Well, I find the video has a long introduction and then finishes off a bit too short with the conclusion that the moving person exists in two reference frames, period. That part, the meat of the paradox, should have been better explained.
@ericlobatograef5186
6 жыл бұрын
I agree, in fact, I didn't understand what he meant. Could you please explain? Doesn't seem to make any sense, I would simply say that we have 3 frames and each of the frames is at rest in relation to one of the observers.
@protocol6
6 жыл бұрын
Yes, it really needed to circle back at 12:25 and expand on what those two very brief bullet points mean rather than just declaring it solved as I bet many missed it and quite a few may not get it on reviewing.
@LarsStokholm
6 жыл бұрын
Yeah, that part I don't understand at all.
@billg.7909
6 жыл бұрын
Agreed
@DanielNogueiraLeitao
6 жыл бұрын
I totally agree.
@dahlenu
6 жыл бұрын
Please make a sequel, the "conclusion" needs more explanation.
@pedroadonish
3 жыл бұрын
Hahahaha, I was waiting until the end to see the final answer... Then he says "and that's why!" Like... what?
@LuisSierra42
3 жыл бұрын
That's from your perspective
@jeremiascristian521
3 жыл бұрын
Pro tip: you can watch series on flixzone. I've been using them for watching lots of of movies lately.
@blakematthew6880
3 жыл бұрын
@Jeremias Cristian Yup, have been watching on flixzone} for years myself =)
@chriswesley594
6 жыл бұрын
Like others here, I don't see the explanation. I hear "two frames of reference" but I can't connect that observation to an explanation I can grasp. It's like you ran out of time.
@trsomas
5 жыл бұрын
See if this explanation is clear. kzitem.info/news/bejne/q4Z5qn-qmmR9iXo
@penguindragon0155
5 жыл бұрын
yeah. if this video was 1322 or longer then the universe would have died then and there so... he did what he had to do
@renedekker9806
5 жыл бұрын
I think this one is a better explanation: kzitem.info/news/bejne/kZ-AwJOHgH99d2U
@BinuJasim
4 жыл бұрын
@@renedekker9806 No, it's factually mistaken, I guess. How can the stationary person measure time for the moving person. Then it will be 10s only!
@renedekker9806
4 жыл бұрын
@@BinuJasim The stationary person does not *measure* time for the moving person. But she can *calculate* how much time should be passing for the moving person.
@bondmode
6 жыл бұрын
I'm sorry but you went all detail with the easy and well understood part, explaining it like we would to a 5th grader, and then just conclude in literally 5 seconds that since the observers B and C are not in one single reference frame (wich could have been explained as well as the rest was) this is the proof for the paradox not being a paradox. While I'm sure this is correct, and not wanting to tell you how to make your videos, this last part ,with no explanation at all to support or motivate your conclusion, didn't really prove anything to me. Still, it did provide for a starting point for me to dwelve deeper into, so thanks for that.
@Guoenyi
3 жыл бұрын
His solution was very good, for debunking the "acceleration" theory. But did not really explain why the paradox is not a paradox.
@DrDeuteron
3 жыл бұрын
@@Guoenyi it's still a paradox, even if it's resolved. If you work in minkowski space(M4), there is no paradox because M4 is manifestly self-consistent.
@BD-np6bv
3 жыл бұрын
This is a horrible example. Think about it guys. Dr. Lincon's example of A being stationary and C and B moving is the SAME as B being stationary and A and C are moving in the same direction (A away from B and C towards B), but C is merely 2x faster than A in the same direction while B is really stationary! The other probability is C is stationary and it's B and A moving towards C, but B moving at 2x the velocity of A, which in this 3rd scenario C is really stationary! To all observers, in all scenarios it would look identical and no one would be able to tell who's really doing the moving! Horrible example. The real reason is the person leaving Earth did the acceleration near the speed of light. That's the same as moving near a black hole and feeling the "acceleration" or the gravity well of the black hole (which relativity tells us gravity is just another form of acceleration and vice versa). Any person moving near a black hole would have their time slowed down, relative to an outside observer.
@DrDeuteron
3 жыл бұрын
@@BD-np6bv If you think |v_C| = 2|v_A| in B's reference frame, you don't understand relativity.
@GrowlinWillie
2 жыл бұрын
It's because the distance to the star looks different for the traveler than it does for the non-traveler. The difference in the distance occurs because the speed of light is always the same, if you're moving toward the light source or away from it. Bingo! I majored in physics at the university of michigan. I went to every single physics professor for an explanation, none of them had one so i switched to math.
@TheoWerewolf
6 жыл бұрын
I'm having a serious problem with this explanation. I get the idea that it's a question of which clock you're using as a reference but nothing shown shows why Ron's choice of his clock as the 'stationary' one is not the same as Don choosing his clock as the 'stationary' one. It's like somewhere in there, there's an assumption of which one is really stationary when in fact, once you exclude acceleration as a factor (which you do), then neither is a preferred frame. Even though it looks like it's solved the mystery - throughout the entire discussion, A is referred to as being 'the stationary person'.. but that's literally the thing we're trying not to say. Take all the math done and flip the contexts and they apply equally well and give exactly the same results relative to each viewer, except you're swapping A and B. That's the problem with this video - it shows the math from the 'stationary' person's view - but not from the 'moving' person's view in the perspective of his being the stationary person. Oh.. one other thought. In another video, you explain that the reason there is time dilation at all is a consequence of the fact that we're *always* travelling at the speed of light. Assuming we're just talking about one spatial axis, x, and one temporal axis, t - the vector must always be a unit vector... so at rest, it points entirely along the time axis and represents 1 second per second. As you change velocities (and I'm avoid saying acceleration intentionally because it's the velocity that causes it, not the acceleration) the unit vector rotates until you hit the speed of light where all of the vector lies in the x axis and there's no vector in t - ie no time movement. It seems like you're offering two different explanations for dilation. Keep in mind, I'm not saying you're wrong - you know way more than I could hope to about the subject.. I'm just suggesting that this explanation could be better.
@ThomasKundera
5 жыл бұрын
No, it wouldn't show a paradox if you flipped the referential (just give it a try). Point is that all used referential in the video are inertia ones. A is not jumping to any other inertia referential, and you can't make a valid Lorentz transform that would show such a behavior, because in all other inertia frames, A is an inertia frame (constant velocity).
@lukecasey2830
5 жыл бұрын
@@ThomasKundera Consider the spaceship reference frame A, consider the stationary person reference frame B and C except with the negative of the velocities used in the example. Perform all of the same calculations. Why would it be wrong to do this?
@ThomasKundera
5 жыл бұрын
@@lukecasey2830 : _"consider the stationary person reference frame B and C "_ B is stationary, C is stationary. But (B and C) are not. So you can't make a computation assuming (B and C) is an inertia frame of reference (as you can do in A, as A is one).
@lukecasey2830
5 жыл бұрын
@@ThomasKundera But we are not considering the stationary person as stationary when viewed from the spaceship's frame of reference. We use two frames of reference to describe the space ship, I do not see why we couldnt in return use two reference frames to describe the stationary person when considering the moving space ship as stationary. How do we even know the space ship is moving and not everything around it? The fact that it isnt expending fuel and accelerating, therefor not losing mass, leads to the conclusion that we dont know if the spaceship is moving or the stationary person (ignore that fact that we are callling the stationary person stationary, what we call the person is beside the point). Can you explain to me how we know the spaceship is moving, not everything around it, and how we know we must use 2 reference frames to only describe the spaceships movement? Please I am trying to figure this out but I cant. I know I am wrong and that I am not understanding something
@ThomasKundera
5 жыл бұрын
@@lukecasey2830 : You can take any of A, B or C as "stationary". But, again, B then C is not. _" I do not see why we couldnt in return use two reference frames to describe the stationary person"_ Because if you need more than one frame, then it's not stationary, by any reference.
@nizamigol819
5 жыл бұрын
I believe that there is an error in 10:25. According to observe C's perspective: the x co-ordinate (position) of event 1 would be -2yl, the x co-ordinate (length) of event 2 would be 0 and the x co-ordinate (length) of event 3 would be again 0. This is because the events' positions are relative to the perspective of C. It can also be supported by the x co-ordinates of the 3 events according to observer A and B's perspective since in the video the x co-ordinates of both perspectives are relative to the observer (i.e. for observer B event 2's x co-ordinate is considered to be 0 as the observer B and event 2 are on the same position). According to example I wrote in parenthesis, the x co-ordinate of event 2 for observer c would also be 0 as observer B and C are on the same position as well as event 2. However, this does not effect the conclusion reached. Please reply me either you believe I am right or explain my mistake.
@camillomarchesi6050
Жыл бұрын
anche io vedo un errore ☹️
@feynstein1004
6 жыл бұрын
I still don't get it. What did he mean by "Observer A exists in only one reference frame but observers B and C exist in 2"?
@trsomas
5 жыл бұрын
B and C are moving relative to each other. So they are in different inertial frames.
@cvasticamuc
4 жыл бұрын
Consider this, the earth moves ( rotation and revolution) yet we feel we are stationary. That's because we are in the same reference frame where everything on earth is moving. Now consider A to be on earth. A is stationary within this reference frame earth. Now B and C have different reference frames each. One when they start their journey ( Earth for B and 2L for C) and when they pass each other ( L for B and C both) and when they end their journey ( 2L for B amd earth for C). Thus these two people have different reference frames therefore there must have been some movement to change those reference frames. Therefore its concluded that B and C were moving and not A. All in all, the paradox arises with the question who exactly is moving. Now since it gets clear that B and C are moving and not A, the paradox gets solved
@jaimeduncan6167
3 жыл бұрын
@@trsomas They are both moving relative to. A. So we can say B is stationary and A and C are moving relative to each other. I belive he should have done that calculation too to convince most people.
@Spironic
3 жыл бұрын
@@jaimeduncan6167 The problem that I have with this explanation is that in the original paradox, B and C are both represented by one person that never moves relative to himself, so what does this explanation have to do with explaining the original paradox?
@wideseen
3 жыл бұрын
@@trsomas And A and C are moving relative to each other and A and B are moving relative to each other. I sense poppycock here. They are all inertial systems and the Lorenz transformation can be applied equally in all permutiations.
@frankharr9466
6 жыл бұрын
That doesn't make any sense. Although I'm willing to admit to being wrong, all observers should exist for everyone else and everyone can measure everyone moving. I'm willing to admit to not getting it, but it doesn't prove it to me. Maybe it's because I'm a humanities guy.
@alexvolkov223
6 жыл бұрын
Can you explain what you mean by the second sentence? I don't quite understand what it is that you don't understand, otherwise I can try to help out.
@trsomas
5 жыл бұрын
One person stays in the same inertial frame of reference throughout and the other shifts from one inertial frame to another. kzitem.info/news/bejne/q4Z5qn-qmmR9iXo
@xwarslayerx
4 жыл бұрын
@@trsomas I'm a believer that time is a universal constant. Who cares what speed or acceleration you are at.... A lightyear still takes you a year to travel at lightspeed...
@xwarslayerx
4 жыл бұрын
And don't get me started on the "observer" bullshit. They see light at light speed. I believe that relativity is something people got confused into believing because of all the variables and confusing names for variables like "light-year". It's a measurement of DISTANCE. It's how far light gets after 1 year of traveling. In all these experiments, they treat travelling a light year at light-speed like it's instantaneous. STILL TAKES A FUCKN YEAR.
@Catmomila
4 жыл бұрын
@@xwarslayerx You don't really know what you're talking about, sorry.
@chrisporter2648
5 жыл бұрын
Hahaha. It isn't due to the acceleration... just due to the change in reference frames... which is an acceleration. I think he spent 13 minutes "debunking" something that is often just an issue of semantics. It has nothing to do with the curving around at the distant star, but everything to do with the boost frome frame to frame.
@johnredberg
6 жыл бұрын
Sorry but you haven't done any actual explaining. Yes, you've set up a thought experiment with a departing and returning frame of reference that does without acceleration. You then arrive around 11:59 at "Duration(moving) = Duration(stationary)/gamma". But this is equally "paradoxical" as the original problem, because "moving" and "stationary" are still relative. You would actually need to show explicitly that the results are consistent if B or C were considered stationary AND independent of which clocks you use to measure the time between the different events. I'm sure it'll all work out but it seems awfully complex (involving relativity of simultaneity) and is definitely not obvious.
@fuseteam
4 жыл бұрын
I have found none that explains it from both perspectives so far
@NeedsEvidence
4 жыл бұрын
You need the relativity of simultaneity to fully explain why things are different for A and C. It's taken care of by the vx/c2 term in the Lorentz transformation for time, but unfortunately Don Lincoln didn't talk about it. Either he doesn't know it, or stayed silent on it by intention and just was focusing on the math.
@ricomartinez458
4 жыл бұрын
@@NeedsEvidence I have watched many of his videos and have to say that this guy really doesn't know how to explain it in a simple way. He unnecessarily makes things complicated. As albert einstein said "if you can't explain it simply, you don't understand well enough". I would recommend listening to "Physics girl", she explains 10 times better than him and gives crystal clear explanations
@fransantoyo
4 жыл бұрын
Best comment. The video doesn,t explain the paradox. When he shows the (x,t) coordinates from B and C perspectives it,s not true. In fact, are the B and C (x,t) coordinates from A perspective. As you say, he should do the same calculations using the perspective of B and C and check that the results are consistent relative to A perspective. In addition there is a mistake on the (x,t)II,C coordinate maths, he shows x = gamma*L but it,s x = 2*gamma*L
@BD-np6bv
3 жыл бұрын
I came to the SAME conclusions. This example of A being stationary can be said that C or B are also stationary and it's the other two moving! The real answer is the acceleration part. When you accelerate near the speed of light, Einstein tell us it's the same as being close to the gravitational effects of a black hole. GRAVITY and ACCELERATION are the same! Time slows down near the gravitational effects of a black hole, which would accelerate you near the speed of light to the event horizon! That is the real answer. Dr. Lincoln is correct on many things, but he's clearly wrong on this one.
@howardOKC
6 жыл бұрын
"When we start the experiment, all 3 observers start a stopwatch." This sentence contains the idea of "simultaneously". Problem is, simultaneous in whose reference frame?
@BluesManPeich
4 жыл бұрын
Imagine someone at location B sending a signal to A and C at the same time. When the observers receive the signal they start their stopwatches.
@xw591
4 жыл бұрын
T=0 for all of them.
@NeedsEvidence
4 жыл бұрын
That's an excellent point Don Lincoln failed to address. It is the vx/c2 term in the Lorentz transformation that takes care of the relativity of simultaneity. In fact, C's "now-slice" corresponds to a future moment of A, and it is for this reason that A sees more time passing than C when C reaches A.
@jeffbguarino
6 ай бұрын
@@xw591 That is what I noticed at the start, but how do you synchronize the clocks ? How do you measure the lengths to know where the center point is.
@xw591
6 ай бұрын
@@jeffbguarino dunno im a mathematician
@onehitpick9758
6 жыл бұрын
This has generated a massive amount of confusion. I think you need to use space-time diagrams.
@Paolo_De_Leva
6 жыл бұрын
Right. Also, the only way for Ron to switch from frame B to frame C (when they meet at position 2) is by experiencing acceleration... and if I neglected that idea, I would be entitled to apply the same argument to the motion of Don relative to Ron (rather than the motion of Ron relative to Don), and I would reach exactly the opposite conclusion, using the same formulas.
@marianskodowski8337
6 жыл бұрын
It is funny how the Einsteinists - the paradox "explanators" bring the human fillings into consideration. Now you have to fill the acceleration - this switches you from frame to another frame, you are only stationary when you don't fill acceleration :) Where it is in Einstein's equations?This is why the theory is crap.
@onehitpick9758
6 жыл бұрын
The theory is definitely not crap, because it is used it many, many times to explain real observations to high degree of precision, where classical kinematics has failed completely. It is not intuitive, and not even required at low relative speeds, so you should be good to go in most of the experiences that we, as humans, deal with..
@mr.h4267
5 жыл бұрын
@@marianskodowski8337 Acceleration is dealt with in general relativity.
@ricomartinez458
4 жыл бұрын
I have watched many of his videos and have to say that this guy really doesn't know how to explain it in a simple way. He unnecessarily makes things complicated. As albert einstein said "if you can't explain it simply, you don't understand well enough". I would recommend listening to "Physics girl", she explains 10 times better than him and gives crystal clear explanations
@fakherhalim
6 жыл бұрын
Since A, B and C were not accelerating, they were moving (parting away or coming closer) steadily with respect to one another by exactly the same amount. Since there is no "Stationary" frame of reference, all three would think that other two inertially moving persons are aging younger by exactly the same amount(e.g. 6 years). A would think B and C are younger by 6 year, B will think A and C are younger by 6 years, and C would think A an B are younger by 6 year. It is understandable why the presenter abruptly cut off the video by just mentioning: it is because to ONE frame vs TWO or THREE frames -- instead of steadfastly reasoning why A would grow older by 6 years from others perspective while others would remain younger despite same relative motion! He could have plugged numbers in those equations that are 100% same for all three and prove why just one of those three symmetrical equations would magically yield no time dilation!
@malsaqer
4 жыл бұрын
Isn't it according to the traveler that the earth observer is the one who switched between two different frames of reference, and hence, symmetry persists?
@philipberthiaume2314
6 жыл бұрын
'Physics is everything', it truly is. (Edit) We shall miss you Dr Hawking. 18-03-14, a triumph we had you so long and sad loss.
@ronaldderooij1774
6 жыл бұрын
Psychology, Social sciences, consciousness anyone? That has nothig to do with physics, but is still very real.
@frankschneider6156
6 жыл бұрын
Ehm psychology is about different states of brains, which are electrical currents within a specific kind of very physical object. That's physics, but instead of trying to go the natural scientific way (like it's today done by trying to map the individual connectome), people just made up some pseudoscience and termed it "psychology". Social "sciences" are about behaviors of humans. Humans are typical animals. Biology is in principle just the result of biochemistry/molecular biology and that's just chemistry, which is in first approximation nothing else than the physics of the outer valence shell electrons. Everything is natural sciences and in the end physics. Exactly that's why social sciences have such a bad reputation among educated people. And of course because hey rely more on citation and who said what, than on observation, thus perverting the scientific method.
@tuele4302
6 жыл бұрын
Ronald de Rooij What he meant is that physics is the most fundamental of the sciences. All arrows of explanation trace back to physics.
@ahitler5592
6 жыл бұрын
Hawking is as fake as Einstein's gravity
@Crazytesseract
6 жыл бұрын
Philip Berthiaume Hawking had no true knowledge about the universe. The universe is much, much more complicated than Hawking could ever imagine. Do you know where is Hawking now?
@guymross
5 жыл бұрын
Some people just have a knack at breaking down complex problems to smaller, more complex problems that are even harder to understand.
@jameswilson8270
6 жыл бұрын
The end of the video was the most critical part to helping people understand why the twin paradox is not a paradox. In my opinion, you failed that task. You hinted at the answer, but you did not clearly spell it out for people who do not understand. (Also, as I understand it, you synthetically created a jump discontinuity, which is equivalent to an "instantaneous" "infinite" acceleration. If true, the example fails to illustrate your point.) At any rate, the animations and video editing were boss.
@parityviolation968
6 жыл бұрын
glad, I'm not the only one to recognize this... Sometimes he prolongs certain passages unnecessarily, almost putting the audience to sleep, and then when the final conclusion is due, he just leaves it up to the listener to spell it out in their minds... His pedagogical style is as discontinuous as his frame jumping that supposedly got rid of "acceleration" / change in direction issues. (which it didn't)
@maythesciencebewithyou
6 жыл бұрын
That's like almost every Physics lecture, starts slow, expands on the simple stuff, and then brushes over the difficult part before you realize it.
@KevinS47
6 жыл бұрын
James Wilson SOOO?? Why the heck wouldn’t you explain it if you understand it so well????! You take the time to write all that (which was a little unncessary considering that you first phrase was enough) and you don’t even explain what that hint means?!? So why even bother stating all that? What’s your line of reasoning? It seems to me as if you are not using your head at all.
@RME76048
5 жыл бұрын
"jump discontinuity"? What is that, and How? Where? Seems to me that B was in constant motion towards +v and C was in constant motion towards -v. All they did was pass information. How is that a "jump discontinuity"?
@omarcarrero3623
5 жыл бұрын
B, and C were already moving, dont think they stoped and accelerated, just that they passed the info every intersection
@philallen2130
5 жыл бұрын
I sort of "get" this, but I also agree with brixomatic about "long introduction" and "bit too short with the conclusion". Do another video please to follow up this one! Three specific comments on this video: (1) I would like to see some sort of comparison of what each of the observers (A, B and C) experience, as I would like to see everything being consistent for observers when they are momentarily at the same point, 1 and 2. (2)I am slightly concerned about how the points 1, 2 and 3 are observed by ANY observer. Is it required that there is a NOW point for 1, 2 and 3 (in at least some observers view) when this all starts? Perhaps, if so, the NOW, or "start time" at 1, 2 and 3 can be called by "you", the passive 4th observer of this situation, in the same inertial frame as 1, 2 and 3. However, for that to be the case 1, 2 and 3 would have to be equidistant from you - and that puts them on a spherical surface. That means that B and C are accelerating when they are moving! (Although I can see the "local" time at location 2 could be irrelevant, in which case it can be on a straight line between 1 and 3.) (3)This video explanation shows that acceleration is not required to resolve the theoretical paradox but it does not mention any additional effect that acceleration might have should it occur. In a real twin paradox experiment, acceleration would have to occur. And, since acceleration is equivalent to a gravitational field (in which clocks run slow), additional effects of acceleration in a real situation should at least get a mention in this video.
@Alex-gl2vh
Жыл бұрын
I do not understand this explanation. In the proposed experiment it is assumed that B and C will meet at location II. For that they have to start from their locations simultaneously. However it is not possible because in special relativity different observer's clocks cannot be synchronized in principle so there is no notion of "simultaneity" as soon as the 2 events are not co-located. To me this explanation is not any better than the "acceleration" one. Sorry.
@zakelwe
Жыл бұрын
@silverrahul That is true. You need to think or a sea of clocks at any point in space. You can set them going instantaneously to be your "big brother" on what subseqently happens.
@jamesr.arnold1615
4 жыл бұрын
This would be a relativistic solution to the "paradox" if the principle of relativity (uniform motion is relative) hasn't been violated. Having 3 observers only complicates the situation where different frames of reference are sloppily switched, almost like a magic trick. Dr Lincoln can breezily claim that acceleration isn't the key to the twin (non)paradox, but he does students of relativity a disservice.
@corwin-7365
4 жыл бұрын
So true.
@jimbob2810
5 жыл бұрын
I found this version to be better than the version without equations. It would have been more clear if Dr. Lincoln had explained what he meant by "the moving observers existed in two [frames of reference]". When he said that, he meant that the moving observers existed in two _separate_ frames of reference. Thus, he debunks the notion that the acceleration explanation for earthbound Don being older than astronaut Ron. So, the twin paradox isn't a paradox. It's just a conundrum ... and the conundrum isn't explained by acceleration, but by the Lorenz transform equations.
@marceloherzogdelunaalencar5041
6 жыл бұрын
Excellent explanation! I noticed there is a mistake for the perspective of the referential frame of observer "C" for event II, where instead of position γL should be 2γl. After struggling with the problem, I saw you already have made the correction. I think it is important to highlight that the origin of three frames started together at the event I. There is an asymmetry to explain the paradox. While observer "A" measures the difference between events in two clocks at rest where these events happened (B-A) and (C-B), each one of the observers "B" and "C" measures the interval of time on their own clocks attached with their bodies. The second intervals are proper times, related to the interval of time measured by "A" for dilation time expression: each time interval for A equals γ multiplied by each proper time interval .for B and C. If we begin with the interval measured by observer "A", we have to subtract the quantity of xv/c² for event B and add the quantity xv/c² for event C because the clocks are advanced in the direction of motion and delayed in the opposite direction by these terms according to relativity of simultaneity . After that, we have the interval of time passed in only one clock in the frame of observer "A" and we must multiply it by γ to obtain the interval for observers "B" and "C". In other words, the origin of asymmetry is the relativity of simultaneity expressed in Lorentz Transformation. Each one observer can claim the other clock is slower, and each one observer can consider moving in the direction of future of the other reference frame as expected by symmetry.
@benheideveld4617
Жыл бұрын
My conclusion from your complicated response here is that the video fails to give a clear explanation. It is completely expected that for A the first interval travelled by B from its passing by A until passing by C and subsequently the second interval travelled by C from its passing by B until its passing by A are of the same duration, namely the duration for A between B passing by A and C passing by, divided by 2γ (two gamma). This, however, does NOT explain why A cannot be seen by B to age much less.
@nadirceliloglu397
10 ай бұрын
Excellent? Are you kidding me? You are probably not a Physicist. Dialect's video is full of flaws. The presentation is excellent, not the content.
@nadirceliloglu397
10 ай бұрын
@@benheideveld4617 exactly. The video is full of flaws.
@physicself
5 жыл бұрын
Nice video, but it seems that the resolution of this paradox still requires acceleration. Without acceleration, each twin will perceive the other as younger; the resolution requires a real comparison, and you at least need one of them to accelerate to the frame of the other in order to do that - no matter how many twins you have.
@azerbajdzan9566
6 жыл бұрын
Presenting itself like the only correct explanation of twin paradox in the world, but in fact it is all wrong. The experiment with A, B, and C only describes relativity of simultaneity in different inertial frames but has nothing to do with ageing like real twin paradox does. For astronaut to age differently than identical twin on earth the astronaut MUST change its inertial frame. And the only way to do it is by an acceleration. So acceleration is a necessity for the twin paradox to occur. I agree that most people and many physicists do not understand twin paradox correctly but at the same time I have to say that Dr. Don Lincoln is among them.
@chriskennedy2846
6 жыл бұрын
Very nice explanation! Einstein himself used acceleration in his 1918 paradox resolution. You are welcome to watch my video rebuttal to Brian Greene's similar non-accelerating explanation for more details.
@LarsStokholm
6 жыл бұрын
I was trying so hard to understand everything, but then you completely lost me at the last point. What the hell is a reference frame and why does A have one why the others have two? You did a really bad job explaining that.
@jadbridge
6 жыл бұрын
I may have missed something here, but in the (x,t) coords for event II for observers B and C there seems to be an inconsistency. Specifically, the location (x) for B is given as 0, but for C is yL (I use y for gamma so it is easier to type). It seems to me that B should be -yL. If not, then C should also be 0, not yL.
@alexotenko6597
Жыл бұрын
Although X coordinate is not used for the demonstration of the time dilation, I think it is useful to work out what happened to it. E.g C takes part in all three events, so X for it is always 0.
@SuryaPrakash-je5qo
Жыл бұрын
@@alexotenko6597 good point. why is every missing this? If i am right, then if you look at 10:14 to 10:32, those equations location are all considering "X" from A's perspective only. Then shouldn't we write equations from B's and C's perspective where X is always 0 from B's perspective and X is always 0 from C's perspective. Then no body is aging faster?
@EugeneKhutoryansky
6 жыл бұрын
You are only talking about Special Relativity. Relative acceleration does play a role in General Relativity, where a single non-inertial reference frame is allowed for the spaceship’s entire journey. The person in the spaceship can believe that he is standing still by believing that there is a gravitational field present throughout all of space, and that gravitational time dilation is what causes him to be older than his twin.
@fakherhalim
6 жыл бұрын
I agree. Pure Inertial frames are too simplistic subsets of reality!
@vacuumdiagrams652
6 жыл бұрын
Well, if the acceleration is only about 1 g, the time dilation due to acceleration will be tiny---it would be comparable to the time dilation we experience by sitting on the Earth, which is not much! So GR adds some (very small) correction, but doesn't change the main picture.
@jmckaskle
6 жыл бұрын
The issue with using general relativity is that spacetime does not curve due to acceleration, and so gravitational time dilation is not a factor in the paradox.
@airplayrule
6 жыл бұрын
stecordas uh....isn't it impossible for an occupant to determine the difference between acceleration and gravity? who says BOTH don't cause curving of spacetime?
@eriknicholas7294
6 жыл бұрын
AirPlayRule For the same reason centrifugal force is not a real force; apparent force is an illusion of your finite senses. The universe doesn't care what your brain is falsely interpreting, it cares what your bundle of atoms are actually doing in -dimensional spacetime.
@gregbishop1654
6 жыл бұрын
I'm 67 and retired, but WHY could I not have had a Prof like you in University. You make complex things so understandably easy. Please keep teaching our hungry minds. Thank you Sir ! ! !
@519stream3
10 ай бұрын
It is still a paradox. A is at one location as he said which explains his reference of movement is that "location" which is independent from the observers, which also decides that A is stationary there are three stationary "locations". But these locations don't exist in real space-time and the only reference is one of the three observers, which is why we do not know who is actually stationary. If you still don't understand let us say location 1 is the earth. Unless you think earth is stationary we don't know who is moving. Or we don't know if earth is always at that stationary "location" but never moves. Or thinks there is a stationary ether in which there is a location 1
@nadirceliloglu397
10 ай бұрын
This is unfortunately not correct! You are changing the entire scenario by inteiducing a third twin,second spaceship! Also, you are removing acceleration completely. How can you? Not possible! Have you read Einstein's solutiin to the Twin Paradox as mentioned in his 1918 documents? He explicitly states that acceleration of the travelli ng twin causes non- reciprocal time dilation which makes the travell8ng twin to be younger. Easy! Also, you can easily deduce this from the worldlines of the stay at home twin and the travelling twin. Whose wordline is shorter? The travellung twin's worldline. So, he remains younger. Why are you complicating it Mr. FERMILAB? 😊
@gabrieletrovato3939
Жыл бұрын
I don't get how is it possible that we have one non-moving observer and two moving observers. Aren't all observers non-moving (according to themselves, of course) by definition? Considering B and C as moving isn't in fact still viewing the situation only from A's perspective? And how is it justified, considering that we have to prove that «Ron is younger» with every system of reference? So, for A, the velocities of A, B and C are: 0, v, -v; for B, they are: -v, 0, -2v; and for C: v, 2v, 0. Therefore, the order of the magnitude also changes: A: a
@MyJ2B
3 жыл бұрын
At 5:32, the equations are ambiguous, without clear specification of the (x2,t2) and (x1,t1) coordinates. The Lorentz transform equations are often written with a - sign inside the bracket where (x2,t2) is the coordinate of an event occurring in an initially co-aligned system moving at constant velocity, relative to another "fixed" observer who logs (x1,t1) for the same event. It's OK to downplay the math for such a wide audience but not OK to the point of spawning confusion. Physics is not pure algebra - the symbols all have physical meaning! Having criticized this omission, I still do appreciate the intuitive explanation of the twin non-paradox using A, B, and C observers.
@lucidmoses
6 жыл бұрын
Two questions then. 1) What part of the equation dealt with the delay of causality (light) it takes to get from 2l to person A? 2) You said person A only has one reference frame. However, In the twin paradox don was on a planet. Which is moving there for he also has multiple frames of reference. In fact. If everything is retaliative then counting the frames of reference is a paradox as they can be flipped. Inertia is still the only thing that separates them irrespective if you can work it out after the change in velocity or not. What have I missed? Example of my thinking based on your experiment. Let's slow things down to very (VERY) small numbers. put the two in cars going 100km/h. It was the previous acceleration that changed person c to 100km/h. So he is the one changing frames. You can see it based on the 100km/h but it's still the acceleration that caused it.
@trsomas
5 жыл бұрын
An assumption has been made that the planet is in an inertial frame. This means we assume that the proper acceleration of the planet is negligible. If you do not want to make that approximation, then instead of a planet, assume that Don stays at rest in some inertial frame of reference.
@jameslam5801
6 жыл бұрын
The original version of the experiment involves only 2 observers, in the explanation it involves 3 observers. Observers B and C see a shorter distance due to Lorentz contraction of length. But for the original version of the paradox, Ron and Don started and ended in the same inertial frame (one can forget about the earth which confuses the issue as it creates a non-inertial frame), it seems that the explanation does not deal with the original paradox. (Sorry, I am not a professional physicist.)
@Arkalius80
6 жыл бұрын
You're right, but the purpose of this scenario is to show how the result of the original scenario can be replicated without relying on acceleration. The point is that while acceleration is a relevant detail in the solution to the twin paradox, it is not the proximal cause of the differential aging.
@saxtant
8 ай бұрын
@@Arkalius80 Acceleration is the primary cause of the ageing though, since the special relativistic component only deals with the perception of time from a distance of objects at different velocity, not the fundamental nature of matter being energy in motion, which is general relativity, this problem is asking the question why are they different ages upon being reunited, which turns out to be how many relativistic rotations they ended up making and why they are different. Turns out the simple point is that matter is only in motion in relation to it's inertia, which is not a euclidean frame, it's actually represented by a matter distribution surrounding an object, using Newton's every action has an equal and opposite reaction, the sum of action and it's inertia are zero. In relativity, even the frame is projected at the speed of light, because no causal influence can happen without time, it takes time to project the frame and so an object's inertia is more influenced by matter that is closer to it. The twin paradox is dealing with the matter ageing differently when an object is accelerating in relation to it's own surrounding inertia, it experiences slower time because the electrons spinning inside the accelerated matter are limited to travel no faster than light speed, the matter slows it's internal rotations compared to the matter that makes up it's inertia. The twin paradox is all to do with it being matter that is ageing differently and general relativity solves it, special relativity is going to have to resolve crossed frames to assign a rest point and then ask relevant questions only, since asking a question must have an observer. It's a general relativity problem, like solving kinetic motion using energy equations, using special relativistic time dilation and length contraction only explain appearances from different perspectives, it doesn't deal with root of the question.
@pjwillis1979
4 жыл бұрын
As a teacher of A-level Physics I found this video interesting, especially as the textbook we supply to our students gives the acceleration & deceleration solution. A past exam question (AQA exam board) explained it by saying the rocket twin was in a non-inertial frame of reference.
@hdthor
2 жыл бұрын
The twins paradox exists in inertial frames without doing the introduction of a new reference frame C. Just imagine twin A is in a high circular orbit, and twin B is in an eccentric orbit that tangentially intersects A’s circular orbit. No rockets, no thrust, no acceleration, no non-inertial frame nonsense. We know high orbits experience time slower than low orbits. GPS satellites lose 1ns per 1s compared with us surface dwellers. But how does the twin B know it’s in a low orbit when it’s in an inertial frame? Orbits are just free-fall, and are inertial frames.
@montagdp
Жыл бұрын
@@hdthor in special relativity, spacetime is flat, so a circular or elliptical orbit would require acceleration.
@hardkraft6894
Жыл бұрын
@@hdthorcircular orbits are non intertidal. They experience constant acceleration. But I agree with you that the acceleration is not needed for the paradox to occur.
@nadirceliloglu397
10 ай бұрын
The solution with acceleration is the solutiin given by Albert Einstein in 1918. You can not solve it without acceleration as the travelling twin must change refence feames through acceleration and deceleration!!
@jeffbguarino
6 ай бұрын
@@hardkraft6894 An object in free fall does not experience acceleration. If you jump of a building you feel no forces until you hit the ground. When standing on the ground you feel the earth pushing you up from your feet. So on the surface of the earth is a non-inertial frame. The moon is in an inertial frame. So if you see an object dropped off a building while you are standing on the ground, you will calculate that it's speed is increasing relative to you and you might say it is accelerating but it is you that is feeling the upward force not the object. So from the objects point of view you are accelerating upward. This is like the equivalence principle that Einstein used at the start of General Relativity. If you are standing at the engine end of a rocket and it is accelerating, you feel a force on your feet pushing you up. When you hit the gas in your car, your seat pushed on your back to accelerate you forward. So if you equate gravity with other forces that accelerate you , just standing on the ground is as if you are accelerating up.
@stevec700
4 жыл бұрын
Sorry that explained nothing. You went through all the Lorenz equations, got to the end of the video with everyone thinking, ok here comes the explanation we've all been waiting for, then said coz frames of reference bye! It seems like you were trying to distinguish the two observers based on their locations. It's true they have different locations, but their distance from each other is the same. You cannot use north, south, up down, etc, in space. Their speeds are the same and their distance from each other is the same. From the point of view of relativity their is absolutely no difference whatsoever between observer one and observer two. Your attempt to distinguish them in the Lorenz equations based on their locations in space makes no sense.
@Raging.Geekazoid
4 жыл бұрын
So what causes time dilation? Why is the traveler younger than his twin when he gets back to Earth? The bottom line is that clocks B and C behave differently from clock A, even though they're supposedly not doing anything special. Why is at least one of them running slower than clock A? According to relativity, there's nothing inherently different about their reference frames. Twin paradox, the REAL real explanation: Einstein's principle of relativity is mystical nonsense. There's no such thing as "spacetime", and Lorentz was right: The vacuum MUST have a preferred frame in order to detect motion and slow down the subatomic processes that underlie the time evolution of moving objects.
@xtieburn
6 жыл бұрын
It appears it wasnt just me left thinking 'but... acceleration is what changes your reference frame. So isnt this rather semantic?' but Im inclined to believe that when an experts explanation doesnt add up to me that I must be missing something. So I was considering the scenario of the twins being in a small spherical universe where one starts off and arrives back by going all the way round that universe without accelerating. Im not sure how difficult a problem that would be to solve, if it needs some heady general relativity or not, but perhaps in this case and other parts of general relativity it could make for a more substantive distinction between the two ways of thinking about this? Edit: I wouldnt mind hearing other possible suggestions. I have to say Im kind of confused by what incite hes really getting at here.
@trsomas
5 жыл бұрын
Yes acceleration changes reference frame but the way some KZitem videos give explanation based on acceleration is wrong. They say that the travelling twin is accelerating, so his clock will tick slower. The correct way is to use general theory of relativity from travelling twin's frame of reference and argue that the stationary twin's clock will tick faster. See this video for more detail. kzitem.info/news/bejne/q4Z5qn-qmmR9iXo
@trsomas
5 жыл бұрын
However, the problem can be resolved without considering the value of acceleration and simply by using special theory of relativity.
@abdullahbinjahed6900
5 жыл бұрын
@@trsomas that's what i want to know .... acceleration doesn't solve the Paradox
@trsomas
5 жыл бұрын
@@abdullahbinjahed6900 According to the paradox, if we use time dilation from A's frame, we find B is younger and if we use time dilation in B's frame, we find A is younger. We should be able to resolve the paradox by pointing out where time dilation has been used wrongly in the paradox. The answer is that the astronaut uses time dilation formula form two different inertial frames and he does not account for changing from one inertial frame to another. This is where time dilation has been used wrongly in the paradox. Acceleration only serves the purpose of changing the inertial frame of reference.
@abdullahbinjahed6900
5 жыл бұрын
@@trsomas say ... a round universe with nothing in it ... now you and me popped up in existence and travel in different directions at a constant velocity ... because the universe is round we will meet again without even changing our direction ... so ... now tell me ... what's the solution ?
@semmering1
6 жыл бұрын
Ohhh no, I did not understand the point with the 2 frames .. and that was key... :-(
@brendanward2991
6 жыл бұрын
(1) I thought an event was a point in spacetime. But your Event I for A and B is located at a different point in space than Event I for C. (2) If instead of a thought experiment you tried to carry out this experiment for real, how would you do it without accelerations? How do B and C reach v and -v in the first place. (3) It is a paradox. It's not a contradiction. It has a rational explanation. But it is still paradoxical. (4) The maths works out, but you are still not explaining what it is that causes the aging of one twin to slow down. I'm still left with the suspicion that the initial acceleration shifts the travelling twin into another timeframe. I'm not saying that the dilation occurs during the acceleration, but without any acceleration there would be no time dilation. From this it seems to follow that acceleration is central to the effect.
@thedeemon
6 жыл бұрын
Coordinates are just labels, like address of a house. Different frames of reference can assign different coordinates to the same point in spacetime. For observer A his position has coordinate 0 and C has coordinate 2L. For C it's different, C is at 0 and A is at -2L. Different frames of reference assign different coordinates.
@maulikparekh776
6 жыл бұрын
@@thedeemon but then event 2 for A would also be 0 (we took it L). An event is a specific set of 4 coordinates, so event 1 should be at (0,0,0,0) for A's and B's frames and (L',0,0,0) for C's frame
@pavelmalena1154
6 жыл бұрын
excellent comments Brendan! ad 2 and 1: I'd do no synced start, just the encounters must happen in the order AB then BC then CA. The velocity is gained and settled before the encounters, so B and C appear as flying eternally. However, C must now additionaly note down also the coordinate of the encounter with A, not just A's clock, which might mean an equal complication so I'm affraid that I'm just shifting the difficulty around. Regarding your point 4, yes, I'm totally with you: if switching the frame on the turn-arround (emulated here by the BC encounter) causes a jump in simultaneity then why not the departure/arrival switches?! My explanation is that the the switch happens when the twins are at the same spot so no alternate simultaneity is possible. And here the SR reasoning departs from the reality because if the realistic acceleration happens over some time interval it also happens along a certain spatial interval, twins not at the same spot anymore - and here the expected shifts in simultaneity can already occur.
@4pharaoh
3 жыл бұрын
This is what he is saying : He "solved" the paradox "mathematically" which means he did nothing at all to clarify it's understanding. A, B and C are all in different reference frames. Observer A happens to be in the same reference frame as Locations 1,2 and 3, Observers B & C are in their own. This is his conclusion @ 12:23. It is simply why Observer A ages faster than B and C. So @11:50 he is stating the obvious really. (For bodies moving with respect the locations 1,2 & 3 as well as observer A, time moves slower, they are in a different reference frame) *But what about the paradox!* you scream! *_Aren't all three observers suppose to see the other two aging slower (Which is impossible of course.)_* The answer to *that paradox* my friends... is not in this video.
@wuqizhidao
5 жыл бұрын
That is funny. Although he claims that C is yonger by using B and C's clock to count. But all the conclusion he did are on A's prospect of view, where A is always treated as stationary in the calculation. That explains nothing at all. Because C could claim that he is stationary but B and A are moving toward him in a speed of V and 2V. in C's prospect of view, C could claim that A is yonger. But this was not show or considered in this video. So this video solved nothing at all. @Fermilab
@juzoli
6 жыл бұрын
PhysicsGirl also has a great video about it, which is less deep, but more understandable for casuals.
@juzoli
6 жыл бұрын
I mean it is not accurate, but it definitely helps if we understand that one, before listening to this one.
@DanielNogueiraLeitao
6 жыл бұрын
The problem is PhysicsGirl attributes time dilation to acceleration, whereas this video says it has nothing to do with it.
@ChenfengBao
6 жыл бұрын
+Daniel Nogueira Leitão This video is wrong in saying the twin paradox has nothing to do with acceleration, although its own explanation itself isn't wrong. Just different semantics, different emphasis.
@rsm3t
2 жыл бұрын
@@DanielNogueiraLeitao She says that you cannot treat an inertial frame the same as a non-inertial frame. The "paradox" arises when the same treatment is applied to both frames. That's not a causal attribution. It's a statement about the proper mathematics needed to compare the intervals traversed by the two paths connecting the two events. They will not be equal in the general case, and in particular, cannot be equal when one is a unique geodesic and the other is not a geodesic.
@alexbaban6435
6 жыл бұрын
I really like how you match your t-shirts with the video content 😃😃
@JanStout
6 жыл бұрын
Splitting Ron into B and C to get rid of accellerations could have been mentioned more explicitly, Still a neat explanation!
@tunichtgut5285
4 жыл бұрын
The acceleration explanation is IMHO the best one. The heart of paradox is that both twins can claim to be stationary and hence after the journey both can claim to be the older (or younger) one since according to relativity you can't decide who was moving and who wasn't. However this is not true. The acceleration breaks the symmetry of the problem. So the argument is not that the acceleration causes you to age more slowly but that it prevents one of them to claim to be stationary.
@Jonathan-uw8dy
4 жыл бұрын
How can the beginning of the experiment be called a single event? How do persons A and B and person C agree on when to start? I thought a relativistic event had to have a four-vector of three spatial dimensions and one time dimension. Absolute time on earth has no meaning at great distances away, does it?
@ChenfengBao
6 жыл бұрын
I'm quite disappointed with this "real" explanation. Isn't "frame jumping" just acceleration? I find the difference only semantic. Although it is wrong to say time dilation happens _only_ because of or _only_ during acceleration, I'm not aware of any person with any relevant credentials claiming this.
@chriskennedy2846
6 жыл бұрын
No, they are not the same - acceleration is real and frame jumping is a shell game. Einstein used acceleration in his paradox resolution in 1918. This doesn't.
@onehitpick9758
6 жыл бұрын
+Chenfeng It's wrong to say that time dilation happens only during acceleration, but it's not wrong to say that it happens because of acceleration. Go back to the real twin paradox (not one without twins that is shown here). If there is no differential acceleration, there is no differential time, period. This is, by accepted definitions of the term, a causal relation between differential acceleration and differential time dilation.
@alexvolkov223
6 жыл бұрын
What if there is a theoretical person A travelling at a constant velocity to infinity, and a variable twin B that just exists in V = 0 - wouldn't that person A age slower, without any change in velocity? If person A was born into the shape-ship already in motion. Of course this is no possible in the Twin example (no one would return to earth here), but just a theoretical example doesn't till still hold true? Especially if you had theoretical person C at the opposite end of the distance from person A, also in motion travelling to the direction of A.
@frede1905
6 жыл бұрын
Chenfeng Bao But that is pretty much the same thing that happens when you go to a point a distance L appart from a stationary observer, and then back again. You change the direction of your velocity when you turn and go back. The only difference between observer B and observer C is that their velocity has opposite directions. So "jumping" from frame B to frame C is equivalent to just "suddenly" turn and go in the opposite direction without accelerating. Of course, this is physically impossible, because you have to accelerate to do so, but this shows that if it was possible, or if you can do something similar to it, then special relativity would still work.
@parityviolation968
6 жыл бұрын
Felis Super You could assume a constant speed, but smooth change in direction (curve) until B's velocity vector is pointing right back at A, if you truly want to make the example "realistic"... But since it is just a thought experiment, there's no need for that! The point is, that a change in direction (no matter how realistic) will always break the (relativity-) symmetry between A and B. When linear motions are involved, all frames of reference are equally valid. But as soon as one of the two observers changes direction (or speed), it will know! (forces etc.). If we truly cared about a realistic change in speed that much, we should also include the traveling twin's acceleration from earth into space to begin with, which is not possible to be instantaneous either....If the creator of this video actually tried to get rid of "change in direction" by introducing new observers, complicating the thought experiment, he should also have introduced a new observer D in order to get rid of the take off discontinuity in velocity, although I guess making B just fly by earth (observer A) while exchanging time information would've sufficed.
@billkelly8222
2 жыл бұрын
I found both of Dr. Lincoln’s clips on this subject helpful. His thought experiment is not quite the same as the traveling twins thought experiment, but his experiment is successful in its own right in showing that acceleration is not key to resolving the twins paradox. For me, the essential point is this. The experiences of the two twins are not equivalent, because one involves motion of the twin with respect to his cosmic (space time) background, and the other does not. You can argue that, from his point of view, the spaceship twin has remained motionless while the Earth, and indeed the entire cosmos surrounding the Earth, have rushed away and back again. But in that scenario, from the point of view of the spaceship twin, the earthbound twin is moving along with his cosmic background; he is not moving WITHIN it. In contrast, from the point of view of the earthbound twin, the spaceship twin is moving within his cosmic background, with corresponding time dilation effects. That, I think, is the essential point. The seeming “paradox” arises because it is difficult for us to set up and explain the different frames of reference involved and how they relate to each other.
@ernestschoenmakers8181
2 жыл бұрын
Like i'm driving in my car and all of a sudden i slam the brakes then i see the car in front of me accelerate away from me and the harder i slam the brakes the harder the car in front of me accelerates away from me. But of course the other car can say the same about me but it was really me slamming the brakes so there's no paradox.
@SpongeWorthy76
2 жыл бұрын
@@ernestschoenmakers8181 you've described an (de)acceleration scenario
@ernestschoenmakers8181
2 жыл бұрын
@@SpongeWorthy76 Yeah but it's a bit the same idea, i was decellerating not the car in front of me who was just driving at a constant speed wrt the road.
@russellstephan6844
Жыл бұрын
Acceleration is still necessary... Acceleration alters the angle of the "now" timeslice. On a typical space time diagram where time is the X-axis and all three dimensions of space are combined into the y-axis, acceleration causes the "now" time slice line to slope negatively. The alteration of that slope is what causes the local clock discrepancy. Brian Greene has a marvelous "now" timeslice visual: kzitem.info/news/bejne/ypqp3W1vjIWofpg
@kemptonka
6 жыл бұрын
I’d like to see you do a video that incorporates the apparent simultaneity into resolving this paradox. As you change frames of reference, what is considered “now” changes. In imagining how the two twins perceive the flow of time, it’s like when the moving twin turns around, his “now” for the other twin changes. At a constant velocity, both would see their own “now” going further into the other’s past. When the one turns around the frame of reference changes so much that the moving twin see’s the apparent “now” jump so far into the other’s future that he can still see the other aging slower with time dilation during the entire trip, but arrives back home finding the stationary twin has aged considerably more than himself. Like Brian Greene talks about “now slices” in this clip: kzitem.info/news/bejne/roWVt5OcaomYhH4
@jonathanbyers791
Жыл бұрын
I don't get this, 'In imagining how the two twins perceive the flow of time' what do you mean by this? And what is 'now' ? You can only have the same now if together, otherwise I'm not sure what you mean by 'now'? I have seen other people talk about 'now' in Relativity related scenarios, but don't grasp it, because 'now' is only relevant to me now, or to someone else, somewhere else, which is somewhen else (not local). They are not linked, unless very local like a telephone call.
@kemptonka
Жыл бұрын
@@jonathanbyers791 It's like trying to keep a clock that shows your own time, and one that will show the other's time and match their clock when you get back together. You can send messages between each other to keep up to date. But if the message came from a light year away, it makes a big difference if your inertial frame of reference is moving toward them, or away from them. That inertial frame has been moving in that direction at a constant velocity for a whole year since the message was sent. www.staskoagency.com/wp-content/uploads/2016/12/b8258-oldnewsroom.jpeg
@johnnet2472
Жыл бұрын
I don't understand something here. The only way the spaceship twin can avoid acceleration is to be going at the close to the speed of light when she leaves earth. That is the spaceship sister flys pass her twin sister on earth as she is flying on her way to the star at close a speed of light. But how does she coordinate her clock with her twin's clock? She must include her speed in determining if the two clocks are synchronous. In fact the sister on earth will see her twin sister's clock on the spaceship moving very slow. The sister on the spaceship will also see her sister's clock on earth moving very slow. Provided neither sister slams on the brakes and undergoes gravity, or what looks like gravity, than neither sister will ever know the age of the other sister because a signal traveling at the speed of light to show the time on the clocks will always be lagging behind the spaceship traveling at close to the speed of light. And it will take this considerable time to catch up with the spaceship. I think Einstein is very careful to state that for two clocks to be determined to be synchronous they must be checked where both clocks are close to each other and in the same frame of reference. But how can the twin sisters clocks be in the same frame of reference or close to each other if one is moving away from or toward the other at the speed of light. This is of considerable error if the third sister, L2, is making her observation from a star 4 light-years away from the sister resting on the planet. Which is to say you do not make the problem any easier to understand by eliminating the acceleration. You just move the complexications to determining what do you mean by saying all 3 sisters, the one on the planet, the one moving away from the planet and the one moving towards the plant are all the same age (clocks are synchronous) at the start of the experiment. Note this is not a trivial acceleration, or gravitational pull, to go from zero to 0.999c to zero to 0.999c to zero in 4 months. No such spaceship exist or can be built if relativity is correct. Provided all three sisters are the same age, that is the clocks are synchronous at the start of the experiment, and no sister undergoes acceleration then the experiment is impossible to conduct. This paradox looks a little like a perpetual motion machine where it works only if you ignore the details. You could say OK all three sisters are to start the experiment from earth at the same time. One sister remains on earth, one flies away to turn around and fly past earth on her way to the star and one flies to the star to turn around and fly back past the earth. The problem is all three sisters will be starting the experiment at different ages and be in different frames of reference. And when the experiment is completed all will be of different ages. But no paradox because you can not compare each sisters space-time travel or synchronize the experiment start.
@hemangidudani4584
4 жыл бұрын
All of his videos starts amazing but cant make a point due to poor explanation ! Please make more detailed videos, the misunderstand time dilation was a brilliant idea and was going on right way but at last things werent clear, your examples are too confusing with given animation.
@onehitpick9758
6 жыл бұрын
A perfectly symmetric scenario is described? B and C are absolutely symmetric. That being said, I understand it all and it doesn't resolve the twin paradox. You have to incorporate the asymmetry, and it is due to acceleration. Acceleration is outside the scope of special relativity and violates the assumptions of both SR and the Lorentz transformations. The twin that experiences acceleration is not even remotely allowed to say she's stationary within the context of SR or Lorentz. This is a part of the assumptions of the theory. You can pseudo-analyze non-inertial frames within the context of SR, but it is a logical violation of assumption. I of course follow your arguments, but they are mathematically, formally inconsistent when applied to the departing and returning twin. A better resolution is required. In the purely SR case, "outliving your enemies" can be achieved by relative velocity, but you have to have differential acceleration to get there and back. There is no denying that. To say that it is all velocity is denying the derivative. All things considered, this is an excellent video and among the best presentations on this topic I've seen. The bottom line is that if a departing and returning traveler and twin experience different accelerations, they will have different times upon reuniting. If they experience identical accelerations, well, they will have identical times. This post will likely be deleted by remote observer with faster clock, but I encourage you to read before.
@karejonsson8264
6 жыл бұрын
If acceleration was the thing the duration of the flight would not matter but thats incorrect.
@pavelmalena1154
6 жыл бұрын
yes, inconsistent, that's the word. the setup is fundamentally different from the twin paradox experiment, it's a different scenario. any proof that the result can be applied to the twin paradox??
@alanjones4358
5 жыл бұрын
@@karejonsson8264 The "gravitational" time dilation due to acceleration is a factor of the distance between the clocks, which indirectly depends on the duration.
@Frydlund
6 жыл бұрын
Ron needs to fly 8 lightyears and it will take him 4 months. Does he need 8 years worth of fuel on the spaceship or 4 months?
@SerenityReceiver
6 жыл бұрын
Time is the same for him as for his fuel (so: 4 months). But: To get to his speed he needs a lot of energy to accelerate. Once his velocity near c is reached, I assume his fuel-cost-efficiency is pretty neat, if he never wants to stop again.
@pavelmalena1154
6 жыл бұрын
no fuel needed, Ron does not accelerate in this experiment! Instead, Ron got schizophrenic, he's now Ron b and Ron c, new approach to interstellar travels, you become two (sorry I'm being sarcastic at the faulty setup of the experiment)
@mr.h4267
5 жыл бұрын
Good question. He'll need enough fuel to accelerate to .99c, then to decelerate to go around alpha centauri, then to accelerate back up to .99c again, and then finally to decelerate to 0 back at earth. He wouldn't use any fuel during the parts of the trip at constant speed. So, no idea...
@allahspreadshate6486
5 жыл бұрын
I'm not sure if you meant to, but you've stumbled across a VERY interesting 'philosophical' question. :D
@caccioman
4 жыл бұрын
Lets give it a twist: does he need oxygen and food supply for 4 months or 8 years? I think its for 8 years, but I might be wrong
@Senekha86
6 жыл бұрын
This was a bid hard to understand. The best explanation I ever heard was in the video "Raumzeitdiagramme und Zwillingsparadoxon • Aristoteles ⯈ Stringtheorie (16) | Josef M. Gaßner" (german) using Minkowski diagrams. Especially about the 26:00 mark was the breakthrough for me. Its totally obvious seeing this. Good video however, as always :)
@thstroyur
6 жыл бұрын
Also MP, and das Wiki :D
@RichardKriske
3 ай бұрын
Hi, I am Richard Kriske and I proposed that a Mobius orbital is needed to understand the twin paradox. The problem with your argument is that it's not about reality, just about plugging values into a simple equation. According to Kepler there are 3 orbitals, the parabolic, hyperbolic and elliptical. 2 of your observers have to be in parabolic orbitals and the stationary observer, A, would have to be performing some sort of triangulation to observe the other traveling actors. You're completely wrong about acceleration not playing a role, as B and C are in orbitals. Anyway, I have a better explanation. There's missing orbital, that is the Mobius. Say observer A, doesn't undergo acceleration, so he remains on earth, and so is stationary. Observer B accelerates into a hyperbolic orbital and escapes the earth, heads for alpha centauri goes into an elliptical orbit, heads back to earth, his overall orbital is elliptical, and the simplest would 360 degrees. The duration between the 2 observers is real. Time is normally imaginary, but can become real using acceleration as seen in orbitals. This acceleration breaks the quantum superposition between the 2 observers, but this can be restored if observer A takes the same trip, and between the 2 of them 720 degrees occurs. Quantum superposition is restored and the two are the same age again. This is how two electrons orbit a nucleus and stay in superposition. The trouble with explaining physics, as you do, by ignoring reality, is that it doesn't lead to any new ideas.
@francescocannistra7915
4 жыл бұрын
Honestly, the provided argument seems to me a fallacy given that saying that an observer "lives" in (at least) 2 different inertial frames is exactly the same as saying that she/he undergoes some acceleration.
@WeAreShowboat
6 жыл бұрын
How do you get them (A,B,C) to all start stopwatches at the same time?
@wr2382
6 жыл бұрын
Easy. 1. Put a light at the mid-point. 2. Turn the light on. 3. A, B and C start their stopwatches when the light reaches them.
@FaelCacilhas
6 жыл бұрын
If you do this then B will start his watch L/c seconds before the others, since he IS at midpoint.
@The_Sandcrawler
6 жыл бұрын
Rafael Cacilhas No, because B started at position 1, where A is. The light would be coming from the midpoint, position 2, and reach position 1, where A and B are, and position 3, where C is, at the same time, signaling person B at position 1, and person C at position 3, to start moving, while person A remains at position 1.
@hanxhancocks1727
5 жыл бұрын
Quantum Telepathy...
@WeAreShowboat
Жыл бұрын
@@wr2382No this doesn’t work. Person A and person C will not agree that they started their clocks at the same moment. Their reference frames are different and clocks will not be synchronized with each other and would claim the other person started their clock at the wrong moment. I mean also, person C will get the light before person A since person C is going to meet the light partway (according to the view that person A is at rest).
@vast634
6 жыл бұрын
How do they synchronize to start moving at the same time? Send a lightbeam as signal?
@Ranoake
6 жыл бұрын
It doesn't matter. It is a thought experiment. It would be hard to organize, but theoretically possible and hence the math can just be applied.
@pavelmalena1154
6 жыл бұрын
indeed, no need for that. that would drown us in the complications of simultaneity. they actually don't start moving because they move eternally, no acceleration allowed. you can imagine that there's an infinite stream of travellers C and this experiment looks at the one guy who meets traveller B at the middle point #2.
@ericl8743
5 жыл бұрын
Yes with a light signal. If you look at a spacetime diagram, light will always move at a 45 degree angle regardless of the speed of the other reference frame. So you can send a light signal to another observer and he starts his clock when the light signal hits him. It's reflected off a surface and send back to the original observer. If you take the total time elapsed for the first observer and divide it by two, you know how long it took for the light to reach the second observer so you then how much to delay your clock for proper calibration
@KRGruner
6 жыл бұрын
Interestingly enough, Einstein himself stated that the acceleration was the only possible explanation. Which of course it is. It's a lot easier to think about this if you start with the twins on board two different spaceships (rather than one being on the earth, which tends to make people automatically think of it as "immobile" while the spaceship is "moving" - but why?). It is impossible in special relativity to get rid of the symmetry issue the two reference frames, because it only deals with inertial (that is, non-accelerated) frames. Acceleration is what makes the difference. Just like Einstein said.
@Arkalius80
6 жыл бұрын
Acceleration is the cause of the fact that one twin is stationary in two different inertial frames while the other only in one. The acceleration isn't the proximal cause, the different reference frames is. So it is correct to say the acceleration is important, but to focus too strongly on it would be misleading, suggesting that acceleration is necessary to produce this kind of result in general.
@trsomas
5 жыл бұрын
We can explain using acceleration also. We use general theory of relativity in travelling observer's frame of reference and argue that the stationary observer's clock will be faster. But it is possible to resolve the paradox purely by using special theory of relativity. kzitem.info/news/bejne/q4Z5qn-qmmR9iXo
@russellstephan6844
Жыл бұрын
Acceleration is still necessary... Acceleration alters the angle of the "now" timeslice. On a typical space time diagram where time is the X-axis and all three dimensions of space are combined into the y-axis, acceleration causes the "now" time slice line to slope negatively. The alteration of that slope is what causes the local clock discrepancy. Brian Greene has a marvelous "now" timeslice visual: kzitem.info/news/bejne/ypqp3W1vjIWofpg
@ep5acg
5 жыл бұрын
The conclusion uses the term "reference frame", a term that did not exist anywhere in the rest of the video. How can a person see the conclusion follows from an argument when the two use different languages?
@ibperson7765
5 жыл бұрын
I still dont know how we know what’s accelerating. Wrt to what?? If it’s some center of the universe why dont I fell acceleration on a rotating revolving planet and galaxy etc.
@Earthspirit1147
5 жыл бұрын
"I'll pause for a moment so you can look at them..." LOLOLOLOL!!!
@davidmurphy563
6 жыл бұрын
I have a notepad full of scribbles which give a very impressive look to my total failure to perform the transformation. I'm not even sure how the additional reference frame solves the paradox. Still, there's nothing better than having something you firmly believed shown to be completely wrong and I'm not beaten yet. Back to my scribbling I go...
@davidmurphy563
6 жыл бұрын
So A's perspective is good old Galileo: Ai. x=0, t=0 Aii. x=L, t=L/v Aiii. x=0, t=2L/v Let's focus on the spacial transformation and employ x2=y(x1 + vt1) Bi. x= It's very obvious B is where the event is happening so x=0 from his perspective. So the maths should be easy and we can confirm we get the right number. We need the x transformation: x2=y(0 + v*0) Great, we get x=0. Quick check for t: t2 = y(t1 + v/c^2 * x1) so y(0 + v/v^2 * 0) = 0. Ok good, zero again. Bi. x=0, t=0 For Bii, the right answer is also obvious but let's do it. First question, it's t1 (so A's then and t=L/v) but whose v?? Is it from A's perspective (so positive) or B's (negative)? It must be A's because the whole point is to calculate B's from A's. Second question, is x1 A's perspective on its own distance to the event or A's perspective on B's distance? I'll try the former: x2 = y(L + v*L/v) so yL. That is not zero. The latter then: x means A's opinion on the distance between B and the event. Jesus... ok. y(0 + v * 1/v) so y(0 + 0). Mmm. I'm getting zero but I'm not convinced. Let's skip ahead to the end to x on the third event for C which isn't zero: Ciii. x=y(2 + v*2/v)=y(2L) - is that the same as your answer 2yL?? I have no idea... I wish I had a working example with velocities and times to check my answers... I have no idea if I'm doing it completely wrong or if these are valid answers... Given this, I think the latter isn't the likeliest option! If anyone wishes to point out my abject stupidity then I'd be grateful!! :-)
@avaescaner
6 жыл бұрын
I got lost at the same place, this guy does not explain or defines half of the things he writes, it is very hard to follow him and understand what he tries to say. I assume constant V (capital) is the speed to the right and -V the speed to the left for the guys in the example. In the Lorenz transformations, there is a lowercase v, which is a variable. For case II, you have as seen from A (x,t) = (L, L/V). So when you replace in the Lorenz transform for the position, you get: x' = gamma (L + v * L/V). Then what is v in this formula? I guess it is the speed of A seen from B, because that is what matches his result: x' = gamma (L + -V*L/V) = gamma (L-L) = gamma * 0 = 0. An then for the Lorenz transformation for time: t' = gamma ( L/V + -V*L/c^2) = L * gamma * (1/V - V/c^2) = > (multiplying by V on both sides) => t'*V = L * gamma * (1/V - V/c^2) * V = L * gamma * (V/V - V^2/c^2) = L * gamma (1 - v^2/c^2) = (hmmm that looks familiar!) = L * gamma / gamma^2 = L/gamma => t' = L/(V * gamma). Oh crap, I just got this one trying to show where I got stuck, I promise! :)
@Reddles37
6 жыл бұрын
For some reason he actually has the inverse Lorentz boost written in the video, which means you need the velocity from B's perspective (negative for B, positive for C). Normally the Lorentz boost is written from A's perspective and the equations have negative signs. There also appears to be a typo in the results, for Cii it should be x = 2 * γ * L I hope that helps.
@Quadflash
6 жыл бұрын
Gonna have to study this video for a while, but gaining clarity about the "paradox" will be more than worth the effort! Thanks, Don!!!
@a.b.5772
6 жыл бұрын
If you haven't seen the videos (4) he references to preface this one, I recommend them like he does. They give the proper background to explain the problem he poses here . Plus you get to see him rollen past the haters in a sweet Corvette.
@schweinehundbullshit9176
Жыл бұрын
I am not so sure.
@warren286
5 жыл бұрын
What I don't understand is why don't we just make the speed of light our zero point/ the point of reference, since it's constant. Everything else is moving relatively to it.
@nikbock9039
Жыл бұрын
6:35 I don't understand how A and B could agree where C is "now" if A and B are moving relative to each other and have different perspective what "now" is in point 3.
@gelmir7322
6 жыл бұрын
So to solve the Twin Paradox you actually need a triplet?
@chriskennedy2846
6 жыл бұрын
Right - why do physicists propose to tell you that there is really no "twin paradox" at all but then when they try to prove it, their example has a traveling twin who never returns to earth? In the tradition of 7 fictitious dimensions I can sell you and a host of super symmetric particles that will be detected any minute now (just you wait!) you will have to believe your twin brother is younger than you even though you will never see him again because they sent him away for life. Watch my rebuttal video to Brian Greene's explanation.
@adizmal
6 жыл бұрын
Dr. Don Lincoln... my guy! :D
@theophilus749
6 жыл бұрын
Help from a physicist please: Don says that there is no acceleration in the case of the twin paradox - but isn't the transition from one reference frame to another what acceleration is? Where am I going wrong here?
@theophilus749
6 жыл бұрын
Don's example still confuses me (though it is new to me, I must confess). In the twins case, the two twins A & B part company then rejoin.
@thstroyur
6 жыл бұрын
+Theo Philus Yer not wrong: describing the motion via 'clock swapping' still requires gluing together different inertial frames comoving with actual observers - i.e., acceleration
@socalfan3268
6 жыл бұрын
"His example shows that the acceleration isn't relevant" But, by definition, the twin paradox REQUIRES that Observer B travel to Alpha Centauri AND return. The ONLY way Observer B can return is by transitioning to Observer C's reference frame at Alpha Centauri. And the ONLY way Observer B can do this is by accelerating from v to -v at Alpha Centauri. Without this acceleration, Observer B continues to travel away from Observer A so (1) there is no twin paradox, and (2) the thought experiment is only 2 separate examples of time dilation added together. The twin paradox requires that the twins MEET in the future to compare ages side by side. Bottom line: 2 twins start and end in the same place. Which twin is younger? The twin who traveled and who experienced the acceleration.
@vampyricon7026
6 жыл бұрын
ScienceNinjaDude But can't we set the rocket person as the stationary frame and say Earth is the frame that's moving out and back? That's using the same treatment with two different frames for the Earth "frame". I guess what I'm trying to say is, why is the rocket the one with 2 frames? Why isn't Earth the one with two frames?
@ChenfengBao
6 жыл бұрын
I agree. Whether it's "acceleration" or "frame jumping" is just a semantic difference. I don't find any deep meaningful difference between the two explanations. Although it is wrong to say time dilation happens _only_ because of or _only_ during acceleration, I'm not aware of any people with any relevant credential claiming this. Credential: PhD student in physics.
@WSFeuer
4 жыл бұрын
Saying the twin switched inertial frames is EXACTLY THE SAME as saying he accelerated. That's literally built into the definition of inertial frames. If you switch from one frame to another, your velocity has changed, and you've accelerated. This video better explains the confusion over acceleration: kzitem.info/news/bejne/z4irvHuFpmlmaWU
@nexus3112
3 жыл бұрын
But wouldn't length contraction of the moving observer make the distance travelled by him shorter than L with respect to the stationary observer.
@yoghurt3643
6 жыл бұрын
Acceleration isn‘t the cause! That cannot be stressed enough, as it is such a widespread misconception! So thanks a lot for that superb video on this topic, Dr. Lincoln!
@thstroyur
6 жыл бұрын
It _is_ ; check out my comment on why. The contrived 'two frames' conclusion here, though seemingly getting rid of acceleration, doesn't do so because it requires swapping a _global_ chart for an _atlas_ of _local_ ones to describe the motion. This is a technicality of diff geo, that relates to things like the stereographic projection, but it's at the heart of the equivalence principle: local inertial motion = acceleration = gravity
@onehitpick9758
6 жыл бұрын
No relative acceleration, no clock difference. This passes many tests of causality. Define cause?
@Arkalius80
6 жыл бұрын
I feel like it's important to say acceleration isn't the proximal cause. It is, however, important in the scenario. The proximal cause is the fact that the traveling twin exists in more than one inertial frame of reference on his trip. The reason he does this (in the classical twin paradox) is because he must accelerate to turn around. So it would be wrong to say the answer has nothing to do with acceleration. However, it would also be inaccurate to focus on the acceleration itself rather than its result.
@yoghurt3643
6 жыл бұрын
Arkalius80 There is also the case of the identically accelerated twins. Here both twins undergo identical acceleration, yet one ends up older. See for example www.researchgate.net/publication/241349452_The_case_of_the_identically_accelerated_twins
@yoghurt3643
6 жыл бұрын
onehit pick That’s wrong. See the case of the identically accelerated twins.
@aashishhegde1525
6 жыл бұрын
sir, suppose both Ron and Don are not familiar with STR & time dilation. Now Ron knows it will take him atleast 4yrs to reach the star since his ship travels at 0.99C. But due to time dilation he realizes he has reached in merely 22 mnts. So he decides to crosscheck his speed and finds out he must be travelling at 2.2C to cover 4 light years in 22 mnts. How is this possible,please explain?
@rikkathemejo
6 жыл бұрын
length contraction?
@alexanderreusens7633
6 жыл бұрын
For Ron, the distance to reach the star was a bit more then 22 lightmonths, or 1.83 ly. Travelling at high speed shortens distances too. Accelerating warps the space around you. I advice you to check this game: Velocity Raptor. It shows you what would happen if the light speed was ridiculously low. (featured on Vsauce's channel DONG) testtubegames.com/velocityraptor.html
@mrjava66
6 жыл бұрын
Aashish Hegde the distance is dilated as well.
@RoboBoddicker
6 жыл бұрын
Distances are relative. A lightyear isnt any more absolute than a mile or a foot. Remember light is moving at c in both reference frames. So a lightyear measured by Ron is much longer than a lightyear measured by Don.
@onehitpick9758
6 жыл бұрын
Ron forgot about length contraction.
@KasiusKlej
6 жыл бұрын
I gather from this video that acceleration myth has been busted. Youthfulness is proportional solely to the number of reference frames, whatever the method of counting those frames is. Now, why did physics design such an awkward thought experiment 100 years ago, full of unnecessary circumstances? No wonder it lead to the myth. Studying this newest explanation (by the way, it's somewhat hard to grasp when sitting here looking at the explanation from the fourth reference frame, looking at paradox that cancels out with another paradox sort of stuff) I can't help looking for simpler explanation. Perhaps some explanation along the lines on how one gets minimum youthfulness in absolute zero temperature environment and every moving beyond that then increases youthfulness, up to a photon in vacuum that doesn't age at all. Something simpler that is. The slippery relativistics make my head spin.
@good4usoul
6 жыл бұрын
See what you think of this: kzitem.info/news/bejne/06iQqWR4pWh_d44 Rather than describe the math, I've put everything into mathematica, and actually make IT do all the calculations to perform the Lorentz Transformation on the spacetime diagram over the course of the traveling twin's journey.
@KasiusKlej
6 жыл бұрын
Your animation is a brilliant head spinner, Jonathan. I like it, it has all the necessary details I think. Of course, I'm just a layman looking for a word that would best describe what makes one twin younger and not the other. All the videos I find have always somehow preestablished that the traveler will come out younger, but what if for example the Earth was really massive, so that the twin on Earth would spend his time in a considerable gravitational free fall, while the traveler would have an easy ride. Could there then be a situation when the earthling comes out younger?
@LuisAldamiz
6 жыл бұрын
Are you saying that the explanation is that the traveler goes through more reference frames (space "slices") than the non-traveler and that's why he ages less (experiences more space but less time)? That sounds much more clear to me than Dr. Lincolns' explanation. Thank you very much.
@buzzbee5840
6 жыл бұрын
Acceleration is NOT a myth. No myth busted here. An instantaneous acceleration of the Twin Paradox rocket occurs at the point of turnaround but is completely ignored by the flawed proposed "two frames of reference" assertion in this video. See my posted comment for more.
@apurvmj
4 жыл бұрын
All the observer can have Lorentz transformation applied to other observer. How is this going to solve this problem
@tomasjirka2670
6 жыл бұрын
Another explanation: kzitem.info/news/bejne/kZ-AwJOHgH99d2U seems to be more explanatory; although I'm not an expert
@ComputerAlgorithm-p4i
8 ай бұрын
Sorry, but this explanation is not solving "Twin Paradox". You have converted Twin Paradox to Triplet Paradox.
@BD-np6bv
3 жыл бұрын
The example doesn't match the example of one person accelerating near the speed of light while other one stays on Earth. This A, B, C example could have been worded in such a way that C is stationary, and A and B are both approaching C at some speed, with B approaching C at 2x the velocity of A approaching C. In this example, all movement would be IDENTICAL with respect to each observer, except C is the stationary one. Yet, they wouldn't know it! You're telling me the math will work out the same exact way despite C being stationary instead of A? The other probability is B is the stationary one and both A and C are moving away and coming at B at the same speed, but in different directions. This time it's B who's stationary but A and C are both the only ones moving. How's the math work out now? Summary: this example of A being stationary can be said that C or B are also stationary and it's the other two moving! The real answer is the acceleration part. When you accelerate near the speed of light, Einstein tell us it's the same as being close to the gravitational effects of a black hole. GRAVITY and ACCELERATION are the same! Time slows down near the gravitational effects of a black hole, which would accelerate you near the speed of light to the event horizon! That is the real answer. Dr. Lincoln is correct on many things, but he's clearly wrong on this one.
@DrDeuteron
3 жыл бұрын
In C's reference frame, v_B is not 2v_A, so paragraph 1 is out. In B's reference frame, v_A is not v_C, so paragraph 2 is out. You can add any fourth frame D at any speed, and the time between B leaving A and C meet A will be more in A's frame (according to D's clock) han the total elapsed time experienced by B and C or their respective legs, whether D=A, D=B, D=C, or D is something else. The math does work out, but you have to do it right.
@Blue_Goat
Жыл бұрын
Can you make a different twin paradox example using A, B, and C experiencing different gravity? Maybe all three are stationary to all observers. Then a black hole moves through the single frame of reference, with A, B, and C at different distances from the black hole. The gravity of the black hole attracts the three observers A, B, and C. Normally this would make the observers closest to the black hole appear to move faster, relative to a fourth observer. But remember in this example all three appear stationary to all observers. So for example, if A is closest to the black hole, A must accelerate away from the black just enough to have no apparent motion relative to itself or any other observers. The same for B and C, although they will require less acceleration to appear stationary because they are farther away from the black hole. After the black hole passes, all observers agree to have observed no motion. However, observer A will have experienced the less time than B and C.
@narendrakrane
5 жыл бұрын
ok.. if the 3 events from A's POV are (0,0); (L, L/v), and (0, 2L/v), then why arent the same 3 events from B's POV: (0,0), (0, L/v), and (-2L, 2L/v) ? Why do they have y (gamma factor) in their perspective? If you are factoring gamma in "B and C's POV", Basically you are taking only A's POV under the names B's POV and C's POV! Can you explain this?
@mikegale9757
5 жыл бұрын
Exactly! An equally valid interpretation for A is (0,0), (L,vL), (0, 2vL). SR cannot distinguish between those two cases. There is a tacit assumption that (to a very good approximation) A resides in the centre of mass reference frame throughout the entire affair.
@LuarAzul2
3 жыл бұрын
From C's reference frame, A and B are approaching, with B approaching at twice the speed of A. Clearly, from C's perspective, B will have the slowest moving clock and A slower than C's but faster than B. From B's perspective both A and C are moving at the same speed, so they have the same gamma factor. I fail to see how seeing things only from A's frame of reference explains the "paradox", because it results precisely from the apparent disagreement of what different frames of reference would predict. What we need to show is how all three perspectives are consistent.
@corwin-7365
3 жыл бұрын
Slight correction. From C's reference frame B is not approaching at twice the speed of A; they are approaching slower than that (although at low speeds it approaches x2).
@roberthansen9876
2 жыл бұрын
So, after reviewing dozens of twin paradox explanations, most bad, some thoughts... As I alluded to previously, this video doesn't address the twin paradox, it addresses why acceleration is not the source of the time dilation. I suppose Don veered off the topic of the twin paradox to the topic of why acceleration doesn't account for the time dilation because the internet is now saturated with bad twin paradox explanations that mangle so many things that he simply lost his place and went after acceleration. Yes, acceleration is not the source of time dilation and this problem does not require general relativity. 8th grade algebra is sufficient. But that doesn't address the paradox. In fact, this isn't even a paradox in the proper sense, which I will explain later. First, the correct interpretation. There are three inertial reference frames, one stationary, one moving to the right at a constant speed, and one moving to the left at a constant speed. Both twins start in the stationary frame. The traveling twin jumps from the stationary frame to the frame moving to the right, and when he reaches the star, he jumps from that frame to the frame moving to the left, and when he reaches earth, jumps back to the stationary frame with the other twin who stayed there the whole time. You do the math and the traveling twin has aged less than the twin who stayed on earth the whole time. Now the alleged paradox. Some will claim (using the principle of relativity) that we should be able to say that the ship's frame is stationary and it is the earth's frame that moves to left and then to the right and thus the earth's twin will be younger. But they both can't be younger! People who make this claim, including me in high school, commit several sins, but it is this first sin that tanks them. Saying that the the ship's frame is stationary or that the earth's frame moves to the left isn't even semantically correct. You don't move inertial frames of reference nor are the attached to objects. They are abstract coordinate systems in space moving with a constant velocity. They are independent of the objects, but chosen to match the problem and to make the math simple. Thus the correct way to state the alleged paradox would be to say "Suppose instead it is the earth (and the whole universe) that jumps from the stationary frame to the frame moving to the left and then when the star reaches the ship (that stayed in the stationary frame), the earth (and universe) jump to the frame moving to the right, and then they jump to the stationary frame when the earth reaches the ship. But now that you have stated it correctly, the alleged paradox is absurd. You have the entire universe minus one measly spaceship going from a stationary frame to a moving frame. The change in momentum of the entire universe is absurd. End of story. The problem only makes sense if it is the ship jumping from frame to frame. Why this isn't a paradox? In a paradox, you solve the problem correctly, but the answer conflicts with your senses and intuition. In this case, people who claim a paradox, solved the problem incorrectly (absurdly even) and besides, we don't have senses or intuition of time dilation. Some people call it a pseudo paradox, which is probably the best characterization. A fake paradox. I have been known to refer to it as a paradox of ignorance. Regarding acceleration. People, including me, will say that acceleration is the reason that the traveling twin is the twin with the slow clock. And what we mean by that is that in order to jump from one inertial reference frame to another, you must accelerate. Remember, these are inertial reference frames, which means constant velocity. If you do not accelerate (change your velocity) then you will remain in that same frame forever. We are not saying that the time dilation is due to acceleration. We are saying that acceleration is the means of jumping from one frame to the other and since the ship (not the universe) is accelerating, it is the ship doing the jumping. Don's example in the video is the same setup. Three inertial reference frames. A is stationary, B is moving to the right, and C is moving to the left. My only nit pick is that he didn't explain why he set it up that way. He didn't address the paradox. I could just as easily set it up such that the crossover was on the left and gotten the opposite result (that A's clock was slow instead of B's). But he set it up to the right because he knew that the ship was jumping frames, not the twin on earth (and the earth, the star, the universe, LOL). Side Note: I need to go back and read the original papers from 1905 or so, but it is possible that this pseudo paradox wasn't the original paradox. The original paradox might have been the way Einstein wrote it (though he didn't call it a paradox). In other words, after you solve the problem correctly, it is paradoxical that the traveling twin (or any twin) ages less. You solve the problem correctly, but get an answer that conflicts with your senses and intuition. That makes more sense than solving the problem absurdly wrong and then the wrong answer conflicts with your senses and intuition, as if you knew what the right answer was supposed to be???? Here is the cleanest analysis and solution to the twin problem I have found thus far (note I did not say paradox) ... kzitem.info/news/bejne/kq6Yk65uk6unfGk kzitem.info/news/bejne/tqNjzpx_gYZifno kzitem.info/news/bejne/t5tm3X2FaZhopKQ kzitem.info/news/bejne/zoJmvm2If4d6n5w Finally, I don't mean this comment in any disparaging way to Don. I am sure he has forgotten more physics than I will ever know. I started looking for a decent explanation for my son, and got drawn into this strange twin-paradox-explanation phenomenon on the internet. Even the wikipedia article was incoherent after all the mangling and distortion.
@marcv2648
Жыл бұрын
Sabine Hossenfelder disagrees with you. She says it's all about acceleration.
4 жыл бұрын
Like the other commenters, I didn't find this explanation adequate. See this video, which explains the twin "paradox" using general theory of relativity: kzitem.info/news/bejne/w6B-spalhGR-ZJw The key is the force of acceleration, which implies a gravitational field across the universe, if the person inside the rocket believes that he is at rest. General theory of relativity tells us, that the time is running slower closer to the source of gravity. Therefore, the time on Earth speeds forward during the time of acceleration. When a rocket starts the journey from the Earth, the clocks tick at virtually the same rate, because they aren't far apart.
@corwin-7365
4 жыл бұрын
True. Or you can also use the _minutephysics_ approach using acceleration under Special Relativity. Both are good. kzitem.info/news/bejne/kZ-AwJOHgH99d2U
@robertbrandywine
3 жыл бұрын
Okay, I think the proper take on this, this lack of symmetry, is that the distance from A to the "goal" (space station or star) is different for the A, B, and C observers. Since A and the goal are traveling at the same speed (more or less) there is no Lorentz contraction involved. A sees the "proper" length. But since B and C are moving with respect to A *and* the goal they see the distance between A and the goal as shortened. A, B, and C all agree on the speed that B and C are moving with respect to A and the goal. This *must* mean that B and C will take less time to travel the shorter distance than A experiences back on Earth. It's that simple.
@robertbrandywine
3 жыл бұрын
@Anshari Hasanbasri It seems to me that the triggering of time dilation isn't the solution because A looking at B and C's clocks will see the same time dilation that B and C will see on A's clock.That's symmetric. What isn't symmetric is that the distant star is in the same inertial frame as is A but it is *not* in the same inertial frame(s) as B and C. This means that A will see the distance to the distant star as different than B and C see it.
@alanjones4358
5 жыл бұрын
So the ship's twin aging less is not caused by his acceleration, it's instead caused by his change in velocity. Got it. ◔ ⌣ ◔ Seriously, if you have to substitute two different inertial frames with two different velocities for the ship's accelerated frame to show that it's "not the acceleration", then it's the acceleration (change in velocity). If you only meant that it's not a physical effect of G-forces, you should have said that instead.
@firdacz
5 жыл бұрын
Poor choice of words. I like Don's videos a lot, but he should not have stated that acceleration is not the answer - it IS, for the same reason you cannot switch frames, which he uses as argument.
@TingleCowboy
Жыл бұрын
A far too complex explanation, where one has the feeling that the actual problem was not understood correctly. The solution of the problem is not to compare any clocks and to solve time equations. Nor is it necessary to fly the route twice and change any reference frames. The real asymmetry lies in the length contraction. With increasing speed, only the length of the spacecraft is shortened for the stationary observer, while for the moving observer the complete distance is shortened. If two observers have strongly different velocities, not only the point of view on the time changes, but also the point of view on the space. So if the traveler at the destination would simply be beamed to the surface and then communicate with the earth with light signals, one would still come to the conclusion that the traveler has aged less. The distance was not the same for both observers, therefore there is no absolute simultaneity. For both observers the clock of the other seems to run slower, but they observe a different arrival time at the destination.
@stewiesaidthat
Жыл бұрын
Clocks measure MOTION. Period. End of discussion. You are trying to read into a measurement something that doesn't exist. A slower running clock just shows that it traveled a greater distance. If you can't fathom that, then you have no business teaching physics. And, since nobody, in every single one of these relativity/time-dilation videos understands that simple fact, it belies the collective stupidity of mankind and the ability to easily brainwash and manipulate these semi evolved monkeys.
@tegami0102
5 жыл бұрын
This guy is telling baloney. It is the acceleration that explains the phenomenom. Your reasoning is valid for each observer, hence you did not explain anything, quite disapointing.
@allahspreadshate6486
5 жыл бұрын
You're wrong. Accerelation has nothing to do with it. It's all about reference frames. Sorry if this is too difficult to understand.
@tegami0102
5 жыл бұрын
@@allahspreadshate6486 Eh, No. You seem to have not even understood the paradox at all. The experience is non symmetrical : the earthling twin is not experiencing any acceleration at all, but the twin traveling back and forth to the eart IS, hence the difference when they reunite. We can use Special Theory of relativity for two observers that are in the same reference frame, but during the acceleration / deceleration phases, the reference frame of the traveling twin changes, it is no more inertial by definition.
@allahspreadshate6486
5 жыл бұрын
@@tegami0102 - When two bodies move apart they both experience the same relative acceleration, but in opposite directions. Same again when they re-unite, for an overall difference of zero.
@tegami0102
5 жыл бұрын
@@allahspreadshate6486 I can't tell if you're trolling me or not. If not, you need to rethink what acceleration is, seriously. There is no such thing as "relative acceleration", you are confusing speed with acceleration. Velocity is relative, acceleration is absolute. This example might help : think of an observer in a train that starts, in comparison with an observer standing on the platform. When the train starts, strongly enough so the passenger can tell he is moving, he can feel the acceleraiton pulling him back in his seat, whereas for the guy staying on the platform, he is not feeling / experincing any acceleration (expect earth's gravity, likewise the traveller). When the train reachs a constant speed, it is true to say that each observer is right saying that they are the one beeing stationnary and it is the other who is moving, and only then can we say we are in a symetrical situation. Hope that helps
@Maldives2011ful
5 жыл бұрын
I am confused. So, acceleration has nothing to do with it. Richard Feynman, one of the greatest physicists that ever lived, writes in Chapter 16 of his lectures, quote: "... the man who has felt the accelerations, who has seen things fall against the walls, and so on, is the one who would be the younger; that is the difference between them in an “absolute” sense, and it is certainly correct."
@betaneptune
5 жыл бұрын
Acceleration is what breaks the symmetry, but it is the uniform motion where the time dilation happens for Ron. For Don there is a speed up when Ron turns around. The other thing to keep in mind is that Don can use SR because he never undergoes acceleration. Ron can't use SR because he does. You can integrate Ron's proper time (the time in his system) over the trip (see the first relativity chapter in J.D. Jackson, _Classical Electrodynamics_ for the actual integral).
@sanketpatil2683
6 жыл бұрын
I think the resolution is incomplete. Three quarters done, to be precise. It has been explained how much time passes on the spaceship according to an observer on earth as well as on the spaceship(s). So far, so good. The time that passes on earth during this ordeal, according to the observer on earth, has also been noted. But how much time passes on earth according to the observer(s) on the spaceship(s), and how that matches with the aforementioned interval (time passed on earth according to observer on earth), has not been explained. This, according to me, is the heart of this paradox, which is also the most difficult part to resolve without considering accelerated frame.
5 жыл бұрын
Exactly, that is what is missing! I think the explanation is the issue of simultaneousness. Two observers can only compare clocks when they are at the same position. That is the whole idea of the set-up. The problem you mention is that B should observe A's clock moving slower. This would give a conflicting result, from B's reference when reaching event II. I think the explanation here is that B can't compare clocks with A at event II because they are not at the same position.
@onehitpick9758
6 жыл бұрын
A point of possible confusion with this is at 8:07 where the statement is made that you can work out how you can get from 1 to 2 and back to 1 again without any acceleration. This is true for non-massive quantities, and it actually would take an infinite, impossible acceleration at position 2 to accomplish this with anything that has mass. You have shown that you can get information from 1 to 2 and back again this way, but not an observer or clock. If you compare the clocks of observers B and C and the "end" of the experiment, there is no difference. This example should be re-presented in a physically realistic point of view from observers starting from a common space-time point. Mixing observers that are in different frames from the start might create confusion and is not the essence of twin "paradox" since the starting point has two opposing frames that are not twins.
@andrzejsikorski2301
4 ай бұрын
Mój eksperyment myślowy jest taki. A stoi w miejscu, B leci w kosmos z prędkością światła 2 lata i wraca 2 lata. I co ? A jest starszy o 4 lata ,a B też jest starszy o 4 lata a cała ta teoria jest całkowitą bzdurą.
@brettfadem2084
6 ай бұрын
While the overall message of the video is great and your version of the thought experiment is enlightening, your treatment of observer C is sloppy. The Lorentz transformations that you apply are derived under the assumption that x=x'=0 at t=t'=0. This works for observer A and observer B, but observer C starts their stopwatch at a different location than observer A and observer B and event I does not occur at the origin of their reference frame (at least not if observer C claims he is at position x=0 at t=0 in his frame). In the end, this discrepancy doesn't matter because the reference frame of observer C and the reference frame you claim is observer C's move at the same velocity, so observer C would be at rest in the reference frame you claim is his, even though he does not exist at the origin of that frame. Still, not addressing this detail confuses people who watch your video and leads to them dismissing your overall correct explanation.
@zakelwe
6 ай бұрын
Observer C does not depend on location, just velocity between them and A and B. Which you state later.
@docholliday7381
5 жыл бұрын
So if observer B just continues to another planet and then communicates with observer A. Who have aged then ? It seems to me that you need to return to Observer A for the "ageing" to occur. Because the conclusion was that. One existed only in one frame while the other existed in two frames. So what happens if they both just exist in one frame.
@allahspreadshate6486
5 жыл бұрын
The 'return' causes the aging to un-occur.
@zacharyknopp4298
3 жыл бұрын
For anyone else confused, this video helped me: kzitem.info/news/bejne/tn-k0naAbYefooY
@danielkovacs1313
5 ай бұрын
Actually this video does not do anything else than divides the traveler twin's path in two sections. Although it is true that the time difference in the end depends on the length of the uniform motion of the travel, it is actually the acceleration part (or the change of the reference frame of the moving twin) that causes a shift of simultaneity for the moving twin. Until that does not happen, there will be no twin paradox, just a usual symmetrical case of time dilation.
@DrDeuteron
3 ай бұрын
"Until that does not happen,"...what does that mean? There is no acceleration. No one accelerates.
@garybergman7690
5 жыл бұрын
In the example, from observer C's perspective, shouldn't the location for all events (I, II and III) be zero? From C's perspective, all events occur at it's "non-moving" location, i.e., at the start, when it is even with B and when it is even with A.
5 жыл бұрын
The events are measured relative observer C's reference frame. Event I does not happen at the same position as C, which means the x value can't be 0 (which was given in the explanation). However, you are right regarding event II and III. Observer C are at these events, and so should measure x as 0.
@asimdahal3249
4 жыл бұрын
This doesn't explain anything. We want to know the age of the twin after he "returns". If he doesn't return at all, there is no need for any explanation because different inertial observer see different things. The main thing is what happens for an accelerated observer and the thing is that he sees time going faster for inertial observers.
@DrDeuteron
3 жыл бұрын
except if you reverse the acceleration, you reverse the time change, so that doesn't work.
@JaredStokes-j2q
Жыл бұрын
How does something reach 99.9% of light speed without accelerating?
@garydeleon
5 жыл бұрын
?? On to the CORRECTION in 10:32, shouldn't the location of event II for observer C be 0, not 2yL? If so, C's locations for events I and III should be 2yL and 0 respectively (not the other way around).
5 жыл бұрын
Right, almost. Notice that C overlaps A at event III. That means x should be 0 from C's perspective for that event.
@abebass37
6 жыл бұрын
Don, you are wrong! You are not explaining the “Twin Paradox”; you are explaining the “Triplet Paradox”! Also in the “Triplet Paradox” the triplet are not at the same place when they start the experiment. The one & only explanation for the classical “Twin Paradox” is acceleration!
@Arkalius80
6 жыл бұрын
I think you're missing the point. The point is that acceleration, while important in the classical twins paradox, is not the proximal cause of the differential aging. The proximal cause is the fact that the traveling twin is stationary in two different inertial frames while the one at home is stationary in only one. This happens because the traveling twin accelerates during his trip to change his frame of reference, but it is possible to produce this scenario without relying on acceleration.
@ashutoshverma5980
4 жыл бұрын
Richard Feynman in his lectures on physics clearly says that acceleration is the answer to this question....... please reply #fermilab
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