Inside a Black Hole: From the Event Horizon to the Singularity
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- Опубликовано: 6 июн 2024
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REFERENCES
Time travel via BH: • How Time Travel is Pos...
Inside a BH: • What would we see if w...
BBC Article: tinyurl.com/22mjo8h2
Space.com article: tinyurl.com/rl6mau2
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CHAPTERS
0:00 What is a Black Hole?
2:10 Best way learn a Foreign Language
3:33 Are Black Holes dense and black inside?
5:48 Light cone explanation
9:52 Spaghettification and time dilation problem
13:41 View from inside the black hole
16:56 What happens at the singularity?
17:39 Could you go back in time in a black hole?
SUMMARY
Most black holes are formed when a massive star at least 30 times the mass of our sun runs out of fuel. It then collapses uncontrolled against all other forces of nature into a theoretically infinitesimally small volume. This region of infinitesimal spacetime is called a singularity. The spherical volume of space around this singularity is what we call a Black Hole. The radius of this region was first described by German physicist Karl Schwarzschild.
The edge of this radius is called the event horizon. It is the point beyond which nothing can escape, not even light. Unlike the singularity at its center, General relativity does describe what happens inside this region beyond the event horizon.
Presuming the mass is concentrated in a tiny volume inside, what we would have between this singularity and the edge of the black hole, is mostly empty space. It may contain things that have fallen through, but if the black hole is not very active, that is, if things are not falling into it, then there would be just empty space inside.
But this empty space would not be anything like the empty space that astronauts see far away from earth. First you wouldn’t see all black on the inside. It would be lit up from all the light that’s falling into it. And everything would be falling towards the singularity. And this singularity would appear to be located in all directions. No matter which way you moved, you would be moving towards it. There would be no other path.
Let’s now follow this astronaut all the way from his spaceship far away from the black hole to the black hole and then to the inside of the black hole, and on to the singularity. Even though time would appear to stop at the event horizon from a perspective far away from the black hole, from the Astronaut’s perspective, time would tick normally and He would simply just go right on through to the inside.
If he were to look back towards you, he wouldn’t see any visible light because most of the light near the event horizon would be so highly blue shifted that it would be in the x-ray part of the light spectrum. Infrared light and the cosmic microwave background light however would now be in the visible spectrum, so the astronaut might see these.
Also the light from all around the black hole may be visible to him, since the severe gravitational well would bend light from all around the black hole. But it would be distorted. What about spaghettification? Ironically, the more massive a black hole is, the less dangerous it is from the perspective of its gravity ripping your body apart.
This is because while gravity grows linearly with mass, it decreases with the square of the distance. Since making a black hole bigger means making its event horizon further away from the singularity where all the mass of the black hole is contained, the net effect is that the gravitational field at the surface goes down. As a consequence, for a sufficiently massive black hole, its surface gravity at the event horizon can be as small as it is on earth.
Now, the astronaut has made it inside the event horizon, what does he see now?
#blackhole
#singularity
The singularity, if it exists, would be felt in every direction. No matter which way the astronaut would try to move, he would still be moving towards the singularity. The true nature of the singularity is still a mystery. It is not clear that it would be a physical place inside.
But what would the astronaut actually see after he went inside? Assuming he is not moving at the speed of light,
he would be able to see the light that entered the black hole behind him. He would still see the outside world from inside the black hole. But this light would be a beam of light that would get smaller and smaller as he continued his journey. It would be a beam because only the light directly behind him could reach him. The light from the sides would be headed towards the singularity, so it would not travel sideways for him to be able to view it.
In front he would see total darkness because no light would be able to move backward toward him. So as he approached the singularity, his world would steadily darken until he gets the last glimpse of light from behind, and he smashes into the unknown physics of the singularity. 
Наука
Brilliance is the ability to fully explain the seemingly unexplainable; Arvin does this in spectacular fashion. Nice trip!
Inexplicable.
My thoery--Black holes aren't holes at all. They are black spheres made of pure dark matter.
Yes, he is the best
I think we call this "imaginative".
As in, having an active "imagination" 😏
Amen!
Ten thousand videos online about "what would happen if somebody fell inside a black hole" all say the exact same thing,
but YOU PRESENT ENTIRELY NEW MATERIAL THAT ABSOLUTELY NONE OF THOSE OTHER VIDEOS DO! Thank you!
I've been watching your channel for years and this is the first time I think I fully understood such a complicated topic all the way through the video. Very well done.
Great to hear!
@@ArvinAsh- Hi there! Re. only seeing a narrow beam of light from the direction you fell from when you're inside the event horizon... wouldn't you also see light from a vast region around your direction of origin that hit the blackholes at an angle and got bent into your trajectory? This might represent light that was emitted further back in time than your origin light for similar distances maybe, so you might see a weird hyperbolic panoramic view in all directions that includes a time gradient as you look away from the direction of origin
What a wonderful video, Professor.
Your research, script, presentation and animated graphics were fantastic! (As always)
Thank you so much 😊
This has got to be your best video yet!!! Absolutely well done and easy to understand and follow along! I've always wondered what it would look like falling into the singularity, now I know! Fantastic job to you and the rest of the staff
It's bizzare to imagine the scenario where everywhere (left, right, up, down) you look there is the singularity even though technically it is a core of a "sphere" and only along one direction
But that's how we are now with time. Every second that passes, is one second in the "forward direction". There is no going back in time, or sideways, etc. (yes, I am aware of time dilation, but that is still going only forward, just at different rates relative to other observers, still no going backwards or sideways).
@@destructionman1 true, but that's a temporal direction... The commenter is saying that the spatial directions will all look the same. No matter how much GR says that space and time are equivalent, they aren't experienced that way by humans... We absolutely experience time and space differently. So it is wild that you'd always be seeing the center
Just wanted to thank you, Arvin, for content that always intriguing and fascinating. Well done.
Exceptionally accurate and clear, clearing up some of those maybe fun but incorrect sci-fi myths. Perfect! 👏👏👏
Oh yes! This is the episode I had been waiting for, I have heard talks about what happens inside a black hole from Neil De Grasse Tyson, Sean Carroll, Brian Greene and Janna Levin but I know for sure Arvin Ash would answer all of my questions on this topic.
Yeah, he is the best. So many concepts are explained so well and easily.
Niel Degrasse Tyson is a hack who's full of more hot air than a balloon.
Also check out Dialect and PBS.
@@creativesource3514i forgot about dialect! Thank you!
@@tomorowsnobodys Dialect is really interesting because he goes out of his way to challenge the RUclips physics community quite bluntly!😂 But his stuff is really good too. I always wonder who he is as he does not say.
13:05 This is such an interesting property of massive black holes, and produces some truly mind boggling sci-fi options, like the Birch World, a Dyson-Sphere-esque construction built around supermassive black holes that provides virtually limitless living space.
ur channel brought me through my covid infection, i had fever dreams while sleeping listeing to ur videos. almost transendential. love u man. and as always. and never ending. its coming up. RIGHT NOW.
Just awesome Arvin loved it … please bring up more !!
Kudos to Arvin for pointing that the unphysical nature of the swapping of the time and space (radial coordinate only) in Schwarzschild coordinates. Nicely done.
Timestamp? What’s unphysical about it?
@@DrDeuteron It's unphysical because it doesn't exist. There is nothing that happens upon crossing the horizon and all world-lines are necessarily future-directed. The space/time switching nonsense comes about from Schwarzschild-Droste coordinates which is an exterior solution. In any other coordinate system there isn't any switch. Curious, what do you even think gets switched in Schwarzschild-Droste?
@@kylelochlann5053 the signs of g_tt and g_rr, which means future light ones point to smaller radii. My understanding is that shwarzschild is exterior to spherically symmetric mass, exactly by Beckensteins theorem, so the horizon isn’t a problem. If it were, why go to other coordinates to removed the coordinate singularity?
Hi. This was amazing!! Never ever found out anything clearer and better explained ❤❤❤❤ thank you so much ❤❤❤❤
Always awesomely explained 🙂
Great stuff, another home run, hooray Arvin!
Great show. The tilted light cone was a really cool way of looking at it. I have a simple question with (to me) far out implications. If we were to observe the astronaut approaching a black hole, I'd assume that as the red shift increased it would to continue to the infra red, and on out into long radio waves. But would it ever stop wiggling entirely? If not, it seems to me to imply that the astronaut (in our reference frame) never quite reaches the event horizon, from which it would follow that in our frame of reference, nothing not there before its formation has ever pierced the event horizon of a black hole.
funny thing is that the black hole itself is that. It is the collapsed star falling towards the singularity, hence, a frozen star
You are correct. The interior of a bh is in our infinite future. I studies these thing under Kip Thorne, and my conclusion is that curved space is hard to grasp, but doable, and curved time is a major mind fuxk. But your comment is spot on.
If I understand your question correctly, yes you are generally right -- every object a black hole has ever absorbed, would to our perspective still be absorbing it and we would still see photons being emitted from the object, albeit rarely. So e.g. say a black hole absorbed an object that emits 1 photon per second (relative to the object itself), we may still see that object, but it (relative to us) is emitting 1 photon every 10 seconds, and that photon is red-shifted (lower energy to us than the energy it had as seen from the object itself). Something like that.
It is hypothesized that we can in principle see a few photons from very very long ago this way. So say a black hole forms 1 second after the big bang and absorbs something then - we can, in principle, see this object (albeit dimmer and red-shifted, as described). Imagine seeing an image of a dinosaur on the rim of a black hole in the milky way? Obviously not gonna happen, but physics does allow it. Mind boggling stuff.
And although we don't actually see the objects that a black hole absorb get absorbed, we can observe the black hole increase in mass (and electrical charge, and change its angular momentum, etc.) and therefore increase in radius.
Needless to say, this universe is fascinating :)
@@DrDeuteron Thanks Dr. Deuteron! So we hear from time to time of black holes merging. But in our reference frame (RF) they will never pierce one another's event horizon, since nothing would ever enter a black hole in our RF. So black holes cannot merge from the point of view of anyone outside. They just circle, I'd assume faster and faster until the relativistic effects take over, then slower and slower. In the end I suppose that by gravitational lensing you'd conclude that in our RF the two black holes were next to each other forever. Is that what we "see"?
@@DrDeuteron Also. I just thought about another cool implication that would seem to be a logical consequence: Take any black hole. In a very long time, we are told, it will disburse its mass through Hawking Radiation until it reappears, I suppose as a Neutron Star. But then for anyone falling in to a black hole, as soon as they reach the event horizon, an infinite amount of time will have passed in our RF, so the Hawking radiation and reappearance of a star will occur before they fall into the black hole. Hence no one, even in their own RF could ever get beyond the event horizon. I know it doesn't sound right, but it seems to me a consequence. I wonder where my error is. Maybe along the lines of the relativity of simultaneity though I'm not sure how.
I always learn something from your videos, and I've been interested in physics for decades. It makes sense that the gravitational pull is weaker the larger the Schwarzchild radius.. I had never even considered this. All the pop-science videos would have you believe spaghettification were inevitable instantly at the event horizon.
Actually, with solar mass bh’s, it’s extremely likely that spaghettification would occur well before the eh as the gradient in the strength of gravity approaching the bh is SO extreme with smaller bh’s.
@@aaronperelmuter8433 the gradient at the horizon for a solar mass is like getting strapped to a gurney and spinning a million RPMs. Your head an feet are coming apart.
There is an online black hole calculator by Viktor Toth that lets you put in any quantity, such as mass, and it tells your the radius, acceleration of gravity, tidal force, Hawking temperature, how long you have to live after falling through the horizon, and how long the black hole has left before it goes poof! due to Hawking radiation. It's great fun to play with. Try putting in one kilogram, or a radius of one meter, or set the tidal at the surface to be one G per meter.
Arvin. I have so enjoyed this video chapter. I leaned something here. Thank you Mr Incredible. You're keeping us informed.
Awesome Arvin
Thanks Arvin! Titling the light cone was a very effective graphic. And I like the casual dropping of a “BS” in there. I like when education channels (Dr Becky does it too) are reflective of their audience and common parlance used today. Makes things more casual and relatable. Society is changing
Yeah that caught me off guard in the most pleasant way.
What a wonderful movie! Thanks a lot ❤Arvin Ash 1:17 ... and time from our perspective far away from the black hole appears to come to a complete stop here at the event horizon. But this region within the black hole unlike the singularity at its center is not completely mysterious. General relativity does describe what happens inside it. And what happens inside is some of the weirdest stuff that you might not even be able to imagine. It's a region where space and time behave in bizarre ways and our intuitions about reality are challenged. We are going to take a journey that we could never take in real life, and survive to tell it. We are going to go inside a black hole and describe both graphically and visually what would happen and what we would see. 1:54 ... 4:46 But presuming the mass is concentrated in a tiny volume inside what we would have between this singularity and the edge of the black hole, also called its event horizon, is mostly empty space. It may contain things that have fallen through, but if the black hole is not very active, that is, if thing are not falling into it, then there would be just empty space inside. But this empty space would not be anything like the empty space that astronauts see far away from from earth. 5:14 it would have some bizarre properties. First while black holes are black when we look at them from the outsie, you wouldn't see all balck on the inside. It would be lit up from all the light that's falling into it. And everything would be falling towards the singularity. And this singularity would appear to be locate in all directions. No matter which way you moved, you would be moving towards it. There would be no other path. 5:38 ... This might not seem intuitive, but it starts to make sense when you dive into the physics of it. And the pphysics says that space and time would get twistd. What does this mean? To better understand what happens to space and time inside a black hole, let's start by briefly reviewing hw we describe movement in spacetime graphically. 5:55 ... 8:38 ... This tilting becomes more pronounced as the gravity of the object increases. And in the presence of a black hole, the gravity is so pronounced that the light cone continues to tilt until at the edge of the event horizon, it tilts a complete 45% towards it. This means that no object including photons have anyworld lines away from the black hole. Everything falls insider once it 9:18 ... enters the event horizon. There is no turning back at this point. It's a point of no return. ... 9:55 at this point you might say wait a minute this is all bullshit becaue the astronaut could never be inside a black hole it would either take forever, because time stops at the event horizon, or he would be pulled apart, that is , spaghettified on his way due to the high gravitational pull. Thiese are legitimate objects. But let me address how the issues of time dilation and spaghettification can be overcome. 10:16 Regarding time dilation, you may have heard that time slows down in a gravitational field. This is correct. And you may have heard that time comes to complete stop at the event horizon. 🕕This is not quite correct. 🕕If you are observing the astronaut falling in the black hole from somewhere far away, it would appear to you that he never enters the black hole, even if you watched him for eternity. This is because his photons can never reach you from the edge of the event horizon because all photons at the edge can only go inside. The gravitational well is so strong there that any photons there cannot escape to the outside. So the last photons you will see are highly redshited photons from just above the event horizon. You will never actually see him go insde. But from the Astronaut's perspective, 🕧time would tick normally as he fell into the black hole 🕜and he would simply just go right on through to the inside. This is just something that you can never observe from far away. If he were to look back towards you, well he wouldn't actaully see any visible light because most of the light near the event horizon would be so highly blue shifted that it would be in the x-ray part of the light spectrum, so he could not really see this light with his eyes. Infrared light and teh cosmic microwave background light now would be in the visible spectrum so the astronaut might see these. 11:37 ... 13:38 ... now the astronaut has made it inside the event horizon, what does he see now? First let's look at what happens to our light cone inside. We know that it was 45 degree 【 C = light speed, the first universal speed limit. 】 at the edge of the event horizon 【No 3d object exists there: 3d(3τ)||(t3)δ3 ---> 2d(2τ)1δ(1t)||(τ1)d1(τ2)δ2 , e.g. an electron (up-spin) plunges into Dirac sea, merging with its quantum field in the form of the equivalent energy. 】. As you might imagine it continues to tilt more and more al the way to the singularity. It goes from 45 degrees at the event horizon, all the way to 90 degrees at the singularity. Some characterize this 90 degree 【 D = dark speed, the second universal speed limit i.e. the maximum rate of spacetime expansion in the second inflationary epoch. 】 shift as a "switching" of place between time and space 【Supposedly the light cone is 90 degree at the singularity of an edge of another event horizon on which Dirac sea sits, in terms of the cosmological model of Bible, the singularity is a geometric point of the cosmological buffer zone from 54 C-QUANTA-R5, the stage of Dirac sea, which plays an important role in generating an electron (down-spin) as long as Dirac sea gets an input of an equivalent energy elsewhere back to Planck world.】This is not an accurate characterization. One of the hallmarks of general relativity is that the choice of coordinate system really makes no difference in the characteristics of spacetime. One could choose a coordinate system where no such switch occurs. But it would describe the same spacetime inside the black hole. The singularity, if it exists, is really every where in the sense that its gravitational well will be felt in everydirection, whether he goes sideays or backwards, NO matter which way eh astronaut would try to move, he would will still be moving towards the singularity. Since time can only flow one way, it means that all future events lie at the singularity. The singularity now becomes an inevitable moment in time. 14:46
I could not find l mathematical symbol tile on my keyboard 🎹 on my smartphone TCL
Super fascinating! Love it!
Beautiful explanation. Thank you.
What about the edge case of a neutron star just shy of being a black hole? What if I add just one gram of matter to it? Would the inside morph into a singularity instantly?
This is a great question that I have also pondered. I imagine there will be "nucleation sites" where microscopic black holes (probably the size of the Planck distance) form and then grow and merge with others. How fast this happens will depend on how quickly all the particles falling into these black holes can shed their momentum, remember they have to somehow go from their current momentum to zero at the singularity. Conservation of momentum says that this energy cannot just disappear, so it has to be radiated as light, gravitational waves etc. and transfer to other particles that will escape the overall gravity well at very high speed probably. This is what I can never understand about these animations: What happens to the momentum of the infalling astronaut?
@@ebenolivier2762 >Conservation of momentum says that this energy cannot just disappear
Nigga please, redshifted photons lose their energy to nothingness
@@ebenolivier2762 It is simpler than that, the momentum is just energy so once it is inside the growing event horizon (imagine some matter falling towards the centre of the neutron star, 'nucleating' a single black hole near the centre and then pulling the rest of the neutron star towards that central black hole) it will just become part of the black hole mass. Probably all of that will happen in a microsecond.
Penrose drew a diagram of core collapse in his famous paper. The horizon forms at a mid radius, before the singularity, and as matter crosses it, it grows to the final radius.
Regarding the mass limits, the neutron star runs out of degeneracy pressure before it’s a blackhole, so it starts to collapse before there is a horizon. The radius at the limit is around 12 km, and the final horizon is around 7.5 km…so there is a no man’s land.
Not sure how fast the collapse is, tho. All I heard was less than second
Lots of uncertainty in the equation of state of nuclear matter….unlike white dwarfs, where we pretty much know how electrons behave.
@@tonywells6990Yes, but if the energy becomes part of the BH mass it is forever cut off from the rest of the universe since nothing can escape a BH. This will violate conservation of energy/mass won't it?
the astronaut falling into the blackhole looks really high. It must make his experience extra special.
Came to the comment section for this lmao
I can only conclude observing this astronaut that the solution to unifying quantum mechanics and general relativity is DMT
This is my favorite Arvin video, to date !!!!!
I like how you explain things and break things down
What blows my mind thinking about this is, gravity becomes so strong that your light cone only points to the singularity. Anything beyond the event horizon is your past. All your possible futures only lead to the singularity.
And on top of that - the singularity is not a point in space, but point in time…. Space becomes time and time becomes space… awesome)))
Very well made video, but I think there is a mistake at the end : after crossing the horizon, the light behind you wouldn't become highly blueshifted, it would instead be redshifted, and it wouldn't be concentrated into a beam but still occupy a whole hemisphere behind you. This can be seen in the simulation by Andrew J S Hamilton which was briefly shown in the video.
Why would it be a hemisphere? Shouldn't it be a funnel (cone like structure) as all lights rays tends to convergence towards the singularity?
@@ActionReplay91 No, ingoing null geodesics look kind of like logarithmic spirals below the Schwarzschild horizon (globally), they are not all falling radially inwards in general. Therfore, they can 'hit you from the sides' as well. In simpler terms, it looks like this bc. of gravitational lensing (as it was successfully quoted from Andrew Hamilton at 12:00 in this video, yet messed up somehow at the end). The relativistic beaming/aberration only happens when you try to maintain a constant Schwarzschild r coordinate (as pointed out by ScienceClic).
@@user-hq3dq3vx5x just a question - let's hypothetically supposed a that an observer is under acceleration due to gravity (before hitting the singularity), and will that observer be able to distinguish the two light rays? The ones radially falling directly inwards Vs. The ones spiralling towards the centre?
@@ActionReplay91 Please do not use the word 'acceleration' in this context. The astronaut is a free faller. Free faller means timelike geodesic motion. On these wordlines, proper 4-acceleration is 0 by def. I am not entirely sure that I understand your question properly, but yes, oc. he can estimate/tell the difference, if he knows how the background stars would look like without the lensing effect of the black hole. (It helps very much of course if he is familiar with GR and raytracing.)
Excellent as uaual. Thanks Arvin
I really enjoyed this one. Entertaining and informative, thank you 🙏🏻
If time appears to come to a complete stop at the event horizon, then does that imply that the event horizon is infinitely far away?
Yes. The reason you cannot leave a bh is that outside is the past, and you can’t go to the past. Curved time is just really weird.
@@DrDeuteronActually, the reason a bh can’t be escaped is due to the gravity preventing anything from doing so. The past is always the past. I can go into my home, when the outside could be considered the past, as it’s where I came from. But I can exit said house because no FORCE is preventing me from doing so. Nothing to do with time. The notion that the past is always outside and the future always inside the eh is merely consequential, but it isn’t what is physically preventing anything from exiting. The spacetime curvature is too high, that’s what prevents escape, but frame dragging also adds to the difficulty of departure.
@@aaronperelmuter8433 I’ll go with Kip Thorne’s explanation over yours.
Error: 11.29. Light falling into the black hole is RED-shifted, not blue-shifted to the in-falling observer. Upon crossing the horizon the in-falling light is stretched to twice its emitted wavelength.
In fact, you're right no matter how fast it's going your reference point is slower than you and you're running away from it or it's going away from you, so it goes red like what we perceive with telescopes and call Hubble constant!
this video is full of misconceptions, errors and popular myths, it's wrong
@@trucker-lolwhere's your video with the correct interpretation and math
nothing stops at the point of no return
@@tylermcnally8232lol he don't have one
Arvin you're the best my friend
Fascinating video.
Aww sweet nighttime upload! Great vid too. Light moving equally in time and space is astounding
It's a convention, a choice of units where "speed of light" = 1. Astounding is that it is the same for all observers.
what an awesome video, great job.
This was so good! Thank you so much!
Astounding explanations !
Fantastic video❤
Excellent episode!
Nicely done
Thanks Arvin
Love your work 😊😊😊
Excellent! I enjoyed this one. Thank you.
The exploration of such fascinating ideas pushes the boundaries of our understanding and drives scientific progress. Keep the curiosity alive - the future might hold some incredible revelations that could change our understanding of space, time, and the potential for traversing the continuum in ways we can’t yet imagine!
This is the best video, I want to hear more about that last bit of inner and outer event horizons
Love this channel
These are among the best science videos on RUclips.
This wasn't actually the sort of content I was in the mood for, but I've such respect for Arvin that when the algorithm suggested it, because it was him, I knew it would be good...
Arvin Ash is one of those fine channels you can confidently click the up-thumb before the video starts :)
First time I understand your video fully
Very well explained
Wow amazing content this guy is the best
It always amazes me how stable black holes appear to be (high entropy, Hawking radiation), it’s already collapsed, but yet it feels like iblack holes are like dark stars in principle.
Black holes if they are not piddlingly pico, femto or atto scale, i.e. smaller than an electron and comprised of several thousands to a few hundred thousands of tons of mass, effectively act like memory devices, near-perfect spacetime capacitors, that only leak "spacetime charge" slowly, like a near perfect capacitor, via Hawking radiation until they are piddling, then they flame out brilliantly like a big bang singularity?!
Look at black holes, the matter disappears into curved spacetime past the event horizons of the near perfect spheres, but the universal acceleration or gravity of the disappeared fermions etc. is remembered and projected outward at the constant speed of light; we'd still orbit our black hole sun if it collapsed to a singularity right now, but darn it we'd get pretty cold after 8 minutes or so? We'd orbit that sun for a very long time, until it got sucked into a larger memory sphere far into the future?
Not to worry, thank Schwarzchild, Chandresekar, Albert and Oppenheimer for the future memories?! Like Dali showed, it's persistent?! As Frank & Furter sang, let's do the time warp again?!
Thank you. I understood everything.
This should be amazing! 😊
This, and other videos like it who base their presentations on the latest theoretical work, are profoundly important to the accurate, popular understanding of science.
Since black holes are so ridiculously far away we will _never_ be able to send a probe or a human to examine them. Thus, this theoretical work is what we will base _all_ of our science on.
Kudos to Prof. Ash! 😊
We do observe them
Thank you! The widespread saying of space and time switching inside a black hole never made sense to me. It always feels more like space gains some time-like property as in it becomes directional towards the singularity. Good to have this verified by your video!
No bullshit here! Love your channel Arvin!
Thanks!
That was an awesome show by the way.
Great video... a question, please if you read this Mr. Arvin Ash: Are you going to release some video about your visit to Copenhagen Atomics? Thank you as always.
Yes, that's coming. It will be a full video on molten salt reactors.
That was nice and I like the notion that time travel may be (maybe) possible with the help of rotating black holes :)
I don't think traveling back in time is possible but I don't feel the need to disprove a theory that hasn't been proven to begin with. The burden is on the time-travel enthusiasts.
Arvin did do a good job of showing the difference between apparent time stoppage and actual time stoppage. Actual time stoppage at the event horizon is impossible. In GR (whether a weak field or extremely strong) clock comparisons run in opposites. If my near event horizon clock is running much slower from your distant perspective, then I will see your clock running much faster (as long as the signals are infrared, as Arvin pointed out). But, if my clock comes to a complete stop, then for me an entire eternity outside of the horizon will fly by at infinite speed. That can't happen because the horizon will still continue to have time intervals as a possible future collision with another black hole would register. Therefore, my clock could never come to a complete stop.
@@chriskennedy2846 I am not a proponent of time travel but look at some QM paradoxes, including delayed choice quantum eraser, and work of people like Aaronov and Vaidman, maybe others as well. Looks like the wave function is propagating forward and backword in both time directions. Not sure if this prooves anything but is strange at least :)
@@tiamnikSabine Hossenfelder has a pretty good video on this "DCQE & time travel" being a misinterpretation of the physics. And, as the commenter above stated, a BH merger would still have to register as "forward in time", even though the far-observer's clock would appeared to run at infinite speeds. Something has to give there, as both cannot be true... And because of all of the logical breakdowns of time travel and causality, I think it's safe to say that TT isn't possible. Obviously no one can prove that (especially not a novice like me), but it takes a lot more leaps in rationale to accept it than it does to reject it.
I like this Arvin Arsh channel.
This is a really nice video about cosmology, thanks Arvin, great!
A lot of people try to explain the functionality of black holes with a vacuum cleaner, and that's a bit superficial in my opinion.
There are different categories of black holes (primordial, normal, massive, supermassive and the powerful variant, the quasar) from galaxy rotor to matter converter and galactic power house, it really has it all.
But one thing is certain: without them our universe could hardly function!
There’s only one single type of bh, what you describe as different “types of bh’s” are actually all the exact same thing, just that some are heavier/more massive than others. But that certainly has no effect whatsoever on the type of bh. You might sub-categorise bh’s with electric charge and those with angular momentum, but even those are STILL the exact same type of physical phenomena as all other bh’s. That’s the very definition and meaning of the famous quote, “bh’s have no hair”.
@@aaronperelmuter8433 "category" was the world, sorry I am not English or Northamerican, the perfect translation sometimes fail...
@@thekingofmojacar5333 my apologies, your English is excellent, by the way. Better than many people who only speak English.
i like how you deskribed the singulaity so much
Thanks Dear Arvin Sir for your detailed explanation videos related to science and universe.
Would you please make a detailed video regarding quantum fluctuations and how these fluctuations give rise to space time matter and energy. Anyways I had enjoyed all your videos and they were great.
Lots of love ❤ and wishing you a longer prosperous life ahead. Love from INDIA 🇮🇳.
Very interesting stuff
I've watched so many of these videos on theory and this is probably the best one yet... where is your video on time travel? I don't see it in the description
@Arvin - How about Higgs field switched off inside the black hole? And all infalling particles (dust) will be massless. And singularity can be visualized as a ball of massless particles occupying a single state.
❤ Very good 👍🏼
masterfull once again my friend!
though, neill de grasse tyson would probably disagree, he recently spoke out that he figures the possibilty for a black hole to actually create an entire new universe inside it with its own tick of time.
much like i hypothesised a couple years ago but my intuition tells me i'm wrong, or at least a whole new set of rules in physics would apply
Arvin,
Could you make a video on the theoretical physics of the possibility of the existence of parallel universes? It will be appreciated by many of your subscribers.
Fascinating I love to learn about blackholes, to rap my head around blackholes I like to think of them in 2D and 3 Dimensions
Arvin, I learned something.
listening to your explanation my visualization of the singularity goes like this, the singularity has a physical "point" but it is not a physical "object" when something passes through/comes into contact with the singularity itself, it will be get "folded" in a sense, like my brain pictures folding a piece of paper evenly until it cant be folded anymore but combine that with like a whirlpool in water, so ur folding in a circular formation overlapping over itself until u fold out of existence
This space-time bending thingy is mind bending. While I find it fascinating, I can never really wrap my mind around it.
Hi Arvin, thanks for this great video. Could you discuss the very controversal position of the RUclips channel Dialect. He published few days ago another excellent video about one important aspect of the Einstein's theory which that he based his whole theories on one important assumption: that the 2 way measurement of speed of light is the same on its way from and back to the signal emitter. But if we assume that the speed of light can vary....well the time dilution and lenght contraction don t exist anymore and time becomes absolute again! This has been tackled 60 years ago already. It would be interesting to hear your toughts on this.
Imagine if you fire a laser pulse at a target, would you think the pulse would be detected at a time when its light is expected to reach based on it moving at the speed of light (the correct answer) or at a totally random time because light speed can vary (the wrong answer)?
*FASCINATING!*
Does the warping of space time include condensing it (aka compacting it)? If so, does that effect how the volume of an object would appear to an outside observer (theoretically of course since an outside observer couldn’t actually observe it)?
For example, volume is a measure of the space an object takes up (a one cubic meter cube is 1 meter x 1 meter x 1 meter). But if space distortion includes it being condensed/compacted would one meter appear smaller if an outside observer could see it?
I’m familiar with length contraction. But to my understanding, that only applies to relative movement and only in the direction of travel. I’m talking about a given physical space being crunched or shrunk (for lack of a better word) such that an object in that space is also shrunk.
Black holes are mind bending as much as they are space bending. As always, thanks for the fantastic video.
Yes, together with gravitational time dilation comes gravitational length distortion, such that 4D volume element in vacuum remains the same - the shorter time gets the longer space gets in radial direction. As for how some object would appear - that depends a lot on where it is, how it moves and where we're looking from.
12:51 That's incorrect, because the "r" coordinate is not a physical distance, it is only a coordinate ( that is spacelike outside the horizon and timelike in the interior).
Actually, in GR textbooks , the "r" coordinate is usually called " the areal radius" , because it is defined by the surface area of cocentric spheres.
The reason why tidal forces are weaker near the horizon for more massive Black Holes is that they're inversely proportional to r^3 {~M/(r^3)}.
The so called " surface gravity" ( this is a GR technical term, it's not the "gravitational force" on the horizon!) is κ= 1/4M ( for the simple non rotating, non charged BHs), where M is the total mass of the Black Hole.
And R_schwarz goes a M, so the tidal “force” at the horizon falls as mass to the fourth….and for a ten million solar mass black hole, the forth power is….big.
Wonderful video, Arvin. So, instead of finding one outside the event horizon, as in Author Clarke's "Neutron Tide", we'd find that star mangled spanner near the singularity.
This is so far the best explanation of what happens when you go to a black hole video.
U are simply aweseom ,
Fascinating! What made of singularity inside the blackhole? Is this point of singularity is ending or beginning of another space?
Wow, that's exactly how I was imagining it. Some internet physicist was arguing with me that you can see in front of you while looking at the singularity behind the event horizon.
WoW! It definitely makes my daily problems look infinitesimal small
Thank you for an explanation of what might exist inside an event horizon. Could it be a singularity that has a physical entity, something like a magnetar but far denser?
it's possible, but as I said in the video, it would have to be an exotic form of matter - that is, it has to be someting that our theories currently cannot describe.
Great !!! Finally someone is been to a black hole 👏👏
Great video as always. One question: are all astrophysical black holes rotating? Is there a mathematical proof of this? If so, wouldn’t the shear stress beyond the event horizon rip apart matter before it gets to a singularity? This is the gist of the firewall hypothesis.
Once you enter the Event Horizon, space and time switch place.
The singularity is not at the 'center'. It's in the future.
Any movement in time, will bring you close to the center/singularity.
Exiting the black hole is just as impossible as going back in time.
As you stated in this video, the 2D space and 1 dimension of time light cone applies in a flat space (or Euclidian space).
What happens to the shape of a light cone in Euclidian space when space-time begins to curve or distort due to gravity?
For example a 45 degree angle in Euclidian space is no longer 45 degrees in non-Euclidian space
ScienceClic would be proud of this video!!!
Arvin, Blackholes are probably canvas for second tier of quarks and we are probably in one and missing the tier before up and down quark and existence of Anyons kinda hints that. what do you think about quantum knots ?
Brilliant review, professor Ash. I have a question about what you say at 10:30... If the light appears to stay there forever as we watch the astronaut fly into the black hole, then we should be able to see the redshifted light of everything that's ever fallen into the black hole. I must be missing something.
That redshifted light has an undetectable long wavelength, so we can't see it!
The unperturbed radially outgoing light at the horizon remains forever. We of course can't see it (unless we fall in behind the astronaut) as it never escapes into the exterior spacetime. That said, you are correct that there are photons in photon rings outside a rotating black hole that contains the history of what fell in.
You’re correct. Curved time is weird.
amazing
Would it be possible if you made an alcubierre bubble to go inside a black hole and then exit it?
I may be way off, but I'm thinking about the spacetime diagram. We always remove a spatial dimension to make it easier to visualize the time dimension and the worldine looks like a 3 dimensional cone. But I think about adding that other dimension back into the diagram and what would that look like. Obviously we can't visualize 4 dimensions, but it seems like it would still appear to expand outward, but in every direction simultaneously since we can't observe a fourth spatial dimension. That sounds a lot like Hubble's law. Everything in the universe is moving. Maybe the expansion of the universe is just the universe moving through time. Is that a thing, or am I way off? Maybe he addressed this in the video, I was too busy typing this.
Could you please do a feynman disc paradox with videos of what happenes? Cause if it works as i believe it works you could use it as propulsion (while rearanging a bit, where the solenoid is toroidaly wound and positive charges are outside, so instead of angular momentum you would get a vector)
There is no paradox (the angular momentum in the field is transferred to angular momentum in the disk) but I don't know what you mean by propulsion.
Well, if you make the solenoid circular (or toroidal) and put the charged spheres on the outside, upon "opening" the solenoid the angular momentum would be directional instead.
Than you could charge the outside spheres negative and close the solenoid, make the spheres positive and again open the solenoid.
You would use the field as propulsion@@tonywells6990
Thank you, Arvin, for your excellent content! I don´t speak english and i'm not physicist, so I'll try to make it understandable. I have one eternal doubt about time dilation near the event horizon: if time stops from our perspective near the horizon, does it mean that the astrounaut see the whole story of the universe in fast motion??
And if that is the case: how is it possible to have black holes that dissapear due to Hawking radiation if nothing have ever entered to the BH in our universe??
I hope I'm clear
Thank you!!!!