[If the universe contains more than three spatial dimensions, as many physicists believe, our current laws of gravity should break down at small distances.]
This is timely because this subject came up on a different thread about the teaching of evolution in Kansas schools. The point was made that there are flaws in the "theory" of universal gravitation:
1)Scientists today don't have a coherent explanation for universal gravitation that doesn't rely on invoking spurious "extra-dimensional" explanations which have never been observed.
2)Einstein understood the flaws in his own theory and even invoked an artificial "cosmological constant" in order to fudge the mathematics to obtain the right answer, and most scientists can't decide on competing theories of universal gravitation like "general relativity" or "super-strings".
3)The theory of universal gravitation lacks logical consistency; If everything in the universe is attracted to everything else in the universe gravitationally, then all matter would soon be occupying the exact same space, a clear impossibility!
4)Alternative theories such as "Benign Directed Stickiness" are not given fair treatment and should be given equal time in classrooms.
There are many more proofs that refute "universal gravitation" that can be seen at "John's House 'O' Conspiracy" Web Site, here:
http://johnf-ingkerry.com/
BTW, satire alert.
One thing that seems to be overlooked in all this is that mass occupies the dimensions of space but is considered separate from the dimensions. I propose that mass is itself a dimensional phenomenon that has the fourth dimensional projection of both particles and waves, but is in actuality neither. Under this assumption gravity is quickly demoted from a fundamental force to a mere happenstance of more basic relationships.