What allows gravity to pull in on things without using energy?

1 Answer
Dec 29, 2015

We don't really know ...

Explanation:

Our current hypothesis is that the gravitational force, or gravity, is brough about by the exchange particle known as the graviton. Our explanation for the function of the graviton is that it is emitted by large masses from the posterior, and moves around behind an object, like a boomerang, so that the two masses are pushed together whilst momentum is conserved.

The problem is, right now, the graviton is purely hypothetical: although string theory predicts gravitons and their existence, they are yet to be observed.