The opposite of gravity is weightlessness

I've always liked the way "gravity" has the meaning of weight, the scientific definition, the force pulling two "massive" (an interesting word in itself!) objects together, as well as that of importance, seriousness. We often hear the expression "the gravity of the situation". Do we constantly wander around appreciating the gravity of our situation? Paradoxically, the gravity of our situation would increase enormously if we drifted off into space! Did Newton appreciate the gravity of his situation when an apple fell on his head? Dangerous things, them apples.

Levity means lightness, as in frivolity, flippancy - we see a few examples on this board - and is an antonym for the "seriousness" definition of gravity. I don't know that levity is ever used to express the concept of lightness as in lack of weight, though, is it?