Could the expansion of space impact the distance between the Earth and the sun?

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Discussion Overview

The discussion revolves around the implications of the expansion of space on the distance between the Earth and the sun, as well as the constancy of the speed of light. Participants explore whether the expansion affects gravitational attraction and orbital dynamics, and question the possibility of varying light speed in the past.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions if the expanding universe should increase the distance between the Earth and the sun, potentially affecting Earth's orbit due to reduced gravitational attraction.
  • Another participant asserts that gravitationally bound systems, like the Earth-sun system, do not separate due to cosmological expansion, which only affects larger scales such as galactic clusters.
  • A participant seeks clarification on whether the smallness of the expansion makes it unnoticeable or if gravitational forces continuously pull the Earth back to the sun.
  • One participant provides an analogy of an expanding balloon to illustrate how local gravitational effects can counteract the expansion of space, suggesting that nearby objects will still be drawn together despite the overall expansion.
  • A later reply confirms that both gravitational attraction and the small scale of expansion contribute to the Earth remaining at a relatively stable distance from the sun, although it is not exactly the "correct" distance.

Areas of Agreement / Disagreement

Participants express differing views on the impact of cosmic expansion on gravitationally bound systems. While some argue that local gravitational forces dominate, others question the implications of expansion on orbital dynamics, indicating that the discussion remains unresolved.

Contextual Notes

There are assumptions regarding the scale at which expansion becomes significant and the nature of gravitational forces in relation to cosmic expansion that remain unaddressed.

AcidRainLiTE
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I have 2 questions:

1. Since space is expanding, shouldn't the distance between the Earth and the sun be getting greater? And shouldn't that affect the orbit of the Earth (greater distance between the Earth and sun ->> less gravitational attraction)?

2. Is it possible that the speed of light could have been faster at one point. For example I was looking at the following:

t = t0(1-(v^2/c^2))^(1/2) (I think this is correct)

I understand why this formula (and the others like it for mass and distance) would imply that no object could travel faster than the speed of light (can't take square root of a negative)...but that doesn't seem to limit what c can be. If c were greater that doesn't cause any problems in the formula. Are there other reasons for saying that the speed of light has always been a constant speed?

Thanks.
 
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Gravitationally bound masses do not separate because of cosmological expansion. It is only on the scale of the distances between galatic clusters that the separation distances increase
 
Is that because the expansion is so small it is unnoticable? Or does the gravitational attraction (continuously) pull the Earth back to the correct distance from the sun?
 
To get a physical picture - imagine a balloon that is expanding - on the surface we place some objects that indent the expanding balloon because they have inertia (mass) ... two nearby objects would tend to fall together because each rolls toward the indentation produced by the other - these objects are the galaxies and the indentations are the local effect (curvature) of matter on space - if the objects are far enough apart they will separate faster than they roll toward one another - this occurs on the scale of galatic cluster - but if they are closer the effect of the indentation causing them to move toward one another will be greater than the expansion of the balloon as a whole - so we see local galaxies like M31 blue shifted (moving toward the Milky Way).
 
AcidRainLiTE said:
Is that because the expansion is so small it is unnoticable? Or does the gravitational attraction (continuously) pull the Earth back to the correct distance from the sun?
Both. Gravitational attraction pulls the Earth back to the sun, but not exactly to the "correct" distance. And the difference is so small that it remains unnoticeable.
 

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