ANSWERS: 4

Because we might have a reasonable explanation or theory, the fact is we are unable to reproduce the effect to show positively that the theory is fact. It is the job of science to attempt to theorize any given thing until such time as there is a positive proof that a theory is a solid law. If more than one theory can exist for any given observed phenomena, then those theories need to be explored in depth, always seeking to test the theory until it breaks or until one theory only survives to be the truth.

They still have to explain why some people improperly use the caps lock key.

Einstein's General Relativity (curvature of space) and Quantum Mechanics (particles) are embarassingly incompatible theories. GR works well on large scales, QM works well on small scales. A graviton would be the QM version of gravity and may help find a theory that works on both scales  something Einstein spent most of his life searching for.

Particles which carry the force are known for the electromagnetic force, weak and strong nuclear forces, but no force carrying particle (the graviton) has been discovered for the gravitational force. Therefore the search is on for the graviton. But gravity has not been fully explained by Newton or Einstein, they describe its measurable effects mathematically, but no one has yet explained why a mass produces a gravitational field, or even what a gravitational field actually is! Newton attempted this and gave up. Einstein did not even tackle the problem, but later did admitt that spacetime must have some substance. See: quarkphysics.50megs.com
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