Pound & Rebka Experiment: Earth's Spin Rotation Speed

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Discussion Overview

The discussion revolves around the Pound & Rebka experiment, specifically addressing whether the speed difference between the source and receiver at different circumferences due to Earth's rotation was accounted for in the experiment's results. Participants explore the implications of gravitational time dilation and the potential influence of relative velocities on the observed redshift.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants calculate the rotational speed of Earth at different heights and question whether this speed difference was considered in the Pound & Rebka experiment.
  • Others clarify that in the rest frame of the experimental apparatus, both the source and receiver were at rest, implying no speed difference needed to be accounted for.
  • One participant suggests that the experiment was conducted at a fixed height and did not involve varying heights, challenging the notion of changing speeds affecting results.
  • Concerns are raised about the relevance of relative transverse velocities and whether they were included in the original analysis of the experiment.
  • Some participants argue that the observed redshift cannot be attributed to speed differences, as the results contradict the expected outcomes based on those assumptions.
  • There is a mention of the gravitational time dilation being significantly larger than any potential effects from speed differences, which are described as negligible.

Areas of Agreement / Disagreement

Participants express disagreement regarding the relevance of speed differences in the Pound & Rebka experiment. While some assert that such differences were not significant, others question the completeness of the original analysis and its implications for the experiment's conclusions.

Contextual Notes

Participants note that the analysis of the Pound & Rebka experiment was performed in a specific frame where both the source and receiver were considered at rest, which may not account for all frame-dependent effects. The discussion also highlights the complexity of gravitational time dilation and the potential for small effects to be overshadowed by larger factors.

  • #31
Sagittarius A-Star said:
In the OP it does not say "the relative velocity between the source and the emitter"
It says "speed difference", yes. That's just a quibble over terminology. You can go back and make that substitution in all of my posts; it won't change anything of substance.

Sagittarius A-Star said:
In the ECI, you can calculate invariant quantities
Sure, but the "speed difference" is not one of them.
 
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  • #32
Vanadium 50 said:
Except Dale.
As far as I can tell, @Dale agrees with me. If I'm mistaken about that, he can correct me.
 

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