Can special relativity result in alternative realities?

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Discussion Overview

The discussion revolves around the implications of special relativity (SR) in a thought experiment involving a traincar rigged with sensors that could potentially explode based on the timing of light signals. Participants explore whether different observers (inside and outside the train) would agree on the outcome of the experiment, specifically regarding the explosion of the traincar.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • One participant describes a scenario where light emitted towards the front and back of a moving traincar reaches a sensor simultaneously from the train's perspective, suggesting the train would explode.
  • Another participant argues that both observers must agree on the outcome of the experiment, stating that the sensors inside the train follow the rules applicable to that frame, leading to the explosion.
  • A different viewpoint emphasizes the need for an observer outside the train to consider the timing of light reaching the sensors, questioning the implications of frame of reference on the experiment's outcome.
  • One participant asserts that special relativity will not result in alternative realities, suggesting that the outcome of the explosion can be determined consistently across inertial frames by answering specific questions about sensor activation.

Areas of Agreement / Disagreement

Participants express disagreement regarding the implications of special relativity on the experiment's outcome. Some believe that the frame of reference affects the result, while others maintain that the outcome remains consistent across all inertial frames.

Contextual Notes

There are unresolved questions regarding how the sensors determine simultaneous activation and the implications of different frames of reference on the experiment's outcome. The discussion highlights the complexity of interpreting simultaneity in special relativity.

Who May Find This Useful

This discussion may be of interest to those exploring concepts in special relativity, the nature of simultaneity, and the implications of observational perspectives in physics.

junglebeast
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Take the traincar thought experiment with light emitted towards front and back of the train. Assume that the train is rigged with mirrors at the wall that will direct the light around the edges of the train wall, ceiling, and then back to the center of the train at the rooftop, where a sensor is located. The sensor is rigged to blow up the train if it receives light from both sides within some small fraction of time.

To an observer from the perspective within the train, the light hits both sides of the sensor simultaneously and the train blows up (killing the observer). To an observer outside of the train, the light hits one sensor long before the other, so the train does not blow up, and the person inside the train survives.

Is this right?
 
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Both observers must give the same result for an experiment such as "does the traincar explode or not"? The idea is that the sensors are inside the train, so they obey the rules that apply inside the train; the train explodes. To analyze it from outside, you have to boost yourself into the inside frame first to see what the sensors are seeing.
 
Matterwave said:
Both observers must give the same result for an experiment such as "does the traincar explode or not"? The idea is that the sensors are inside the train, so they obey the rules that apply inside the train; the train explodes. To analyze it from outside, you have to boost yourself into the inside frame first to see what the sensors are seeing.

Suppose that the sensor device is see-through and the observer is watching with a telescope that allows him to see in great detail what is going on inside that sensor. The sensor is governed by simple mechanical principles. If he does not observe the light to enter both sides of the sensor at the same time, then he will not observe those visible principles to trigger the sensor. So, if what you are saying is true, he must observe some great "action at a distance" in order to explain the spontaneous explosion of the train.

Secondly, if what you are saying is true, then the frame of reference makes a difference for the experiment...and I thought that one of the principles of relativity is that it should not make a difference what frame of reference the calculations are done in...
 
junglebeast said:
Is this right?
No, SR will never result in alternative realities.

Your description of the scenario was a little confusing, but there are really only two questions that need to be answered to show whether or not the bomb explodes:
1) where and when does each sensor trigger in some inertial frame
2) how does the bomb determine if the sensors were triggered simultaneously

No matter how you answer those two questions, the result will be the same in all inertial frames.
 

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