Length contraction: Is it permanent?

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Discussion Overview

The discussion revolves around the concept of length contraction in the context of special relativity, specifically questioning whether the length of an object remains the same after it has been in motion and then brought to rest. Participants explore various scenarios involving observers and rods, examining the implications of different acceleration methods and the nature of measurement in relativistic contexts.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that if rods are accelerated Born-rigidly, their lengths will remain the same, while others suggest that material modeling is necessary if they are not accelerated in this manner.
  • One participant raises a question about whether the length of an object (like a rod) is perceived differently depending on the observer's frame of reference, particularly when comparing lengths before and after motion.
  • Another participant discusses the analogy of rulers and clocks, suggesting that both measure intervals differently and that their measurements are consistent when at rest relative to each other.
  • There is a debate about whether Lorentz contraction is a physical change in the object or a result of differing perceptions of space and time by observers in different frames of reference.
  • Some participants express uncertainty about the implications of acceleration methods on the perceived lengths of objects and the necessity of defining terms like "Born rigidity."
  • Questions are raised about the permanence of length contraction once an object returns to rest and whether observers can agree on the lengths of objects based on their relative motion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether length contraction is a permanent effect or a result of relative motion. Multiple competing views remain regarding the implications of acceleration methods and the nature of measurement in different frames of reference.

Contextual Notes

Participants acknowledge the complexity of the topic, noting that assumptions about acceleration, the properties of materials, and the definitions of rest frames significantly influence the discussion. There is also an emphasis on the subjective nature of measurements in relativity.

  • #31
Bertrand Boucquillon said:
I'm not looking to argue what the sun is made of
Neither are we. We are just pointing out that everything around you is made up of a mix of matter that has traveled at relativistic speeds relative to its current state and matter that has not. Your idea would have physical consequences that we don't see. It's a non-starter I'm afraid.

Edit: not to mention, what does an observer co-moving with the moving rod see? According to Bob the rod accelerated from rest. According to this new observer the rod decelerated to rest. Should it be showing these after-effects of length contraction (because it has decelerated according to the new observer) or not (because it hasn't yet decelerated according to Bob)?

Like I said repeatedly before I understand that everybody believes that length contraction doesn't change the physical properties and that it is about perception, but did you guys just accept it because it's what has been said by scientists 50 years ago or did you research the proof?
Please see my previous paragraph. And my previous post. And the post by Orodruin that you quoted...
 
Last edited:
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  • #32
Bertrand Boucquillon said:
Please be patient with me because I take this thread very seriously(I've been ignoring my customers for the past couple days just to focus on my research), I do hope you guys can keep an open mind about things and not get upset just because I'm questioning what is believed by the community.
There is an overwhelming amount of experimental evidence for the consequences of SR and GR. So much in fact that any description even attempting to build further must include them. This quoted text rings large warning bells to me as it seems to suggest you do not "believe" in the effects of relativity and therefore has started to work on your own theory. This is doomed to fail. The effects are well established experimental facts. Also note that Physics Forums, while encouraging asking questions to learn and understand, forbids the discussion of personal theories and speculation.

The original question has been answered several times over. I am therefore closing this thread.
 

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