Evidence of Expansion: Redshifting of EM Radiation

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Discussion Overview

The discussion centers on the evidence for the expansion of the universe, specifically questioning whether redshifting of electromagnetic radiation is the only supporting evidence. Participants explore various interpretations and models related to cosmic expansion.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants suggest that the Cosmic Microwave Background (CMB) provides evidence for an earlier hotter and denser universe, supporting the idea of expansion.
  • One participant argues that the redshift observed in electromagnetic radiation from galaxies indicates they are moving away from each other, which aligns with the Big Bang model.
  • Another viewpoint posits that the redshift could alternatively be interpreted as a result of a shrinking space-time rather than an expansion, challenging the conventional interpretation of redshift as evidence of cosmic expansion.
  • Concerns are raised about the reliance on concepts like inflation, dark matter, and dark energy to defend the Big Bang model against competing interpretations.
  • It is claimed that some textbooks may misrepresent the redshift as evidence of space expansion, suggesting that such an expansion would not be observable without light being affected in a specific way.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of redshift and its implications for cosmic expansion. There is no consensus on whether redshift is the sole evidence for expansion or if alternative models should be considered.

Contextual Notes

Participants highlight the dependence on interpretations of redshift and the assumptions underlying various models of the universe. The discussion reflects unresolved questions regarding the nature of cosmic expansion and the validity of competing theories.

Calimero
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Are there any evidence that universe is expanding other then redshifting of EM radiation?
 
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The existence of the CMB shows that the universe was once a lot hotter and denser, which is the conclusion you reach if the universe is expanding.
 
The redshift in the EM radiation from galaxies increases in proportion to their distance from us.

If interpreted as a Doppler shift, galaxies are rushing away from each other, matter inside galaxies remaining largely unaffected. This interpretation has lead to the Big Bang model, which has been so eagerly defended against evidence by postulating inflation, dark matter and dark energy.

It can also be interpreted as a successive shrinkage of space-time, if it is assumed that light is not shrunken. This leads to various models of the Universe that are dispreferred, mainly for non-scientific reasons.

Although some text-books say so, the redshift cannot be interpreted as due to an expansion of space as such. Such an expansion could not be observed, unless the light was not expanded on its way. But in this case, we would see a blueshift.
 

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