Gravity is a force that acts on physical particles. Gravity does not contain molecules, but it acts upon molecules by pulling them toward molecules with a greater gravitational force.
There are two forces acting on every molecule. One is gravity, and the other is magnetism. Sir Isaac Newton (1642–1727) experimented with gravity and came up with a mathematical formula to express how gravitational force works on objects. He determined that it was gravity that pulled the moon in its orbit around earth and that gravity held the planets in their orbits around the sun.