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Does special relativity require faster than light information transfer to verify length contraction and time dilation?

How does the "outside observer" measure these variables? I guess the outside observer cannot exist within the universe and is "outside" the universe somehow observing. Also would the outside observer somehow need to have the objective definition of a meter and a second?

Also isn't the only way to record length and time, by light?

If you could refer me to experimental techniques and evidence that would be great!! Theory is everywhere but what would we be without the experimentalist!

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  • $\begingroup$ We calculate the time dilation and then we verify it, as in the muon experiment en.wikipedia.org/wiki/Muon I suggest you look up wikipedia for length contraction experiments $\endgroup$
    – user167453
    Sep 14, 2017 at 19:26
  • $\begingroup$ Like in the muon experiment, we're usually forced to appreciate the measurement as a black box. I really want to know HOW they do these insane experiments $\endgroup$ Sep 14, 2017 at 19:27
  • $\begingroup$ youtube.com/watch?v=2e9ltbbOwtc Hope this is worth it, have not got time to look at it. And a paper adsabs.harvard.edu/abs/1963AmJPh..31..342F $\endgroup$
    – user167453
    Sep 14, 2017 at 19:33
  • $\begingroup$ "Also isn't the only way to record length and time, by light?" - More precisely, the only way to record distance is by time it takes light to pass it. And yes, it is exactly how the current standard of length is defined: 1 meter is 1/299,792,458 part of light-second. Recording time is a separate matter addressed by the atomic clock. $\endgroup$
    – safesphere
    Sep 14, 2017 at 20:56
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    $\begingroup$ Why do you think it takes faster than light travel to measure length contraction and time dilation? $\endgroup$
    – Striker
    Sep 15, 2017 at 3:04

1 Answer 1

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Analysing the constant speed of light for Special Relativity starts as thought experiments. The thinker knows when and where things actually happen, and then works out what observers must see, and when, so that the speed of light is always constant.

From that you get time dilation, the Lorentz contraction, and the relativity of simultaneity.

These three then tell the thinker what else must be true about where and when things happen, and how the when must depend on the movement of the observer. When has to be different for different observers.

Experimenters checking the theory have to correct the 'when' they see for the time it takes for them to see it, to get the theoretical answers.

It all checks out.

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