Very sensible. One of my favorite presentations on Special Relativity. He does not overwhelm you with complex scenarios, his progression is piecemeal and smooth, and without too many side distractions like other presentations that seem to get you lost in the maze of intensive informations and too many scenarios.
The best video on special relativity equations explanation I could ever get. Very nicely explained. Conclusion, I could understand by special relativity is the basis that the speed of the light is constant irrespective of the fact whether the observer is moving or the source of light is moving which is not the case with other bodies except light. Many many thanks to the professor of the video.
I love your videos, I wish I had tried harder at science at school. You have a wonderful way of explaining complicated ideas in a straightforward fashion. A life long love of science fiction has brought me here to learn more about relativity and then I get lost in your other videos on nuclear fusion in stars and others on black holes and dark energy. Thank you for making these videos!
Yes I did. Its in the Special and General Relativity playlist. I have produced this version specifically for the A Level course where it is not necessary to go into the detail I have included in the earlier video. I will shortly do another General Relativity video which just covers the A level material.
Wow. I am amazed how articulate you are in explaining rather convoluted topic. You are truly remarkable person and I really appreciate this. I watched this video as if I am watching a movie.
You are right. If two observers are moving apart at a relative velocity of v, each will see the other's clock move more slowly. It doesn't matter if one is stationary and the other moving. They will both observe the time dilation effect in the other's clock.
UNDERSTANDING TIME (AND time dilation), AS ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE): E=mc2 is taken directly from F=ma. BALANCED inertia/INERTIAL RESISTANCE is fundamental, as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). This explains F=ma AND E=mc2. The stars AND PLANETS are POINTS in the night sky. Importantly, gravity (as it has been written) is an INTERACTION. TIME is NECESSARILY possible/potential AND actual IN BALANCE, as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). Gravity AND ELECTROMAGNETISM/energy are (CLEARLY) linked AND BALANCED opposites (ON BALANCE), as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). This NECESSARILY represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual IN BALANCE. TIME dilation ULTIMATELY proves ON BALANCE that ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). This explains F=ma AND E=mc2. Again, BALANCED inertia/INERTIAL RESISTANCE is fundamental; as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). Gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE (ON BALANCE), as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE) !!! This explains F=ma and E=mc2. This NECESSARILY represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual (IN BALANCE), as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). This ALSO (CLEARLY) explains why the rotation of WHAT IS THE MOON matches it's revolution !!! Great !!! (Carefully consider what is THE SUN along WITH the fact that the stars AND PLANETS are POINTS in the night sky. NOW, ON BALANCE, carefully consider what is the speed of light (c) !!! LOOK down at what is THE EARTH/ground ON BALANCE. NOW, LOOK up. The sky is blue, AND THE EARTH is ALSO BLUE !!!) Inertia/INERTIAL RESISTANCE is proportional to (or BALANCED with/as) what is GRAVITATIONAL force/ENERGY (ON BALANCE), as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE) !!! This explains F=ma AND E=mc2. This NECESSARILY represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual (IN BALANCE), as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). AGAIN, BALANCED inertia/INERTIAL RESISTANCE is fundamental. Gravity is (CLEARLY AND NECESSARILY) proven to be ELECTROMAGNETISM/energy (ON/IN BALANCE). It ALL CLEARLY makes perfect sense, as BALANCE AND completeness go hand in hand !!! AGAIN, TIME dilation ULTIMATELY proves (ON BALANCE) that ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). Great !!! This NECESSARILY represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual (IN BALANCE). INDEED, TIME is NECESSARILY possible/potential AND actual IN BALANCE; as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). AGAIN, the stars AND PLANETS are POINTS in the night sky !!! Consider what is the speed of light (c) ON BALANCE. Great !!! NOW, CLEARLY consider what is THE EARTH/ground (ON BALANCE). Finally, also notice what is the black “space” of the physical structure that is THE EYE. NOW, carefully consider what is THE SUN !!! It ALL CLEARLY makes perfect sense. Great. By Frank DiMeglio
I was wondering whether it is possible to download and save these videos, and if not whether that's something that could be made available by you. I love your content, use it all the time. Also, thanks for all the effort you put in the vids. Keep it up.
18:00 I'm left confused because x' is defined as x' = x - vt = 0, and then immediately c is defined as x'/t' (which means c =0?), and the equation is later divided through by x' (division by zero). I think x' needs clarification between its definition as x' = x - vt = 0, and x' = ct'.
the best explanation i've ever seen...... i was searching for such an explanation for a long time... i couldn't understand how time dilates if light speed is constant for all frame of reference... thanks.... this is kind of explanation i was looking for... HOWEVER THE VIDEO DIDNT EXPLAIN HOW MASS IS RELATIVE..... OR DID I MISS SOMETHING??
if you look in the playlist on special and general relativity you will find a series of five videos on special relativity and I deal with mass there, in particular the final video.
Robert Eagle I have many doubts regarding this.. your response is highly appreciated... we have reached x' = x - vt ------------(a) and we get x = x' + vt assuming t = t' we get x = x' + vt' -------------(b) now (a) and (b) are two different equations... how can we apply same error terms in both..... those could be two different errors... we cannot be sure those are same errors... my point is, it should be taken like this..... x' = (x - vt) Y x = (x' + vt') B where Y and B are error terms..... after watching your video, i searched every where about lorentz tranformation... but it very long and complicated everyhwere else not as simply illustrated as in your video... thats why i am coming back to you.. thats why i tweet you on twitter.. if you are willing to respond i have other questions too.....
Shabeer Mohammed As you will appreciate, I'm trying to keep the explanation is simple. The essence of the argument that neither observer has any reason to think that they are any more or less wrong than the other.
At 11:26,the speed of the ball isn't 10mph+30mph=40mph.Actually,it will move slighty slower than 40mph and the speed of the ball will be 39.99999999964mph. The formula is (v1+v2)/(1-v1*v2/c^2).
Relativity does produce weird results. But as other others have tried to explain, it is precisely because the speed of light is constant that you get these relativistic effects of length contraction and time dilation. The important point is that from your perspective everything in your frame of reference appears to be normal but in everybody else's frame of reference you will measure shorter lengths and slower times.
Your explanations r fantastic!! They've really helped me a lot in understanding special relativity and why does the bizarre phenomena actually occur. Looking forward to watch ur other vids.
A frame or "reference frame" essentially means everything that is at rest local to you. So if you were on earth and I was on a spaceship, we would be in two separate reference frames. The point being that if I try to measure a distance or a time in your reference frame I might get a different result from the one you would get by measuring it local to you.
How beautiful to see the E=MC^2 famous equation comes from!!! Brilliant presentation, Thank you. Surprising to see how simple SR equations compare to GR where it’s more complicated.
I got to 5.04 and my head went fuzzy and I fell off me chair. I've cracked my screen. Can I put a claim in? Can anyone know ensigns email adress. Can somebody help I think I hurt me head. I've got fuzzy fluffy yellow pants on now.
Don't worry...he is rather trying to keep it extremely simple....for example when he derived the Lorentz transform...it was rather to be derived in a much more complicated manner...so try to be calm and devoted to understanding this and I am certain you will
Awesome! Thanks a lot for this video! For the first time I understood why length contraction makes sense and the thorough way you explained the formula's really helped me vision how and why it actually works(and how those formulas were derived). I am wondering though,if you devide ct=ct'(some stuff)*gamma by c, you don't devide gamma by c. Why is that?
But that was the point. Since the earth is moving one would expect that if the measured speed of light was determined by the speed of the source/ observer then the speed of light would vary depending on whether it was being measured in the direction the earth was traveling or perpendicular to it. But no matter how they varied the angles of measurement they couldn't get a difference.
It's always the relative effect which matters. If you travelled onboard a photon then from your point of view time would pass in the usual way. But all the clocks in the world around you would appear to stand still. Similarly everyone observing your watch would say that it was standing still.
Very interesting. But what remains unclear is at 18:09 when you write c=x/t =x'/t', this applies only if x and t refers to the distance and time spent by light. But then on you assume that x, x', t and t' are universal coordinates, so it is confusing because in that case v=c so gamma is actually 0 (limit case)
I only did CSE level maths at school with very basic algebra (many years ago), but I managed to follow this excellent video. I wish I'd had someone like you as a teacher at school instead of the monotonous old hag I did! Thanks :)
You (Dr PhysicsA) say (9:01): "But the trouble was that every time they (Michelson and Morley) moved the equipment, the fringes didn't change". But Michelson and Morley themselves reported: "The relative velocity of the Earth and the aether is probably less than one sixth of the Earth’s orbital velocity, and certainly less than one fourth." In other words, the fringes DID move. Please explain the discrepancy between their and your versions.
That's a good question. If we move side by side on a motorway with identical acceleration then we will stationary with respect to each other. Yet each of us can clearly tell we are accelerating.
Towards the end of the video when you were using the binomial expansion, how come you ignored any additional terms simply because they would be too small? Surely whether it’s very small or not doesn’t change the fact that it’s more energy that the equation isn’t accounting for
On internet people are saying that Michelson and Morley had a null result because the light source was on the moving earth and not in the stationnary eather.
hey i understand all the video , but the only part that i have questions about isn't covered : Why mass is subject to relativity i do understand why distance and time is subject to but not why mass is, What is the mathematical prove of that. THANKS FOR ANY ANSWER p.s Sorry for my bad english not my language.
(** Please donot ignore my doubt **) I cant Understand one thing in TIME DILATION that """If Gamma varies from 1-infinity(i.e. its value is increasing ) ,then anything multiplied by Gamma get bigger and bigger, so here Gamma is multiplied by " t' (local time) " so the value of " t' (local time) " should be bigger than " t (remote time)" .Hence in the video it shows that moving clock runs fast.
At 18:27 you said that c=x/t and c=x'/t' and then you replaced the values in x=x'+vt, but in the value of c, x and x' are the distance traveled by light and in the equation x=x'+vt, x and x' are the distance traveled by the observers so they do not refer to the same value. That's a bit confusing! Thanks.
Omar, because as your velocity approaches the speed of light time slows down and length contracts. However from your perspective time hasn't slown down at all.
I should have been clearer. The point I was making was that if a body is moving at constant velocity then you would be able to play snooker without realising you were moving. But if you were accelerating, the snooker balls would move across the table - for the same reason you feel pushed back in your seat when a car accelerates.
At about 33:20 speaker says "the light doesn't move" which is absurd. What he should say is the light moves perpendicular to V direction or direction of relative motion and not horizontally along V or direction of relative motion. This allows the person in moving frame to measure time in same horizontal place or what is called proper time. It is for this reason that x' becomes zero i.e that time is being measured in same horizontal place in the x' frame. The other i.e. the (static) observer does see the same (perpendicular) light beam travel diagonally and thus a longer distance.
The divide by zero isn't really an issue as x' = x - vt can also be written x = vt + x' when x' is non zero (I.e. when you move in your frame and I measure your total displacement). However it would be nice if there was a version of the video that explained this because it could be confusing.
Time and length contraction paradox. Imagine that a laser light is turned on during 1s at the back of a train towards the front of that train, moving across the x axis. The length of the train is c, at rest (for the observer in the train as well). The train travels at c/2, so gamma is 1.155 or 2/sqr(3). At t=0, both clocks are synced, and x=0. The laser is at the rear of the train, at x=0, at t=0. For a passenger in the train, the light reaches the front of the train after 1 s, as the length of the train is c. (Note that there is simultaneity for this event: the light reaches the front of the train at the same time and location, for any observer.) When calculating the elapsed times and positions for a stationary observer... there seems to be a contradiction: Method 1) If we apply time dilation formula, the time elapsed between the two events for the observer at rest is t2 = 1 * gamma = 2/sqr(3) seconds... In that time, the light has travelled 2c/sqr(3) = 1.155c, and that's where the front of the train must be. However the back of the train has also travelled at v=c/2, so it is now at 1c/sqr(3). The length of the train is x2 - x1 =(2c/sqr(3)) - (1c/sqr(3)) = 1c/sqr(3) = 0.577 ! BUT If we apply length contraction, the perceived length of the train is c*sqr(3)/2 = 0.866c, which contradicts that result. Method 2) If we apply length contraction formula, the length of the train for the observer at rest is 0.866c. That is 2c/sqr(3). The time front of the train is at x1=t2*c/2. (t2 is the time when the light reaches the front of the train). As light has travelled at c speed = x2 / t2, and the length of the train is x2 - x1, we get t2 = 4 /sqr(3), x2 = 4c/sqr(3), which contradicts the previous result. Method 3) If we apply the transformation x = (x'+vt') gamma, x2 = (x'+vt')g = (3c/2) g = c * sqr(3), t2 = x2/c = sqr(3). So I have missed something...
Isn't x always going to be larger than x'? Since it's always going to be between 0 and 1. and the root will also. X' times a number less than 1 will always make it smaller than it was originally. So therefore x is always larger?
At 10:30 I think there is a big leap from the speed of light being constant with respect to the aether to c being constant independent of the speed of the observer or the source. The experiment described would not definitively lead to the latter conclusion because the speed of the observer and source were 0 relative to each other.
Great lecture thanks. You tied a lot of stuff together for me. Finally i can derive the famous E=MC^2 formula. I feel like i should call some friends and celebrate,hahaha. :) Cheers!
Fantastic lecture. Thank you very much for the detailed and adequately paced run through the formulae. I have one question that despite my best efforts to research online I cannot figure out: Between minutes 00:40-02:20 in your lecture you explain the concept of the relative perceptions of two observers, none of whom can determine which one is actually in motion (or if both are in motion). If I am not mistaken this is the relativity of motion. However, all the calculations after minute 12:45 in the lecture assume that the observer on the platform is stationary, and the observer on the train is in motion (and this seems to be chosen arbitrarily as far as the relativity of motion is concerned). In fact, the observer on the platform could just as well be considered to be moving - together with the platform, etc., while the observer on the train could be stationary together with the train). The implications of this change in perspective are evident at 34:20-34:25 minutes, when the conclusion of time contraction should be that the local time (of the observer on the platform) is shorter because this time IT is travelling at close to the speed of light (which is the opposite of what we would get if the observer on the train were travelling, as assumed in the lecture). Perhaps my logic above is flawed, but I can't figure out where this is, and please help me settle this apparent paradox. My BIG question is why is the Lorentz transformation applied unidirectionally (only to the observer on the train), when in fact motion can be attributed to either observer? Why isn't the observer on the platform travelling at close to the speed of light; especially since to the observer on the train things would appear to be so. If we attribute all the motion to the observer on the platform (inversely than assumed in the lecture), or indeed we share it between the two observers, the Lorentz transform factor would apparently need to be applied differently. In particular, with regards to time contraction, if we (arbitrarily?) assume that the observer on the platform is travelling (with the platform and all), then time as measured by this observer would contract, while the observer on the train will measure a longer time. The thought experiment at minute 39:50 would mean that the observer on the Earth is travelling at close to the speed of light, and the observer on the spaceship ages by 10,000+ years. I must admit that applying the same principle of relativity of motion to the muon experiment at 41:20 would argue that muons stay still (which I appreciate is impossible ) and the Earth is travelling at 0.99 of the speed of light (which again I appreciate is impossible, because that would make the mass of Earth close to infinity). However, how can we be sure that the Earth is not in fact travelling at close to the speed of light (in relation to a frame of reference moving away from the Earth at close to the speed of light? Thank you very much for any insights!
+WX15 You make several points but all are resolved by the fact that yes, relativity of motion does indeed apply to all the situations. Do specify any of your questions though.
6:58 sir why you said both distance are about same not same ????? I am asking it because it confused me ....!! This is because as far is known this laser interferometer are super Extremely sensitive for naino or or pico levels of distance , so if we don't account both distance then its results will be huge error ??
Hi, I am a bit confused about the derivation of the lorentz transformation. The first thing it says is that (x = vt). Secondly it states that (c = x/t) which would mean (x = ct). Does that mean that (ct = vt) and subsequently (c = v)? But great video overall thanks!
Oh another thing is that you later established that (c = x'/t'), but earlier you established that (x' = 0). If you combine these 2 equations, doesn't that mean that c = 0) which cannot be the case since (c = 3x10^8)?
Very well presented. However, there is an anomaly. Einstein is stated to have claimed that he did not know about the Michelson Morley experiment. If that is actually correct, how would he have made the assumption that the velocity of light is constant in all frames of reference? Is there an alternative way of deriving this?
The idea was that if the experiment had two beams of light travelling at right angles to one another, then if the whole experiment were rotated and on the assumption that the Earth was travelling through the ether, then there would be a variation in time for the light to travel out and back again and that this would be reflected in an interference pattern.
Here's something to look at... Ship1 at rest at top: T--------------------N N--------------------T The moment when T of ship1 is lined up with N of ship2 must be the same moment in both frames of reference because there is only 1 moment when this occurs. At this moment for someone at N of ship1 to see T of ship2 they have to look in 2 different directions simultaneously. This is impossible. N of ship1 is simultaneously both passed and not passed T of ship2. This is impossible.
With regard to the Michelson-Morley experiment - if they were trying to detect a difference of elapsed times for c through each arm of their apparatus how were they able to determine if the returning "split-twin" photons were from the same original photon split at the beam splitter? If the aether doesn't exist why does The Standard Model of Physics say photons propagate (are waves) through the electromagnetic field? Where does physics say a photon detaches from the electromagnetic field and travels through empty space? My reasoning via The Standard Model of Physics says the aether does in fact exist - but today we just call it the electromagnetic field. Further reasoning says the electromagnetic field sits idly by (at rest) in the back ground throughout the universe. Does this give us a preferred reference frame? Maybe the reason physics is stuck is because we are hanging onto the belief that space exists - even though we have zero direct proof it exists - all physics, events, forces, energy, etc., are accounted for with fields. Maybe space is just an aggregate of all the fields that make up our universe.
If a remote observer sees a uniformly moving frame shine a light in the direction of motion then the remotely observed net velocity of the light cannot exceed c, but the frame is moving, so the light has to go slower 'inside' the frame but due to the frame motion it is still remotely observed to be moving at c. So the remotely observed light is in 'slow motion' which puts all events in the frame in slow motion which is a way to say time is going slower because we have no universal idea of time outside of comparing amounts of stuff happening, unlike Newton. Is that right?
Great vid, really helps. I tried deriving gamma like you showed and of course went wrong at the first opportunity! Around 16 mins you say from x=vt then 0=x-vt, and I'm good with that. My brain, however chose to go the other way and say 0=vt-x, mathematically fine I thought, but it's lead me by following through with the subsitutions of x and x' to the conclusion that v=2c which is clearly nonsense! Is there a reason other than "it works out well" to take the route that you did? Is there a reason why my version has gone so wrong or am I making some fundamental error? Surely it should work out fine either way!
I think you made a small error at 12:20. If the direction of the light was travelling as you indicated the expected measurement of the speed of light to the observer on the platform would be c-30. Not that it matters because the expected value is wrong anyway! Thank you for the video :)
And that means: a given X is passed in t(v) time when travelled by you or me and in t(c) when travelled by light itself. So c/v = t(v)/t(c). Why do we now need a correction term here?
....continuing at about 19 minutes he writes x' = ct' having called x' = zero at 16 minutes. Were x' zero as speaker claimed, then t' would have to be zero destroying all subsequent argument. So x' should NOT be made zero irrespective of its state of motion. One can still write x' = (x - vt) or more fully, x' = (x - vt)gamma. Overall the speaker is doing a very fine job. Better than most. My congratulations FWIW.
Yet again at about 37:52 speaker says that in Alice's frame "light is not moving". Better to say that light does move but does so perpendicular to relative motion so that Alice measures proper time in same horizontal place. It is for this reason X' becomes zero. "Non moving" or "stationary" light is not respectable. Speaker should introduce concept of "proper" time and time being measured at same versus different horizontal places. Otherwise dumb expressions as "light is not moving" get bandied around. Any time interval read using a horizontal beam of light i.e light directed along the direction of relative motion will be read at different horizontal places and will not be "proper" time. These times will differ depending upon whether the light is shone forwards or backwards to direction of relative motion demonstrating "failure of simultaneity". The different sign before vx/c^2 and vx'/c^2 represent this asynchrony. I don't believe speaker addressed this. Nevertheless he did a good job.
lets assume bob is stationary and i am moving near speed of light, so that time bob measure is t and I measure is t prime. according to time dilation, t is larger than t prime which means t prime is smaller than t. That means the time i measure is shorter than which bob measures and also that mean bob measure large time than me. In the beginning i told i was moving near the speed of light. but what i feel is i am stationary and the environment including bob moving away from me at near the speed of light. now the time i measure is t and bob measure is t prime. according to time dilation t is larger than t prime. so this time i measure larger time than bob measure and also than mean bob measure shorter time than me. could this both could be possible? Confusing!!!!!
If you push the ball in a direction perpendicular to the direction of the train the person on the platform would measure a different speed to the one he would get if you push the ball in the direction of the train.
However, in the MM experiment the device, the person looking at the results, are all attached to the earth and moving with the earth. In order to prove that the speed of light is an invariant, you would need to get away from the earth and use a telescope to see that the beams of light take the same amount of time. As things are, it's like you're on a moving train throwing balls at the roof and at the wall in front of you. If the distances the balls travel are the same, you will find that they travel the distances at the same time.
How do you know which side to apply the Lorentz transformation to? Is it always the remote side? If one side is the "remote" side, does that mean the result you get will be from the reference frame of "remote" or "local"?
This is very good presentation. However, the first derivation on the value of gamma has stumped me. It just seemed like an algebraic wizardry, the physical basis of which is not at all clear. However, the very basic observation that the speed of light is constant in both frames of reference is highly counter intuitive.
I think he confused t' for moun with t for observer. He used t' = 6.73...which is our or observer's measurement?? According to his formulas before t>t' ... he changed the formula but the results are ok.
In the Last part we find E=mc2. So, that means photons dont have energy? Since they dont have mass? But sun light gives energy to earth, how does this happen?
in minute 19:00 there is a bluffing - if x=vt, then u cant say that x=ct... x and t in the first equation are different from the ones in the second equation, Am I right? or wrong?
Hi, as for the muon experiment that you mentioned, isn't the muon accelerating as it falls? How can we apply special relativity in this case? Thank you.
For Michelson and Morley's experiment, let's say that the speed of light is affected by the earth's movement through what they called the "ether", this means that no matter what angle you rotate the setup, the time for one beam to reach the meeting point will always be more or less than the time taken for the other beam to reach that same point and they will also get the same result always! what is my mistake here?
Mind if I take a stab at this one? At about 5 mins in, there's an explanation involving rowing across river. The experiment is very like that, rotating the experiment is the equivalent of rowing in different directions, the time taken will vary, in m&ms experiment, the pattern should vary ＩＦ the light has been moving at different speeds.
Very sensible. One of my favorite presentations on Special Relativity. He does not overwhelm you with complex scenarios, his progression is piecemeal and smooth, and without too many side distractions like other presentations that seem to get you lost in the maze of intensive informations and too many scenarios.
Your videos are so easy to follow and learn from. Cheers from a second year physics major in the US.
The best video on special relativity equations explanation I could ever get. Very nicely explained. Conclusion, I could understand by special relativity is the basis that the speed of the light is constant irrespective of the fact whether the observer is moving or the source of light is moving which is not the case with other bodies except light. Many many thanks to the professor of the video.
I love your videos, I wish I had tried harder at science at school. You have a wonderful way of explaining complicated ideas in a straightforward fashion. A life long love of science fiction has brought me here to learn more about relativity and then I get lost in your other videos on nuclear fusion in stars and others on black holes and dark energy. Thank you for making these videos!
I'm a mechanical engineer and my major have nothing to do with this, but I'm interested and you're a good teacher :).
Before this video, I only had a shaky understanding of special relativity, but now I can clearly grasp all the concepts involved, so thank you!
Yes I did. Its in the Special and General Relativity playlist. I have produced this version specifically for the A Level course where it is not necessary to go into the detail I have included in the earlier video. I will shortly do another General Relativity video which just covers the A level material.
Wow. I am amazed how articulate you are in explaining rather convoluted topic. You are truly remarkable person and I really appreciate this. I watched this video as if I am watching a movie.
Nice, that was one of your best. You really should win some kind of award for your didactic prowess. Keep em comin!
You are right. If two observers are moving apart at a relative velocity of v, each will see the other's clock move more slowly. It doesn't matter if one is stationary and the other moving. They will both observe the time dilation effect in the other's clock.
UNDERSTANDING TIME (AND time dilation), AS ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE):
E=mc2 is taken directly from F=ma. BALANCED inertia/INERTIAL RESISTANCE is fundamental, as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). This explains F=ma AND E=mc2. The stars AND PLANETS are POINTS in the night sky. Importantly, gravity (as it has been written) is an INTERACTION. TIME is NECESSARILY possible/potential AND actual IN BALANCE, as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). Gravity AND ELECTROMAGNETISM/energy are (CLEARLY) linked AND BALANCED opposites (ON BALANCE), as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). This NECESSARILY represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual IN BALANCE. TIME dilation ULTIMATELY proves ON BALANCE that ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). This explains F=ma AND E=mc2. Again, BALANCED inertia/INERTIAL RESISTANCE is fundamental; as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE).
Gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE (ON BALANCE), as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE) !!! This explains F=ma and E=mc2. This NECESSARILY represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual (IN BALANCE), as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). This ALSO (CLEARLY) explains why the rotation of WHAT IS THE MOON matches it's revolution !!! Great !!! (Carefully consider what is THE SUN along WITH the fact that the stars AND PLANETS are POINTS in the night sky. NOW, ON BALANCE, carefully consider what is the speed of light (c) !!! LOOK down at what is THE EARTH/ground ON BALANCE. NOW, LOOK up. The sky is blue, AND THE EARTH is ALSO BLUE !!!) Inertia/INERTIAL RESISTANCE is proportional to (or BALANCED with/as) what is GRAVITATIONAL force/ENERGY (ON BALANCE), as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE) !!! This explains F=ma AND E=mc2. This NECESSARILY represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual (IN BALANCE), as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). AGAIN, BALANCED inertia/INERTIAL RESISTANCE is fundamental. Gravity is (CLEARLY AND NECESSARILY) proven to be ELECTROMAGNETISM/energy (ON/IN BALANCE). It ALL CLEARLY makes perfect sense, as BALANCE AND completeness go hand in hand !!! AGAIN, TIME dilation ULTIMATELY proves (ON BALANCE) that ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). Great !!! This NECESSARILY represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual (IN BALANCE). INDEED, TIME is NECESSARILY possible/potential AND actual IN BALANCE; as ELECTROMAGNETISM/energy is gravity (ON/IN BALANCE). AGAIN, the stars AND PLANETS are POINTS in the night sky !!! Consider what is the speed of light (c) ON BALANCE. Great !!! NOW, CLEARLY consider what is THE EARTH/ground (ON BALANCE). Finally, also notice what is the black “space” of the physical structure that is THE EYE. NOW, carefully consider what is THE SUN !!! It ALL CLEARLY makes perfect sense. Great.
By Frank DiMeglio
this is one of the most beautiful physics/math videos i've ever seen
Very good explanation, very clear. We need more videos like this !
This was the best explanation of the special relativity I've ever seen on anywhere, I guess.
A very comprehensible explanation of the math behind the formulas. Very nice!
I was wondering whether it is possible to download and save these videos, and if not whether that's something that could be made available by you. I love your content, use it all the time. Also, thanks for all the effort you put in the vids. Keep it up.
Indeed. You are absolutely right. No excuse for sloppy English.
18:00 I'm left confused because x' is defined as x' = x - vt = 0, and then immediately c is defined as x'/t' (which means c =0?), and the equation is later divided through by x' (division by zero).
I think x' needs clarification between its definition as x' = x - vt = 0, and x' = ct'.
the best explanation i've ever seen...... i was searching for such an explanation for a long time... i couldn't understand how time dilates if light speed is constant for all frame of reference... thanks.... this is kind of explanation i was looking for...
HOWEVER THE VIDEO DIDNT EXPLAIN HOW MASS IS RELATIVE..... OR DID I MISS SOMETHING??
if you look in the playlist on special and general relativity you will find a series of five videos on special relativity and I deal with mass there, in particular the final video.
Robert Eagle
I have many doubts regarding this.. your response is highly appreciated...
we have reached
x' = x - vt ------------(a)
and we get
x = x' + vt
assuming t = t' we get
x = x' + vt' -------------(b)
now (a) and (b) are two different equations... how can we apply same error terms in both..... those could be two different errors... we cannot be sure those are same errors...
my point is, it should be taken like this.....
x' = (x - vt) Y
x = (x' + vt') B
where Y and B are error terms.....
after watching your video, i searched every where about lorentz tranformation...
but it very long and complicated everyhwere else not as simply illustrated as in your video... thats why i am coming back to you.. thats why i tweet you on twitter.. if you are willing to respond i have other questions too.....
Shabeer Mohammed As you will appreciate, I'm trying to keep the explanation is simple. The essence of the argument that neither observer has any reason to think that they are any more or less wrong than the other.
DrPhysicsA ok....
At 11:26,the speed of the ball isn't 10mph+30mph=40mph.Actually,it will move slighty slower than 40mph and the speed of the ball will be 39.99999999964mph.
The formula is (v1+v2)/(1-v1*v2/c^2).
Excellent. Delighted to hear it. Well done.
Hear what?
Thanks so much for these videos!
Helped me get a B and an A in AQA Phya 4 and 2 in January :)
Thanks for the clear explanation. It is magic what lightspeed and mathematics can mean for us.
Relativity does produce weird results. But as other others have tried to explain, it is precisely because the speed of light is constant that you get these relativistic effects of length contraction and time dilation. The important point is that from your perspective everything in your frame of reference appears to be normal but in everybody else's frame of reference you will measure shorter lengths and slower times.
You my friend, just saved my life! Thank you!
This is so low tech and so damn good.
Your explanations r fantastic!! They've really helped me a lot in understanding special relativity and why does the bizarre phenomena actually occur.
Looking forward to watch ur other vids.
Don't get hung up on the Doc's methodology. He just kind of does what he does and whatever it is is always fun and informative. Good stuff.
A frame or "reference frame" essentially means everything that is at rest local to you. So if you were on earth and I was on a spaceship, we would be in two separate reference frames. The point being that if I try to measure a distance or a time in your reference frame I might get a different result from the one you would get by measuring it local to you.
This is best video on special relativity for beginners. Absolutely amazing!!!
How beautiful to see the E=MC^2 famous equation comes from!!! Brilliant presentation, Thank you. Surprising to see how simple SR equations compare to GR where it’s more complicated.
29:18 I'm too immature to be studying this stuff! xD
LOL!!!!
I got to 5.04 and my head went fuzzy and I fell off me chair. I've cracked my screen. Can I put a claim in? Can anyone know ensigns email adress. Can somebody help I think I hurt me head. I've got fuzzy fluffy yellow pants on now.
Don't worry...he is rather trying to keep it extremely simple....for example when he derived the Lorentz transform...it was rather to be derived in a much more complicated manner...so try to be calm and devoted to understanding this and I am certain you will
Did u grow up since ? :)
@@anjalidutta8471 did you get the fucking joke?
t' = γ(t-vx/c^2) is right. I'm not sure how you got to the next stage. Perhaps this is part of the question which you haven't given to me.
Thank you so much for all your videos!! You are helping so many of us out here haha :D
Awesome! Thanks a lot for this video! For the first time I understood why length contraction makes sense and the thorough way you explained the formula's really helped me vision how and why it actually works(and how those formulas were derived).
I am wondering though,if you devide ct=ct'(some stuff)*gamma by c, you don't devide gamma by c. Why is that?
But that was the point. Since the earth is moving one would expect that if the measured speed of light was determined by the speed of the source/ observer then the speed of light would vary depending on whether it was being measured in the direction the earth was traveling or perpendicular to it. But no matter how they varied the angles of measurement they couldn't get a difference.
It's always the relative effect which matters. If you travelled onboard a photon then from your point of view time would pass in the usual way. But all the clocks in the world around you would appear to stand still. Similarly everyone observing your watch would say that it was standing still.
Very interesting. But what remains unclear is at 18:09 when you write c=x/t =x'/t', this applies only if x and t refers to the distance and time spent by light. But then on you assume that x, x', t and t' are universal coordinates, so it is confusing because in that case v=c so gamma is actually 0 (limit case)
I only did CSE level maths at school with very basic algebra (many years ago), but I managed to follow this excellent video.
I wish I'd had someone like you as a teacher at school instead of the monotonous old hag I did!
Thanks :)
You (Dr PhysicsA) say (9:01): "But the trouble was that every time they (Michelson and Morley) moved the equipment, the fringes didn't change". But Michelson and Morley themselves reported: "The relative velocity of the Earth and the aether is probably less than one sixth of the Earth’s orbital velocity, and certainly less than one fourth." In other words, the fringes DID move. Please explain the discrepancy between their and your versions.
That's a good question. If we move side by side on a motorway with identical acceleration then we will stationary with respect to each other. Yet each of us can clearly tell we are accelerating.
As fine and concise an explanation of SR/E=MC2 as I have seen.
Towards the end of the video when you were using the binomial expansion, how come you ignored any additional terms simply because they would be too small? Surely whether it’s very small or not doesn’t change the fact that it’s more energy that the equation isn’t accounting for
On internet people are saying that Michelson and Morley had a null result because the light source was on the moving earth and not in the stationnary eather.
WawWW! This guy knows how to teach boom
hey i understand all the video , but the only part that i have questions about isn't covered : Why mass is subject to relativity i do understand why distance and time is subject to but not why mass is, What is the mathematical prove of that. THANKS FOR ANY ANSWER
p.s Sorry for my bad english not my language.
(** Please donot ignore my doubt **) I cant Understand one thing in TIME DILATION that """If Gamma varies from 1-infinity(i.e. its value is increasing ) ,then anything multiplied by Gamma get bigger and bigger, so here Gamma is multiplied by " t' (local time) " so the value of " t' (local time) " should be bigger than " t (remote time)" .Hence in the video it shows that moving clock runs fast.
You don't multiply, you divide. It's t/gamma
At 18:27 you said that c=x/t and c=x'/t' and then you replaced the values in x=x'+vt, but in the value of c, x and x' are the distance traveled by light and in the equation x=x'+vt, x and x' are the distance traveled by the observers so they do not refer to the same value. That's a bit confusing! Thanks.
MaroniteCatholic ofJesus not confusing. It’s fraud because it’s confused from head to toe.
Great video. Very clear and well explained. thanks a lot! :)
Good job, I really appreciate your videos!
Omar, because as your velocity approaches the speed of light time slows down and length contracts. However from your perspective time hasn't slown down at all.
I should have been clearer. The point I was making was that if a body is moving at constant velocity then you would be able to play snooker without realising you were moving. But if you were accelerating, the snooker balls would move across the table - for the same reason you feel pushed back in your seat when a car accelerates.
At about 33:20 speaker says "the light doesn't move" which is absurd. What he should say is the light moves perpendicular to V direction or direction of relative motion and not horizontally along V or direction of relative motion. This allows the person in moving frame to measure time in same horizontal place or what is called proper time. It is for this reason that x' becomes zero i.e that time is being measured in same horizontal place in the x' frame. The other i.e. the (static) observer does see the same (perpendicular) light beam travel diagonally and thus a longer distance.
Another great video man...thanks for your work...
Nice derivation, i needed it. Thanks!
Thank you, thank you! This is amazing!
thank you for this. But didnt you already make a vid like this in the E=mc(sq) series?
The divide by zero isn't really an issue as x' = x - vt can also be written x = vt + x' when x' is non zero (I.e. when you move in your frame and I measure your total displacement). However it would be nice if there was a version of the video that explained this because it could be confusing.
Brilliant , many thanks.
Legendary explanation
Time and length contraction paradox. Imagine that a laser light is turned on during 1s at the back of a train towards the front of that train, moving across the x axis.
The length of the train is c, at rest (for the observer in the train as well). The train travels at c/2, so gamma is 1.155 or 2/sqr(3).
At t=0, both clocks are synced, and x=0. The laser is at the rear of the train, at x=0, at t=0.
For a passenger in the train, the light reaches the front of the train after 1 s, as the length of the train is c.
(Note that there is simultaneity for this event: the light reaches the front of the train at the same time and location, for any observer.)
When calculating the elapsed times and positions for a stationary observer... there seems to be a contradiction:
Method 1) If we apply time dilation formula, the time elapsed between the two events for the observer at rest is t2 = 1 * gamma = 2/sqr(3) seconds... In that time, the light has travelled 2c/sqr(3) = 1.155c, and that's where the front of the train must be. However the back of the train has also travelled at v=c/2, so it is now at 1c/sqr(3). The length of the train is x2 - x1 =(2c/sqr(3)) - (1c/sqr(3)) = 1c/sqr(3) = 0.577 !
BUT If we apply length contraction, the perceived length of the train is c*sqr(3)/2 = 0.866c, which contradicts that result.
Method 2) If we apply length contraction formula, the length of the train for the observer at rest is 0.866c. That is 2c/sqr(3). The time front of the train is at x1=t2*c/2. (t2 is the time when the light reaches the front of the train). As light has travelled at c speed = x2 / t2, and the length of the train is x2 - x1, we get t2 = 4 /sqr(3), x2 = 4c/sqr(3), which contradicts the previous result.
Method 3) If we apply the transformation x = (x'+vt') gamma, x2 = (x'+vt')g = (3c/2) g = c * sqr(3), t2 = x2/c = sqr(3).
So I have missed something...
A Level is the exam taken by students aged 17-18 in the UK. A stands for Advanced.
Isn't x always going to be larger than x'? Since it's always going to be between 0 and 1. and the root will also. X' times a number less than 1 will always make it smaller than it was originally. So therefore x is always larger?
At 10:30 I think there is a big leap from the speed of light being constant with respect to the aether to c being constant independent of the speed of the observer or the source. The experiment described would not definitively lead to the latter conclusion because the speed of the observer and source were 0 relative to each other.
Great lecture thanks. You tied a lot of stuff together for me. Finally i can derive the famous E=MC^2 formula. I feel like i should call some friends and celebrate,hahaha. :) Cheers!
Fantastic lecture. Thank you very much for the detailed and adequately paced run through the formulae.
I have one question that despite my best efforts to research online I cannot figure out:
Between minutes 00:40-02:20 in your lecture you explain the concept of the relative perceptions of two observers, none of whom can determine which one is actually in motion (or if both are in motion). If I am not mistaken this is the relativity of motion.
However, all the calculations after minute 12:45 in the lecture assume that the observer on the platform is stationary, and the observer on the train is in motion (and this seems to be chosen arbitrarily as far as the relativity of motion is concerned). In fact, the observer on the platform could just as well be considered to be moving - together with the platform, etc., while the observer on the train could be stationary together with the train). The implications of this change in perspective are evident at 34:20-34:25 minutes, when the conclusion of time contraction should be that the local time (of the observer on the platform) is shorter because this time IT is travelling at close to the speed of light (which is the opposite of what we would get if the observer on the train were travelling, as assumed in the lecture).
Perhaps my logic above is flawed, but I can't figure out where this is, and please help me settle this apparent paradox. My BIG question is why is the Lorentz transformation applied unidirectionally (only to the observer on the train), when in fact motion can be attributed to either observer? Why isn't the observer on the platform travelling at close to the speed of light; especially since to the observer on the train things would appear to be so.
If we attribute all the motion to the observer on the platform (inversely than assumed in the lecture), or indeed we share it between the two observers, the Lorentz transform factor would apparently need to be applied differently. In particular, with regards to time contraction, if we (arbitrarily?) assume that the observer on the platform is travelling (with the platform and all), then time as measured by this observer would contract, while the observer on the train will measure a longer time.
The thought experiment at minute 39:50 would mean that the observer on the Earth is travelling at close to the speed of light, and the observer on the spaceship ages by 10,000+ years.
I must admit that applying the same principle of relativity of motion to the muon experiment at 41:20 would argue that muons stay still (which I appreciate is impossible ) and the Earth is travelling at 0.99 of the speed of light (which again I appreciate is impossible, because that would make the mass of Earth close to infinity). However, how can we be sure that the Earth is not in fact travelling at close to the speed of light (in relation to a frame of reference moving away from the Earth at close to the speed of light?
Thank you very much for any insights!
+WX15 You make several points but all are resolved by the fact that yes, relativity of motion does indeed apply to all the situations. Do specify any of your questions though.
DrPhysicsA , thank you all useful videos .Can you tell me useful theorical physics books or send me ?
Think about the single legendary pen that he uses in every video. I want home to continue this legacy and use the in every future videos
6:58 sir why you said both distance are about same not same ?????
I am asking it because it confused me ....!!
This is because as far is known this laser interferometer are super Extremely sensitive for naino or or pico levels of distance , so if we don't account both distance then its results will be huge error ??
Hi, I am a bit confused about the derivation of the lorentz transformation. The first thing it says is that (x = vt). Secondly it states that (c = x/t) which would mean (x = ct). Does that mean that (ct = vt) and subsequently (c = v)? But great video overall thanks!
Oh another thing is that you later established that (c = x'/t'), but earlier you established that (x' = 0). If you combine these 2 equations, doesn't that mean that c = 0) which cannot be the case since (c = 3x10^8)?
If V equals C then the term in the square root becomes zero. That means that X equals zero not X'.
Very well presented. However, there is an anomaly. Einstein is stated to have claimed that he did not know about the Michelson Morley experiment. If that is actually correct, how would he have made the assumption that the velocity of light is constant in all frames of reference? Is there an alternative way of deriving this?
The idea was that if the experiment had two beams of light travelling at right angles to one another, then if the whole experiment were rotated and on the assumption that the Earth was travelling through the ether, then there would be a variation in time for the light to travel out and back again and that this would be reflected in an interference pattern.
I was with you up until around 16 minutes. I'll watch a few times over. Thanks.
Here's something to look at...
Ship1 at rest at top:
T--------------------N
N--------------------T
The moment when T of ship1 is lined up with N of ship2 must be the same moment in both frames of reference because there is only 1 moment when this occurs. At this moment for someone at N of ship1 to see T of ship2 they have to look in 2 different directions simultaneously. This is impossible. N of ship1 is simultaneously both passed and not passed T of ship2. This is impossible.
With regard to the Michelson-Morley experiment - if they were trying to detect a difference of elapsed times for c through each arm of their apparatus how were they able to determine if the returning "split-twin" photons were from the same original photon split at the beam splitter? If the aether doesn't exist why does The Standard Model of Physics say photons propagate (are waves) through the electromagnetic field? Where does physics say a photon detaches from the electromagnetic field and travels through empty space? My reasoning via The Standard Model of Physics says the aether does in fact exist - but today we just call it the electromagnetic field. Further reasoning says the electromagnetic field sits idly by (at rest) in the back ground throughout the universe. Does this give us a preferred reference frame? Maybe the reason physics is stuck is because we are hanging onto the belief that space exists - even though we have zero direct proof it exists - all physics, events, forces, energy, etc., are accounted for with fields. Maybe space is just an aggregate of all the fields that make up our universe.
Thanks for this explanation!!!. Where did you study physics?
+Lestatfol Kings College London.
If a remote observer sees a uniformly moving frame shine a light in the direction of motion then the remotely observed net velocity of the light cannot exceed c, but the frame is moving, so the light has to go slower 'inside' the frame but due to the frame motion it is still remotely observed to be moving at c. So the remotely observed light is in 'slow motion' which puts all events in the frame in slow motion which is a way to say time is going slower because we have no universal idea of time outside of comparing amounts of stuff happening, unlike Newton. Is that right?
Great video sir !
Great vid, really helps. I tried deriving gamma like you showed and of course went wrong at the first opportunity! Around 16 mins you say from x=vt then 0=x-vt, and I'm good with that. My brain, however chose to go the other way and say 0=vt-x, mathematically fine I thought, but it's lead me by following through with the subsitutions of x and x' to the conclusion that v=2c which is clearly nonsense!
Is there a reason other than "it works out well" to take the route that you did? Is there a reason why my version has gone so wrong or am I making some fundamental error? Surely it should work out fine either way!
I think you made a small error at 12:20. If the direction of the light was travelling as you indicated the expected measurement of the speed of light to the observer on the platform would be c-30. Not that it matters because the expected value is wrong anyway! Thank you for the video :)
And that means: a given X is passed in t(v) time when travelled by you or me and in t(c) when travelled by light itself. So c/v = t(v)/t(c). Why do we now need a correction term here?
Brilliant lecture!! Thank you
....continuing at about 19 minutes he writes x' = ct' having called x' = zero at 16 minutes.
Were x' zero as speaker claimed, then t' would have to be zero destroying all subsequent argument. So x' should NOT be made zero irrespective of its state of motion. One can still write x' = (x - vt) or more fully, x' = (x - vt)gamma.
Overall the speaker is doing a very fine job. Better than most. My congratulations FWIW.
Yet again at about 37:52 speaker says that in Alice's frame "light is not moving". Better to say that light does move but does so perpendicular to relative motion so that Alice measures proper time in same horizontal place. It is for this reason X' becomes zero. "Non moving" or "stationary" light is not respectable.
Speaker should introduce concept of "proper" time and time being measured at same versus different horizontal places. Otherwise dumb expressions as "light is not moving" get bandied around. Any time interval read using a horizontal beam of light i.e light directed along the direction of relative motion will be read at different horizontal places and will not be "proper" time. These times will differ depending upon whether the light is shone forwards or backwards to direction of relative motion demonstrating "failure of simultaneity". The different sign before vx/c^2 and vx'/c^2 represent this asynchrony. I don't believe speaker addressed this.
Nevertheless he did a good job.
he means light bulbs are not moving.
lets assume bob is stationary and i am moving near speed of light, so that time bob measure is t and I measure is t prime. according to time dilation, t is larger than t prime which means t prime is smaller than t. That means the time i measure is shorter than which bob measures and also that mean bob measure large time than me.
In the beginning i told i was moving near the speed of light. but what i feel is i am stationary and the environment including bob moving away from me at near the speed of light. now the time i measure is t and bob measure is t prime. according to time dilation t is larger than t prime. so this time i measure larger time than bob measure and also than mean bob measure shorter time than me. could this both could be possible? Confusing!!!!!
If you push the ball in a direction perpendicular to the direction of the train the person on the platform would measure a different speed to the one he would get if you push the ball in the direction of the train.
However, in the MM experiment the device, the person looking at the results, are all attached to the earth and moving with the earth. In order to prove that the speed of light is an invariant, you would need to get away from the earth and use a telescope to see that the beams of light take the same amount of time. As things are, it's like you're on a moving train throwing balls at the roof and at the wall in front of you. If the distances the balls travel are the same, you will find that they travel the distances at the same time.
How do you know which side to apply the Lorentz transformation to? Is it always the remote side? If one side is the "remote" side, does that mean the result you get will be from the reference frame of "remote" or "local"?
Brilliant! thank you so much.
This is very good presentation. However, the first derivation on the value of gamma has stumped me. It just seemed like an algebraic wizardry, the physical basis of which is not at all clear. However, the very basic observation that the speed of light is constant in both frames of reference is highly counter intuitive.
I think he confused t' for moun with t for observer. He used t' = 6.73...which is our or observer's measurement?? According to his formulas before t>t' ... he changed the formula but the results are ok.
One says that there is no absolute rest but what about the view of one's own reference frame.
Around 33:30 you say that x'=0 because my light is fixed. What do you mean by fixed? The light is always moving with speed c.
Thank You! Peace to you from Qatar
Adnan Fekri good for you continue with your physics & drop the imaginery wizard daddy in the sky
At 24:24... I thought that when you take the square root of a quantity, you'll get 2 results. Why did you only consider the positive result?
In the Last part we find E=mc2. So, that means photons dont have energy? Since they dont have mass? But sun light gives energy to earth, how does this happen?
in minute 19:00 there is a bluffing - if x=vt, then u cant say that x=ct... x and t in the first equation are different from the ones in the second equation, Am I right? or wrong?
Hi, as for the muon experiment that you mentioned, isn't the muon accelerating as it falls? How can we apply special relativity in this case? Thank you.
I downloaded this Whenever I drink more that two beers my inertial reference frame begins spinning ....
Then it's no longer an inertial reference frame :D
For Michelson and Morley's experiment, let's say that the speed of light is affected by the earth's movement through what they called the "ether", this means that no matter what angle you rotate the setup, the time for one beam to reach the meeting point will always be more or less than the time taken for the other beam to reach that same point and they will also get the same result always! what is my mistake here?
Mind if I take a stab at this one? At about 5 mins in, there's an explanation involving rowing across river. The experiment is very like that, rotating the experiment is the equivalent of rowing in different directions, the time taken will vary, in m&ms experiment, the pattern should vary ＩＦ the light has been moving at different speeds.
dave oil Ohh! I got it now! thanks alot :))
the best video
Thanks for correcting captions.