Relativistic Effects on CMB and Cosmic Rays

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Discussion Overview

The discussion revolves around the effects of relativistic speeds on the observation of the Cosmic Microwave Background (CMB) and cosmic rays. Participants explore how relativistic aberration and blueshift influence the visibility and flux of the CMB, as well as the implications for other types of radiation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant imagines an object moving at relativistic speeds and questions the observed flux of the CMB from the forward direction, considering the effects of blueshift and aberration.
  • Another participant seeks clarification on the relationship between relativistic velocities and the CMB, expressing confusion about the connection between the two phenomena.
  • A participant notes that various types of radiation, not just the CMB, will experience similar relativistic effects.
  • It is proposed that at high gamma-factors, cosmic rays from the rear hemisphere may be absorbed by the front shields of a moving object.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between relativistic speeds and the CMB, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

There are limitations in understanding the specific conditions under which these relativistic effects occur, as well as the definitions of terms like "flux" and "gamma-factor." The discussion does not clarify these aspects fully.

qraal
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Imagine moving at relativistic speeds. The moving object sees the Cosmic Microwave Background blueshift and become moved into the forward field of view due to aberration. Of course the hemisphere behind becomes even darker due to red-shift, while the forward hemisphere contracts towards a point. My question is: once the object is moving fast enough for the CMB to become visible, then what is the flux observed coming from the forward direction? And is it concentrated into a 'beam' by aberration or merely visible as a central point in the forward direction of all co-moving observers?
 
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Is this about what one observes as one approaches relativistic velocities? Or is it about the CMB? I'm having trouble understandfing why you are relating these two phenomena.
 
DaveC426913 said:
Is this about what one observes as one approaches relativistic velocities? Or is it about the CMB? I'm having trouble understandfing why you are relating these two phenomena.

The CMB at extreme levels of relativistic aberration and blue-shift.
 
qraal said:
The CMB at extreme levels of relativistic aberration and blue-shift.
OK well, there's all sorts of radiation out there that's not CMB. They will undergo the same effect.
 
DaveC426913 said:
OK well, there's all sorts of radiation out there that's not CMB. They will undergo the same effect.

Indeed. Above a certain gamma-factor the cosmic rays "from behind", the rear hemisphere, will be absorbed by the front shields.
 

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