Ask Slashdot: Math Curriculum To Understand General Relativity?
Negative mass/energy is NOT antimatter, but rather "exotic" matter. At the physics one level, antimatter is just matter w/ the opposite charge of the normal particle. If you find significant amounts of negative mass around, let me know and I'll build you a wormhole. I'll need approximately a galactic mass of said matter....
Jonathan Zdziarski Answers
Gravity is not a law - it is a theory. Newton's theory of gravity is incorrect (it fails when the gravitational field gets too large). Einstein's theory of gravity is also wrong - it also fails in certain instances (it predicts an infinte gravitational field strength at the very center of a black hole). Any theory which has an infinity in it is wrong. It may work well for most situations, but it is only that a theory. It's fairly easy to see when Newton's theory fails: F = GMm/r^2 - when r -> 0, the field strength becomes infinite. If either theory were a "law" both would be correct and a lot of physicists would be/have been out of business, say like Einstein.