How do physicists use redshift to determine the expansion of the universe?

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Discussion Overview

The discussion revolves around how physicists use redshift to understand the expansion of the universe. Participants explore the implications of redshift, the nature of the universe's expansion, and the relationship between galaxies and space itself.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants suggest that the redshift observed in most galaxies indicates they are moving away from our galaxy, implying that the universe is expanding.
  • There is a question about why redshift is observed universally if galaxies are moving alongside each other, leading to a proposed analogy with the Doppler effect.
  • One participant argues that if the universe is infinite, it cannot be expanding, while others counter that an infinite universe can still expand.
  • Another point raised is that the observable universe is finite and has been increasing in size over time, constrained by the speed of light.
  • Some participants discuss the concept of the unobservable universe and its potential finiteness, suggesting that unobservability does not imply a lack of finiteness.
  • There are references to the pioneer anomaly and its relation to the Hubble constant, with differing opinions on its implications for understanding expansion.
  • The relationship between causality and observation is debated, particularly regarding the unobservable universe's disconnection from the observable universe.
  • Several participants discuss the philosophical implications of infinity, questioning its nature and how it relates to physical reality.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of the universe's expansion, the implications of redshift, and the concept of infinity. There is no consensus on these topics, and the discussion remains unresolved.

Contextual Notes

Limitations include assumptions about the nature of space and infinity, as well as unresolved questions regarding the relationship between redshift and the expansion of the universe.

  • #31
But, is there such thing as infinite in physics?
 
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  • #32
Arifz said:
But, is there such thing as infinite in physics?

only one thing is infinite, that is universe...the emptiness

physics is to deal with singularities like matter energy stuff like that which spawned out of nowhere in the emptiness

Bigger picture of universe go beyond physics
 
  • #34

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