The Relativity of Simultaneity: A Fundamental Concept in Special Relativity

[harrylin]

[..] If there is a universal present moment, then events which are simultaneous in the universal present, are simultaneous for all observers; that is, they are simultaneous in my present, and in your present, and we share the same present moment.

RoS is not compatible with that.

Well ... after many weeks of discussions and explanations, you keep on denying that observers can not know true simultaneity. However, we explained that that is a basic result of SR that is related to RoS which directly follows from the Lorentz transformations, as we also showed. So, take it or leave it!

 

[yuiop]

The question also remains as to whether RoS is a philosophical interpretation of clock synchronisation;

RoS is not a philosophical interpretation, but a consequence of what can actually be measured and applies equally to SR and LET.

insofar as RoS refers to events which are simultaneous in one reference frame being non-simultnaeous in another, it is not compatible with the concept of presentism provided. If LET is compatible with that concept of presentism, then it suggests that RoS cannot be a necessary consequence of the LT, because RoS is not compatible with presentism.

Assuming that presentism is the notion of a absolute reference frame that defines a universal "now" (as embodied in Newtonian physics) then SR says IF there is a universal reference frame it cannot be detected and LET says there IS a universal reference frame, but it cannot be detected. Both theories acknowledge that the universal reference frame is undectable. Both SR and LET agree that by any measurements any observers with relative motion will disagree on the simultaneity of events. RoS is a consequence of the LT in both SR and LET. IF presentism is the concept of a universal "now" that can be measured, then presentism is incompatible with both LET and SR, but is compatible with Newtonian physics which has been shown to be wrong by experimental evidence.

So, the question of presentism being a philsophical viewpoint does not resolve the issue, because RoS is arguably a philopsophical viewpoint also - regardless of the assertions to the contrary.

We cannot measure a universal "now" or conduct any experiments that can detect a universal absolute reference frame but we can measure RoS. Therefore presentism is philosophical (unmeasurable) and RoS is not philosophical, in that it can be measured.

The question of whether or not presentism is compatible with, or incorporated into, LET would help to resolve the issue.

Presentism, in a form that can be measured, is not compatible with LET.

Insofar as LET is based on Newtonian, or Galielan time and space, then it suggests that LET does not allow for events that are simultaneous in one reference frame to be non-simultaneous in another.

LET is not based on Newtonian or Galilean time and space. In Newtonian physics, time as measured by clocks and space as measured by rulers is absolute. LET on the other hand has time dilation and length contraction and so time measured by clocks and space measured by rulers is not absolute in LET.

Is RoS compatible with Newtonian physics, and Galilean relativity?

No, it is not.

It's been mentioned that LET is essentially based on the Newtonian concepts of time and space, and Galilean relativity. If that is correct, and RoS is not compatible with those, then it probably means that RoS is not compatible with LET, I would think.

That is not correct.

It might be worth asking if Newtonian mechanics allowed for RoS, or did it incorporate the idea of a universally shared present moment?

Newtonian mechanics does not allow for RoS but it did have a universally shared present moment. Newtonian mechanics has been experimentally shown to be incorrect.

 

[Dale]

I wasn't sure of the answer, as to what the experimental consequences of presentism are,

Well, once you have clarified the question then we can work on answering it.

I think it would have experimental consequences, similar in nature to the Principle of Relativity; I probably risk an infraction by stating what they are though, as I suspect it might be classified as a personal theory. I would probably need express permission to do so.

If it has experimental consequences then the only reason it would be a taboo topic is if those predictions were contrary to existing observations, in which case presentism is already falsified.

Is RoS compatible with Newtonian physics, and Galilean relativity?

No, the Galilean transform does not have RoS.

If there is a universal present moment, then events which are simultaneous in the universal present, are simultaneous for all observers; that is, they are simultaneous in my present, and in your present, and we share the same present moment.

Prove it. Simultaneity is well defined, as are the transformations between reference frames. If your concept of the universal present works as you say then you should be able to start with one reference frame and two events which are simultaneous in the universal present, show that those events are simultaneous for some observer, transform to another observer moving at an arbitrary velocity relative to the first, and prove that they are simultaneous for that observer also.