[Phoenix-D]

Gravity first: the best explanation at the moment is Einstein's. Gravity is -not- considered a force there, and doesn't 'use' any energy. Rather its something mass does to spacetime, with the side effect of making masses move toward each other.

Even that theory isn't complete yet, though, as it doesn't work on the level of atoms (possibly because gravity is so weak at that scale).

Magnetics: same general idea. Its caused by the movement of charged particles though, and to explain those you get into QM, which is mind-bendingly freaky.

Something to remember: Newton's theories are *wrong*. Darwin's theory was *wrong*. In both cases however, they still serve as a strong base for use and further experiment; the areas where they are wrong are small enough they don't impact day-to-day work.