Yeah I wanted to compile a list of theories of gravity once - maybe write a PhD on it or something
One theory explains it that everything is expanding at the rate of 9.8 m/s/s or something like that . What another crock
Newton assumes it is attraction between centers of objects with substantial mass - actually with any mass. Two bowling balls lying under the table will be attracted to each other and an experiment was done back in the 1700s to prove it too. Amazing fellas back then.
Then the Ether - Space is full of tiny little balls that all together in great concert act like a fluid so space and so on behaves like a fluid. Two geeks went looking for effects which should be produced if there were an ether but found feck all so OneBall had the bright idea of declaring "No ether"
Then OneBall with his warping of space and time.
After him everyone except Tesla gave up thinking about gravity in terms of anything other than space or time.
The great Quantum Mechanical picture of the world does not really take Gravity into account the way EinBall described it though - warped space and time has no validity when describing atoms, electron shells, quantum numbers and all that jazz. So in order to explain gravity in these terms, theoretical physicists have to cook up Superstrings, 28-dimensional space and all sorts of Twistors and Quarks and all exotic stuff, worse than what's in the treaty of lisbon.
I think the Ether research didn't get enough funding, personally.
Portal 
5 alternative universes - on video
