Dr. Lincoln Is Wrong About The Twin Paradox (Special Relativity) 

Very good script and graphics. You demonstrate through you presentation and demeanor your intellectual authority.

Ok, it seems you gave a good explanation that agrees with Dr. Lincoln. The question in the twin paradox is whether the rotation of the traveling twin's line of simultaneity at the turn-around has an action at a distance effect on Earth twin to age him faster? I rather think not. I think that traveling Twin can know that Earth twin is older by simply reading the star clock and acceleration is NOT the answer.

Great explanation! You helped me understand more of what Dr. Don was really saying about them by emphasizing what happened in your animation. This is the first time I've seen the Lorentz transformation with the additional term, and it's kind of mind-blowing. However, I believe the key to solving the Twin Paradox, at least not in general relativity like curved spacetime, is to consider the plane of simultaneity. The moving observer has to switch the plane as they change the frame of reference. When they do that, the plane flips, and there is an instant delay in time. However, if it were instant, this would mean it's like a sharp corner worldline, not continuous. So acceleration is a process when an observer occupies a non-inertial frame, constantly passing through infinite planes of simultaneity. This is when they see time for the rest of the universe changing, and I also consider an alteration in explanation using a uniform gravitational field. However, in the reference frame of Special Relativity, we can think of this as an observer passing through an infinite number of inertial frames and infinite planes of simultaneity without requiring the existence of a gravitational field. The gravitational field is just a way to strengthen the first postulate of Special Relativity. My own solution is the following : If we create a station attacted with two light bulbs seperated. where both light bulbs ignite at the same time, the moving Twin will see a difference in the order of events in the outgoing case and the return case due to the effect of simultaneity . This is my solution to the Twin Paradox. What do you think? In the end, both B and C will agree that A is older, but they will all say the others have experienced time dilation, which is symmetrically beautiful!

I questioned Dr. Lincoln's explanation. When it comes down to the twin's paradox, it boils down to the question why, if each twin was travelling at the same speed relative to the other, will one have aged faster than the other when they meet up again on the return. It can only be due to a difference in their experiences, and the only thing that breaks that symmetry is that one of them was changing their inertial frame of reference, and that only happens if they undergo acceleration. Sabine Hossenfelder's explanation in her video involved the acceleration and change of inertial frame of reference, and Dr. Lincoln did a follow up video and with a rather hand-waving argument said that they were actually in agreement, but had taken a different way in explaining it. That really threw me. I should add that, in the "real world", the stay at home twin is undergoing his own accelerations, but we can get rid of that by allowing him to just follow a geodesic. Being in an orbit in space would do that. I would also add that I've also seen a lot of very misleading statements about what the nature of the paradox is with the twins.

The absolute best explanation can found on the FloatHeadPhysics channel.

What a mess, but I thought the same about Doc Lincoln's explanation.

simultaneity is relative to what stationary basis you take yes. basically, in SR everyone takes the basis corresponding to sitting still in the medium, the ambiguity in simultaneity isn't physical it is just the notion that you do not know what basis is correct. but you are correct that setting this experiment up in this exact way requires synchronizing clocks non locally which is not really possible to do unambiguously without some sort of broken symmetry. but it isn't strictly necessary to do that for this setup, what you can do instead is just send c away to a far away planet and tell him that you will send a light signal to him such that he can start traveling back towards you at a certain velocity relative to whatever, you just wing it and wherever you end up having the meeting place between c and b is kind of irrelevant, you only need c to record b's time and reset his own clock, then when he gets back to a we should always see a have a long elapsed time no matter the velocity of b or c. and no matter the stationary frame basis you took :). the twin paradox is kind of independent of convention so synchronizing clocks is not really an issue fundamentally. but the deeper problem with saying it has nothing to do with acceleration is that acceleration is just a change of velocity, instantaneous acceleration is identical to the setup here, it has no effect on the clocks at all anyway, and the reason for the solution to the twin paradox is just to say one path is longer in every frame you could view it from, which is true and that is the end of that story. but if you do it simultaneously in every medium based basis there is also the funny property that the uniform motion trajectory always has the longer time elapsed no matter what you do, even if you assume an ether where the moving observers time definitely ticks slower than the uniform motion twin but also ticks faster for part of the journey, for a very simple reason, the part where it ticks faster than the uniform motion twin gets much much shorter in the "objective ether time" when compared with the two other paths of uniform motion where the round trip twins long leg always moves faster and therefore their total time elapsed is slower. as you boost them in the ether so to speak to look for faster and faster representations of the situation, the "faster legs" gets closer and closer to 45 degrees the kink gets flatter and flatter but ultimately the elapsed times are conserved anyway for any representation. it is always just a triangle that gets deformed until its three legs are approaching the same light cone in either direction, the elapsed times and what each of them sees is always conserved anyway.

I would be interested to hear your comments on gravitational time dilation. Particularly as it applies to light frequencies and distance calculations between galaxies.

In _special_ relativity acceleration has to be involved to move a single observer between reference frames. But the acceleration itself is not the cause of time dilation. This would go directly against the Clock Hypothesis. A clock's rate only depends on its instantaneous relative velocity. The time along the path is equal to the sum of the times along its inertial parts. Acceleration in SR can be modeled as a series of instantaneous inertial frames. What fermilab is showing is that the twin paradox can be broken down into the path length considerations without having to think about the actual turnaround and still get the same result at least qualitatively. (I am not actually sure the integral over the acceleration period always yields the exact same result as the sum over the total path length, though) Blaming acceleration for the time dilation is attractive but misleading. This becomes more relevant in General Relativity, when we can have diverging/converging spacetime paths without any proper acceleration. I think Dr. Lincoln can be forgiven for not involving the full Poincare group transformation, since it doesn't add much to the final result. Though it does lead to open questions, like the symmetry of the observers.

could you do a video or explanation on this scenario please. triplets. 1 triplet E stays on earth. 1 triplet R goes right at some speed close to light 1 triplet L goes left at same speed close to light. they stop and turn and come back to earth. by my understanding. the triplet on earth should be older and the other two triplets R and L the exact same younger age as each other. But here's where i get confused again. Now same exact scenario if we remove triplet E from the scene. we get left with just triplet R and L. Now triplet R and L can both argue each other is moving away and coming back, whilst they themselves are staying still. Without earth as the reference point they can argue they are stationery. So how would their ages be the same? when they meet up. Cos it seems like I've now suddenly entered into the twin paradox and 1 twin should be younger than the other. what am i missing here in my understanding.

I see what Dr. Lincoln demonstrated was quite right. It's an application of the 'reverse' triangle inequality in Minkowski spacetime. So sometimes acceleration is the reason but not necessarily. Imagine a triangle with 2 'curved sides', that's acceleration. Second Observer C can actually have their (0, 0) at ANY event (here event 1), it's just coordinates. Their set of Lorentz transformations do have to be modified accordingly as you pointed out.

Instead of just saying acceleration is resonsible for age difference, I would say the uniform motion parts are also responsible. Because if we slice the 'history' into a family of spacelike hyperplanes (simultaneity planes), i.e. treating the problem in a manner of 'intial value problem', that's exactly what's happening when we slice by slice look into simultaneity planes. The 'selfish' observer-wise analysis is more 'practical' in terms of local measurements, but in my opinion it means all we can say is 'just compare intial and final events' or 'just calculate length of ENTIRE worldlines'. If we stick to local measurements, it's no way for observer C to figure out the corresponding simultaneous event far away, etc. We can't talk about intermediate process at all with local measurements unless we change the setting by introducing a continuous exchange of signals between observers. Intead, the intial value problem set up really leave a room for talking about intermediate process, in which age of observers are just mechanical observables parameterized by spacelike hyperplanes. We can talk about for a given parameter, what are readings of age. And this fundamentally reduce to the fact that everything has a Lorentz symmetric dynamics (at least when energy is not too high considering the possibility of Lorentz violation) thus every clock including human aging would obey clock dilation which, differentially speaking, has nothing to do with acceleration but only depends on instant speed. (You only need first derivatives to calculate length of a worldline.) (Btw it's really weird to me to say 'time dilation' since 't' is nothing more than a parameter while readings of clocks are real observables.)

Absolutely brilliant. Side note: at 08:16 the correction terms in green need to be exchanged between x' and t', but you correct the issues in the following calculations. Overall the best explanation I've seen on youtube about the paradox.

I just came across your video on the twin paradox. Great job! I have a very fundamental question. It seems that all the discussions are based on the rocket twin being younger upon return. My question is how do we know this to be true? Is their any experimental data that supports this?

The only issue I have is that your animated rocket engines have a flame out the back.

Consider a "paradox" where I walk along two sides of a right triangle, while you walk along the hypotenuse. From your perspective I'm always walking at an angle (therefore slower), while from my perspective you're the one walking at an angle - I'm always moving faster than you are in the direction I'm currently going. So if both of us always think the other person is slower, why do you get to the end before me? You can either go through my observations step by step and show that when I turn the corner I go from thinking you're behind me to thinking you're ahead of me, so our observations match by the end and there's no paradox. Or you can just say "don't worry about comparing people who aren't at the same point in space. One of them took the straight path and the other took the curvy path, the end."

I don't see how that Fermilab video gets at the twin paradox at all. It CAN'T, because it doesn't account for the effect that turning around at location 3 has on B's simultaneity lines.

I think the thing that most people struggle with when it comes to the twin paradox is that they are looking for a single reason for why the one twin ends up being younger when they reunite. In that I mean one that both the traveling and stay at home twin will agree upon. But instead what you have is that while the two agree at the end who aged less, they have different views on how this came about, and both of their views are equally valid.

Good job. However, there's a point which everyone muddles. When B leaves Earth, does he accelerate from v= 0? Or does he start already at high speed ('born fast', so to speak)? These are two different scenarios. Same question for traveler C. Your video would be improved by clarifying these questions.

I remember trying to figure out the twin paradox, running into Don Lincoln's video after watching several others, and thinking, "Finally! I understand!" But I guess I didn't understand. Of course not being a physicist myself, I'm still not sure. If the experts disagree, how can I adjudicate between them?

the mathematics is completely redundant really, all you need is the length contraction of a longitudinal light clock in a space time diagram, and you can make the right triangle, by changing basis in the stationary frame or ether frame, you simply shift the angles of the trajectories and theory respective length contractions around, and the bounces back and forth inside the light clock as drawn on the spacetime diagram keeps perfect track of time in all the representations easily. you can show it just by assuming length contraction of the right sort from the time dilation of transverse light clocks matching a longitudinal light clock by means of that form of length contraction draw the longitudinal light clock in the 1+1 space time diagram, don't worry about correct coordinate transformations, transform the state instead by adjusting only the length contraction of the light clocks in the diagram depending on angle, that is one equation to put into an animation and the time keeping simply takes care of itself, then you can just show what is going on for all possible frames of reference by simply transforming the space time diagram.

Very clear explanation! Thank you a lot!

3 observer universe , all equal . 2 blast away in opposite directions 1 remains at their centre of gravity . That one has standard time for the entire system . the 2 that are moving , at the same velocity in opposite directions have slowed clocks perfectly in synch. The 1 left at the centre ages faster because HIS clock is not slowed. For systems with large mass vs very small mass , it is the MASS that determines the governing body in the results . Time in a rocket slows . Time on earth doesn't. To make time on earth slow would require a huge amount of energy to move the earth away from the rocket at velocity.

Thanks! I felt that his explanation was way too "good". I was not smart enough to see why Dr. Lincoln was wrong, but I know that SpaceTime on the other side of our universe is moving ftl relative to us.

No, it happens as the traveler is turning around, and it doesn't matter whether you turn around slow and gracefully with low acceleration (which takes a long time) or infinitely fast with a "sharp corner" in the world line. The simultaneity lines still shift, and that is how the Earthbound twin gets older.

Well done. I debunked also several times his video as Dialect ones that are in many many places full of bullshit « physics » and totally false reasoning. But they are both so arrogant that they deny every contradiction of their obvious flops

It is great that you show that Lincoln's treatment of observer C is sloppy and contains incorrect coordinate transformations. However, notice that despite Lincoln's sloppy handling of the coordinate transformations for observer C, you both arrive at the same time elapsed for the trip as measured by each observer. Your overall result agrees with Lincoln's overall result, i.e. 2*L/(gamma*v) for the astronauts combined measurements. Later, you assert that all the aging takes place during the acceleration. This is wrong. By your own calculation, clock B reads a shorter time at Event II than clock A. This literally means that the time between Event I and Event II is shorter for observer B than it is for observer A. The symmetry is broken because observer B is present at both event I and event II while observer A is not. If observer A were to compare the time interval for half the trip between the two stars, observer A's measurement would already disagree with observer B's measurement by the same factor.

SR doesn't say anything about acceleration. Each observer is given identical clocks and measuring rods. One moves at constant velocity, the other doesn't. In SR it doesn't matter who is A and who is B. They both measure the same values within their respective inertial frames, for example, they measure the same value for the speed of light. Time dilation and length contraction falls from a comparison of A to B or B to A. Without the comparison there is no time dilation nor length contraction. Both will experience time dilation and length contraction depending on the point of view. A says B is moving. But B says A is moving. Swap your perspective and you get the same answers. The twin paradox arises because we compare the twins (thru observation of clocks) and say one is older than the other (time dilation). We define a point of view and define 'who' is 'moving'. We interpret that time dilation to be persistent once both twins return to the same inertial frame. Is it real? Perhaps neutrino decay is the best evidence for this? But, isn't there a larger concern here? If it is real, then can't we claim there is a preferred inertial frame. Wouldn't such a preferred inertial frame justify the ether? Wouldn't an ether change physics completely?

Please remember that when muons are created in the atmosphere, they travel with almost constant speed before decay, which tell us muon experience time differently than the observer on earth. Thus acceleration cannot be used to explain the twin paradox.

How about agreeing with Poincare and the whole paradox is solved?

I like that there is a real discussion brewing inside RU-vid about the twin's paradox! We have Physics - problems and solutions against Dialect and Fermilab and then we have Dialect against ... well ... everyone! And maybe we have other channels against eachother than I dont know! The thing is - this is getting really interesting! Because where there is conflict - there are things to find out and new things to learn! I don't know yet which one to believe, they all sound very convincing... I guess I will wait and see!

Exact! IMHO with accelerations out of the equation you have indeed exact symmetry between the two twins and you are facing the paradox.

I don't think Dr Lincoln is wrong. He is just using a though experiment idea that C leaves at a time that would make him get to the middle point at the same time B would. The thought experiment is to show that no one accelerated but there was no paradox. The best way to see this is Minute Physics video on the twin paradox.

I find it fascinating that people are still disagreeing on this twin paradox resolution yet nevertheless all are fully confident that it is resolved and that there is no problem for our ontological interpretation of special relativity. I believe Einstein was one of the first to suggest the acceleration part as a way to understand the asymmetry between the two observers. Yet I still see in philosophy of science recent claims that this is not strictly required, and that from the proper time of Minkowski space-time equations alone we can solve it. The issue I think goes quite deep into the issue of what ontologically relativity is actually saying about reality. I have my own way of resolving it which involves some quite specific philosophical concepts, but that is a whole can of worms of its own that requires an ontological shift in our whole perspective and I am still working my way through figuring it out to see if it all fits properly.

I thought that guy was at CERN. Or did he move to Fermi lab recently?

The extra term of the Lorentz transformation must be coherent, and that is just what Dr. Lincoln wants to show. t'=gt - gvx/c2 on the other hand I can imagine that S' is fixed and S goes with -v, then this must also be true t=gt'+ gvx'/c2 There is a seemingly contradiction when looking at the times. Let's look at dt'/dt in both formulas, assuming a certain x or x' fixed. Let's assume x'=0, which means x=vt, and let's derive dt'/dt for this point, the results must be the same. Taking the first formula dt'/dt= g-gv2/c2=1/g Using the second formula, it is even easier dt/dt'=g => dt'/dt=1/g => We get the same result.

1) it's called a "Poincare Transform" or an inhomogeneous Lorentz transform--it is a nuisance. 2) The point of 3 observers is that there are 3 straight world lines in the problem, and each one integrate "d(tau)" along the leg, so it all works out. However, integrating d(tau) along any worldline always works in all frames because it is a covariant operation in Minkowski space (M4), and special relativity if self-consistent, and thus there are no paradoxes in M4. That is not a satisfactory resolution to the paradox. The paradoxes appear when comparing different 3 + 1 breakdowns while forgetting linear transforms have a slope (time dilation) *and* an offset (clock bias).

You are still facing the paradox, I mean.

Nice video and presentation. Time dilation doesn’t take place on those who don’t understand SR.

Thank you for these videos. I like your explanations. Here is what ChatGPT4 says. ChatGPT4 agrees with you. I'd like to learn more about proper time and world lines. Maybe make a video about those? Also you drew a simultaneous line (or something). What is that? Me: How would you resolve the twin paradox in special relativity? ChatGPT4: The Twin Paradox is a thought experiment in special relativity that involves identical twins, one of whom makes a journey into space in a high-speed rocket and the other remains on Earth. Upon the traveling twin's return, the paradox is that the traveling twin would age less than the twin who stayed on Earth, due to the effects of time dilation-a prediction of special relativity that time passes at a slower rate for an object in motion compared to one at rest, relative to an observer. The apparent "paradox" arises because, from the perspective of the traveling twin, one might argue that it is the Earth-bound twin who is moving and therefore the Earth-bound twin should age less. However, this misunderstanding is resolved through the realization that the situation is not symmetric. The key to resolving the paradox lies in the fact that the traveling twin experiences acceleration and deceleration during the journey (turning around to return to Earth), which breaks the symmetry of the situation. Special relativity's resolution to the Twin Paradox involves understanding the role of acceleration: 1. **Inertial Frames**: Special relativity applies fully in inertial frames of reference-that is, frames not accelerating. The Earth-bound twin remains in an inertial frame (for practical purposes, ignoring Earth's rotation and orbit around the Sun), while the traveling twin does not because the journey involves acceleration when turning around to come back. 2. **Acceleration and General Relativity**: The traveling twin's frame of reference changes when they accelerate and decelerate. This non-inertial frame (one that is accelerating) means that general relativity must also be considered to fully understand the scenario. General relativity predicts that time runs slower in stronger gravitational fields, which is analogous to the effects of acceleration due to the equivalence principle. 3. **Proper Time and Worldlines**: In relativity, the aging of the twins can be accurately calculated by considering their worldlines (paths through spacetime) and the concept of proper time (the time measured by a clock following that worldline). The twin on Earth follows a relatively straight path through spacetime, while the traveling twin's path includes a turn that represents the acceleration and deceleration. The proper time along the Earth twin's worldline is longer than that along the traveling twin's path, meaning the Earth-bound twin ages more. Thus, the resolution of the Twin Paradox is that the traveling twin indeed ages less due to the effects of time dilation experienced during the high-speed segment of the journey. The asymmetry introduced by the traveling twin's acceleration and change in inertial frames is the key factor that resolves the paradox within the framework of relativity.

In the journey from point A to point B a traveler accelerates and equally decelerates ( equally in the total quantity of energy used to do it per each procedure ) to get to point B. So, the traveler becomes younger at acceleration and older at deceleration, because what's making the process real at acceleration should be backward-symmetrical real at deceleration, therefore, there's no net change in age. The same coming back from point B to point A. This is not about how a second relatively stationary person sees the traveler. This is about the supposed "real effect" of acceleration on the real process of aging - not that I believe Einstein's idiocy called "relativity" ( Relativity is just a mathematical trick, not a real phenomenon. The approximate congruence with Newton's gravity expression has been made intentionally to be that way. Marcel Grossman has worked very hard to obtain that congruence. The whole relativity theory is just a huge erroneous and useless theoretical epicycle, Copernicus-times style, that has nothing to do with the real dynamic of the Universe. A superfluous mathematical trick, and nothing more than that. )

The Twin Paradox Just confuses the situation even more. It is more simple to state : The faster you travel through space, the slower you are traveling in time. Whether you are accelerating or a constant speed there is time Dilation. At Constant speed the time Dilation is constant throughout the ship. If the ship is accelerating the back of the ship is moving slower in time the front of the ship is traveling faster in time. When the ship is traveling close to the speed of C there is length contraction. What the observer on earth would notice that the ship is traveling close to the speed of C. The observer on earth would notice that the spaceman is moving very slowly in the ship. Since the spaceman is moving slowly he will observe the observer on earth to be moving slowly, there is and has never been a paradox.

Firstly, light and observers have nothing to do with time. Turn out the lights and you may start to get a sense of what time is. Any experiments involving light and observers will be inconclusive. Everything happens in the present. Time dilation is merely the change in the rate at which objects age due to gravity warping space. Those objects are still in the present its just the rate at which they age is different.

The problem is that space IS time, and vice versa. A cannot observe c, or even b for that matter. Thus relying on the record of b. There is no simultinaity, as you say. No way for a to know or prove anything,

13:19 Hannibal Smith type of moment lol

Excellent breakdown and graphics. I'm glad I'm not the only one finding poor physics on youtube.

So what happens if we add something to the classical Twin Paradox? This paradox always assumes that the observer that stays on earth sits like Buddha for 10 years or more without ever accelerating or decelerating. So to make it more clear that it should not be the case, let's have both Twins starting in the same rest frame on earth. Then Twin B gets in his spaceship, accelerates to.0.87c in 1ms and then keeps that speed until it reaches a place that's 5 light years away from earth, at which point he turns around (deceleration and acceleration again in 1ms to 0c and 0.87c respectively) and heads back to earth. On arrival again decelerates from o. 87c to 0c in 1ms. Till here everything as usual. But let's introduce a twist: Twin A after a while gets bored of sitting like Buddha (let's say after a couple of years in his clock) and decides to also jump in his own spaceship and have a short trip to around the moon and back. For it, he accelerates and decelerates equally to his twin, but his round trip just takes a couple of seconds as measured on earth. Then he goes back to sit like Buddha until his twin comes back to earth. What's the end result now? Due to the same acceleration in both twins during the whole period, are they now indistinguishable from each other, both young and innocent? Or has Twin A still got older and wiser than Twin B? And if so, why? If not acceleration or the 2 frames BS, what's the only other possible thing that breaks the symmetry? It can't be velocity through time, since velocity is always relative, right? Or is it? 🤔

Great job!

Prof Lincoln is correct when saying that is wrong to claim the difference occured during accelaration. However, the only consistent explanation of why the effect is asymmetric is acceleration. So trying to ignore acceleration in the twin paradox is misleading.

Nice work

Why not peer reviewed papers yet? I know why.

Your unwanted conclusion that twin paradox iz false is correct. Anf obviousl acceleration wont change it.

Excellent

Thanks man!!!

The fallacy is the the Lorentz transforms indicate an actual change in the "moving" system. They indicate what the observer measures about the moving system IMO, NOT about any actual changes because of relative velocity. Thus, the "paradox" is a misuse of the equations.

I don't think you understand the situation correctly. In Dr. Lincoln video observer C is only introduced to show that to observe the twin paradox you need to change your reference frame from one inertial frame to another. Without this change there is no twin paradox as A and B will never meet again, therefore A will forever see B aging slower than he while B will forever see that A ages slower then her. The explanations including gravity or acceleration are used only because then observer B can change their inertial reference frame from the one a moving away from, to the one moving toward A, and when someone hears the word "observer" usually a human observer (or in this case a single atomic clock) comes to mind. But you don't really need an accelerating observer to explain what's happening, it is enough that you switch from an inertial reference frame to another. BTW at around 6:12 you state that simultaneity is relative. But that is only true for observers who move relative to each other. When they are not moving relative to each other their clocks can be synchronized so that both B and C may start at t=0. However there is no need for that it only simplifies the explanation. The only requirement is that C must move in the opposite direction than B with the same velocity relative to A. When they meet anywhere C synchronize the clock with B. The line of simultaneity between A and B and A and C is different. See the figure on page 169 in 'Spacetime Physics' (E.F. Taylor & J.A. Wheeler, 2nd ed.) The reason that although both B and C see A aging less during the periods they can observe, while A sees both B and C aging less still C will be younger than A is that the observations of B and C exclude a large portion of the time that passes on Earth while they are travelling.

No

Space and Time are separate frames of reference. Clocks are instruments that measure motion in space. The energy from the sun accelerates plants through the lifespan. Going faster in space doesnt necessarily change the amount of energy in the system. Not when you can just add more.

Thanks for video dude.. these "guys" aggravate me also. This topic always contains many unrealistic assumptions so it can make nonsensical claims about time dialation. Which confuse and frustrate. In end i decide people explain this as if its a magic trick not in a way to understand Consideer these assumption, travellor accelerates at 1g same as earth human. Velocity is not constant, but gra it is for both on entire trip. Spacecraft rotates to acellerate so both feel exactlt same gravity. Both are in same inertal frame Also both humans move away and toward each other by same velocity. So by relativity both have same age at end. Therefore relative velocity and acceleration/gravity same for both and age are same. I think people become confused with senational claims about cesium clocks on airplains, trying make this all about velocity, but moving around a rotating mass has other considerations, you can attribute to gravity or velocity if you wish to confuxe and excite people.

Just another nonsense

You lost me. What if we make the problem 100% symmetrical. Let's consider two twins (A and B) moving at a constant speed in opposite directions on the surface of the Earth. Assume a motionless Earth. The twins are each moving at a speed of 0.25 times the speed of light, but in opposite directions. Their trajectory is circular, orbiting the Earth, and they cross each other twice per revolution. From the perspective of twin A, twin B is moving at 0.5 times the speed of light in one direction. And from the perspective of twin B, it is twin A who is moving at 0.5 times the speed of light, but in the opposite direction. When they meet (twice per revolution), who’s younger and who’s older?

It's hard to find a video of Lincoln where he doesn't make at least one inaccuracy. He carries around a set of misconceptions in his head that he then uses to confuse his students and send them on their way lol

In any case, the solution to this "paradox" is to calculate the proper times of the two world lines. Without a clear definition of proper time, a confusion arises.

I agree with you 100% - I saw that Fermilab video years ago and absolutely rolled my eyes. For someone to declare themselves an expert and get in front of people on RU-vid like that, and get it WRONG, is just pathetic.

here's some more sand on the gears= DEFINE SIMULTANEITY. how can any 2 beings , separated by any distance worth measuring agree on what it means NOW? a mirror gives you a reflection of your past self. no relativity involved, simply, how long it takes for light to go to your eyes from the mirror.

But guys. Its easy to come up with a scenario of the twin or triplet paradox which doesn't require any accelerations. I think you're all wrong!

About what I see at 9:20 for Observer A: why is AE2 = (L/v, L) but at 4:33 it is (L, L/v) ? Assuming the "convention" (x,t), since it is an event of A why is it (L, L/v) and not (0, L/v_B) ? Why there isn't γ involved as if the calculations weren't considering the γ factor?

Doesn't the expansion of the universe screw things up?

Wrong, wrong, wrong: Your twin goes to Centari very fast. You stay on earth. Due to SR your twin sees you as much older. But you see your twin as older. Then your twin comes back to earth. Due to SR you are both the same age. Ergo, there is no paradox. It seems to be a paradox because standard methods do not consider direction of motion DUH. I know this because I understand SR.You don't.

Thanks for the video, this was very helpful.

Einstein was wrong about the twin paradox, along with all of his disciples. There is no such paradox if you use the correct equations for relativity. If there is a slower clock in frame of reference S', as Einstein theorizes. then the correct way to represent the time of that clock starts with these equations. x'=x-vt y'=y z'=z t'=t Since the equation for time shows that t'=t, these equations say nothing about a slower clock in frame of reference S'. To represent a slower clock in S', you need to use a different set of Galilean transformation equations with different variables for velocity and time. x = x' - (-vt/n')n' y = y' z = z' n = n' n' is the time of the slower clock in S'. (-vt/n') is the velocity of frame of reference S(x,y,z,n) relative to frame of reference S'(x',y',z',n') according to the time of the clock that shows n'. The equation n=n' shows that the time of the clock that shows n' is being used in both frames of reference. There is still a preferred frame of reference because if you cancel out the (n')'s in the equation for x, you get x = x' + vt which is the same as our equation for x' in the original set of Galilean transformation equations. What we are observing is an energy difference, not a length contraction or a twin paradox.

You can never ‘know’ or prove what when things happens at a remote location because light is always involved in that determination. So talking about simultaneity at two remote points is not meaningful. You can only deal with different paths between the same two spacetime points and the difference in in the time that passes traveling on two different paths. There is only one path that has a single reference frame for any two given points. All other paths involve more than one reference frame and therefore will see less time expire, which is Don’s point more or less.

What always bothered me in the original twin paradox, where one stayed home and one went across the galaxy, was that the one traveling at relativistic velocity would be younger after the trip. But my question is why? There is no reference frame that is standard. No difference between the first one or the second one moving. They BOTH move RELATIVE to each other. At 1/2 c, or less. There is no ground to stand on.

Very good videos

From the point of view of observer A, the experience of observer B is equivalent to that of observer C (observer C travels a distance equal to 2L in the frame of observer A) It's possible to consider the Lorentz Transformation: t' = gamma * (t - vx/c^2) from which we obtain t = t'/gamma + vx/c^2 If t' = 2L/(gamma*v) and x = 2L then we obtain t = 2L/v t = 2L/v and t' = 2L/(gamma*v) are the same times according to the point of view of observer A: paradox solved! It's clear that if we consider the motion of observer A in the frame of observer C then observer A is younger, but we are interested in the Earth-star journey and then the star-Earth journey (observer B is younger, the game is over) So I think Dr. Lincoln is right about the twin paradox!

I watched the whole vodep without understanding a thing lol but I like him he is pretty sure what he is talking about and besides he looks very smart his face like a genius

Super video! 👍

The twins paradox is only a "thought experiment", that is to say that it is an experience in name only. This is not an experiment (done in a laboratory), it is a prediction. Everyone is free to believe or not in this imaginary prediction.

There are no twins in his scenario, twins start in the same location with the same velocity. I like these videos, Post your nano address and I'll send you a tip.

Quoting Stewiesaidthat - Space and Time are two separate frame of reference. Clocks are instruments that measure motion in space. Combining the two frame to believing that clock measures time is what creates the paradox. Space-Time diagram? That shows one person is experiencing more space in the same amount of time.

Great video man - thanks for setting things straight. I have studied GR and SR as a "hobby" and it's amazing how much "bad" information is floating around youtube.... I am looking forward to your next video.

If you are in strong gravity you age less as time flows slower. Gravity and acceleration are equivalent according to Einstein. So it is obvious that acceleration is what makes the traveler age less.

Looking at the video now, surely the suggested solution of Lincoln is immediately incorrect as he has assumed an ability to synchronise clocks with a distant observer, disobeying relativity of simultaneity.

Another possible angle to look at the problem is invariance of space-time intervals. Take time component of 1-2 flight space-time interval add time component of 2-1 flight space-time interval and compare it with A proper time space-time interval. What do we get? Is the time component of 1-2 flight space-time interval the proper time of B observer? Is the time component of 2-1 flight space-time interval the proper time of C observer? Did we compare proper times of a 'round trip'?

At Constant Velocities... A observing C will initially be observing C at the Propagation Latency of 2L in the past, so will not see C start to move until Propagation Latency of 2L after the actual start of movement as the Photon from the actual start of movement will take that Propagation latency of 2L , but as C moves closer to A, from A's perspective, C's clock will have to seem to be constantly speeding up as the Propagation Latency of the light from the instantaneous location of C decreases until when C reaches A, there will be no Propagation Latency and so A will be seeing C in real time in the Present. A observing B will initially be observing B in real Time with zero Propagation Latency, but as B moves away A, from A's perspective, B's clock will have to seem to be constantly slowing down, each 10 clicks would have to be longer than the previous 10 clicks... as the Propagation Latency of the light from the instantaneous location of B increases until when B reaches the mid point where it passes C, at Propagation Latency 1L in the Past as viewed by A, and on to the starting point of C at distance 2L, there will be maximum Propagation Latency of 2L and so A will be seeing B at a Latency of 2L in the past. A will not see B arrive ar the same time C arrives as it will take Propagation Time 2L for that light to reach A... From Observer A, both clocks DO NOT change linearly, but exponentially as the Latency increases or decreases. B observing C, and C observing B, will first see the other at 2L Propagation Latency in the past, reducing to Zero Propagation Latency at the center point when they meet and pass each other (twice as fast as the reduction of C as viewed by A), but then they will see the Propagation Latency increase again to 1L Propagation Latency in the past when the ships are then only half way between the center point an the final destination, so they will not actually observe the other ship reach the 1/4 or 3/4 point until a long time after the ship actually got there, due to the increasing latency... and continue to on the the destination at distance 2L from the other ship, so each will not observe the other arrive at their destination until the Propagation Latency of 2L after they themselves arrived at their destination... Though They arrived AT The Same Time.... Each will view the other's clock to be Constantly speeding Up from start at Latency 2L in the past to midpoint meeting point at Zero Latency in the Present, due to constantly reducing propagation latency that has to be accounted for, and then from the point where the clocks start to move apart to again slow down to account for the increasing Latency form Zero to the Propagation Latency of 2L. Both clocks DO NOT change exponentially, but exponentially squared as the Latency increases or decreases at a much faster rate than that to Observer A... Zero Paradox. Only Doppler SHIFT! Add in Aceleration or Deceleration, and the effect is further amplified...

Would it not be simpler to have an observer “D” at “2” (point L) that is in the same inertial frame of reference as 1, 2 & 3? That way D could send a signal at both B & C and as they are equal distance away they would get the “GO” signal at the same time and then they would meet at point “L” / ”2”. B and C are moving in opposite directions but the Lorentz length contraction they experience with points 1, 2 & 3 are the same as their speed compared to the 1,2,3 frame of reference is the same although velocities are opposite. If you view it this way it all seems to make sense as Lincoln described it and a lot less complicated. Or am I missing something?

All matter is electrons being held by the strong force, via electromagnetism. Time is measured by comparing atomic rotations here and atomic rotations there. All matter is under constant rotational acceleration because of this. When matter is accelerated linearly, the simple fact that the electrons cannot travel faster than light is why real time dilation occurs. Accelerated compared to what? There's no absolute frame. That doesn't mean there isn't acceleration, it means acceleration is relative and always operates in balance, energy exchange. When electrons are held spinning, they are under constant acceleration. We have been taught that inertia is equal to an object's mass. The real definition of inertia should be relativistic, it's actually equal to the sum of all relational vectors between this object and all other objects in the universe, these pairs of vectors all add up to zero, so, in a universe where everything needs a time delay to have any influence, inertia itself is time delayed by the inverse square law in space, as determined by the speed of light. This is Mach's principle. So, the inertial frame is relativistic and defines how motion occurs. Linear and rotational motion of electrons or matter is defined entirely by it's relation to the location and density of surrounding matter, because there is no origin and no absolute frame. Rotational motion is the interesting one, when an object is spun in a relativistic universe, it's inertia spins the other way the exact same amount to ensure the sum of vectors in this universe adds to to zero, according to Newton's action and reaction pairs. So, if matter is merely held and spun electrons, under constant acceleration for sometimes billions of years, there is a counter rotation in the inertia surrounding it. You would expect to observe no rest point in such a universe where energy's effects are time delayed. You would expect to see the counter rotation of matter within it's inertia, which surrounds it. That's gravity. Gravity isn't quantum in nature because it's merely kinetic energy within a relativistic universe. It's the counter rotations of atomic rotations themselves. Matter is an intricate web of relations and locality is relevant because of the rotational motion case. All the math checks out, I like that you managed to apply special relativity correctly, as difficult as that was, changing frames and having to calculate all the pairs of objects and frames. When an object is accelerated initially and then left to drift away at high velocity from the initial point, it is under constant acceleration simply by being made of matter. That is why it continues to effect the time dilation once the initial linear acceleration stops. Simply combine the linear and rotational motion mathematically to ensure electrons don't travel faster than light and it's going to give you the same answers as special relativity does when applied correctly as above.

Yeah that dude is a science ‘communicator’ who undoubtedly has others do his physics for him, he tries to confidently explain deep ideas on a surface level for the interested layman, so I expect mistakes in both theory and interpretation.

I prefer my explanation since it also reveals the absolute cause of the Special Relativity phenomena.

Where's the acceleration video?

Well done!

Very good jop.

Dr Lincoln is also wrong about six foot tall talking rabbits. When in all the fictitious wave function collapse, universe splitting events, did the laws of Physics change, such that those that govern genetic expression meant that my genes now code for a six foot tall talking rabbit?

The whole reason they need observer B and C is to avoid any accelerations, just keep all observations at uniform velocities. This was originally proposed byLord Halsbury and others were able to eliminate any acceleration. The travelling twin moves his clock reading to a third, which is moving in the opposite direction. The solutions using acceleration are commonly referred to a dynamic whilst non accelerative are known as kinematic solutions of the twin paradox. So who is right? Well, in the example given there is only one twin, and the change in reference frame is caused by acceleration of one twin determines the relative clock values. However, as Dr Lincoln points out, acceleration is not needed to cause this, just uniform velocity. The paradox is solved by having different uniform reference frames rather than changing between them, that of ( B and C ) being different to A. So his statement is also true, perhaps a more general formation. As someone once wrote :- "I am sure that the twin paradox will provoke again and again papers since it is not a problem to solve but it is in itself a social and psychological phenomenon. There is no end." Even more so now with all these youtube videos, there are dozens of them.

Thanks for your clear demonstration! After watching Dr. Lincoln says that acceleration played no role, I was quite skeptical because you can imagine a case where both twins have the same age at the end despite one staying on Earth and the other becoming relativistic: Imagine that B takes a rocket with a constant acceleration g, so that after 1 year he is close to c. At midway (T/4, L/2) he rotates its rocket by 180° then at (T/2,L) his speed relative to A becomes 0 and he begins his travel back to A. At midway (3T/4,L/2) on his comeback he rotates its rocket by 180°, and he finishes on Earth with no speed (T,0). During all this time both twins have experienced the same constant acceleration of g, so due to the equivalence principle they have to have exactly the same age at the end

Nicely calculated. Don Lincoln doesn't understand relativity beyond what you'd learn in high school. To be fair his understanding of particle interactions is excellent.

I think Don’s explanation is pretty good. Acceleration has nothing to do with time dilation. Is is the longer physical path that matters. If you travel the longer path the total number of vibrations is less, so slower clock. This in because clock is determined by vibration in the space medium, with is a fixed rate.

Every video on RU-vid explains twin paradox differently. This proves that this is a hole in the theory of relativity