Is relativity of simultaneity measurable?

We know enough about time dilation to account for any difference in the rate of clocks in different frames. We could even use the same technology used in the GPS satellites to keep clocks in different frames ticking in sync... That would decrease the absolute accuracy some but, the accuracy should still be enough to determine a variation in the timing of two events as measured from two frames.

You could also use a variation on the M&M experiment. You would not know the absolute timing but by measuring the interference pattern of light from two sources, you would be at least confirming the relative simultaneity of the two events. If the interference patterns vary the events were not measured to be simultaneous in both frames... And yes this would require some controls to establish first how the two interferometers record two remote events when the interferometers are co-located...

But given today's technology and accurate atomic clocks. One could design an experiment such that two remote flashes are initiated from the midpoint between the two... Confirmed by flipping a switch and then measuring the flashes to be simultaneous. That establishes the rest frame of the flashes and simultaneous detection at the midpoint between the flashes. Using a fiber optic trigger mechanism the time from flipping the switch to the flash(es) could be known. Knowing the delay from the trigger and the flashes, the experiment can be redesigned so that a moving detector triggers the device such that the flashes occur when the two detectors are next to one another. The stationary detector would detect the flashes simultaneously, while the moving detector would detect the flashes sequentially.

If CERN can measure the velocity of neutrinos to billionths of a second... The only real issue is that this can only be acomplished in vacuum and with distance or velocity that makes it impractical, in atmosphere. Satellite tests have been proposed but they are expensive.

 

Log in or Sign up to hide all adverts.

I don't follow you; the whole point is that the clocks tick at different rates in different frames. We would certainly need two pairs of clocks (one synchronized in each reference frame), but the goal then would just be to show that one pair of clocks stops at simultaneous times while the other does not.

As for the radar gun, I don't see how, but I wouldn't rule it out. What did you have in mind?

 

Log in or Sign up to hide all adverts.

As in, the time recorded on the clocks may not be representative of simultaneity. A bit hard to explain.


We have two objects launched simultaneously with equal and opposite velocities colliding at a midpoint. In another frame, we measure the velocities. If the measurements are non-classical, it means both were launched at different times.

 

Log in or Sign up to hide all adverts.

There is no need to establish a common notion of simultaneity shared by both frames, or whatever it is you are worrying about. The whole point is that the two frames do not share a common notion of simultaneity. Both frames agree that there are two events:

1. The meeting of ground-clock A with rail-clock A
2. The meeting of ground-clock B with rail-clock B

We only need to consider one frame at a time. Are those two events simultaneous in the ground frame, yes or no? The answer is yes. Are those two events simultaneous in the rail frame, yes or no? The answer is no. Then, once we have the answers to those two questions, we demonstrate RoS by showing that the events were simultaneous in only one of the two frames.

 

As Fednis48 said, we can use synchronized clocks.

Yes, it is specified in the first post of this thread:

It is done using synchronized clocks.

 

no, here clocks are only synchronized at remote areas. How are you going to meaure remote measurements?

Got the point?

 

No, I don't get your point at all. Did you read the first post of this thread? It is all explained there. Why don't you tell us all specifically which part of that post you have a problem with. Thanks in advance.

 

I'm still a little unsure about how we can demonstrate that. Hmm..

 

I think you may not be aware that you sound kinda rude. Nevermind, just be more mindful.

 

[Please bear with me, I am just trying to identify where your concerns are.]

Do you agree that the momentary alignment of ground-clock A with rail-clock A is a unique event which both frames can identify as it happens?
(If so, then I'm sure you must also agree that the momentary alignment of ground-clock B with rail-clock B is also a unique event which both frames can identify as it happens.)

Do you agree that the rail frame can determine whether or not those two unique and identifiable events happen simultaneously in the rail frame?
(If so, then I'm sure you must also agree that the ground frame can determine whether or not those two unique and identifiable events happen simultaneously in the ground frame.)

Do you agree that if the ground frame determines those two events were simultaneous, and if the rail frame determines those two events were non-simultaneous, then RoS has been demonstrated?

 

I got it. They don't need to be clocks, just signal emitters. In both set-ups, we place an AND gate midway between the emitters. In one frame, the AND gate will be triggered, but it won't in the other frame. It's similar to the radar gun example I brought up earlier.

 

Nice! I can certainly agree with that. However, I also hope we agree that Pete's "synchronized-clock-method" would also work. His clocks are synchronized in a way that ensures the clocks in each frame will always agree with your AND gate, in each frame.

 

Rude? C'mon!! I was not being rude!!

 

Just popping in to say that I'm still thinking over Tach's latest position.

I think it's a valid objection, but I'm not sure that he's considered the cost - it means giving up well-defined simultaneity in any reference frame and potentially using the space-like separation notion of simultaneity, and discarding the Lorentz transform for something broader.

 

Hi ash, eram said you "sounded" rude, not that you were being rude. Please don't take offence. Try to stay focused on the actual points of the discussion, and not be distracted by personal undertones.

 

Well, the question is how are you going to make two remote measurements at the same time?

 

To me it seems like Tach is just trying to prolong the discussion by throwing up stuff. I might go with Ned and eram.

 

@ash yes don't be distracted, I was also trying to say that you were unintentionally bringing up strong personal undertones.

 

correction, this is the position of mainstream physics as explained.

You don't fully understand the test theories yet. For one, they do not "discard the Lorentz transform".
Anyway, I do hope that after some lengthy reflection you will come to the correct conclusion: you cannot construct a realizable test for RoS. You have been given the tools to understand why what you tried to accomplish is impossible, what you do with the tools is up to you.

 

What about measuring velocities to see if they transform relativistically, indirectly testing RoS.