Is there a solution for the behavioural contradiction in RT?

  • Context: Undergrad 
  • Thread starter Thread starter Foppe Hoekstra
  • Start date Start date
  • Tags Tags
    Contradiction
Click For Summary

Discussion Overview

The discussion revolves around a thought experiment involving a train-wagon system and its behavior under special relativity, particularly focusing on the apparent contradictions arising from simultaneity and length contraction in different frames of reference. Participants explore the implications of these concepts in both linear and circular motion contexts.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants describe a scenario where a train-wagon with synchronized printers marks dots on a rail, leading to a discussion about the distance between these dots as perceived in different frames.
  • Others argue that in a circular motion scenario, the wagons experience different directions of motion, resulting in a loss of simultaneity between them.
  • A participant questions whether the stretching of the train is a physical effect or an optical illusion caused by relative motion, raising concerns about the nature of length contraction.
  • Some contributions emphasize the importance of simultaneity conventions in different frames, particularly in the context of rotating systems versus inertial frames.
  • There are assertions that the behavior of the rotating system contradicts that of an inertial system, despite both being described under Lorentz transformations.
  • Participants note that the paradoxes often arise from ignoring critical aspects of special relativity, such as the relativity of simultaneity and length contraction in varying directions of motion.

Areas of Agreement / Disagreement

Participants express differing views on the implications of simultaneity and length contraction, with no consensus reached on the resolution of the contradictions presented. The discussion remains unresolved, with multiple competing interpretations of the thought experiment.

Contextual Notes

Participants highlight the complexity of simultaneity in special relativity and its impact on length measurements, indicating that the setup may overlook critical aspects of the theory.

  • #31
Foppe Hoekstra said:
Nevertheless it is the shorter wagon that puts its dots at the larger distance!
I don't believe this is correct, assuming you mean "further apart as measured by the track rest frame". It would be correct if you were Einstein synchronising your clocks, but you aren't.

With Einstein-synchronised clocks, the "simultaneous print" of the wagons is non-simultaneous in the track rest frame. Thus the length contracted wagon produces a longer spacing because its back printer prints before its front printer (as described in the track frame).

But you aren't using Einstein synchronisation - all your clocks are synchronised in the track rest frame, even when they are in motion (I assume the clocks in the inertial wagon are not Einstein synchronised either). Thus the length-contracted wagon will print a short spacing.
 
Physics news on Phys.org
  • #32
Foppe Hoekstra said:
RS: From the full story: "Every printer has a clock that is synchronized when the train is at rest and thereafter the train is accelerated to a constant velocity v. Thus all clocks are accelerated in the same way and so all clocks will develop the same deviation in relation to SF. So all clocks will still be synchronized in RS when the train is at speed."
As soon as the clocks are accelerated they will no longer be synchronized along that direction (your choice of direction spoils any symmetry). I believe they will, however, return to synchronization if the train is brought to rest.
 
  • #33
hutchphd said:
I believe they will, however, return to synchronization if the train is brought to rest.
Yup. A simple argument from symmetry guarantees this. No clock is treated any differently than any other, so they must all share the same reading when re-united.
 
  • #34
Foppe Hoekstra said:
Which brings us to another point: namely that a consistent theory does not necessarily need to be true.

You're referring to Newtonian mechanics, of course?
 
  • #36
The OP question has been answered in a number of different ways. The thread will remain closed.
 
  • Like
Likes   Reactions: weirdoguy

Similar threads

Undergrad Explore Clock Synchronisation in a Moving Train Frame
  • · Replies 32 ·
2
Replies
32
Views
4K
Undergrad ##x'=0## and ##t'=0## axes in railcar thought experiment
  • · Replies 25 ·
Replies
25
Views
2K
Undergrad Some thoughts about Bell's string paradox alternatives
  • · Replies 75 ·
3
Replies
75
Views
7K
Undergrad Micromass' big October challenge
  • · Replies 125 ·
5
Replies
125
Views
20K
Challenge Math Challenge - June 2019
  • · Replies 46 ·
2
Replies
46
Views
14K
Series of questions about Special Relativity
  • · Replies 4 ·
Replies
4
Views
1K
Graduate A graphical explanation of Special Relativity
  • · Replies 5 ·
Replies
5
Views
4K
Graduate Concerns about ontological interpetations of Theory of Relativity
  • · Replies 70 ·
3
Replies
70
Views
9K
Undergrad How Do Waves Propagate on a String?
  • · Replies 0 ·
Replies
0
Views
5K
Graduate What is the Theory of Elasticity?
  • · Replies 35 ·
2
Replies
35
Views
29K