MadSci Network: Astronomy

Re: Could not Gravity be a repulsion from Space and not an attraction of mass?

Date: Thu Feb 7 15:07:46 2002
Posted By: Chris Lintott, Undergraduate, Physics
Area of science: Astronomy
ID: 1008292286.As

Dear Ben,

Thanks for your question; as you know the best theory of gravity we have 
is Einstein's general relativity. This describes gravity as the effect 
matter has on space (actually, spacetime, for in relativity we consider 
time as just another coordinate but that doesn't matter here). I should 
say first of all that general relativity has passed (so far) the most 
important test of a scientific theory; it predicts things which are seen 
in observation and in experiment. The theory, for example, was only 
accepted after Eddington had observed the bending of light rays due to the 

I can see two major problems with the theory you propose (which would, of 
course, have to make all the same predictions relativity does). Firstly, 
the strength of the gravitational attraction is directly dependent on the 
amount of mass present. I suppose this could be explained by saying that 
space pushes harder on more mass, but in my opinion this solution is not 
as elegant.

Secondly, if gravity was due to space acting on a mass we'd have to take 
into account the space between the two objects attracting each other; 
something we can get by without in our current theory.

In short, I can't see any reason why your theory couldn't be made to work, 
but it would not offer any predictions above and beyond general 
relativity, at the cost of a much more complicated theory.

Hope that helps.

Chris Lintott

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