Gravity as consequence of universe expansion

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Discussion Overview

The discussion centers around a proposed explanation for the nature of gravity, suggesting it may be a consequence of the universe's expansion. Participants explore the implications of this idea, its relationship to existing theories, and potential methods for validation.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that gravity could be explained as the result of the warp of space caused by the accelerating expansion of the universe, using analogies involving elastic surfaces and expanding balloons.
  • Another participant points out that the idea of elasticity in space-time is not a new concept and emphasizes that analogies do not constitute a theory, noting that gravitational forces can be explained without assuming such elasticity.
  • A later reply references an article that discusses a similar concept, indicating that the expansion of the universe may influence gravity through a shadowing effect, but acknowledges that this is not a mainstream idea.
  • One participant raises a question about the relationship between an object's speed and its gravitational field, referencing general relativity, and seeks confirmation from others regarding the correctness of this thinking.

Areas of Agreement / Disagreement

Participants express differing views on the validity and novelty of the proposed explanation for gravity. While some find the idea interesting, others challenge its theoretical foundation and relevance, indicating that multiple competing views remain unresolved.

Contextual Notes

There are limitations regarding the assumptions made about the nature of space-time and gravity, as well as the dependence on analogies that may not fully capture the complexities of the theories involved. The discussion also highlights the need for further exploration and validation of the proposed ideas.

Blade Runner
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I would like to suggest an explanation of the nature of the force of gravity. First I will state some well-known facts, then I will suggest an explanation and finally a hint for the way it might be proved correct.

Facts:

1. Analysis of the spectrum of light from galaxies reveals a shift towards longer wavelengths proportional to each galaxy's distance in a relationship described by Hubble's law indicating that space-time is undergoing a continuous and uniform expansion (Wikipedia). The longer its distance from us, the faster the speed it moves away from us.
This fact is usually exemplified with the simile of two points on the surface of an expanding balloon, moving apart from each other as it is inflated.

The pull of gravity is usually explained as the fall of objects down a slope in a surface warped (sunk) by more massive objects (simile of the balls on an elastic surface) falling towards a bigger ball down the subsidience the latter creates. Now, this model describes very well HOW objects move in space because of gravity, but not WHY, since they should not fall in abscence of other forces, no matter how big the subsidience is.

2. Apparently the most recent observations claim that this expansion is accelerating.
Going back to the simile of the balls on an elastic surface, they could fall towards each other’s holes if this elastic surface was accelerating upwards. Let’s imagine that the whole set of balls on an elastic surface is in a lift or elevator traveling upwards with an increasing speed. Its very acceleration would make the balls warp the surface they are on and the lightest balls would fall towards the heaviest.

And here comes my speculation:

Imagine the elastic surface (two dimensions) of a sphere or globe (three dimensions) is a simile of our universe (three spatial dimensions) as a surface of a hypersphere (four dimensions) which is expanding at an accelerating speed.

That accelerating expansion (like a tour dimensions balloon being blown) make the objects placed on its surface sink warping it. The more massive the objects, the deeper the warp and as a result lighter objects fall into them.

This would explain gravity in an easier way than nowaday’s speculations where gravitons (not founded) or masses placed in other dimensions are needed to provoke its effects in our universe. (In my opinion, the latter theory implies an endless series of masses pulling from equally endless dimensions...)

Hint to a method to check this speculation:

How could we possibly prove this theory right? I suppose we could by comparing the value of the acceleration of the expansion of the universe (I ignore it) and the Gravitational Constant (G = 6.67 × 10-11 N • m2/kg2 ). But that is too far away from my capabilities. I drop the idea for cleverer ones.

To sum up, gravity would simply be the result of the warp of the space, caused by the inertia of the mass placed in it and as a consequence of its accelerating expansion. Namely, in a universe with no expansion there would be no gravity and objects would not be attracted to each other. With a zero expansion the Gravity Constant G would be zero. Going back to the simile, if the lift or elevator stopped accelerating, the balls would stop pressing on the elastic surface.
 
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This is not, as I am sure you understand, a new idea. Unfortunately, an analogy is not a theory. It has been shown that the no assumed "elasticity" of the space-time surface that would be warped can result in the observed gravitational force.
 
Thanks a lot HallsofIvy. Could you recommend me any author or article too learn more about this topic?
 
Blade_Runner, this article has a similar idea, in that the expansion is causing gravity by a shadowing effect. It's not a mainstream idea, as you can imagine.

http://arxiv.org/abs/gr-qc/0108026v1
 
Interesting idea, especially since the faster an object is moving the more mass it has(as shown in GR) hence it would have a stronger gravitational field. Is this thinking correct anyone?
 

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