@AlbertusMagnus It is generally considered that a ship can not exceed its hull speed without climbing up the back of the bow wave and essentially moving out of the water. This is not available in 3-D spacetime. The photo shows how the bow wave grows and grows, requiring more and more power to increase speed by less and less. Exactly the way that an object nearing c behaves.

Kinetic time dilation already has a perfectly simple explanation in terms of geometry: an object "in motion" has a world line that is at an angle to a "stationary" one. This is symmetric, unlike your and the OPs explanation.

@EricSmith your world line concept is a mathematical description. Unfortunately, just like there are no lines of longitude painted on the Earth and converging at the North Pole, there are no world lines painted in space with which a relativistic rocket interacts. The op is looking for a physical explanation. Perhaps you can provide an alternative.

Bob and Alice synchronize their atomic clocks and odometers before leaving New York at noon on Monday. Alice drives straight to Los Angeles at a constant speed and arrives at noon on Thursday (Los Angeles time). Bob drives faster but takes a detour through San Francisco, so he arrives in Los Angeles at the exact same time as Alice. Both their clocks and odometers will show different values. The reason the odometers show different values on them is that they took different paths. Their clocks are different for the same reason.

I mean, you could try to construct some elaborate "physical" explanation for why the odometers are different, involving wind or a mysterious aether affecting odometers. Or you could try to explain it by noting that Bob has to accelerate to change direction in San Francisco. But really, the simplest explanation is geometrical: Bob's path through space is longer than Alice's, and the odometer measures the length of that path. Similarly, Bob's path through Minkowski spacetime is "shorter" than Alice's, and his clock measures that length.

@EricSmith Your explanation of a longer journey in the same time is absolutely wrong. And has nothing to do with distance and it also has nothing to do with acceleration. The ONLY reason for the clock difference is the speed. Imagine that Alice accelerates to 1000kph and them immediately slows to 50kph drives to LA at 50kph. Bob waits for a few days and drives the same route at 1000kph. His clock will also be younger. Time dilation has nothing to do with the route or acceleration, just the speed and the length of time (or distance) at that speed.

@EricSmith In the above example, Alice could claim that Bob drove away from her at 50kph and then she caught up to him at 1000kph. Or Bob could claim that Alice drove away from him at 50kph and he caught up to her at 1000kph. Both are equally valid and both will show the exact same worldline. But we know that only Bob's clock will be younger. This is why I came up with my idea of the bow wave. There must be some physical reason why Bob's clock will be younger and that reason only concerns speed. A bow wave fits that requirements.

So your explanation of the difference in odometers (in the original example) is that it's because Bob drove faster? I mean, that isn't completely wrong, in some sense an odometer indirectly measures speed. But most people would say that Bob's odometer has a higher reading because he drove further. That explanation works all the time, not just in the specific example I gave.

Similarly, in that original example Alice's super-sensitive atomic clock will show less elapsed time than Bob's, for basically the same reason: Bob took a "longer" path through spacetime (which because space and time are in some sense opposites, translates into a shorter clock reading).

When you talk about Alice and Bob moving at 50kph and 1000kph you say they show "the exact same worldline". But they do not. They show the same path in space, but definitely not the same time in spacetime, if they accelerate at different times. You must always take time into account.

Correct, the only reason why Bob is younger is because he drove faster, ie. he drove a longer distance in the same time. But the distance doesn't matter. Only the speed. As I showed, if he drove the same distance in a shorter time, ie at a faster speed, he would also be younger. But no, there is no instance where Alice's clock will show less elapsed time.

Finally, your "bow wave" model requires an absolute definition of speed, i.e. it hypothesizes an aether. That's entirely superfluous.

Both world lines are interchangeable. Either Alice or Bob could claim that they were stationary and the other person was moving. That is the whole basis of SR.

I am way too smart to claim an aether. But I absolutely do know that quantum fields do exist. My theory is based on a quantum field.

If two people travel the same physical route at different times, then by definition their worldlines are different (because the time component is different, in any frame you choose to measure in).

Unfortunately the michaelson morley experiment only measured using light. That's the scientific equivalent of saying a medicine works on a worm, so it would work on a human.

If Bob and Alice start at the same point and end at the same point, then they cannot both claim to be stationary the whole time -- one or the other (or both) of them must undergo acceleration at some point in order to meet up again.

You are wrong about the world lines because either person could say that they were stationary and only the other person moved. There is no absolute under SR

Michelson-Morley is only the first (and hence most famous) experiment.

You need to look up what a "worldline" is. It's a graph of space versus time. Try drawing that for Bob and Alice. They will not be the same if they start and stop at different times (relative to whatever frame you choose to pick). They may end up being the same length, if that's what you're trying to say. But they certainly won't be the same line.

Both of them covered the same distance in the same time. Its just that Bob was standing still for the first few days. To make it easier you could say that he was walking towards LA while she was driving at 50kph. They both moved from NY to LA in the same time.

Quantum field theory is based upon special relativity, and the developers of QFT all (so far as I know) subscribe to the geometric interprataion of SR. Certainly Feynman and Weinbert did, they both wrote textbooks on relativity. The geometric view of relativity is entirely uncontroversial among physicists, and no physicist I know thinks some additional mechanism is required to explain time dilation

When someone shows me a reasonable real world experiment where the faster twin says to the slower twin "hey, thats funny but I think you are younger", then I'll undertand it. Lots of experiments have shown that the faster twin is younger. Not one has shown where the faster twin thinks the slower is younger.

A worldline encompasses both time and space. I'm still not sure what you're trying to get at with the Bob and Alice example. That may be my misunderstanding, but as far as I can see in every example you've given their worldlines (as opposed to their spatial paths) are different.

The whole point of relativity, as you pointed out before, is that speed is relative. So how do you decide which twin is "raster" or "slower"? If the twins both remain inertial, then logically each can claim the other is younger.

It's only if they meet up again that it becomes an issue.

To use a spatial analogy, if two cars are driving in the same direction and same speed but at angles, each says the other is "behind" -- as long as they keep going in a straight line.

It's only if one of them changes direction (accelerates) that any kind of absolute comparison becomes possible.

Imagine that both twins are in a box, asleep, so they have no idea they are moving or where they start or where they end up. All they know is that they were separated from their twin for some period. There is no circumstance or opinion where Alice is younger than Bob from either twin's point of view, or from any other outside frame point of view.

Not sure I see your point there. If Alice and Bob are asleep and know nothing, then they know nothing: that's a tautology.

OK, here's another question: Alice and Bob are in deep space, moving apart at 0.866c. Which one is aging slower?

You said "The whole point of relativity, as you pointed out before, is that speed is relative. So how do you decide which twin is "raster" or "slower"? If the twins both remain inertial, then logically each can claim the other is younger. " This is where you are making your mistake, and I have to admit that this mistake is very common. The simple fact is that only the faster moving twin will be younger, by any measure.

The whole question of "which one is faster" is frame dependent though. Again, that's the whole point of relativity, which you acknowledged earlier but now seem to be denying.

If they are always moving inertially, than both can claim to be at rest and hence that the other is moving fraster.

(Boy my typing sucks today, sorry :) ).

You ask Alice and Bob are in deep space, moving apart at 0.866c. Which one is aging slower? Now you are starting to see the misconception. Yes, relativity does say that speed is frame dependent. I'll agree to that because it is meaningless. All that I care about is kinetic time dilation. And guess what, kinetic time dilation does not have the same freedom of frame and the various twin paradox questions prove that.

As I said before, quantum fields do exist. In my theory I'm most interested in the gluon field. I'd say that anything with gluons in it interacts with the gluon field, leading to the warping of spacetime as mentioned in the OP. The faster the thing moves, the greater the bow wave in the gluon field and the greater the warping of spacetime.

I'm sorry, but you are the one making the mistake. That kinetic time dilation is symmetric is well documented in the literature. I can dig up quotes from my general relativity textbooks if you'd like, although I suggest that you look it up yourself (e.g. in Taylor & Wheeler's Spacetime Physics, which is an excellent introduction).

And of course the symmetry of kinetic time dilation follows immediately from the principle of relativity.

What you seem to be overlooking is the relativity of simultaneity.

Find me a single test that shows the stationary twin is younger in the eyes of the moving twin. I'd love to read that paper.

I've been looking for this for several years now with no luck. I have also asked on the stack exchange several times, with no luck.

Bernard F. Schutz, "A first course in general relativity", pages 20-23 has a nice explanation of this.

Or Taylor & Wheeler's Spacetime Physics: phys.libretexts.org/Bookshelves/Relativity/…

Or, well, pretty much any relativity textbook.

The thing is, determining the rate of a "moving" clock requires using two stationary clocks, one at the start of the interval and one at the end.

I'm looking at Schultz right now. All he does is restate the generally held, but I believe incorrect, interpretation of SR. All the other texts do the same thing. There have been lots and lots of tests showing that the moving twin is younger. But as far as I know not a single test has shown that the stationary twin is younger in the eyes of the moving twin.

With this being such a contentious issue, wouldn't some phd candidate have taken it upon himself to prove it?

You know, you might want to consider that if "all the texts do the same thing" they might be right and you might not quite understand the theory. Which is perfectly OK, the relativity of simultaneity is really hard to grasp the first time through.

It's not a contentious issue at all in the physics community.

Which is why all the textbooks agree, and if I walk down the hall and ask one of my colleagues in the physics department they would also agree.

I would be happy to be proven wrong on this. But I just can not see any evidence that I am wrong. Ask your colleagues for a real world test to show that I'm wrong.

Trying to prove a negative is really hard. Can you provide a test that shows that there's such as thing as "absolute" speed?

I suppose you'll answer with any of the differential aging experiments, but those all have an explanation in terms of relativity (as the textbooks all say).

At the very least, if you want to study physics you need to understand why the existing theories work and what they say. Only once you've done that will you be in a position to go beyond them.

I'm not asking to prove a negative. My question is that since there are many tests showing clearly that the moving twin is younger in the eyes of the stationary twin, there must have been at least one good test showing that the stationary twin is younger in the eyes of the moving twin.

There are many, many tests of the principle of relativity and of Lorentz invariance (see the Wikipedia page on modern tests of Lorentz invariance for examples).

That time dilation is symmetric is an immediate and obvious consequence of relativity. It may seem somewhat counter-intuitive, which is why so much ink has been spilled on the twin paradox, but again it's not contentious.

I've been studying this for 8 years now, so I'm not a beginner. My problem started 10 years ago when I realized that absolutely no one can provide an explanation for what actually causes gravity. I'm still shocked at this. So I spent 6 years and came up with a theory. So far no one has provided a single point to show where I've made a mistake, even the PHd who reviewed it prior to publication.

Watch this video for a good explanation for why all other explanations of the twin paradox are wrong; youtube.com/…

Using world lines and the like.

Sigh. Sorry, if you think that "no one can provide an explanation for what actually causes gravity" then I don't think you do understand general relativity after all, despite all your study. Again, this isn't a failing on your part, the theory can be hard. But relativity isn't a mystery among physicists. Feynman has a nice quote about how once someone came up with relativity everyone agreed with it and understood it, but nobody understands quantum mechanics.

I've seen some of Dialect's videos before and remain utterly underwhelmed

When you can explain how/why mass causes a warping of spacetime, then I'll agree.

It is not enough just to say that mass warps spacetime. I want to know how that occurs.

Sometimes the answer to a why question is "it just does". At some point there are raw brute facts about the world. However, as far as the "how" goes the Einstein field equations give an exact description, as you should know from your studies.

My neighbours are devout Christians and when I was telling them about how I am working to understand gravity, they responded "God did it and we just have to accept that". My theory is probably wrong, but at least I've given an exact mechanical description of exactly how mass warps spacetime. This led directly to my theory on kinetic time dilation and dark matter.

I have to go. I doubt I'll convince you of anything, but do please keep in mind that even if you aren't satisfied with some explanations, you should at least be able to see why they are consistent. Relativity may well be wrong (that's a matter for experiment) but it is logical and self-consistent.

The reply "it just does" is not good enough.

Have a good day. Take a look at my paper when you get a chance.

Take care, and good luck with your studies.

I just found a quote that I was looking for; "Einstein himself referred to the gravitational field and the motion of the fixed stars. He said that just as the motion of an accelerated charge induces a changing electric field, so should an accelerated mass induce a changing gravitational field" This is exactly what I am saying with the gluon field combined with spacetime as the embodiment of the gravitational field.