Same experiment performed in different inertial reference frames

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Discussion Overview

The discussion revolves around the conditions under which the same experiment can be considered to be performed in different inertial reference frames, particularly in the context of relativistic transformations and wavefronts of light. Participants explore the implications of measuring physical quantities in different frames and the nature of the experiments conducted.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that observers in different inertial reference frames perform the same experiment if the physical quantities measured are related by relativistic transformation equations.
  • Others argue that any particular experiment should yield the same results in any reference frame, but measurements must be adjusted using relativistic transformations when observed from a different frame.
  • A participant introduces the concept of wavefronts, suggesting that while the wavefront is a sphere in both frames, it appears as an ellipsoid when detected from another frame, raising questions about whether the same experiment is performed.
  • Another participant clarifies that both frames should observe the wavefront as a sphere, indicating that detecting different shapes would contradict the principles of relativity.
  • There is a suggestion that while the same experiment can be performed in both frames, it may be more accurate to state that it is performed in one frame and observed from another moving frame.

Areas of Agreement / Disagreement

Participants express differing views on whether the same experiment can be considered as performed in both frames, with some asserting it can be while others emphasize the need for careful distinction between performance and observation. The discussion remains unresolved regarding the exact conditions that define the equivalence of experiments across frames.

Contextual Notes

There are limitations in the discussion regarding the assumptions about the nature of experiments and the definitions of measurements in different frames. The relationship between the Lorentz transformations and the experiments is also not fully resolved.

bernhard.rothenstein
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under which conditions we could say that the same experiment is performed in different inertial reference frames. I have formulated for myself the following answer:
We say that observers from two inertial reference frames perform the same experiment if the physical quantities they measure are related by the corresponding relativistic transformation equations.
should i say more?
 
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bernhard.rothenstein said:
under which conditions we could say that the same experiment is performed in different inertial reference frames. I have formulated for myself the following answer:
We say that observers from two inertial reference frames perform the same experiment if the physical quantities they measure are related by the corresponding relativistic transformation equations.
should i say more?

Hi Bernhard,

Most of the times we deal with an experiment performed in one frame and observed from another frame, do you have instances when you are interested in having the same experiment performed in more than one frame?
If I misunderstood your post above it may mean that your question needs to be clarified a little.
 
Last edited:
bernhard.rothenstein said:
under which conditions we could say that the same experiment is performed in different inertial reference frames. I have formulated for myself the following answer:
We say that observers from two inertial reference frames perform the same experiment if the physical quantities they measure are related by the corresponding relativistic transformation equations.
should i say more?
Well perhaps I do not understand what you mean my understanding is that any particular experiment performed in a particular reference frame, inertial or not, should give exactly the same results in any other reference frame.
However if one measures something from a different frame of reference then the measurements need to be adjusted by relativistic transformations.
 
clj4 said:
Hi Bernhard,

Most of the times we deal with an experiment performed in one frame and observed from another frame, do you have instances when you are interested in having the same experiment performed in more than one frame?
If I misunderstood your post above it may mean that your question needs to be clarified a little.
I have in mind the problem of the wave front relativity. If I consider that at the origin of both reference frames I have a source of light then the wave front is a sphere in both reference frames and we say that in both of them the same experiment was performed. If I consider that at the origin of one of the reference frames I have a source of light then there the wave front is a sphere but when detected from another reference frame it is an ellipsoid and the space time coordinates of the same event genertated by a light signal are related by the Lorentz-Einstein transformations. Can I say that the same experiment is performed in the two frames?
Sine ira et studio
 
bernhard.rothenstein said:
at the origin of both reference frames I have a source of light...at the origin of one of the reference frames the wave front is a X ... but when detected from another reference frame it is an Y

See how I have edited your comment. Here is your experiment:

Source at the origin of two different reference frames. Measure wavefront in one frame. Measure wave front in other frame.

If my interpretation of your post is correct, then yes, you performed the same experiment in two different reference frames, namely measuring the shape of the wavefront.
 
bernhard.rothenstein said:
I have in mind the problem of the wave front relativity. If I consider that at the origin of both reference frames I have a source of light then the wave front is a sphere in both reference frames and we say that in both of them the same experiment was performed. If I consider that at the origin of one of the reference frames I have a source of light then there the wave front is a sphere but when detected from another reference frame it is an ellipsoid and the space time coordinates of the same event genertated by a light signal are related by the Lorentz-Einstein transformations. Can I say that the same experiment is performed in the two frames?
Sine ira et studio

Well, first of all, in BOTH frames the wavefront is a sphere since you are using light. Otherwise, the experiment described above would violate both postulats of relativity by detecting a different shape wavefront in the two frames (ellipsoid vs. sphere).
Yes, you can say that the same experiment is performed in two frames but the cleaner statement would be that it is being performed in frame A and it is being observed from frame B in motion with constant speed v relative to frame A.

The above experiment is one of the many thought experiments used to derive the Lorentz transforms so you cannot mention the Lorentz transforms until the very end.
 
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