the same idea. What happens to momentum here. The portal (or the object it is placed on) would decelerate giving it's momentum to the cube. But I cannot rationalize how that interaction would occur.
This was my thought too, but when I went to write out a comment about it explaining the math, I think I found the solution. Newton's first law states that an object at rest stays at rest and an object in motion stays in motion, until acted on by an external force. But also, motion is relative. An external force acts on the platform to move it down towards the cube, so the cube is already in motion relative to the platform before it even enters the portal. When the cube goes through the portal, no additional external forces act upon it (aside from small ones like air resistance and gravity) so it retains the momentum relative to the portal. This does seem completely illogical based on the laws of physics we know, but that's because our laws of physics don't allow for moving portals. If you imagine a similar situation in space, it might make more sense. If wormholes had no field of gravity, then an object entering a wormhole would come out the other side at the same speed it entered relative to the wormhole. It doesn't matter whether the wormhole or the object is moving, as motion is relative. No external force would have to act upon the object for it to retain its relative velocity.
@@mithrandireichner2667 The answer is basically that the cube doesn't actually accelerate and no additional momentum is required, so none is taken from the platform. The cube is already in motion relative to the portal as soon as the platform starts moving, it simply continues at the same relative velocity because no additional external forces act upon it to slow it down. It makes no sense with our current laws of physics, but, if wormholes area real (and traversable) our laws of physics are wrong anyway.
@@ayylith The way I see it, the system encapsulates the portals and the cubes. One side could argue that the *cube is moving* relative to the portals, but when discussing physics, or math, especially linear math, the discussion happens within systems. We could go on discussions about the properties of this system, but I'm going to ignore that for my comment. Assuming the system includes gravitation, that should logically include the exerting body of that gravitation. So the basis of this system is Earth, the cube and the portals. With both portals, gravitation is negative in both cases, so towards the basis ground of the system. This does not change regardless of any other factor. It is a fact, then, that the cube is resting relative to Earth and the portal is, in fact, the object that is moving. So it stands to reason to assume that the *portal is moving* relative to the cube. So my interpretation of this problem more or less disregards the portals themselves as effect sources since the basis of the problem is the cube in resting position. The only thing that should really be affecting the cube is gravity, assuming the portals don't add, subtract, convert, transfer, etc in the process, and that itself is a question based in unrealized information of the *game's universe*, not ours.
@@mithrandireichner2667 From the cube's frame of reference the portal has velocity, but from the portal's frame of reference the cube has velocity. Relativity says whichever frame of reference you measure from the total energies involved are conserved (don't change over time), but that individual components of the system can measure different readings depending on the frame of reference you use. You can even use moving frames of reference such as the portal as long as you account for that movement. We can simplify everything by measuring from the blue portal. And since when traveling through the portal the point in the middle of the orange portal is in the exact same place as the point in the middle of the blue portal (there is no spatial or time difference between them) We don't need to change to a different frame of reference, and therefore no adjustment is necessary (we'll call this point A). The velocity of the box going into the portal, as measured from point A = the velocity of the box exiting the blue portal, as measured from Point A.
This is a good way of visualizing it and it makes complete sense, to me if the exit portal is stationary it's a no brainer that the cube is flung as the cube is literally pushing itself. Think of it in layers, the first layer is transposed as it touches the portal surface to the other portals surface, but when the next layer comes out pushes the previous one out of the way, so when the entrance portal is moving it's velocity is transferred to the cube via the force of the cube pushing on itself.
@FantasTik Boom exactly! He is trying to make a hole, a lack of energy and matter, be a frame of reference to impart force on another object. His formula has 1 variable, a box, and a hole accelerating at it. If the box somehow was accelerating through the hole with no force acted upon it then light itself would accelerate through thw same hole and exit faster than the speed of light.
@@xelgodis80085 Someone named "Diego G" strongly argued with me, until I gave him an experiment. Then he deleted his comment. That experiment is: "We stop the portal halfway of the cube. Did the cube move? Before I answer: you clearly see the platform and the cube. The answer: If you apply author's equation here, the result will be different. The cube will get enough speed from the portal to fly out. And what you see is exactly why this equation is wrong. Cube didn't move and wasn't pushed, but it flyed out. Right result would be: cube didn't move at all." I just pasted some part of reply... actually because I saved all my replies... I thought them being cool lol
@FantasTik Boom I was a bit brash myself, but it seems everyone who has argued with me seemed to shut up real quick when I asked the how a void passing over an object interacts with the object, and if a void can accelerate something passed through it then light itself must accelerate past the speed of light. These people assume the entire universe has a single inertial frame of reference and nothing else matters, which is the flat earth argument for gravity-denial. Not understanding basic principles is how we get radical conspiracy theorists, and it's dangerous.
With that stationary test, it seems like the part of the cube that has exited is moving relative to the exit portal. I'd actually expect that part of the cube to have a pulling effect on the rest of the cube (that is still on the other side of the portal). I wonder how far you'd need to extend the entrance portal down, before the rest of the cube is pulled out by this force alone. What do you think?
That's what I thought but as the entrance portal comes down on the object with the same speed the object is technically being pulled out the end while appearing to be stationary. If the entrance portal stopped before reaching the ground but after reaching the object, the object should be pulled out or (if it is not solid enough so not the cube for example) be stretched or teared off.
While, yes the part past the portal excerts a pulling force against the rest, it can not pull the rest through, since it also excerts an equal pulling force against the part past the portal, because of Inertia. The only part of the force not negated is the effect of gravity. The cube would fall if half the cube is through and the exit portal is pointing down, and slide to one side if the exit is not horizontal.
I would imagine it depends on how fast the entrance portal stops. If it can stop immediately with no "cooldown", it would probably shear the cube in half in real life depending on the material (in-game it is impossible as the game defines it as a single particle). This is cuz the half that enters the portal would have energy while the other side abruptly stops. It's similar to half of a stick being hit by a moving truck while the other half is anchored in a tree or something. If the material had a weak point, it would break at the weak point instead (as that's how energy travels).
Actually the cube never gains momentum. I don't know how a portal which does not itself transfer its momentum to objects that pass through it makes sense. The portal is a direct spacial link to a different location. It doesn't matter how fast the portal itself is moving.
I typically don't like or comment on videos, however I respect the fact the this guy got to the point and didn't drag out the video. I also find his solution to the moving portal questions to the best answer I've heard.
Suggestion/Question: In your version, could you remake the demonstration done in this video from a few years ago? ruclips.net/video/0TZd95BCKMY/видео.html A portal sandwich type scenario is both a common thought, and is also not an easy thing to intuit, and I am curious if you would yield similar results as they did. I'm also not sure if their method (from Portal 2 which does allow moving portals in one level) would work for testing the portal paradox, but would be interesting to see if you could implement it and compare your results from this video.
i imagine it would prevent the portals from getting closer to each other than the height of the cube, as I would think weirdly the two opposite sides of the cube would be pressed against each other. would be cool see if this actually happens though
I like it. If the rule is velocity is preserved between portals, if one portal is moving and the other is not that velocity needs to be preserved. The only situation that I think might be weird is you do the reverse. Where you try go through the none moving portal to the moving one. You might not have enough speed to get through a stationary portal and may get shot backwards.
@@darkcoeficient momentum=mass*velocity We know that mass must be preserved through the portal in order for it to be a portal therefore velocity is the parameter we care about. That's why his calculations don't consider the mass of the object at all, just their relative velocity. Not there relative momentum.
This is so weird to think from the cube's perspective, though. Like Imagine being in its place, you'd see the portal come toward you and then your feet would lift from the ground apparently without any force pulling you.
@@Celia_Dawn Eeeh... kinda, but not really. You wouldn't really have an object hit you and transfer its velocity, the portal is coming toward you and then you'd fly in the OPPOSITE direction of its velocity. I think it's more similar to being in a car moving at constant velocity and not feeling its movement, then hitting a brick wall and flying out of the windshield and die after some agonizing pain because you weren't wearing a seatbelt. From your perspective you were stationary and the wall was coming toward you, then when it hits you you fly out of the car and into the outside reference frame. ...Actually now that I think about it IT IS pretty much just that!
@@KombatGod Portals don't transfer momentum themselves though, they are holes. The Hoolahoop analogy works well, the only different is the space fuckery of the top of the hoolahoop being somewhere else. It's still a hole.
For me I always saw it like a simple door. If you dropped an open door and the frame slammed down around you, you’d still be standing there. But if you went across the frame Mach 1, you’d just come out the other way with the same speed. Since portals aren’t just doors tho, I can see how you’d carry its momentum into the other side. But it’s weird, because it’s as if the whole room, or the whole OTHER side of the portal was moving toward you. So when the portal slams down on top of you, it’ll be like the whole room was pushed down under your feet which results in you in the air. Same thing you the portal came at you from the side. You’d get through the portal as if the whole environment was moving on one side.
What a weird sensation that would be, one moment you're standing still the next you'd be at great speed but without having felt the acceleration of it. Suddenly being blasted by air from air resistance and seeing the room around you at speed heading towards you.
Very cool! I'd argue that you have to take into account the relative velocity between the 2 portals. If your reference is the orange portal (it stays still) then the box AND the blue portal move up toward the orange portal at the same velocity. So the box enters the orange portal with some velocity, which has to be the same velocity as the blue portal. In that case, the velocity of the box would be added to the relative velocity of the blue portal, doubling the velocity of the box as it exits the blue portal, which is not consistent with another frame of reference. I think it's less that speed is conserved, and more that energy (momentum) is conserved. In that case, there is no energy added to the box, so it can't change momentum, so it just falls out of the blue portal.
So much more well put then what I was gonna say, yeah no this is a pretty fantastic project and it is very impressive to reimplement portal’s mechanics this way. But yeah sadly I agree it’d be slightly lamer reality lol.
This is super impressive stuff, props my man. Super late response, but I think the answer to this squarely sits on if you believe the space in between the portal can enact force onto the cube. For me, I see the portals as a mere translative motion across space, so I would say the only force on that cube as it leaves the blue portal is gravity. So I’d say it plops. But if you see the portal as a movement arm that pushes the portal out at the same velocity the arm moved onto it, then it’d launch as shown.
The box already has momentum relative to the orange portal. That momentum is carried through to the other side, which is why you see it launch out the blue portal.
@@APaleDotIt has momentum, but I believe that gravity acts against it, so it would result in a slight hop at most. After all, the acceleration that tbe box experiences should be equivalent to what would happen if you moves the tile that the box is on upwards at the same speed that the portal travels down and then suddenly stop. It would hop, but not as far as if it were launched at an angle.
@@darthplagueis13 The original question doesn't specify how fast the orange portal is moving. The implication is that if you answer 'A', the cube will **plop** out of the blue portal regardless of how fast the orange portal is moving.
My question is what happens if the descending portal only descends half-a-box's height from the floor the box is resting on? The half below the portal is unaffected, but the part passing through gets momentum. I'm guessing the part passing through pulls on the part not passed through the portal and it comes out but with a slower velocity.
the net velocity of the cube is zero as the two directions cancel until more than half the cube has moved through the portal. if the portal continues down it may eventually be overcome by gravity, otherwise it will only move maximally at the speed of the moving portal. energy in = energy out
The problem with the equations is the assumption that portals can have momentum. Portals are connections between regions in space. The cube doesn’t interact with the moving platform, it interacts with the portal *on* the platform. Since the portal cannot impart momentum and the cube is stationary, the cube simply drops as soon as it crosses the portal.
@@zeynaviegas thorough history there are paradoxes that became solvable with modern tech but still are called paradoxes, there's a video on the many types of paradoxes called "the five kinds of paradoxes" by jan Misali
I think the true "Portal Paradox" lies not in the clear, discrete time behavior of the system, but how the motion works in a slowed, more continuous case that probes that discontinuous boundary and mixed forces/momenta (gravity pulls 'down' on some volume of the cube yet the remaining volume has momentum in non-orthogonal direction). For example, a really tall, stretched rectangular cube and an accelerating portal. What happens in your implementation?
the cube would slide out slowly at first andthen faster ,as the moving portal sped up , out of the stationary portal before being thrown out like in this demonstration. i think
I was also thinking what would happen in the portal's velocity wasn't constant while an object was corssing it's boundary, since e.g. if we stop the portal, the parts of the object that were stationary relative to some other objects around it are expected to remain stationary, but the parts that got through are expected to retain momentum and start pulling on the rest of the object. I guess I kinda answered my question, but it would probably mean that a deccelerating portal would "suck" any object it comes into contact into itself. As for this specific implementation, it seems to be using a very simple principle and the object is considered to be on one side right until it's center passes the portal, at which point it's teleported (unlike in Portal, where, if I recall correctly, the objects can actually smoothly transition through the portals).
An interesting quirk of this interpretation of portal physics is that if the cube is moving and the portal is moving, the cube will be sped up or slowed down by the portal its moving through which is quite strange and not how I think portals should work they aren't supposed to mess with the momentum of an object. If you just took the *entranceportalvelocity* out of the equation it wouldn't change much other than these strange momentum transfers from a portal to an object.
I think this scenario helped me actually understand what's happening in this video. From the blue portal's perspective it would be as though the cube would be moving towards it, so it would keep that momentum it has coming towards the orange portal i think So I guess it would be doing the same with a long cube? I... Assume it would be kinda stuck in place until it fully goes through the orange portal, and then when it exits the threshold of the blue portal it would keep the momentum from the orange portal and plop out? That's my best guess. But this hurts my brain and portal is black magic to me so I have no idea.
Since we're mixing gravity into the equation...would gravity not travel through the portal as well? Portals are, what, connecting regions of spacetime? So any spacetime affect would be able to traverse the portal boundary, or...? And we know now that gravity travels at the speed of light, so it might propagate out of the portal...
I think gravity would be more of a factor than inertia. Arguably, the portal itself has no velocity, since it's just empty space. The platform has velocity, sure, but the portal might as well be a hole in the platform. Air would move freely through it, as if nothing were there. The same would apply to the box, no? The flaw in your code is that you designated the portal as an object, and one that has a velocity. The box would, thus, simply fall out of the exit portal, due to an inconsistent gravitational pull moving the center of gravity of the box.
I'm glad you took relative velocity of the box and both of the portals. Everyone I've seen discuss the Portal paradox seems to neglect that. Speed and velocity are relative to objects in space. It doesn't really matter if the object is moving or the space around it is moving, because relative to the position of the object, it might as well be moving regardless
What happens to an object thrown in to a stationary portal while the exit portal moves forward relative to its face at the same speed. Awesome video it's got me curious.
This makes sense, scientifically speaking. See, one might argue that, in order to move the cube, it needs energy, but the portal, since it doesn't come into contact with it directly, can't possibly give it any kinetic energy, which means it shouldn't move. But here's the thing: we aren't dealing with normal spacetime here. These portals are wormholes. It's like bending spacetime to "travel faster than light." You yourself, or the cube itself, doesn't move, but the space around it does. What the orange portal is doing is basically slamming space at and around the cube, which means, relatively speaking, it is moving. And since space is kind of our ultimate frame of reference, we can only ever experience this interaction as the cube moving in space, even though, technically, the cube is stationary and space is moving around it.
The portal shouldn't have velocity. The experiment you showed at the start, at some point deletes the cube on the orange side and spawns a new one on the blue side. Portal allows you to put things halfway through a portal. What would the result of your experiment be if you stopped to orange portal 1/3 of the way through the cube? What about 2/3 of the way? If I were remaking portal, I'd have two rooms. You can mirror all the object states in both rooms. Chel would not notice that there are two rooms because the object states are mirrored. When Chel goes through the portal she walks into the other room. In the case of our cube, when the Orange Portal interacts with our cube, it would come out of the Blue Portal in room 2, and the cube in room 2 would come out of the Blue Portal in room 1. Since the cube didn't have any movement it would still be resting on the surface of the floor. However that floor is at 45% at the Blue Portal position. At that moment, the force of the box is still 90% to the floor (where gravity was), but 45% to gravity (where it is now). This would cause the cube to begin spinning violently forward, as it normalizes those forces through rotational energy.
If the mass is uniform, you can assume a very proportional relationship between the resulting speed, and the distance the moving portal goes over the object. 1/2 the distance = 1/2 the exit speed 2/3 the distance = 2/3 the exit speed and so on
The block should plop out cuz ur not giving the block any energy when u hit it with a portal, there is no force acting on the cube so if you follow the rules of physics the block would not move because no force was put onto it, you only change its place in space. So the if you slam a block with a portal the block should pop out the second portal with the speed at which the first portal is moving but won't fly out and instead would just sit on the second portal until it starts falling towards gravity.
@@nikoveliki4132 I'm not saying the portal is pushing the cube, but I am saying that surely transporting the object takes some sort of energy. Anyway, the way I like to think of it is that from the perspective of the portal (like looking in through the blue portal) you'll see the cube rushing up at you, and from there it would continue on it's path upwards because it's relative momentum would be added to the portal's momentum (which would be zero) to get a final momentum of moving upwards. If the blue portal were also moving downwards at the same speed then the cube would just plop out for a moment then fall back in.
@@godlyvex5543 so ur theory is that if 1 portal is moving towards me and i throw a ball through it, the ball would fly out faster through the second portal? I look at the portal more like a window, but the 2 sides of the window are in different places, so whatever goes through the portal would act the same way as if you put it through a window frame except with the portal the other side of the window frame is somewhere else
@@nikoveliki4132 The portals are windows, windows where the two sides are detached. It's common sense that if one side were moving, the portal's movement is added to the ball's movement. You can't really even look at it like a normal window, because the world on one side of the window is moving.
First off, well made video, and I always love more portal content. My core argument against this result is that the space contained within the ring of the portal is not a physical object that can exert force, OR have force exerted against it. It's just the space that exists on the other side of the exit portal. Therefore, this space has 0 relative velocity. The only forces that are exerted on the cube in this situation would only be gravity and nothing else. The surface that the portal rests upon can have velocity, since it is an object, but the portal itself is not subjected to the same physics, since what the portal represents is just whatever space exists on the other side of it, and that space is not moving, hence 0 velocity. A portal is just a Quantum Tunnel, right? So imagine a Cube placed on a floating platform in space. Now drop a large hollow pipe (the quantum tunnel) around that Cube and platform in such a way that it never collides with the Cube. Despite the Cube traveling through the tunnel, (or more accurately, the tunnel moving around the cube) no force is being exerted against it, and when it arrives at the other end of that tunnel, it has no more velocity than when it entered the tunnel. Portals combine two disjointed places through a similar tunnel, so when you shove the portal down around the cube, the cube will simply arrive on the other side of the portal with the exact same relatively velocity that it had when it was sitting there minding it's own business. Zero.
Not enough people have mentioned the god-tier move of making this video exactly how long it needed to be and that’s it. If any other creator covered this topic, this would’ve been a 14 min video at least. Bless you, sir. Subscribed.
One thing that sucks is he's wrong, but I do agree, 5 minute or less videos are the best 👌🏻
@@BalognamanforyaHow is he wrong though?
@nintardo2231 you can check my other comments to see the explanation, but here's a hint, it has to do with the conservation of energy 😉. This guys great at programming, but he's not so great at physics.
@@BalognamanforyaPortals already fundamentally break the conservation of energy regardless, so any further violations are a moot point.
@sharcc2511 no, they literally don't. Sure, if you look at it from a glance, it would seem like they do, but they don't.
Kinda cool that your de-make is now, at least in this particular regard, technically more advanced of a game than the actual original source version
The Wuffle house has found it’s new host
@@CBNST its* 🤓
@@CBNST The trebuchet is important!
@@kip258 me -> 💀
@@lod4246 Begone, BOT!
It always amazes me what games were possible on the old consoles if only someone had thought to make them at the time.
Has always been like this in all the aspects of technologies
think about now, what's possible
The Ocarina of Time devs made portals back in the day, but they weren't implemented.
game design is its own technology
a lot of new things are possible on old hardware, just because of how much more we know about stuff like 3D rendering and programming now! back then stuff like this was POSSIBLE, but probably would've never happened
What would happen if you:
- Incrementally change how far down the moving portal moves, will the cube be "sucked" up and out the other portal?
- Both portals are moving in opposite directions, will the cube get the sum of the portals speed?
- Move the portals toward each other, having the object in the middle?
Just interjecting with my own thoughts:
1. Yes, the cube would be sucked up a bit. I think about it as a person that were standing and the orange portal slamming into me from the top. All the air above me has exited the blue portal at a high velocity, then comes my head, which has just entered another end of the world at a high velocity (this would be the same if the orange portal were stationary and I ran/fell head-first into it), so my head would definitely get tugged into the other end. Now if the portal stops midway, my head will retain the inertia and in the worst case, I'll be decapitated. Again, I think of it as jumping out of a moving train and the train immediately stopping to 0 when only my head is out of the door.
2. Logically, yes.
3. Depends entirely on how the atoms are recreated/phased on the other end. Ideally, they would either phase into each other or be in superposition. But logically, the atoms would layer/intertwine and you would end up with a fine Chell paste.
So the first question you had can be answered two ways, the previous commenter included velocity which is one of the ways to interpret it. I think you meant in a slower way as in how far would the portal need to go before it was sucked out. If the portals are both on a surface that faces the direction of gravity then it’s just when the center of gravity of the cube goes through that or would be “sucked” up and out. The second question is actually demonstrated in the video when he puts a portal through a surface and essentially it is the answer to your question. Its basically like if you were to drop a hula hoop over yourself, one side is moving (relatively) exactly at an opposite velocity of the other side. The third question is a bit harder to answer but I’d imagine it would be like trying to stuff the cube into a place with zero volume. In a real life scenario where we magically have portals to test this, I’d imagine that any object you put between the portals would make contact with itself and begin resisting whatever is pushing the portals together until it yields to the pressure.
This is the logical set of answers based on what the math is trying to simulate. What would actually happen in the N64 physics engine depends entirely on how James is simulating the "teleport."
1. Half the cube should appear on each portal face, at first. Gravitational forces on the Portal B side will immediately take effect on only the mass that is present on that side, and effect the whole cube as a calculation of the opposing forces on the other side, Portal A.
2. Yes, both logically, and according to the math.
3. It would look exactly the same as if there were no portals at all, and it was just two panels sandwiching the cube. Logically, the portals (or more accurately, the objects the portals are moving on) would either be forced to stop with the cube in the middle, or the opposing sides of the cube would crush the cube itself, depending on the force objects that the portals are painted on are exerting on the cube. It would be ultimately the cube crushing itself, but the force applied to the cube would be equal to the objects that the portal are moving on.
If we talk about just physic and not how he simulate the portal.
1. Think of it like the portal is grabing part of the box and throwing it like how you lift a box. So the answer is yes.
2. Since we are dealling with portal, we are dealing with relative position and velocity we have to take that into account. If you are talking opposite here as in from your POV in a room one go left and one go right with the direction facing the place they are heading. What would happen would be the velocity of the cube = the velocity of red portal + the velocity of blue portal. Imagine the slam experiment but the stationary one also moving forward. But opposite here mean how the portal is moved base on it orientation like one is going forward and one is going backwards then it will stay still like the hoola hoop example in the video.
3. The box will be destroy as it will try to exist in the same space. Imagine it more like slamming the middle box with 2 other box exactly the same down to the attom and the imperfection toward the middle one.
@@VarunGupta3009Yeah that phase/superposition answer doesn't really make sense, it's not like the portal instantly teleports an item into a different point in space, it lets the item "enter" that position from a specific direction, so the cube wouldn't have to phase into anything. The correct answer is what herewegoagain wrote: the cube would simply find itself in the middle of its own two sides crushing itself with the same force as the moving panels.
If you assume the portals to magically be unstoppable then sure, they would push until the cube disintegrates into atoms but you're just asking what would happen if you put the cube in an infinitely strong press.
“I could make you wait for it, but I value your time more than retention rate.” Mad respect for that.
I just told my friend about this project and his first question was if the ch_createairboat command will be in the de-make. 😂
Would be a sick easter egg if it also required the N64 keyboard to pull up the console!
@@VariaPrime the what now
I see no reason for this, unless he first made a de-make of half life 2 and was building his current project on top of it. But that would be... fuckin weird my dude
@@inanna8782 locale man has never heard of an Easter egg
@@inanna8782 How to make portal on N64:
Step one: Remake all of half-life 2
Step 2: Add portals
Step C: That's it. You win.
Test idea: what happens when you halt the piston mid-way through the box?
If the box is being treated as a point (with a 3D hit box built around it), I imagine the box won't "jump" out of the exit portal until the entrance portal has crossed the box's reference point. If you treat the box as a bunch of infinitesimal boxes rigidly bound to each other, perhaps more interesting stuff can occur, like having only half as much momentum when it leaves, or being dragged by gravity due to half of the box being affected by it in different directions.
That's actually a great question. My guess is that he will simplify the problem and make the mass point like somewhere at the centre of the object rather than having it distributed. It sounds to me that having a distributed mass might be computationally a bit too much for a 64. But as you point out that would lead to some edge cases not behaving with the correct Physics while for the majority (where that simplification works well) he's got it spot on.
if the portal stopped halfway through the box you'd simply have half the momentum and so half(i cant remember physics its either this or a fourth) the velocity it would have had if the portal went all the way
Wouldn't the force be cancelled by the stopping of the portal piston?
While the engine would likely require changes to account for this, I also think it would logically exit at half the velocity:
If the matter inherits the relative velocity of the portals, and only half of it exits the portal, half of its matter inherits the velocity. The affected matter would continue to shoot forward and either pull the rest of the object along - and as the rest of the mass has no relative velocity, the object would equalize to about half velocity - or it would tear itself in half. This would be entirely based on the structural integrity of the object. If the bonds are strong (like a block of metal) they will stay as a whole object, but if they are extremely weak (like jello) it would be torn apart.
There is no momentum on the box as the box never moves, it is the universe that is moving ... Its a stationary box on a moving universe...
If the universe stops relatively to the box mid way the box will appear to stop...
That would mean interestingly that if the portal would stop at any time in the period the box is in the air after "Jumping" out it woul lose its aperent lateral velocity.
Now another way to look at it is... It's more of an information teletransportation. In that case every particle on the box gets deleted and recreated in its state including relative velocity vector. In this case the box would probably be shred apart as an instantaneous stoppage of the portal would produce an infinite acceleration capable of riping the box at the bond level that separate a moving particle from a non moving one..
Now tell us what happens when you smash two portals together with something in between them. 🤔
my shot in the dark is that the object would crash with its own edges
In "reality" I think the object would be crushed, and if the force moving the portals isn't enough to crush the object then the portals would just stop moving.
THIS is the question. Using the box as the example, I agree with the others - it would collide with itself. But what is hard to answer is if the portal act as a window, with no physical connection with the box, will it be able to meet the other portal and create infinite force? Surely that's impossible? But so are portals, probably...
In game world I'm sure the box would just go flying or teleport to a random coordinate, probably out of any feasible range and crash the game.
OP can you try this with a long pole, but the pole is on an angle, if at the right angle, surely the portals could meet since the pole would never collide with itself.
This is as fascinating as playing Portal was for the first time, thank you to all cause that's all I've ever wanted to feel again.
Edit: After thinking about it, it wouldn't be infinite force, but just a lot of force, or enough to collapse any object down to what I would assume to be a micro black hole? Too much mass in a certain space - which actually happens with stars etc... That seems reasonable if we allow portals to exist. I'm content with this theory.
@@EldeNova So.... The EASY answer to that paradox is to realize that the cube doesn't have infinite rigidity. If it can exert force on itself through the portals, then that means it's under compression. It will immediately begin to heat up. Depending on the material properties of the cube, it could crumble, crack, deform, or crush. If it crumbles, then parts of the cube will be expelled from between the portals. If it cracks, the parts of the cube will slip relative to each other, again possibly being expelled as a result. If it deforms, then mass will squeeze out the sides, again being expelled. And if it crushes, it'll get hotter. If the cube melts or vaporizes, see "deforms". If something somehow prevents the mass of the cube from escaping, then eventually you're going to trigger nuclear reactions and the mass will turn into energy, escaping from the trap. And yes: if somehow THAT'S prevented from happening, welcome to Black Hole City, population Cube, though the moment the portals move apart again it'll instantly vaporize via Hawking radiation and kill everyone around.
The COMPLICATED answer to that paradox is that you have to figure out where the energy to push the cube into itself comes from. The answer to that gets into some... pretty complicated physics. The short version is that moving the portals relative to each other must necessarily require the input of energy because it changes the geodesics of spacetime. (That is, there's potential energy bound up between the portals just like there's potential energy bound up in a ball at the top of a hill.) A realistic implementation of the physics would mean that a surface without a portal would be easier to move than a surface with a portal attached to it. And where does the energy to move the portal come from? From the piston attached to the surface, of course! So that means that trying to push a cube into itself would cause it to become harder to move the portal by AT LEAST as much as it would take to crush the cube if the portals weren't there. If the piston isn't strong enough to crush the cube, it'll stop moving.
Welcome to the Hydraulic Press Portal! Today we are going to crush... cubes.
If the object could fit side by side with itself, it would push itself out of the way and sit next to itself, and the portals would get closer and closer until the object couldn’t repeatedly push itself out of the way anymore.
once the object is balanced on itself or cannot fit anymore next to itself, then it would lay against itself and the side of the portal. The portals would be forced a certain distance apart but could be shifted together after overcoming friction to pass over the object infinitely.
To bring the portals together would compact the object, causing pieces to fall from between the portals.
If you smack the portals together really hard, I bet the air would begin nuclear fusion and blast the portals apart. This brings the question of what would be made if an atom fused with itself? Would nuclear fission be forced to take place if the portals were separated? Strange stuff.
I want to thank you.
1) giving the answer early, its why i stuck around for the rest of it, a sign of respect for a genuinely interesting video that gave a little more information and context to cement the findings presented
2) exactly how long it needed to be, tests, findings, results repeated tests with different settings and end. This earned a sub, if everything else on this channel is presented like this im going to be watching a lot
gosh, I remember this project when you were just testing out how much "depth" the N64 could render when looking at portals through a portal. this is amazing
There ARE moving portal in Portal 2.
They're being used specifically in one scene in which you need to use a laser and a moving surface to cut through pipes.
Although I think I've heard there more of a hack and don't really work find with actual objects.
yeah, there is a command to enable them in any map, however he was talking about the original Portal, not Portal 2
those use hacks and mess up whenever theres an actual object
trouble is... those only move laterally, as soon as they rotate or extrude, portal's gone
All the portals are moving since earth and moon moove aswell
@@dopi3220 so true, god everyone’s dumb it’s like they don’t even consider the movement of the solar system relative to the Milky Way or the movement of the milky way relative to… ? on a daily basis lmao
valuing the viewers time and immediately grabbing my attention by briefly explaining its an N64 demake was such a good way to start the video to keep me hooked, well written and well done.
Isn't long form media also valuing the viewers time? I feel like my time was just wasted by a guy saying "my engine proves I'm right now complain in the comments"
@@pappi8338 To be honest, somebody could make a perfect video that has no loopholes in the explanation and somebody will still want to be the underdog and go "yeah, but" and get 1K likes.
So, are you expecting him to debate himself to save you the time of doing it?
He has an opinion and a logical argument to back that opinion, and he doesn’t hide the fact that he created an engine to do what cannot be done with the original engine, based on physics and relative motion.
Your argument is more of a “because I said” than anything in the video.
I always thought the portal paradox is what happens when you move one portal through the other.
I think there's a Veritasum video about it
I think you live under a rock 😂😂😂
Nothing happens. The one portal comes out the other, nbd
You tear the fabric of space-time and the universe implodes, only to create a super mass that explodes in a big bang that starts this whole reality all over again.
Its the momentum of the part of the cube that's already exited the portal that pulls the rest of the cube forward with it.
portal 2 contains moving portals. you have to cut the lines to the neurotoxin and you do it using lasers through moving portals. it's the only implementation of moving portals in the series.
Well, theres also the in motion add-on
They're only enabled in that one room, far away from the player or any physics objects, because the developers were never able to get them to work properly. Moving portals in the Source engine are very buggy, and will fling things around that aren't even touching them.
True. This is achieved by changing the config settings when the map loads. You can always allow this using the command “ch_allowmobileportals 1”. However, portals cannot slam down on stationary objects, as the game hasn’t been coded to do so
Yeah, but they only move parallel to the portal, not forward and back.
you just gave me the biggest mindf**k of the day. cause until this time I just thought that the in game universe doesn't allow moving portals for some reason. now it all doesn't make sense
Both examples shown feel so beautifully intuitive and natural. Love the work! Will there be a windows 98 port?
(let's start a chain of going to older and older versions)
Will there be a Windows 95 port?
@@tygical Will there be a Windows 3.1 port?
@@polorchen1592 will there be a Windows 2.0 port?
Why not DOS 3.3 with CGA, EGA, and VGA graphics options. Also don’t forget Roland MT-32, SoundBlaster, and pc speaker audio options?
A nes port??
So, important question, what happens if you don't slam the entrance portal all the way down, but instead stop halfway through the cube?
in game, idk
Using real world physics, my guess is the top/front half of the cube will have velocity, because it's already through the portal, but the bottom/back half won't, so it's just about whether that velocity is enough to overcome the cube's inertia and pull the rest of it through. I'm not sure of the exact numbers, but it should definitely move at least a little... probably.
A good guess would be it goes half as far, but I suppose it'd need a test, to be sure.
@@Bluhbearyou are 100% correct. Let’s say the piston stops half way through the cube, it depends on how much the cube weighs obviously and how fast the piston is moving. Just like you said if the top half overcomes the inertia of the bottom half then the cube will go through.
If the piston stop 1/4th of the way at the top leaving the other 3/4th on the bottom, you’ll probably get the cube to do a little “hop” but not go all the way through the portal.
oh damn, thats a good point
I'm going to say that all of the replies explanations so far are wrong, though the results may be similar. Imagine not the orange portal moving, but the floor instead. What happens if you stop the cube halfway through the orange portal is almost exactly the same as if you move it all the way through (minus the bottom half of the cube still being in a different gravity zone for longer without being pushed, if you push it halfway through). So if you slam the floor with cube onto the orange portal, the speed is the same as when you slam the orange portal onto the floor as explained in the video, and if you stop the slamming halfway through the cube (minus the small correction as written) because the "slam" speed was the same. Ofcourse this correction is going to have a bigger and bigger effect as you go to an infinitesimal part of the cube.
@@woud3404I'll point out a small potential flaw in your logic; (but props! I wouldn't have thought this through all the way without reading your post) just that slamming the portal down from above and the floor (with cube) up from below aren't quite equivalent. When the portal is moving down the floor and cube are stationary with one another. When the floor moves the cube up it imparts momentum to it, which is all fine and well until the floor stops moving up, which from the point if view of the cube is like it accelerating downwards away from it.
If we look at the portal-stops-halfway-down case one would lead the to top half of the cube having velocity relative to portal, and converting that velocity to momentum upon exciting. This would impart half the momentum of a full portal drop, it would pop out the exit portal at half speed as the top half yanked the bottom half through. Maybe slightly more, actually. Between the portal starting to clip the top of the cube and it's final position the cube should start moving as portions of it pull 'upward' on the rest, causing the relative velocity to increase. This would make a great word problem for calculus students.
In the floor-stops-halfway-up case the cube would be entering the portal at the regular full speed, and as the floor stops gravity would act to deaccelerate it, but only the back half is still in a gravity-down zone, the front half is experiencing gravity as 45 degrees off from 'forward' (direction of travel). This would nearly cancel, impart some spin, and let the momentum carry the cube the rest of the way through at nearly full speed. Again, calculus for the exact answer.
The explanation at 2:02 made the first experiment make SO MUCH MORE SENSE. Amazing video
Except his explanation makes no sense when you understand that momentum is conserved between portals. Think of it like a baseball in a car. If you remove air, a car driving over a baseball will not move the baseball. Because before the car drove over the baseball, its momentum was 0. Therefore, after it drives over the baseball, the momentum would be 0. In the first clip where the cube goes flying, the car drives over the baseball and stops, then causes the baseball to go flying in the opposite direction as fast as the car had been moving, having never touched the baseball. Somehow, the car imparted momentum to the baseball, having never touched it.
@@trmerc7635 Except that's not really how this works. Imagine it from the perspective of the exit portal. The moment the entrance portal touches the cube it starts coming out the other end. This happens regardless of whether it falls into the portal or if the portal moves towards it. Assuming the velocity of the cube falling is the same as the portal moving towards it the cube is coming up out of the other portal at the same speed in either situation. And this is where the momentum plays a role. The exit portal does not care how the cube is coming through, all that matters is how fast it's coming through. Momentum doesn't just stop as soon as it's come through and plop down, it's going to want to keep moving in the direction it was coming out of the portal at. If actually look at the exit portal you can see the cube come closer and come through the portal. From the exit portal's perspective the entrance portal may as well have been static and instead the platform the cube is on got pushed upwards. This is why relative velocity is key here. All that matters is the relative velocity of the cube compared to the portal.
@@RNeeko It really is how it works. Instead of a portal, imagine a car. If you throw a baseball at a moving car and it goes through the open windows, does the ball get faster or slower? No. Because the ball did not interact with a physical object to impart momentum. The portals are just points in space that are connected. So is a long tube. If you throw a ball through a tube that is moving, as long as the tube doesn't touch the ball, it doesn't affect the speed of the ball. For some reason, people seem to think because it is a wormhole and not a physical tube, it somehow changes the laws of physics.
@trmerc7635 the cube has to leave the exit portal with the same speed it has entered the portal... thus giving it momentum. Witch causes the box to accelerate upon exiting the stationary portal.
I think you are misunderstanding how the portals work in the game. The portals are not physical objects that can move and interact with other objects, they are just openings in space that connect two locations. The velocity of an object that passes through a portal is relative to the portal, not to any other reference frame. This means that if a portal is moving, it will affect the velocity of an object that exits the other portal, even if the object itself is stationary.
To illustrate this, let’s use your analogy of a baseball and a car. Imagine you have a car with two open windows on opposite sides, and a baseball that is resting on the ground. Now, suppose you drive the car over the baseball, so that one window is above the baseball and the other window is on the other side of the car. If you ignore air resistance and friction, what will happen to the baseball? Will it stay on the ground, or will it fly through the car?
The answer is that it depends on how you look at it. From the perspective of someone standing on the ground, the baseball will stay on the ground, because it has no horizontal velocity and nothing is pushing it. From the perspective of someone inside the car, however, the baseball will fly through the car, because it has a horizontal velocity equal to the speed of the car in the opposite direction. This is because motion is relative, and different observers can measure different velocities for the same object.
Now, imagine that instead of windows, you have portals on opposite sides of the car. The portals are connected, so that anything that enters one portal will exit the other with the same velocity, relative to the portal. What will happen to the baseball now? Will it stay on the ground, or will it fly through the portals?
The answer is that it will fly through the portals, regardless of how you look at it. This is because the portals are not physical objects that can move and interact with other objects, they are just openings in space that connect two locations. The velocity of an object that passes through a portal is relative to the portal, not to any other reference frame. This means that if a portal is moving, it will affect the velocity of an object that exits the other portal, even if the object itself is stationary.
To see why this is true, let’s look at what happens to the baseball from different perspectives. From the perspective of someone standing on the ground, the baseball will enter one portal with zero horizontal velocity and exit the other portal with a horizontal velocity equal to the speed of the car in the same direction. This is because when an object enters a portal, it inherits its velocity relative to the portal. Since from this perspective, the portal above the baseball is moving with the speed of the car in one direction, the baseball will exit the other portal with the same speed in the same direction.
From the perspective of someone inside the car, the baseball will enter one portal with a horizontal velocity equal to the speed of the car in the opposite direction and exit the other portal with zero horizontal velocity. This is because when an object exits a portal, it preserves its velocity relative to the portal. Since from this perspective, the portal below the baseball is moving with the speed of the car in the opposite direction, the baseball will enter the other portal with the same speed in the opposite direction.
As you can see, both perspectives agree on what happens to the baseball, even though they measure different velocities for the same object. This is because the portals are not physical objects that can move and interact with other objects, they are just openings in space that connect two locations. The velocity of an object that passes through a portal is relative to the portal, not to any other reference frame. This means that if a portal is moving, it will affect the velocity of an object that exits the other portal, even if the object itself is stationary.
"So... why am I demaking Portal for the Nintendo 64?"
BECAUSE IT'S FREAKING AWESOME!!!!!!!!!!!! I've been following that little project for a while now! Absolutely fantastic work!!!!!
"We do what we must because we can"
¯\_(ツ)_/¯
...why aren't YOU demaking Portal for the Nintendo 64?
Science isn't about why. It's about WHY NOT!!
So, lets say the portal lands on top of a human (really fast), but makes a sudden stop half way. Would then upper part of human (the part that has gone through the portal) be set in motion on other side of portal, and then pull lower part with it?
If speed of portal slamming down was fast enough, subject could be ripped in half. #Spagettification
Yeah, that is exactly what would happen.
@@james.lambert but would you get ripped in half though? If you think about it, the moment the first hair on your head enters the portal it's already pulling on your body. When your head is through, its already pulling your torso.
It's easier with "ticks" because you don't have to worry about individual atoms, but if you think about it an insanely fast portal might just rip you to shreds instead.
A portal stopping that fast might rip itself apart, too.
Yeah I always likened it to any changes in motion to a portal is like moving the entire universe on the other end of the portal. If you moved a portal (aka: accelerated a portal), you'd actually need to move/accelerate the whole universe along with it to match, unless the exit portal moved in a matching speed and direction to cancel it out. In "reality" you would be able to theoretically have a moving portal relative to its exit but it would have to continue moving in that direction and never change - absolutely no acceleration (no changes in direction or speed) would be possible as that would take infinite energy to do. Having the portal change direction or rotation would be akin to literally moving the entire universe on the other side of it. The reason is because of what you said, the person would get spaghettified if you went half way and then stopped. That's because the whole universe is suddenly 'stopping' (aka: instantly accelerating) on the other torso end of the portal relative to the other side of the portal that his legs are standing in.
Rotation of a portal is especially impossible; When you rotate a portal, the outer edges of the universe would be accelerating relative to your viewpoint at a rate of speed approaching infinity the further out you observe. If the universe is infinite then the rotation speed at the far corners of the universe also becomes infinite, and it would require not only infinite energy but also an infinite speed limit in the universe to move the whole universe on a swivel at infinite accelerations, as it must happen in order to conserve momentum between the two portals.
Also just to be technically correct, you can't have a moving portal anyway due to relativistic effects in spacetime. Spacetime is not uniform, so movements through it would not be a simple x universe moving relative to y universe, but rather you'd encounter shifting spacetime due to differing gravity at different points, and therefore even a totally uniform movement in one single direction relative to the exit portal would be varying all over the place, growing in differences the further out into the universe you look. For this same reason it would probably even disqualify a stationary portal just because of the immense energy required to reconcile the two reference frames - aka: the two 'universes' on either side of the portal.
Interestingly, the force between the two parts of the human would be directly caused by the portal's deceleration.
The next question would then be: What's the consequence of that?
Would a human/ an object that's halfway through a portal be able to hold the portal in place?
Would a heavy object sticking halfway through the portal increase the inertia of the object that the portal is attached to?
Would (as DeSinc conjectures) a moving portal have the inertia of the whole universe? I don't expect that: moving portals would not cause any effects, unless an object sticks through. But I would still not be 100% surprised if we figured out that portals that have objects sticking through would have infinite inertia while the object is sticking through; and in that case one _could_ argue that - since it's independent of the object - the cause isn't the object at all and all portals would have infinite inertia even when nothing is sticking through.
So if you throw a cube in a stationary portal while the other is travelling backwards at the same speed, you kill the momentum.
It looks very consistent to me.
No it wouldn't, the momentum would be kept. Rather, the distance traveled and trajectory would be altered.
@@Wild_Dice it's like jumping from the back of a vehicle at the same speed it is going forward
@@rogercruz1547 Yeah exactly, you inherit the *difference* of velocity (momentum and direction) between the portals.
@@rogercruz1547 exactly that!
I don't get it, the portal is just a link between 2 different places, it doesn't matter at which speed the portal is moving you remain unaffected by that, the only difference is that you get through the portal faster
First of all, appreciate the video length. Secondly - test your solution with the piston stopping half-way through the cube.
The way physics should work, the half that's already flying out of stationary portal should pull the still stationary half from the other end, losing a bit of energy. But would be interesting to see how it would actually work in the physics you coded.
it would depend on the vector of the exit portal and the speed of the piston. it would need to be enough force to pull the cube out of its state of rest and then overcome gravity. you could write this as a physics equation easily enough.
@@adultdeleted True. I was writing that assuming the rest of experiment is same (angles and the speed of the piston).
Would be interesting to play around with different setups, though. Like what if exit portal is stationary on the ceiling, i.e. facing same direction as the entrance. Then depending on combination of speed and what chunk of it goes through the portal the cube would either remain stationary or get pulled through... This could be a fun toy like 4D Toys.
Probably (in the engine) the cube shoots out if its center is through and stays in place if it's not
Logically, the entrance portal is rushing down and then stopping, so the cube should rush out partway but then suddenly stop when the entrance portal stops.
I think the trick is that portals only conserve momentum relative to the portals, not relative to the room. So if the cube is going through the portal a force on the portal to make it stop moving is equivalent to a force on the cube to make it stop as well. The same would be true if the entrance portal is stationary halfway down the cube but you start moving the exit portal around, it should drag the cube with it.
Typically objects in physics engines don't have mass density fields, but rather are point objects with discrete momenta. So it will either jump or not jump, but not half jump.
Personally I'm not very into physics but I understand GLaDOS saying that the portals do not affect momentum to mean that my momentum will never be affected by the portals. Otherwise the forces acting on different parts of me might be so different as I pass through a portal, that I might conceivable be torn apart by a portal falling fast enough, as each part that enters the portal suddenly accelerates into the portal.
Thing is, momentum is relative to your reference frame. If the portal is moving towards the cube, from the perspective of an observer moving with the portal, the portal is stationary and the cube is moving, so the cube has momentum.
Also in-game portals already change momentum. Momentum has magnitude and direction and the portals in the game change the direction no problem.
That's only true when the falling portal changes its speed quite a bit or suddenly stops.
it's actually the opposite interpretation that has this problem.
Say you have an orange portal that's stationary, and a blue portal travelling sideways at 1000 m/s. If you stick your head into the orange portal, this game dev's logic states that your head should poke out of the blue portal at 1000 m/s- you'd move along with it, so the most you'd feel is a strong wind whipping your hair.
However, if you don't think your body should inherit the momentum of a moving portal, then sticking your head out of the moving blue portal would cause your head to emerge at 0 m/s, as the portal flies away- (low-speed head goes in, low-speed head comes out-) snapping your neck clean off.
@@NotaWalrus1If you have a drone flying stationary and put an open window on the back of a truck and drive at the drone will it pass through and not move or will it suddenly ping off into outer space
@@Xtv1234I feel if you came out the back end you'd be perfectly fine and would just drop but if you came out the front end it would just blow you back in.
A lot of people's theories seem to forget air exists and is real and we aren't just surrounded by empty space void of atoms. The air would be going through too. You wouldn't just put your head through and have it suddenly be 100% different
It's incredible what people can do, people would do such great lengths to make it possible, I love it every inch of it.
What happens if you stop the moving orange portal while the cube is only halfway through? Would the momentum of the cube coming out the blue portal make it so the cube gets sucked inside the the orange portal and out the blue? If it doesn't go fully through, would it at least jump up a little?
I wanted to see this too!
I think that the cube would stop moving when the portal stopped moving, that's almost entirely based on my own intuition though
here's my hypothesis (at least in a real-world physics sense, no idea about his engine): in the instant the orange portal stops, half of the cube has had the momentum transferred to it, while the other half hasn't. therefore, the cube will only receive half of the momentum! the non-moving part gets pulled along by the moving part, and the moving part gets slowed down by the non-moving part. so, it'll still be launched, but only half as far!
I think it would still get launched, just not as far, like if you threw a ball, but stopped your hand halfway.
in-engine, it will probably either move or not depending on which side the origin position of the object stops at. in the real world or a physically accurate simulation, the momentum would be imparted in proportion to the weight of the object on either side of the portal
@@axollyon Agreed. For completeness though, if the cube could deform, the resulting tension would actually _stretch_ the cube.
Funny thing about moving portals is that they are in portal 2 when you're using lasers to cut the neurotoxin tubes
And they are so frigging bugged
yeah they're also in the hydra DLC
They're not accelerating though. Earth is rotating at fixed speed so all portals are moving
@@pinwheelmotorbike Gravity is acceleration. So anything on earth IS accelerating as is everything else in the universe influence by gravity fields.
@Vaasref
I mean your conclusion is kinda right because relative to a fixed point in space earth is accelerating and so am I but saying gravity is acceleration is a gross oversimplification and the way you worded it implies that I am accelerating downwards regardless of the normal force from my chair right now… TLDR all motion is relative, including acceleration.
You could show a case where the blue portal isn't directly above the yellow but is still moving down to show the effect as well.
The hula hoop analogy and your explanation for how it worked was solid and earned my subscription!
also "i value your time more than my retention rate"
simply based.
Absolutely. I got about halfway through the video, sure that the answer was A, and spent about 30 minutes thinking about it, looking it up, and reading the comments before I understood why B makes more sense. Then I resumed the video and he answered it in 30 seconds lol.
Except it's wrong. We've actually demonstrated this as false as we've created "white holes" for qubits that instantly communicated information over distances and didn't impart any extra energy when doing so.
All you're doing is taking the outside of a window and moving it somewhere else. Just as if you had stuck your hand through a window you would not get flung through it, the location of the exit is all that changes. If you drop a hula hoop over yourself you are not flung out the other side.
Not only does he lack a basic understanding of inertial frames of reference and light cones, but he's asserting that the universe has an inherent "orientation", or an up and down locked to one position in the universe. This is a very stupid idea postulated by flat earthers, and has been debunked at every turn.
@@xelgodis80085 lmao, it must suck to be so conceited you can’t finish a video before rage commenting. You literally just used the hula hoop example that the video proves is different from the Portal Paradox.
@Scottish Cheese except both he and you don't understand inertial frames of reference. If his model held true, light itself would be accelerated through a portal, which is stupid to say the least. It's a white hole, and the laws of thermodynamics are conclusive about the effects of a white hole, and have been demonstrated in real lab settings.
That you lack the fundamental knowledge to begin understanding *why* you're wrong isn't my problem. Grow up.
Realistically wouldn’t a cube be stationary as if on a flat surface and only be affected by gravity, normal, and friction forces once out the other portal. I mean if you did that same thing but stopped halfway through the cube it would be odd for it to fly off the ground and gain speed from nowhere. Unless there are some unique portal physics I don’t know about. It’s a pretty cool video either way.
Portals aren't just doorways, but that completely redirect momentum for no cost. The only truth is that any velocity vector going in, is equal going out. To the Portals, an object moving towards the portal vs a portal moving towards an object looks exactly the same.
On the blue (exit) side, while the entrance side is halfway through, they see the Box emerging at speed. Once the entrance hits the ground, the box is still exiting at speed.
My theory is that a portal stopping half-way over a cube would cause it to partially fly off. Half the molecules of the cube would be stationary, half would be "moving", so the forces would balance out.
In-game, it would probably only matter if the object's origin or Center of Mass made it through the portal plane.
@@Appletank8 They redirect momentum but they don't create it. A portal is like a doorway, connecting two spaces in otherwise impossible ways
Portals do not thrust things out at specific velocities; they do to make the game work of course, but all they do is connect space
I do not see how he cube would gain any sort of momentum from a portal falling over it. The space through the orange portal is dictated by where the blue portal is. And even if that space is rapidly changing, there is no force causing the cube to move
@@100Darkspine technically going from a low portal to a high portal creates potential energy outta nowhere. that's why you can make perpetual motion out of a floor/ceiling pair.
Anyways, the only rule of portals is that if something enters the portal at speed, it will exit at speed. In order to exit a portal at all, you need some sort of velocity, otherwise nothing happens. From second 1 to second 2 of going through the blue portal, the box has a noticable change in position, therefore it now has a speed, Distance/time.
There is no way for the blue portal to tell the difference between the entire room moving at constant speed towards the portal, vs the portal moving at constant speed towards the box, so the results will be identical regardless.
@@100Darkspine
The portals are not creating the momentum. The cube already has momentum relative to the orange portal. Expecting it to stop once it leaves the blue portal is expecting its momentum to change for no reason.
Well, that's friggin cool. 😲
I'd also argue that in theory the orange portal should experience resistance when it hits the cube, such that it performs equivalent work to flinging the cube out of the blue portal. That conserves energy-though not momentum, because having portals facing different directions has already broken that permanently in this universe.
My position is that to properly use conservation laws through portals you must use the reference of the portal, in this case to conserve energy, velocity, relative to our reference, must remain constant at input and output (ignoring non conservative forces obviously) if we consider the portal as a system energy in must equal energy out… in any case energy is not conserved as potential energy can be increased with a portal eg perpetual motion machine using portal on floor and ceiling.
@@DracoTorment The object traversing the portals is ALWAYS the reference frame. Portals are only transformations of the vectors. If a person sat on the floor and the portal slammed down around them, they would feel acceleration and would fly out the exit. This is consistent with he person's interpretation; if they'd looked up, they would have observed the wall and ceiling careening toward them at speed, a sight consistent with them flying out the exit at speed. Further, we know the object's reference frame is the only view point we should examine because it is the object which possesses the momentum, velocity, and energy we are concerned with. The portals are just a boundary in space with an appropriate transformation that stitches space together at that boundary.
“Moving portals aren’t implemented in portal”
That one random moving portal level in Portal 2: 👀
What level was this? I don't remember
@@LotharLivewhen you destroy the neurotoxin with lasers
Iirc, that’s a matter of just changing a single value to allow for it, but the logic required for the portal paradox isn’t implemented, as it was never intended to be used outside of that set piece.
So instead of either result happening, the box doesn’t go through. I may be wrong, this is just going off of what I remember.
@@MasterHyperionMC if the portal paradox was correct, moving a portal at a laser would accelerate the photons in a laser beyond c.
@@xelgodis80085 Ok? I feel like I’m the wrong person to say this to, given I didn’t actually express an opinion either way.
I would say the issue with this discussion is the difference between momentum and velocity. If you're basing your coding on velocity, then the cube should move at the same relative speed as the slamming portal, but if you're basing on momentum, as the orange portal can't impart any energy to the cube, the cube should just fall out, based on the possible position of the blue portal.
Agreed, and I feel that the velocity is also a bit of a red herring, since it assumes both sides of the portal are the same frame of reference, which I don't think is a simple answer.
My thoughts exactly. His setup violates conservation of momentum. I reasoned it out slightly differently though. If we assume that slamming the portal down on the cube launches it through the other portal, then there must be some force applied by the portal to the cube. If this force is proportional to the speed of the portal and points through the portal in the opposite direction of its motion, then the hula hoop example will actually launch the cube into the air!
@@1925683 not quite, as I could be reasoned that in the same way the orange (down) portal imparts energy to the cube, it could be argued that the blue (up) portal could rob it of the energy, and that addition/subtraction of energy could be based relative of the two portals position in space/ velocity/momentum.
@@1925683 even stationary portals violate conservation of momentum. if you throw a cube down into a portal and it shoots out horizontally from a portal on the wall then momentum wasn't conserved
the hula hoop example is fine because you still have the cancellation of the motion of the exit portal and the cube being pushed through
Nope. e=mc² applies in both scenarios. Speedy thing goes in, speedy thing goes out. It does not matter how the relative speed came about. In fact, the portal paradox is nothing more than people arguing against relativity.
It does not matter if it's the cube moving towards the portal or the entire planet being lifted up to the portal by a piston. The difference in speed remains the same. The only argument there is room for is whether the game is programmed with realistic physics or inconsistent and arbitrary ones. And in my opinion, any portal mechanic that doesn't impart momentum in such a scenario has sloppy programming if momentum is supposed to be preserved between portals.
i like how you showed the results first. it really hooked me and made me want to see the rest of the video. super interesting !
bro the texture of the paint on the wall and his skin as well as his shirt and arms are literally so similar that I thought there was a static filter applied to the entire video.
watching this was trippy as all hell.
I’m really torn on this, I may lose sleep over it, thanks for making it in N64 though, keep up the good work!
So this is basically the same as the "shooting a cannonball from a moving car" experiment from Mythbusters.
Id love to see a video on "shooting the cube in to a portal where the exit is moving the same speed as the shot cube but in the other direction (maybe for when you imolement the bouncy pads (if you haven't done that already))
Right when you talked about the "hula-hoop" analogy, it made sense. Everyone proposes the paradox when only taking in consideration the entrance portal, never the exit.
While they make a womehole while in tandem with one another they have their own unique positions in space, be it speed, or direction. Which does make a lot of sense.
My next portal paradox, is what if you do this across lateral direction, while moving?
So, imagine the portals are like the window of a car.
but, because the portals exist unconnected to two different inertial reference frames, then what occurs outside the blue portal, is not connected to what occurs outside the red portal.
So lets imagine you have a stationary red portal. And a moving blue portal.
If you stick your arm through the red portal then your scenario is best described like this.
Everything inside the car, is the red portal. The car is stationary and not moving.
Everything outside the blue portal is sticking out a car window. It is moving relative to the rest of the world. (Great - this explains that you will feel wind on your arm).
But what happens now, when the "blue portal" car stops. Well, in a normal car your entire body would feel a decelerating force and would struggle against it.
The parts of your body in "Red space" are in a stationary car, so those parts feel no decelerating force.
The parts of your arm in "Blue Space" now want to keep moving forward, while the blue portal entrance slows down. But, the tube of your arm in red space is connected physically to the tube of your arm outside the window in blue space.
So now, your arm in red space "Pulls" on your arm in blue space (in the direction of the deceleration the blue portal is undergoing). Your arm in blue space wants to keep going, but the blue portal is changing the acceleration, and applying that via the portal boundary.
Assuming the deceleration the blue portal is undergoing is low enough that it doesn't tear your arm off, you would decelerate your arm to the same relative velocity of the blue portal.
IE, in short, your arm in bluespace would "feel heavy" in the same way that your limbs feel heavy when you slow a car down. And your body (which is strapped in via seat belt or whatever) "pulls" your arms to the same relative velocity of the car. But in this instance, your body in redspace doesn't feel the deceleration, only the arm in bluespace does.
Haha thank you for clearing that up!
There's nothing applying force onto the cube itself...
Portals are basically wormholes... You're treating the ends of the portals as two separate entities, when they're one and the same.
If we're using the logic used for the angled portal, then it should have been shot out the top when it was in the hula-hoop orientation. Simply by adding rotation (180° rotation in the hula-hoop example), doesn't add velocity.
IF ANYTHING, what would occur if the portals were theoretically wide enough, is that you'd be stuck in a constant state of free-fall, until you gained enough momentum from the gravity and/or air pressure on the "stationary" end of the portal, to reach the edge of the portal.
Think of it like this. Assume you're floating in space. And both ends of the portal are 1km wide, and the orange end is moving at you at 100km/h. And the blue end is moving in the opposite direction at 100km/h as well. You'd be in a constant state of free-fall until you gained enough momentum to reach the edge of the portal. Remember, the portals are one and the same, the physical space between each end is arbitrary.
In this, the portals act like a small scale black-hole, requiring you to increase your momentum beyond that of the wormhole in order to escape. The wormhole isn't imparting momentum onto you.
@@notmyregret No, it isn't. But you already had momentum when you went in.
it always makes sense. its a easy physical behaviour. it was never paradox or a problem
haha I love that all of my favorite niche projects wouldn't exist if talented people like you didn't just do it for no particular reason but to satisfy your passions/obsessions. And the world is a better place for it.
I'm actually really glad that you brought this question up because I decided to wrack my brain on this question as a serious question regarding what would really happen, suffice it to say that yeah, GLaDOS literally explained it, speedy thing goes in, speedy thing goes out, and that speedy thing is from the relative point of view of the portals which from their view are always stationary while everything else moves around or through them.
A fun side piece I realised though is angular momentum and forces acting through a portal, as well as a very interesting scenario of "What happens if the portal stops half way? Does it stop like nothing happened or what?", and the answer is "moment of inertia still exists, however much mass passed the portal will have inertia, pulling on the rest of the mass of the object through the portal like a harsh yank but through the entire intersecting plain.", which leads to very weird potentials of indirect forces acting on portal surfaces.
I don't remember everything on the matter off the top of my head as this was like a year and a half ago that I thought about this and logically approached it as, but there's a lot of weird and cool edge cases regarding physics and portals, I have the entire argument and logical set written down somewhere if anyone wants to chat about it as it's a very interesting extended problem.
I've also thought about these some time ago. iirc If you place the exit portal on a rail, facing a wall, and then start pushing a long stick into the entry portal, when the pole touches the wall, instead of stopping you from pushing further, the exit portal will start moving on the rail, even though it's not in contact with anything. super weird behaviour but that's what makes it interesting!
As much as I’d love to talk about this privately, I feel like it actually deserves a video of its own 😁
@@kantoros Ooh! Very interesting.
@@kantoros yeah, that leads into the whole "weird potentials of indirect forces" thing.
On the one hand, in theory, there shouldn't be any effect on the portals as they are not being contacted.
On the other hand, in theory, there _should_ be an effect on the portals due to their ability to impart moment of inertia.
And while I don't remember my original conclusion, I'm actually leaning toward the latter thanks to some recent physics concepts I came to know about recently.
The way it'd work would likely end up acting like an air spring or pneumatic piston with a pressure gradient leading to a "spooky force acting at a distance" to appropriately quote Einstein.
You're still applying force to the wall on the other side of the portal, but with it acting as a stopping, stationary force, the force will instead start being imparted on the portal as it effectively acts as an inverted form of the same effect that causes imparting of moment of inertia.
@@RonWolfHowl dude I would _love_ to make a video on this but I do not have the means to do so on my own, and it's kind of sad given there is an absolute ton of amazingly fun nuance to the brain breaking physics of this that would be amazing video content.
For example a visual representation of exactly what is going on with the other reply I just made would work wonders for explaining it better.
It also just sucks in general because if I had the means to making a video on this subject I'd also absolutely be working on the two portal 2 mod campaigns I've been writing up every now and then when inspiration strikes. Moving portals and their properties was going to be a thing I was going to attempt after having thought about them and their physics.
Portal 2 actually has _two_ examples of a portal on a moving surface. When we shoot a portal at the moon at the end of the game, it's easy to forget that the moon is actually moving substantially fast relative to the Earth. The moon portal is moving like 4000 km/h relative to the Earth portal, and yet when Chel and Wheatley enter it they aren't suddenly launched off the moon's surface at mach 3.5. The portals preserved their relative speed, as in this video.
Here’s the second example of a moving portal
ruclips.net/video/mCQiwhik8nc/видео.htmlsi=eNjSeNuZoeoGpVRC
@@ThePokeGod That's actually the one level in the entire game where they intentionally enabled the moving portals mechanic
Still: the movement is faked. It's just paralax, the moon does not actually move in engine
But that's an EXIT portal. The Entrance portal is "almost" stationary compared to Chell so there is no "speedy thing comes in" predicate. All checks.
surely they didn't actually model the relative orbital speeds of the Moon and Earth for that so that.
You had me the moment you told me you valued my time more than your retention. Subscription inbound
2:10 Yes! Exactly. Relativity says that your implementation is correct. Well done sir.
I've always wanted to know for sure what would happen if a person/object was between two moving walls, both with portals on the surface, as they move towards the person/object from either side.
My belief is the person/object would make contact with itself on the sides facing the portals and then crush itself - though the physics are hard to imagine, because if the portals went perfectly over them/it, then in theory there'd be no resistance placed onto the walls to prevent them from fully closing and having the person/object perfectly pancake themselves imbetween.
Others believe you'd somehow stumble into some kind of imbetween portal space, though I believe this doesn't add up, because they're portals and not wormholes - there is no space between one portal and the other which one has to traverse to reach the other side.
Generally in a case like this, any theory that violates physics is probably wrong. Sometimes a theory makes no sense but the math all checks out, and it turns out to be true. The mystery then is figuring out why it works that way. In this case, I feel like pancaking something between the portals is probably wrong, as is the in-between space, as neither seems consistent with what we know about physics. A more logical outcome is for the object to exert a force that prevents the walls from closing completely. How is anyone's guess, but it probably depends on how exactly portals work in the first place. Or something else might happen, which would lead to new discoveries in physics.
@@Greywander87 Perhaps some kind of force would be exerted on the walls when the two portals reach the edge of the person/object they're simultaneously closing in on - but that would rely on the portals themselves being receptive to resistance, and them then also transferring resistances onto the surface they're on - imo that doesn't add up logically.
E.g. if you had a portal on one unstable and loose wall (say an office wall tile) which someone is primed to run and jump through, and a portal on another wall which is solid, and then you seal that portal off by placing another solid and immovable object infront of the portal the person would be exiting from, the person moving through the entrance portal would be meeting that object blocking the exit portal, exerting force on that - both the portals and the walls they're attached to encounter no resistance or force.
Imo this is why a person stood between two portals moving towards them would simply be pancaked by themselves by a force that encounters no resistance from said pancaking - it would in theory work with infinite mass but relative velocity.
I feel like, it'd be the same as imagining that your left and right are copies of you, being pushed towards you, then my right shoulder gets pressed against the right copies left and vice versa. They keep pushing more, with deadly force and all 3 of us (tho we're all just 1) are squashed
I think the most intuitive way to answer these questions is to convert the problem into an equivalent one where the portals do not exist. If you were to instead have two people stuck between what is essentially a hydraulic press, then yes, they would be pancaked.
This technique helps solve the subsequent question of whether the portals would need to exert additional force to pancake the person - they would, since the press would. This conclusion is supported by the requirement of energy conservation, as energy must be expended to deform an object.
@@the1necromancer I think you're overlooking the fact that the portals are the whole point of the thought experiment though - they don't obey any known laws of physics, hence why it's so interesting to speculate how a portal (as depicted in the game) would function in ways beyond what is demonstrated - it's more about intuiting the information about how the portals work that we already know - they're not wormholes, they're seemingly without a physical presence themselves, they're simply magical doorways which can be dynamically relocated.
The moving walls with the portals on their surface would provide the velocity at which something is pancaked between them, but they don't tangibly interact with anything except the surface they're placed on (they stay relative to it) - the surface doesn't experience any resistance or impact or any sort of force from an object passing through a portal on it - therefore we have to assume if two portals simultaneously moved across either side of a person meeting in the middle of them, that the person would be crushed by themselves in a manner where no resistance is experienced by the walls (unless part of the person sticks out beyond the surface of the portal.)
this is sick! glad this got in my recommended, this sort of project is right up my alley. looking forward to more.
I actually appreciate you using the logic of conservation of momentum to solve the portal paradox. The portal moving over the cube at, say, 60mph, is no different from the cube moving into the portal at 60mph. This is very logically sound and I appreciate your approach
that's why it's not a paradox, it's solved by a fundamental law of physics lol
It is different, by the same logic a cube going 60mph not losing any speed from going through portal proves that portals have no mass, thus a portal colliding with a cube shouldn't increase its speed
I tried explaining this to my dad, he disagrees because the box didn't have energy to begin with. I told him to watch this video later, so hopefully I can win the argument through this video.
@@lasadaf5336 The portal is attached to a piston, which does have mass, therefore energy that can be passed to the cube.
@@lasadaf5336 Portals also create and destroy energy, so really they can behave however people want them to behave.
But you can also think of it that in order for the box to actually come out of the blue portal at all, each part of the box that comes out must be pushed out of the way by the next part of the box coming out behind it, and this will happen at the same speed that the orange portal moves over the box.
0:38 - So, why am I demaking Portal for the Nintendo 64?
"Science isn't about 'why', it's about 'why not?' " - Cave Johnson
A portal does not _transfer_ its momentum to objects passing through it; a portal _preserves_ the momentum of things passing through it.
It's the same thing because momentum is relative. A portal moving towards an object is the same as the object moving towards the portal.
@@kremitthetaco8725 the way I picture it is the same as if you took a hollow box with a hole in the bottom and dropped it onto the platform with the cube. The box’s momentum would be absorbed by the platform and the cube wouldn’t move. Here, because the portal transports the cube to the slanted surface, to me the cube would slide off.
“Cube moving towards the portal is the same as the portal moving towards the cube” is valid as a way to explain conservation and is true given specific reference frames, but it disregards initial conditions. For example, depending on the reference frame me shoving you is the same as you shoving me, yet we both know there are more factors involved and in all likelihood the two actions would not yield equal results.
@@Scuuurbs Your analogy with the hollow box doesn't take into consideration that the cube already enters the portal before it touches the platform. What is absorbing the relative momentum of the cube from the moment it enters the portal to the moment the portal touches the platform? Let's say it takes 1 second to fully push the portal over the cube. That's 1 second of relative momentum basically pushing the cube through the portal until it stops.
If the cube truly had no momentum when leaving the portal, then the same would apply to every single particle the cube is made of, right? If every particle of the cube is static relative to the portal, they would all try to materialize on the same location on the surface of the exit portal Do you know what happens when you force 2 particles to exist in the same location? I don't. I don't think anyone does. But it probably wouldn't leave the cube intact.
The only thing which would stop that from happening is if the following particles push the preceding particles out of the portal, which would once again apply the relative momentum to the cube. So this also leads to the result shown in the video.
I'm also really not sure what "initial conditions" you're talking about. The entire point of the Portal games is that you're in a test facility for portals which exists particularly to eliminate external factors.
@@kremitthetaco8725The particles of the cube are "pushed" by the same atomic forces that maintain the cube's shape, irrespective of any qualities the portal possesses.
The only momentum that exists for the cube in this scenario is from the reference frame of the portal itself, which is unintuitive. Better to use the reference frame of an observer - in which case the momentum exists entirely in the piston/panel the portal is attached to, and its momentum is absorbed by the platform the cube was on, as well as whatever the piston is connected to.
@@Scuuurbs The laws of physics don't care much about what is perceived as "unintuitive" by some observer. If the camera was attached to the moving platform, your entire point of view on the experiment would change but the laws of physics remain the same.
The cube and portal have relative momentum to each other and that's the only thing that matters.
And if you're saying the particles of the cube are pushed through the portal, then they must have momentum when exiting the portal. And how fast would they be pushed? Is it some arbitrary number? Or is it simply the speed at which the cube is pushed into the portal?
Sounds right. reminds me of Tom Scott's video on that unconventional auger wherein the tube and its openings are spun, but the auger itself remains stationary yet still elevates grain.
Also when you think about it, on a cosmic scale, all velocity is relative.
The Wuffle house has found it’s new host
Just a nitpick, the physics of the rotating auger aren't the same as the physics of the stationary auger with rotating shaft, I believe the grains will move in distinguishable ways and have a different stress distribution. This is because in Newtonian mechanics rotating reference frames are non-inertial and so aren't related by such a simple transformation. Fictitious forces such as coriolis forces and centrifugal forces appear in them. Read about Mach's bucket experiment. In an idealized Newtonian (non-relativistic) universe, spinning the entire universe around a bucket won't cause the water to form a parabolic curve on its surface.
unless its light, that speed is absolute
This is incredible man, original hardware running this feels like a miracle
The Wuffle hose has found it’s new host
@@CBNST the orphanage center has found it's new orphan
@@fran5678can I like the implications of this one
I love that you're just saucy enough for the people who are inevitably going to kludge together rebuttals to the really well-explained mechanisms you've posited.
I've never even had N64, but I'm still impressed by this project. Keep up the amazing work! 👍
Bro really just said that relative velocity is the same as conservation of velocity and then broke conservation of momentum. EPIC!
actually the conservation of momentum stays true because relative to the space outside of the exit portal the the cube is actually moving so as its coming out it gains momentum making it fly off
@@MommysGoodPuppy Couldn't you also say that the space relative to the exit portal is moving towards the cube? The global velocity of the cube is still 0 and relative motion only describes motion from a particular frame of reference
I think it is introducing some dire consequences. If "cube" has some more traction with the surface (glued, welded, etc), there is potential to tear objects apart.
Also, normally, objects are getting momentum in some natural ways based on their structure/joints, but if the portal is the thing that you are getting momentum from - momentum passing to some 2d slice of an object with is potentially can break it internally.
This would of course be true regardless if the weld/glue/bolts/fasteners by any other name were too weak. That by itself though wouldn't necessarily prove this unsound. Would just mean that if something was weak enough to be moved, it would be moved. Portals rarely care about fasteners anyway, see GLaDOS about all the cameras I knocked off her walls
The issue is not in the cube though. This comes from the portal suddenly stopping after it slammed down.
If the cube were on a pillar the portal could continue downwards, with no damage to the cube. Only when the portal stops moving you introduce an acceleration between the two frames, potentially causing a break in the pillar.
The real issue is thusly not relatively moving portals, but relatively *accelerating* ones
I feel like all you have to do is imagine the process frame-by-frame. The cube has to appear on the outside of the blue portal at the same instant that it passes through the orange one. The speed at which that happens has to be the same as the speed of the moving portal. So, when the box exits the moving portal, there's no reason it should lose the momentum it just gained.
@@ningaification nope
You instantly got me to subscribe by prioritizing my time before your retentionrate. Hats off. RUclips needs more creators like you.
Same.
Thank you for respecting our time. just for that you got my like, subscribe, and loyalty to finish watching the video.
I am looking forward to your N64 Portal game. That sounds like lots of fun!!
Great job keep it up! We love your work!
Yeah very cool, although one of original devs stated that should plop down rather than adding velocity.
if you still have doubts, think about this: let’s say the cube is 1m long, and the orange portal is rushing towards it at 10 m/s. That means that in 0.1 seconds the cube will be through the orange portal. But think about the blue portal now, the cube should also exit the blue portal at the same speed it entered the orange one, obviously. So the cube will come out the blue portal in 0.1 seconds too. If a one meter cube moves through a hoop in 0.1 seconds then 1/0.1 = 10 m/s.
I sincerely hope you make this into a fully fleshed out game. Would love to play this on the 64!
What I find weird about it is that it implies when you move a portal, you're effectively moving the entire world towards the opposite end
but that's how relative speed works, doesn't it?
yes it doesn't make sense, the object should maintain the velocity relative to the plane
this is a big issue people are trying to solve about "how would a real wormhole act"
as it is simply a tunnel from one point to another based on general assumptions and maths - and by that, moving the tunnel, if it were to serve for instantaneous traversal, would likely yield a similar result
and the way a portal's function is described is not entirely dissimilar from a wormhole, and in fact, people study the idea that maybe portals if achieved like this in real life would actually be wormhole technology.
@@KingOfRedPlays I'm a bit curious. What is more realistic, a portal that is simply a hole and has an exit somewhere else? Or an actual tunnel with a bit of length to it?
@@amitbar5691 I don't know... For the cube to shoot out like that, it must have made a pretty big impact. And I mean, the impact doesn't have a limited range, after all, or does it? It has to be the entire universe colliding with itself, unless there's a logical error in my thinking. Maybe this is actually realistic given we accept the idea of portals, but it seems to give portals a ton of power that goes beyond traversal which doesn't seem to fit the use case they've been assigned in-universe
Then I think it also gets even weirder... because if it works like this, then the entire gravitational force of the planet must have an effect through the portal onto itself, so frankly, I can't imagine that it could possibly physically work like the way he coded this
The other form of reasoning I use to come to the same conclusion is to try and think about the situation 1 frame at a time, for lack of a better term. When the Cube first has the moving portal coming down on top of it, then that portion of the cube is sticking out of the other portal. 1 Frame later the entrance portal has moved down slightly and thus more of the cube is now sticking out of the exit portal. But in order for that to happen, the portion that was already sticking out of the exit the previous frame had to have moved out of the way. It is essentially pushed by the previous portion of the cube trying to make room for itself. And the speed at which it was pushed would be equal to the speed that the entrance portal is falling down over the cube.
So while the portal is falling over the cube, the cube must be moving in order to physically move through the exit portal. But maybe it doesn't move beyond that point? Well that doesn't make much sense either. When the entrance portal finishes hitting the floor, the cube will have still just been moving due to it pushing itself through the portal, and inertia would still apply. So it still needs to lose all the energy that it just gained. There's nothing stopping it from moving other than gravity and air resistance. So it would slow down accordingly to those properties. Thus if the portal was fast enough to launch the cube, the cube will naturally fly out the other portal.
The other counter argument I've seen is that it doesn't make sense cause there's no clear source of the energy that propels the cube out of the other portal. but this is simply a fundamental property of portals as we see them. The simple act of placing one portal above another one creates energy from nothing. After all if you put a portal on a ceiling and floor and ran water through it, you could have a perpetual motion infinite energy device if you stuck a turbine in it. I mean you can do this in-game after all. So while I do argue that Newton's Laws still apply to the physics of portals, they do inherently break the fundamental law that energy cannot be created or destroyed. (similarly going from a higher elevation portal to a lower one effectively destroys energy as well)
Waitttttt that’s a really good explanation! I still didn’t get it after the video until I read this, but that makes sense to me! (Much more than some coding equation)
very good explanation
This is a fundamental misunderstanding of what a portal is. You assume that the cube is being moved through the portal, that it had to gain some energy to continue to push through threshold. This assumes that a portal is two separate objects. A portal is just a hole. For all intents and purposes, it's the exact same as dropping a hula hoop on a cube. The hula hoop represents a singular hole in space that is itself represented by two portals in this scenario. The entire hole is moving (which is NOT represented in the video, and why it only works when setting it up as a single moving hole in his engine). There is no force to overcome. When the moving portal has firmly stopped against the ground, the cube is still sitting on that ground. Any movement of an object that has a portal dropped on it is purely an illusion. The object has not moved. It is still sitting where it started. The only difference with an angled platform is that the axis on which gravity effects it would change and eventually drag it off the platform, provided the ground and cube themselves are not providing enough friction to counter that.
You also never create energy from nothing in Portal, nor do you destroy energy. The terminal velocity example you mention is simply providing an infinite corridor in which something can fall to reach terminal velocity due to gravity. You aren't creating any energy with the portals. As far as destroying energy, we don't do that either in the game and I'm not entirely sure what example you were trying to give for that.
@ChaoticNature portal above portal. place a copper coil around this collumn and drop a magnet through. boom- infinite electricity. how is this not creating energy out of nothing?
@@sydssolanumsamsys You're mistaking the conversion of one type of energy into another with the generation of energy. You're converting kinetic energy (gravitational and magnetic) into electricity. The portals themselves are making no energy, they're simply removing the work needed to reset the magnet to the top of the coil.
That's also not infinite as the coil would heat up, and beyond a certain point would melt and break down the system.
Thank you for not making a 23 min video, talking about literally everything else before getting to your point. You’re a good dude
I’d love to see how your game engine handles the orange and blue portals both moving but at different velocities, i.e. the orange portal moves down onto the box while the blue portal is elsewhere moving at a different velocity than the orange portal (and perhaps even at different angles to see what affect gravity plays). Particularly if the blue portal is moving in the same direction as the orange portal, how does the cube handle going from one to the other when they’re different speeds?
He did it already! the first experiment that is shown is exactly that. as you can see, the angle of the blue portal is not the same as the orange, and both move at different speeds, all that will happen is the speed of the cube will vary in the exit following the equation he proposed
While both portals were moving at different velocities, one portal was _not moving_ at all.
@@DWal32 Mathematically that is just a different speed though. Going by the equations shown in the video, only the relative velocity of the portal and object matters, so varying the speed of the blue portal only changes the resulting speed of the cube as it flies (or plops) out of the blue portal, maintaining the relative speed between the cube+portal system.
@@DWal32 In terms of the math involved that really isn't important. Combining the two velocities and changing their vector would work the same way, just with different magnitudes of velocity input and thus different magnitudes of velocity resulting.
the implementation already handles that because it uses the relative velocities of both portals so you can work out what that would do very easily
Portals are basically kinetic energy / potential energy translations. If you have a velocity difference between them, it translates onto the object passing through. An object passing through a portal higher than another is just an object going through an instantaneous PE adjustment in the form of space displacement . A moving portal is basically a KE translation, which necessarily involves a velocity difference between frames of reference.
This is the best reasoning I found so far, nicely said!
why do we imagine that a portal separates spaces and if the portal moves, then its space moves? It always seemed to me that the portal only teleports objects while maintaining their kinetic force, only in the case of the game Portal this force rotates at the angle of inclination of the portal itself
@@TheDEFCHER If you put the portal at a higher altitude, you already have a change in potential energy, and if you consider that velocity also varies according to how far away it is from the center of Earth's rotation (or when faced on a completely different orbital body like the moon), it will also necessarily need to have a change in velocity which also requires a change in kinetic energy.
When you go out of the moon portal, you do not get flung at the speed difference between the orbital speed of the moon and the velocity of rotation of the Earth, which is a difference of several hundred kilometers per second.
There's really no argument, just unwillingness to see that potal physics would just be too inconsistent otherwise.
the portal paradox gets even weirder when you ask what would happen if the the portal were to accelerate as it moves towards the cube.
I mean, it does. The test shown when it drops is accelerating at -9.81 m/s^2. The blue portal is also accelerating in the opposite direction, so it cancels. Like Portal itself, there's still probably a terminal velocity limit, so it isn't uncapped acceleration. Where this still isn't completely resolved is if there is a delay in rematerializing something after it enters the orange portal. If there is any delay, then the cube will have a slightly slower exit velocity than as it was derezzed. That would cause it to be compressed... I probably don't want to be the first living thing to pass through an accelerating portal.
It kinda doesn’t get weirder. In-game it’s just the center of the cube that counts as either being in or out of the portal.
In real life, the cube would experience a “pulling” force (just like with the moving portal) but if the portal accelerates, the force just becomes bigger. As long as the structural integrity of the cube holds, it’s like picking it up with a vacuum hose around the cube.
So appreciative of you not baiting us with the answer, that I watched again months later after having forgotten the solution.
I wasn't onboard until you did the "hula hoop slam" and it changed my mind the instant you pointed out that the exit portal was also moving. Nicely done
Great video, man. The first of yours I've seen. I like your non-sensationalist, calm approach to editing and content! Keep it up.
What kind of content do you watch that is sensationalist lol? You and I have two very different experiences on this platform
What bothers me about this problem and this solution is: what exactly gives the velocity to the cube?
From the cube's perspective, what pushes it away from the floor? Does it suddenly feel a force upwards and away from the portals? How does the Orange Portal transfer it's velocity to the cube if it never even touches it?
Say you place a portal on a ceiling and another on the floor and you drop a cube into it, allowing it to fall infinitely. As it passes through the portals it keeps picking up speed and if it wasn't for air resistance it would in fact pick up speed forever. Where is the energy coming from in that process? You might say gravity but no amount of height would allow you to fall at speeds reaching the speed of light within earth's gravitational field. No the portals themselves convey energy to objects that pass through them simply by their very nature of being able to transport objects to disparate points in spacetime.
But to give a more practical answer, the cube essentially pushes off of itself and the floor below it. Looking at purely the blue portal, what you would initially see in slow motion as the orange portal descends, is a small portion of the cube sticking out of the blue portal. Then a moment later more of the cube would be sticking out of the portal. But that would mean that the first portion of the cube would have to have moved out of the way in order for that to happen. Essentially the lower portion of the cube is pushing the higher portion forwards in order for it to exist the portal. And then the next portion does the same and so on and so on. By the time the cube fully exits, the entire cube is moving at the same velocity as the orange portal.
@@BlazeMakesGames No, it wouldn't keep picking up speed. The energy comes from gravity, that is a fact. You're in freefall, like jumping off a cliff, but you keep teleporting back up. The portals are doing absolutely nothing. The cube would reach terminal velocity and it would just keep falling at that same velocity. There is a limit to the speed. If we were in a vacuum, and you tossed a cube into portals that faced each other, the cube would keep the velocity you threw it at, because there are no other forces acting on it. If none moving portals did act on objects going into them, then everything would be shot out of stationary portals equal to the amount of force they exhibit. however, the portals do not interact in that way. They do not interact with objects going through them.
Portals are more like doorways. If a moving wall with an open doorway came towards you, and you go through, are you inheriting the wall's velocity? The difference here being the space on the other side, and how the forces on the other side interact with you, not the portal.
@@BlazeMakesGames By your definition, if you even touched a portal, it should suck you through it. On your gravity example, if you had infinite height, with a constant acceleration due to gravity, an object would speed up to its terminal velocity. This is what is happening in your example. This just can't happen outside of portals because A: get too far from earth and gravity decreases, and B: get too close, and the ground stops you.
The portals really just move one location in space to another, they don't pull objects through themselves (unless one is in space, sucking objects in because of the pressure difference).
@@ianwalsh3868 So portals work literally like doorways.
@@fantastikboom1094 Yes, that's my understanding.
its crazy how when i notice a video is gonna wait til the end to show results i just skip, see the results then leave the video, but here seeing the results first made me wanna watch the entire thing and i would have watched a whole 20 minute video going more in depth about these physics and complications. amazing video with out using predatory tactics 10/10
Honestly this makes the most sense, velocity being based off both the portals and the object
My issue is that the hula hoop analogy is always how the portals work. They're just holes, the ends just happen to not physically connect. There's no reason for the energy of the portal to be conferred to the cube. Momentum is conserved between portals as well as the lack thereof. All of this with the caveat that I flunked out of high school. Regardless, loving the progress on the project, can't wait to see more!
I think if one portal moves, the other would have to move, too. The energy transfer from the portal to the cube seems to be a trick that gets around the space/occupation constraint on the other side.
Normally the entrance portal is static. This means forces acting on the cube have to push it through the portal. But if the portal moves, how is there going to be enough room on the other side, if the cube is not moving? I think the relativity trick is just a trick.
Or the portals are actually atom rematerializers.
@@user-zu1ix3yq2w I just assumed these things were like Loony Tunes holes.
Portals convey energy to what passes through them all the time. If you simply place a portal above another portal and pass an object through it, then it has just magically gained energy via passing through the portal. After all think about the times when you place a portal on the floor and ceiling of a room and fall infinitely. You continuously build up speed because the portals are in effect conveying energy to you by granting you more potential energy than should be possible.
Momentum is conserved through portals, but energy is not. Similarly if you go through a high portal to exit at a lower elevation, you will have effectively destroyed energy as well. Portals by their very nature allow you to create and destroy energy at will.
@@BlazeMakesGames In your example the energy isn't coming from the portals, it's coming from gravity. With nothing to slow an object down, gravity will cause it to accelerate through the portals until it's stopped. The energy is not magically gained. Momentum *is* energy, and is conserved through portals, but the portals themselves neither add nor take it away from the object.
I’d love to see this on Steam. I hope Valve would allow for you to put it on their platform.
It uses a n64 rom file so it would need a n64 emulator which Nintendo doesn’t like
@@Pop4484 well portal isn't a nintendo ip so I doubt they would care that much even if you used an emulator since they don't own the game so they can't really do anything about it
@@jlewwis1995 yeah you’re actually correct
@@Pop4484 it could be ported to run natively on PC, mario 64 was ported even whitout the source code.
@@PANCHOTRON5000 I forgot that while writing the comment
Nah, absolutely 100% spot on. Another way to show it is to pull the exit portal back the same velocity as the entry portal drops. The cube would then lose all velocity again.
You, sir get a instant like and subscribe for
a) not waiting with the result towards the end of the video
b) making the video as long, as it needs to be
c) seeming like a good youtuber overall
Great work, I love it! I feel like the cube should not shoot out like that, because it rests still on the ground and the teleport just happens faster - I guess the ground would absorb the momentum here...
Well, your feelings are absolutely right. It won't fly at all.
@@fantastikboom1094 why not?
I just finished all Portal 2 achievements and was craving more. And whoop- here you are! Thank you for your videos, they always brighten up my day!
Clicked on the video just to make sure you were gonna say the right answer. Was not disappointed 👍
i always thought of it as the total momentum of all three objects remaining consistent, so i figured the cube should stop, but admittedly i struggle to keep track of everything
I have the same idea. What happens to momentum here. The portal (or the object it is placed on) would decelerate giving it's momentum to the cube. But I cannot rationalize how that interaction would occur.
This was my thought too, but when I went to write out a comment about it explaining the math, I think I found the solution.
Newton's first law states that an object at rest stays at rest and an object in motion stays in motion, until acted on by an external force. But also, motion is relative. An external force acts on the platform to move it down towards the cube, so the cube is already in motion relative to the platform before it even enters the portal. When the cube goes through the portal, no additional external forces act upon it (aside from small ones like air resistance and gravity) so it retains the momentum relative to the portal.
This does seem completely illogical based on the laws of physics we know, but that's because our laws of physics don't allow for moving portals. If you imagine a similar situation in space, it might make more sense. If wormholes had no field of gravity, then an object entering a wormhole would come out the other side at the same speed it entered relative to the wormhole. It doesn't matter whether the wormhole or the object is moving, as motion is relative. No external force would have to act upon the object for it to retain its relative velocity.
@@mithrandireichner2667 The answer is basically that the cube doesn't actually accelerate and no additional momentum is required, so none is taken from the platform. The cube is already in motion relative to the portal as soon as the platform starts moving, it simply continues at the same relative velocity because no additional external forces act upon it to slow it down. It makes no sense with our current laws of physics, but, if wormholes area real (and traversable) our laws of physics are wrong anyway.
@@ayylith The way I see it, the system encapsulates the portals and the cubes. One side could argue that the *cube is moving* relative to the portals, but when discussing physics, or math, especially linear math, the discussion happens within systems. We could go on discussions about the properties of this system, but I'm going to ignore that for my comment. Assuming the system includes gravitation, that should logically include the exerting body of that gravitation. So the basis of this system is Earth, the cube and the portals. With both portals, gravitation is negative in both cases, so towards the basis ground of the system. This does not change regardless of any other factor. It is a fact, then, that the cube is resting relative to Earth and the portal is, in fact, the object that is moving. So it stands to reason to assume that the *portal is moving* relative to the cube.
So my interpretation of this problem more or less disregards the portals themselves as effect sources since the basis of the problem is the cube in resting position. The only thing that should really be affecting the cube is gravity, assuming the portals don't add, subtract, convert, transfer, etc in the process, and that itself is a question based in unrealized information of the *game's universe*, not ours.
@@mithrandireichner2667 From the cube's frame of reference the portal has velocity, but from the portal's frame of reference the cube has velocity. Relativity says whichever frame of reference you measure from the total energies involved are conserved (don't change over time), but that individual components of the system can measure different readings depending on the frame of reference you use. You can even use moving frames of reference such as the portal as long as you account for that movement.
We can simplify everything by measuring from the blue portal. And since when traveling through the portal the point in the middle of the orange portal is in the exact same place as the point in the middle of the blue portal (there is no spatial or time difference between them) We don't need to change to a different frame of reference, and therefore no adjustment is necessary (we'll call this point A).
The velocity of the box going into the portal, as measured from point A = the velocity of the box exiting the blue portal, as measured from Point A.
This is a good way of visualizing it and it makes complete sense, to me if the exit portal is stationary it's a no brainer that the cube is flung as the cube is literally pushing itself. Think of it in layers, the first layer is transposed as it touches the portal surface to the other portals surface, but when the next layer comes out pushes the previous one out of the way, so when the entrance portal is moving it's velocity is transferred to the cube via the force of the cube pushing on itself.
You don't understand quantum entanglement and it shows.
Tell me, what force acts upon the cube?
No, my dude, it's doesn't make any sense. His equation is wrong. Not in math, but by itself.
@FantasTik Boom exactly! He is trying to make a hole, a lack of energy and matter, be a frame of reference to impart force on another object. His formula has 1 variable, a box, and a hole accelerating at it. If the box somehow was accelerating through the hole with no force acted upon it then light itself would accelerate through thw same hole and exit faster than the speed of light.
@@xelgodis80085 Someone named "Diego G" strongly argued with me, until I gave him an experiment. Then he deleted his comment.
That experiment is:
"We stop the portal halfway of the cube. Did the cube move? Before I answer: you clearly see the platform and the cube. The answer: If you apply author's equation here, the result will be different. The cube will get enough speed from the portal to fly out. And what you see is exactly why this equation is wrong. Cube didn't move and wasn't pushed, but it flyed out.
Right result would be: cube didn't move at all."
I just pasted some part of reply... actually because I saved all my replies... I thought them being cool lol
@FantasTik Boom I was a bit brash myself, but it seems everyone who has argued with me seemed to shut up real quick when I asked the how a void passing over an object interacts with the object, and if a void can accelerate something passed through it then light itself must accelerate past the speed of light.
These people assume the entire universe has a single inertial frame of reference and nothing else matters, which is the flat earth argument for gravity-denial.
Not understanding basic principles is how we get radical conspiracy theorists, and it's dangerous.
With that stationary test, it seems like the part of the cube that has exited is moving relative to the exit portal. I'd actually expect that part of the cube to have a pulling effect on the rest of the cube (that is still on the other side of the portal). I wonder how far you'd need to extend the entrance portal down, before the rest of the cube is pulled out by this force alone. What do you think?
That's what I thought but as the entrance portal comes down on the object with the same speed the object is technically being pulled out the end while appearing to be stationary. If the entrance portal stopped before reaching the ground but after reaching the object, the object should be pulled out or (if it is not solid enough so not the cube for example) be stretched or teared off.
While, yes the part past the portal excerts a pulling force against the rest, it can not pull the rest through, since it also excerts an equal pulling force against the part past the portal, because of Inertia.
The only part of the force not negated is the effect of gravity.
The cube would fall if half the cube is through and the exit portal is pointing down, and slide to one side if the exit is not horizontal.
Now THIS is the real question.
I would imagine it depends on how fast the entrance portal stops.
If it can stop immediately with no "cooldown", it would probably shear the cube in half in real life depending on the material (in-game it is impossible as the game defines it as a single particle). This is cuz the half that enters the portal would have energy while the other side abruptly stops. It's similar to half of a stick being hit by a moving truck while the other half is anchored in a tree or something. If the material had a weak point, it would break at the weak point instead (as that's how energy travels).
Actually the cube never gains momentum. I don't know how a portal which does not itself transfer its momentum to objects that pass through it makes sense. The portal is a direct spacial link to a different location. It doesn't matter how fast the portal itself is moving.
I typically don't like or comment on videos, however I respect the fact the this guy got to the point and didn't drag out the video. I also find his solution to the moving portal questions to the best answer I've heard.
Suggestion/Question: In your version, could you remake the demonstration done in this video from a few years ago?
ruclips.net/video/0TZd95BCKMY/видео.html
A portal sandwich type scenario is both a common thought, and is also not an easy thing to intuit, and I am curious if you would yield similar results as they did. I'm also not sure if their method (from Portal 2 which does allow moving portals in one level) would work for testing the portal paradox, but would be interesting to see if you could implement it and compare your results from this video.
ruclips.net/video/zDAE9A_1NA4/видео.html This minutephysics video gives a satisfying answer to the portal sandwich situation.
i imagine it would prevent the portals from getting closer to each other than the height of the cube, as I would think weirdly the two opposite sides of the cube would be pressed against each other. would be cool see if this actually happens though
Yes!
Please crush yourself between two portals.
It would simply be an unstoppable force vs unmovable object paradox, I'd think.
@@DrowGM exactly this. It's all about normal forces and inertial reference frames.
I like it. If the rule is velocity is preserved between portals, if one portal is moving and the other is not that velocity needs to be preserved.
The only situation that I think might be weird is you do the reverse. Where you try go through the none moving portal to the moving one. You might not have enough speed to get through a stationary portal and may get shot backwards.
Not velocity: momentum.
@@darkcoeficient momentum=mass*velocity
We know that mass must be preserved through the portal in order for it to be a portal therefore velocity is the parameter we care about.
That's why his calculations don't consider the mass of the object at all, just their relative velocity. Not there relative momentum.
This is so weird to think from the cube's perspective, though. Like Imagine being in its place, you'd see the portal come toward you and then your feet would lift from the ground apparently without any force pulling you.
It would be functionally very similar to being hit by a moving object and having its velocity partially transferred over to it via the collision.
@@Celia_Dawn Eeeh... kinda, but not really. You wouldn't really have an object hit you and transfer its velocity, the portal is coming toward you and then you'd fly in the OPPOSITE direction of its velocity.
I think it's more similar to being in a car moving at constant velocity and not feeling its movement, then hitting a brick wall and flying out of the windshield and die after some agonizing pain because you weren't wearing a seatbelt. From your perspective you were stationary and the wall was coming toward you, then when it hits you you fly out of the car and into the outside reference frame.
...Actually now that I think about it IT IS pretty much just that!
@@KombatGod Portals don't transfer momentum themselves though, they are holes. The Hoolahoop analogy works well, the only different is the space fuckery of the top of the hoolahoop being somewhere else. It's still a hole.
For me I always saw it like a simple door. If you dropped an open door and the frame slammed down around you, you’d still be standing there. But if you went across the frame Mach 1, you’d just come out the other way with the same speed.
Since portals aren’t just doors tho, I can see how you’d carry its momentum into the other side. But it’s weird, because it’s as if the whole room, or the whole OTHER side of the portal was moving toward you. So when the portal slams down on top of you, it’ll be like the whole room was pushed down under your feet which results in you in the air. Same thing you the portal came at you from the side. You’d get through the portal as if the whole environment was moving on one side.
What a weird sensation that would be, one moment you're standing still the next you'd be at great speed but without having felt the acceleration of it. Suddenly being blasted by air from air resistance and seeing the room around you at speed heading towards you.
I subbed because you did the most kind and generous thing a RUclipsr could do: the selfless act of getting right to the point.
Very cool! I'd argue that you have to take into account the relative velocity between the 2 portals. If your reference is the orange portal (it stays still) then the box AND the blue portal move up toward the orange portal at the same velocity. So the box enters the orange portal with some velocity, which has to be the same velocity as the blue portal. In that case, the velocity of the box would be added to the relative velocity of the blue portal, doubling the velocity of the box as it exits the blue portal, which is not consistent with another frame of reference.
I think it's less that speed is conserved, and more that energy (momentum) is conserved. In that case, there is no energy added to the box, so it can't change momentum, so it just falls out of the blue portal.
So much more well put then what I was gonna say, yeah no this is a pretty fantastic project and it is very impressive to reimplement portal’s mechanics this way. But yeah sadly I agree it’d be slightly lamer reality lol.
Yeah I agree, but there would be a rush of air throught stationary portal
This is super impressive stuff, props my man.
Super late response, but I think the answer to this squarely sits on if you believe the space in between the portal can enact force onto the cube. For me, I see the portals as a mere translative motion across space, so I would say the only force on that cube as it leaves the blue portal is gravity. So I’d say it plops. But if you see the portal as a movement arm that pushes the portal out at the same velocity the arm moved onto it, then it’d launch as shown.
The box already has momentum relative to the orange portal. That momentum is carried through to the other side, which is why you see it launch out the blue portal.
@@APaleDotIt has momentum, but I believe that gravity acts against it, so it would result in a slight hop at most. After all, the acceleration that tbe box experiences should be equivalent to what would happen if you moves the tile that the box is on upwards at the same speed that the portal travels down and then suddenly stop. It would hop, but not as far as if it were launched at an angle.
@@darthplagueis13
The original question doesn't specify how fast the orange portal is moving. The implication is that if you answer 'A', the cube will **plop** out of the blue portal regardless of how fast the orange portal is moving.
My question is what happens if the descending portal only descends half-a-box's height from the floor the box is resting on? The half below the portal is unaffected, but the part passing through gets momentum. I'm guessing the part passing through pulls on the part not passed through the portal and it comes out but with a slower velocity.
I was wondering something similar about the situation. Is the cube still affected by gravity?
the net velocity of the cube is zero as the two directions cancel until more than half the cube has moved through the portal. if the portal continues down it may eventually be overcome by gravity, otherwise it will only move maximally at the speed of the moving portal. energy in = energy out
Nobody knows the answer because we still don't know how it would look like in reality
@@realdragon i disagree, in the game and in real life it is just math. ask something like chatgpt or wolframalpha
@@JohlBrown You can rocketjump in games, it's just a math but I can assure you in real life it does not work like in games
The problem with the equations is the assumption that portals can have momentum. Portals are connections between regions in space. The cube doesn’t interact with the moving platform, it interacts with the portal *on* the platform. Since the portal cannot impart momentum and the cube is stationary, the cube simply drops as soon as it crosses the portal.
The Moon moves relative to Earth. Chell shoots a portal on the Moon. Canonically, portals can have momentum.
I love this change up in the structure of your content, and I am so happy to see your project come so far 😁
I always thought the portal paradox was solvable
MinutePhysics has a great video on the portal paradox. I recommend it, it's interesting!
Why would even someone call it a paradox if there is no conflicting math?
@@expioreris my thoughts exactly.
it aint a paradox if it's solvable
@@zeynaviegas thorough history there are paradoxes that became solvable with modern tech but still are called paradoxes, there's a video on the many types of paradoxes called "the five kinds of paradoxes" by jan Misali
@@expioreris Because there is conflict in math, box suddenly out of nowhere have energy
I think the true "Portal Paradox" lies not in the clear, discrete time behavior of the system, but how the motion works in a slowed, more continuous case that probes that discontinuous boundary and mixed forces/momenta (gravity pulls 'down' on some volume of the cube yet the remaining volume has momentum in non-orthogonal direction). For example, a really tall, stretched rectangular cube and an accelerating portal. What happens in your implementation?
the cube would slide out slowly at first andthen faster ,as the moving portal sped up , out of the stationary portal before being thrown out like in this demonstration. i think
I was also thinking what would happen in the portal's velocity wasn't constant while an object was corssing it's boundary, since e.g. if we stop the portal, the parts of the object that were stationary relative to some other objects around it are expected to remain stationary, but the parts that got through are expected to retain momentum and start pulling on the rest of the object. I guess I kinda answered my question, but it would probably mean that a deccelerating portal would "suck" any object it comes into contact into itself.
As for this specific implementation, it seems to be using a very simple principle and the object is considered to be on one side right until it's center passes the portal, at which point it's teleported (unlike in Portal, where, if I recall correctly, the objects can actually smoothly transition through the portals).
An interesting quirk of this interpretation of portal physics is that if the cube is moving and the portal is moving, the cube will be sped up or slowed down by the portal its moving through which is quite strange and not how I think portals should work they aren't supposed to mess with the momentum of an object. If you just took the *entranceportalvelocity* out of the equation it wouldn't change much other than these strange momentum transfers from a portal to an object.
I think this scenario helped me actually understand what's happening in this video. From the blue portal's perspective it would be as though the cube would be moving towards it, so it would keep that momentum it has coming towards the orange portal
i think
So I guess it would be doing the same with a long cube? I... Assume it would be kinda stuck in place until it fully goes through the orange portal, and then when it exits the threshold of the blue portal it would keep the momentum from the orange portal and plop out? That's my best guess. But this hurts my brain and portal is black magic to me so I have no idea.
Since we're mixing gravity into the equation...would gravity not travel through the portal as well?
Portals are, what, connecting regions of spacetime? So any spacetime affect would be able to traverse the portal boundary, or...? And we know now that gravity travels at the speed of light, so it might propagate out of the portal...
I think gravity would be more of a factor than inertia. Arguably, the portal itself has no velocity, since it's just empty space. The platform has velocity, sure, but the portal might as well be a hole in the platform. Air would move freely through it, as if nothing were there. The same would apply to the box, no? The flaw in your code is that you designated the portal as an object, and one that has a velocity. The box would, thus, simply fall out of the exit portal, due to an inconsistent gravitational pull moving the center of gravity of the box.
Thanks for valuing our time James. You utter legend.
Also, level editor? That would be siiiiiiiick
I just use blender. I could document how to create levels sometime
Hammer editor for n64??
I'm glad you took relative velocity of the box and both of the portals. Everyone I've seen discuss the Portal paradox seems to neglect that. Speed and velocity are relative to objects in space. It doesn't really matter if the object is moving or the space around it is moving, because relative to the position of the object, it might as well be moving regardless
What happens to an object thrown in to a stationary portal while the exit portal moves forward relative to its face at the same speed. Awesome video it's got me curious.
This makes sense, scientifically speaking.
See, one might argue that, in order to move the cube, it needs energy, but the portal, since it doesn't come into contact with it directly, can't possibly give it any kinetic energy, which means it shouldn't move.
But here's the thing: we aren't dealing with normal spacetime here. These portals are wormholes.
It's like bending spacetime to "travel faster than light." You yourself, or the cube itself, doesn't move, but the space around it does. What the orange portal is doing is basically slamming space at and around the cube, which means, relatively speaking, it is moving. And since space is kind of our ultimate frame of reference, we can only ever experience this interaction as the cube moving in space, even though, technically, the cube is stationary and space is moving around it.
The portal shouldn't have velocity.
The experiment you showed at the start, at some point deletes the cube on the orange side and spawns a new one on the blue side. Portal allows you to put things halfway through a portal. What would the result of your experiment be if you stopped to orange portal 1/3 of the way through the cube? What about 2/3 of the way?
If I were remaking portal, I'd have two rooms. You can mirror all the object states in both rooms. Chel would not notice that there are two rooms because the object states are mirrored. When Chel goes through the portal she walks into the other room. In the case of our cube, when the Orange Portal interacts with our cube, it would come out of the Blue Portal in room 2, and the cube in room 2 would come out of the Blue Portal in room 1. Since the cube didn't have any movement it would still be resting on the surface of the floor. However that floor is at 45% at the Blue Portal position. At that moment, the force of the box is still 90% to the floor (where gravity was), but 45% to gravity (where it is now). This would cause the cube to begin spinning violently forward, as it normalizes those forces through rotational energy.
Basically, the object has the same velocity to appear in the other side but without momentum.
If the mass is uniform, you can assume a very proportional relationship between the resulting speed, and the distance the moving portal goes over the object.
1/2 the distance = 1/2 the exit speed
2/3 the distance = 2/3 the exit speed
and so on
Where does the energy to move the cube come from? Does the piston feel resistance as it transfers energy to the cube, so as to launch it?
The block should plop out cuz ur not giving the block any energy when u hit it with a portal, there is no force acting on the cube so if you follow the rules of physics the block would not move because no force was put onto it, you only change its place in space. So the if you slam a block with a portal the block should pop out the second portal with the speed at which the first portal is moving but won't fly out and instead would just sit on the second portal until it starts falling towards gravity.
This makes a lot of assumptions about portals, like assuming that portals can't act with force on something.
@@godlyvex5543 do you mean that the portal could be pushing the cube through
@@nikoveliki4132 I'm not saying the portal is pushing the cube, but I am saying that surely transporting the object takes some sort of energy. Anyway, the way I like to think of it is that from the perspective of the portal (like looking in through the blue portal) you'll see the cube rushing up at you, and from there it would continue on it's path upwards because it's relative momentum would be added to the portal's momentum (which would be zero) to get a final momentum of moving upwards. If the blue portal were also moving downwards at the same speed then the cube would just plop out for a moment then fall back in.
@@godlyvex5543 so ur theory is that if 1 portal is moving towards me and i throw a ball through it, the ball would fly out faster through the second portal? I look at the portal more like a window, but the 2 sides of the window are in different places, so whatever goes through the portal would act the same way as if you put it through a window frame except with the portal the other side of the window frame is somewhere else
@@nikoveliki4132 The portals are windows, windows where the two sides are detached. It's common sense that if one side were moving, the portal's movement is added to the ball's movement. You can't really even look at it like a normal window, because the world on one side of the window is moving.
First off, well made video, and I always love more portal content.
My core argument against this result is that the space contained within the ring of the portal is not a physical object that can exert force, OR have force exerted against it. It's just the space that exists on the other side of the exit portal. Therefore, this space has 0 relative velocity. The only forces that are exerted on the cube in this situation would only be gravity and nothing else. The surface that the portal rests upon can have velocity, since it is an object, but the portal itself is not subjected to the same physics, since what the portal represents is just whatever space exists on the other side of it, and that space is not moving, hence 0 velocity.
A portal is just a Quantum Tunnel, right? So imagine a Cube placed on a floating platform in space. Now drop a large hollow pipe (the quantum tunnel) around that Cube and platform in such a way that it never collides with the Cube. Despite the Cube traveling through the tunnel, (or more accurately, the tunnel moving around the cube) no force is being exerted against it, and when it arrives at the other end of that tunnel, it has no more velocity than when it entered the tunnel.
Portals combine two disjointed places through a similar tunnel, so when you shove the portal down around the cube, the cube will simply arrive on the other side of the portal with the exact same relatively velocity that it had when it was sitting there minding it's own business. Zero.
Thanks for this explanation. I was thinking the same thing but couldn't figure out how to put it into words.