How does gravity work?

The force of gravity is the attraction between every piece of matter, even the smallest particles. The more matter is in something, and the closer its particles are packed together, the stronger the attraction. Stars are large and very dense bodies, and so they have a strong field of gravity. It is our sun's force of gravity that holds the planets in their orbits. The Earth's gravity keeps the Moon in its orbit. Small bodies such as the Moon have a very weak gravity. This explains why astronauts on the Moon's surface were able to jump up high with very little effort.