Frame of reference of any observer

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Discussion Overview

The discussion revolves around the possibility of defining a local coordinate system for any observer in flat 4D Minkowski spacetime, focusing on whether these coordinates can represent time and spatial position as measured by the observer. The scope includes theoretical considerations and references to existing models and coordinates, such as Rindler and Fermi normal coordinates.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant proposes that it is possible to define a local coordinate system for any observer in flat 4D Minkowski spacetime, drawing from a successful construction in 2D Minkowski spacetime.
  • Another participant references Fermi normal coordinates as potentially relevant to the discussion, suggesting there may be complications with observers on a rotating disk.
  • A participant expresses uncertainty about the usefulness of previous posts by Fredrik and Demystifier, while suggesting that a post dealing with synchronization might be more relevant.
  • There is a mention of ambiguity in the description provided by one participant, indicating that Fermi normal coordinates might be a better fit than their initial description.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the applicability of the proposed coordinate systems, and multiple competing views regarding the relevance and clarity of existing models remain evident.

Contextual Notes

There are unresolved aspects regarding the application of coordinate systems to rotating observers and the clarity of descriptions provided in the discussion.

Who May Find This Useful

This discussion may be of interest to those studying general relativity, spacetime coordinates, and the implications of observer-dependent measurements in theoretical physics.

paweld
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Let's consider flat 4D Minkowski spacetime. Is it possible to define (local) coordinate
system for any observer (its natural reference frame) so that these coordinates
posses interpretation of time and spatial position measured by this observer?

It can be done in two dimensional Minkowski spacetime. One coordinate is time
measured by the observer - the length of its world line, the second is the spacetime
distance from the world line measured along the line of constant time (for the comoving
inertial the observer). I proved that there always exist an open set containing
observer world line in which these coordinates have sense. An good example of
such coordinates are Rindler coordinates for uniformly accelerated observer.

I wonder if it's possible to generalize my construction to four dimensional spacetime.
 
Physics news on Phys.org
http://arxiv.org/abs/gr-qc/0104077

Maybe also see Fermi normal coordinates
http://relativity.livingreviews.org/Articles/lrr-2004-6/

I think there may be a problem with observers on a rotating disk, but I don't remember the resolution of that. Fredrik and Demystifier had good answers sometime ago.
 
Last edited by a moderator:
Thanks for answer.
Could you give me a link to post by Fredrik and Demystifier.
 
Atyy probably means posts 138-144 here. I'm not sure how useful those posts will be for you. This post that deals with the synchronization procedure might be better.

In GR, I think my description is a bit ambiguous and that Fermi normal coordinates is what should replace it.
 
paweld said:
Thanks for answer.
Could you give me a link to post by Fredrik and Demystifier.

Demystifier is the author of this very useful paper.
 

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