Relativity of Simultaneity: An Overview

In summary, the clocks are out of sync for the observer in S' because he sees the time as being different than it is to the observer in S.
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wildebeest44
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I recently started studying Special Relativity an my book discusses the following:

Say I have synchronized two separated clocks in a reference frame S, if then an observer in another reference frame S' for whom the clocks are moving sees the clocks he would say those clocks are out of synchronization for him, as for him the light that was used to sync the clocks reaches one of them before the other.

Up to this point, I think I understand what is happening, but if then the observer in S' knowing about the relativity of simultaneity applies a Lorentz transformation to try and "see" the clocks as an observer in S would, it will, nevertheless, still find a non-zero difference between the times "shown" by the clocks, proportional to the distance separating them.

What does this mean?
Isn't the Lorentz transformation an attempt to find the space and time coordinates as they would be seen from other reference frames, and if so, why is it unsuccessful here?

What's the physical interpretation of the difference in time the observer in S' just found, considering is neither the difference he sees from his reference frame or the one seen by the original observer in S?

Thank you, and excuse me for not showing the math I don't how to write it here in a readable way.
 
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  • #2
Welcome to PF.

This is difficult to answer without the maths. Just below the reply box there's a link to how to use LaTeX for maths. An example: $$x'=\gamma (x-vt) $$ Reply to my post to see how it's done.

An obvious guess is that if you transformed from S to S' using v=u, did you transform from S' back to S using v=u (wrong) or v=-u (right)? If that's not it have a read of the LaTeX link and post what you did. Then we can help without guessing. :wink:
 
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  • #3
Ibix said:
Welcome to PF.

This is difficult to answer without the maths. Just below the reply box there's a link to how to use LaTeX for maths. An example: $$x'=\gamma (x-vt) $$ Reply to my post to see how it's done.

An obvious guess is that if you transformed from S to S' using v=u, did you transform from S' back to S using v=u (wrong) or v=-u (right)? If that's not it have a read of the LaTeX link and post what you did. Then we can help without guessing. :wink:

I just saw the guide, thanks, i'll give it a try.

So, suppose that clocks are placed in ##x_1## and ##x_2##, in S they are in sync so,
## \Delta t=0 ##

However in S', which is moving with speed u relative to S, we have for each clock
##t_1'=\gamma(t_1-\frac{u}{c^2}x_1) ##
##t_2'=\gamma(t_2-\frac{u}{c^2}x_2) ##
then for this observer the time interval between them is
##\Delta t' = t_2'-t_1'=\gamma(\Delta t - \frac{u}{c^2}\Delta x) ##
with ## \Delta t=0 ## because the clocks are in sync in S, then
##\Delta t' =- \gamma \frac{u}{c^2}\Delta x ##
Therefore, the clocks are out of sync for the observer in S'. But if I now tried to apply
##\Delta t'=\gamma \Delta t##
I would get
##\Delta t=-\frac{u}{c^2}\Delta x ##
Which is different to 0. This is the result I find troubling.

Thanks for your reply, I hope is clearer now :)
 
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wildebeest44 said:
But if I now tried to apply
##\Delta t'=\gamma \Delta t##
I would get
##\Delta t=-\frac{u}{c^2}\Delta x ##
Which is different to 0. This is the result I find troubling.
Try the Lorentz transform again, but reversing the sign of ##u##. Don't just use the time dilation formula.
 

1. What is the relativity of simultaneity?

The relativity of simultaneity is a concept in Einstein's theory of special relativity, which states that the notion of "simultaneity" is relative and depends on the observer's frame of reference. This means that two events that may appear simultaneous to one observer may not appear simultaneous to another observer in a different frame of reference.

2. How did Einstein's theory of relativity change our understanding of time?

Einstein's theory of relativity revolutionized our understanding of time by challenging the traditional notion of time as an absolute and universal concept. Instead, it introduced the concept of time as a relative and malleable quantity, dependent on an observer's frame of reference and the relative speed at which they are moving.

3. What is the thought experiment used to explain the relativity of simultaneity?

The thought experiment used to explain the relativity of simultaneity is known as the "train and platform experiment." It involves two observers on a moving train and a stationary platform, with a light source positioned in the middle. The experiment demonstrates how the perception of simultaneous events can differ based on the observer's frame of reference.

4. How does the relativity of simultaneity impact our understanding of causality?

The relativity of simultaneity challenges our traditional understanding of cause and effect. In the theory of special relativity, the concept of causality is relative and can differ between observers in different frames of reference. This means that events that may seem causally connected to one observer may not appear as such to another observer.

5. Are there any practical applications of the relativity of simultaneity?

Yes, the relativity of simultaneity has practical implications in fields such as GPS technology and telecommunications. It is important to account for the time dilation effects predicted by Einstein's theory of relativity in order to accurately measure and synchronize time for these technologies to function properly.

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