Can Atomic Clocks Yield the Same Time Dilation Equation as Light Clocks?

[Herman Trivilino]

If you insist that clocks of different design are always in sync for all observers, you'll have to introduce this statement as a separate (third) postulate of special relativity

The same can be said of a large number of pieces of information, whether you call them assumptions or postulates. It is not true, however, that history needs to be rewritten to accommodate them. When the consequences of a theory don't match observation the theory gets modified or replaced. Does the modification you suggest have any consequences that can be measured experimentally, even in principle?

Einstein's theory assumes far more than just the two postulates he used in 1905. Everybody knew that then as well as now. Because it's true of all theories. One hundred fourteen years later we are not going to add a third postulate to the theory.

Clocks measure time and events are invariant. That is part of the physics of special relativity.

 

[A.T.]

you can jump between frames with different velocities and see the bomb as exploded in one frame and not exploded in the other one.

It's not about whether the bomb has already exploded at some time. It's about whether it will ever explode at all.

For example, If the trigger is deactivated after one of the two clocks reaches a certain timeout, the bomb can never explode according to it's rest frame. But it must explode before the timeout, according to any inertial frame where the clocks were ticking at different rates. This is the contradiction, which means there are such inertial frames.

 

[meopemuk]

Does the modification you suggest have any consequences that can be measured experimentally, even in principle?

Yes.

R. de Sangro, G. Finocchiaro, P. Patteri, M. Piccolo, G. Pizzella, "Measuring propagation speed of Coulomb fields", Eur. Phys. J. C 75 (2015), 137.
arXiv:gr-qc/1211.2913v2

Eugene.

 

[pervect]

Yes.

R. de Sangro, G. Finocchiaro, P. Patteri, M. Piccolo, G. Pizzella, "Measuring propagation speed of Coulomb fields", Eur. Phys. J. C 75 (2015), 137.
arXiv:gr-qc/1211.2913v2

Eugene.

The note by Gitman, Shabad, and Shishemarey, published in response to this paper, i.e. https://link.springer.com/article/10.1140/epjc/s10052-016-4108-7 , suggests that Feynman's formulation (which I'm not familiar with), doesn't give any different result that the than using the Lienard-Wiechart potentials. Which is what I'd expect, otherwise Feynamn's formulation would not be classical electromagnetism, but a new theory.

In connection with the discussion and the measurements fulfilled in Ref. (Eur Phys J C 75:137, 2015), the full identity is demonstrated between the Feynman formula for the field of a moving charge and the Liénard-Wiechert potentials.

 

[meopemuk]

The note by Gitman, Shabad, and Shishemarey, published in response to this paper, i.e. https://link.springer.com/article/10.1140/epjc/s10052-016-4108-7

To be fair to the authors I should mention that they have published a response to their critics:

R. de Sangro, G. Finocchiaro, P. Patteri, M. Piccolo, G. Pizzella, "Why the interpretation of ``Measuring propagation speed of Coulomb fields'' stands",
Eur. Phys. J. C, 77 (2017), 75. arXiv:gr-qc/1611.06935v1

Eugene.

 

[PeroK]

To be fair to the authors I should mention that they have published a response to their critics:

R. de Sangro, G. Finocchiaro, P. Patteri, M. Piccolo, G. Pizzella, "Why the interpretation of ``Measuring propagation speed of Coulomb fields'' stands",
Eur. Phys. J. C, 77 (2017), 75. arXiv:gr-qc/1611.06935v1

Eugene.

In any case, I would say that a "B" level thread has been well and truly hi-jacked!

 

[benorin]

So then the clocks are separated along an axis perpendicular to the motion, right? Boom! Now what?

 

[Ibix]

So then the clocks are separated along an axis perpendicular to the motion, right? Boom! Now what?

You need to include the effects of the boost on the communication between clocks. Since the clocks are moving, whatever signal says "tick completed" has a different distance to travel and possibly a different velocity compared to measurements when the clocks are at rest. These differences will always result in the "tick completed" signal arriving at a given location simultaneously in all frames, or non-simultaneously in all frames. And since the bomb can only be in one position, whether the "tick completed" signals are received at its position at the same time is the only thing that matters.

Avoiding this unnecessary complication was why I proposed a thought experiment with colocated clocks.

 

[PeroK]

So then the clocks are separated along an axis perpendicular to the motion, right? Boom! Now what?

In that case, the clocks are equidistant from the bomb in both frames. I.e. equidistant in the rest frame; and equidistant in the moving frame.

It doesn't need to be a bomb, it just needs to be a device that confirms that communications (ticks) from each clock arrive at the same time.

If the clocks were running at different rates in the moving frame, then the communication with the central device would get out of synch, which would be a physical fact at that central location. This is then the element of "reality". Because the central device is a single device at a single location, you can't have two realities: two communications arrive at the same time or they do not and this cannot be dependent on whether the device is seen to be moving or not.

Dramatically, you could use the device to trigger a bomb and then the reality becomes whether the bomb goes off or not.