Questions about Universe expansion

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Discussion Overview

The discussion revolves around questions related to the expansion of the Universe, specifically addressing local gravitational effects on expansion and the implications of observing distant galaxies. It touches on theoretical aspects, observational interpretations, and conceptual clarifications regarding the nature of cosmic expansion.

Discussion Character

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

Main Points Raised

  • One participant questions why there is no local expansion around us, suggesting that local gravitational fields may be strong enough to prevent this and inquires about the directional effects of gravity on expansion.
  • Another participant agrees that while the universe expands at all levels, local expansion is countered by gravitational attraction at stellar and galactic scales.
  • A participant expresses unease with the phrase "the farther Universe expands faster," likening it to historical misconceptions about Earth's centrality in the Universe.
  • It is noted that while the Earth is at the center of the Observable Universe, this does not imply a preferential frame, as all points can be considered at the center of their own observable universe.
  • One participant mentions that the apparent acceleration of distant galaxies is a consequence of a scale factor over a larger area of space.

Areas of Agreement / Disagreement

Participants generally agree on the influence of gravitational forces on local expansion, but there are differing views on the implications of observing the expanding Universe and the interpretations of statements regarding its acceleration.

Contextual Notes

Some assumptions regarding gravitational effects and observational interpretations remain unaddressed, and the discussion does not resolve the complexities of cosmic expansion versus local gravitational influences.

Who May Find This Useful

Individuals interested in cosmology, gravitational physics, and the nature of the Universe's expansion may find this discussion relevant.

AlSo
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I have two questions about the expansion of the Universe. 1. Why is there no local expansion around us, is local gravitational field strong enough to prevent this? How does the vector of gravity act to prevent expansion in multi-directions? 2. When scientists observe the expanding Universe, and comment that "further Universe expands even faster", have they considered the fact that what they see "at the edge" had actually happened nearly 14 billion years ago? Thank you.
 
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1) Yes you are correct. Theoretically universe expansion holds on all levels, but any expansion on the stellar, or even close galactic level is canceled out by gravitational attraction.

2) Yes they do.
 
thanks Vorde!
 
thanks phinds, that is very useful. I always feel uneasy when I hear scientists say "the farther Universe expands faster"----this seemed to commit the same mistake we made centuries ago----placing the Earth at the centre of the Universe. Cheers!
 
AlSo said:
thanks phinds, that is very useful. I always feel uneasy when I hear scientists say "the farther Universe expands faster"----this seemed to commit the same mistake we made centuries ago----placing the Earth at the centre of the Universe. Cheers!

The Earth is at the center of the Observable Universe but this doesn't imbue it with any preferential frame - all points are at the center of their own observable universe - due to the expansion of the Universe and the finite speed of light.

The furthest places we can "see" do appear to be accelerating away from us but in actuality it is just the consequence of a scale factor over a bigger area of space - its quite a logical assumption.
 
thanks Cosmo Novice!
 

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