Background Radiation: Is It From Beyond Our Galaxy?

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Discussion Overview

The discussion centers around the origins of cosmic microwave background (CMB) radiation and whether it can be confirmed that this radiation comes from beyond our galaxy. Participants explore various aspects of the CMB, including its properties, effects, and implications for understanding its source.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that the CMB is redshifted, which may indicate its distance from our galaxy.
  • There is a request for concrete evidence to confirm that the background radiation originates from outside the galaxy, with some noting that only inferences can be made.
  • One participant asserts that the CMB travels through the dust in our galaxy, which affects it, and mentions the Sunyaev-Zel'dovich effect as evidence that the radiation comes from beyond galaxy clusters.
  • Another participant introduces gravitational lensing of the CMB as a means to support the claim that the radiation is from outside the galaxy.
  • There is a discussion about the nature of the CMB, with some participants agreeing that while the CMB we detect today comes from outside the galaxy, it originally radiated from all points in the universe, including our own galaxy.
  • One participant clarifies that the CMB emitted from nearby sources long ago does not contaminate the CMB emitted by distant sources.

Areas of Agreement / Disagreement

Participants express differing views on the certainty of the CMB's origins, with some asserting it comes from beyond the galaxy while others emphasize the need for more definitive proof. The discussion remains unresolved regarding the extent to which the CMB can be confirmed as originating from outside our galaxy.

Contextual Notes

Participants express uncertainty about the implications of redshift, the effects of galactic dust, and the interpretations of gravitational lensing and the Sunyaev-Zel'dovich effect. The discussion includes assumptions about the nature of the CMB and its emission history.

david graham
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Can I confirm that the background radiation is from out of our galaxy?
 
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Well, the CMB appears to be hugely red shifted, that might be a clue.
 
(Btw, I have changed the level of this thread to "B".)
 
Yes but I am after a fact to prove it's from out of our galaxy, you know ? Can only see inferences
 
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Gravitational lensing of the CMB; https://arxiv.org/abs/1502.01591, Planck 2015 results. XV. Gravitational lensing, should be sufficient to dispel any lingering doubts.
 
Would it be accurate to say the CMB we detect today came from outside the galaxy, but CMB originally radiated from all points in the universe, including our own?
 
  • #10
stoomart said:
Would it be accurate to say the CMB we detect today came from outside the galaxy, but CMB originally radiated from all points in the universe, including our own?

Absolutely.
 
  • #11
The CMB emitted from nearby departed our neighborhood long ago, so it does not contaminate CMB emitted by distant sources - assuming that is where you were leading.
 
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