Do Observers at Rest See Time Dilation When Others Stop Instantaneously?

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Discussion Overview

The discussion revolves around the relativistic effects observed when a line of synchronized clocks, moving at the same speed, stops instantaneously from the perspective of an observer at rest. Participants explore the implications of this scenario on the perception of time and simultaneity, delving into concepts such as time dilation and the Doppler effect.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that while the clocks are synchronized in the moving reference frame, they will not appear synchronized to the observer at rest, leading to a perception that the clocks stop at different times.
  • One participant suggests that the observer at rest will see the clock at the end of the line stop first, followed by the clocks closer to the head of the line, indicating a sequence of stopping that reflects the relative motion.
  • Another participant expresses concern over the complexity of the question, suggesting that it may have led to confusion in the discussion.
  • A later reply introduces a reference to a paper discussing radar detection and the Doppler effect in uniformly accelerated frames, implying a connection to the original question but not directly addressing the main discussion.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the scenario, particularly regarding the perception of simultaneity and the sequence of events. There is no consensus on the interpretations presented, and the discussion remains unresolved.

Contextual Notes

The discussion involves complex relativistic concepts that may depend on specific assumptions about the reference frames and the nature of acceleration. Some mathematical steps and definitions are not fully explored, leaving certain aspects open to interpretation.

actionintegral
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A line of people are moving at the same speed, clocks all sync'd. They agree that at a certain time they will stop! Let's pretend they can stop
instantaneously.


Relativistically speaking, what will we who are at rest see?
 
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actionintegral said:
A line of people are moving at the same speed, clocks all sync'd. They agree that at a certain time they will stop! Let's pretend they can stop
instantaneously.


Relativistically speaking, what will we who are at rest see?
Their clocks are syncronized in their ref. frame but not in our. So, we will see they don't all stop at the same time: we will see the one at the end of the line (relative to the direction of motion) stopping first, the one at the head of the line stopping last. So, the total length of the line, after they have stopped, is the same as the length in their ref. frame when they're moving.
 
Thank you, lightarrow. Now please go to the train and platform thread and stop the madness!
 
What madness? That's exactly what JesseM has been saying throughout that thread.
 
Doc Al said:
What madness? That's exactly what JesseM has been saying throughout that thread.

You are right. And you have too, I see. I was referring to the fact that
the thread is into three pages and growing! It seems to me that the question as posed was too complex and led to the self-perpetuating confusion of the original poster.
 
acceleration

actionintegral said:
A line of people are moving at the same speed, clocks all sync'd. They agree that at a certain time they will stop! Let's pretend they can stop
instantaneously.


Relativistically speaking, what will we who are at rest see?
have please a critical look at

Radar echo, Doppler Effect and Radar detection in the uniformly accelerated reference frame
Authors: Rothenstein, Bernhard; Popescu, Stefan
The uniformly accelerated reference frame described by Hamilton, Desloge and Philpott involves the observers who perform the hyperbolic motion with constant proper acceleration gi. They start to move from different distances measured from the origin O of the inertial reference frame K(XOY), along its OX axis with zero initial velocity. Equipped with clocks and light sources they are engaged with each other in Radar echo, Doppler Effect and Radar detection experiments. They are also engaged in the same experiments with an inertial observer at rest in K(XOY) and located at its origin O. We derive formulas that account for the experiments mentioned above. We study also the landing conditions of the accelerating observers on a uniformly moving platform.
Comment: 15 pages, 8 figures, includes new results on radar detected times and distances
Full-text available from: http://arxiv.org/abs/physics/0609118
 

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