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Gravity as consequence of universe expansion

by Blade Runner
Tags: consequence, expansion, gravity, universe
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Blade Runner
Feb23-08, 10:38 AM
P: 2
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.


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 otherís holes if this elastic surface was accelarating upwards. Letís imagine that the whole set of balls on an elastic surface is in a lift or elevator travelling 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 accelarating 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 nowadayís 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 ē 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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Feb23-08, 03:08 PM
Sci Advisor
PF Gold
P: 39,682
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.
Blade Runner
Feb24-08, 05:36 AM
P: 2
Thanks a lot HallsofIvy. Could you recommend me any author or article too learn more about this topic?

Feb24-08, 12:35 PM
PF Gold
P: 4,087
Gravity as consequence of universe expansion

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.
Mar2-08, 08:22 AM
P: 12
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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