Gravity is an attractive force exerted by every object with mass and felt by every object with mass. Gravity is a field force, which means that it acts at a distance even if objects are not in contact. Other field forces include magnetism and electrical force. Newton explains that mass generates a gravitational field that affects the space around it. This field is what interacts with other masses to create the gravitational force. Gravitational force cannot be shielded or stopped.

Gravity keeps planets in orbit, and holds stars together in galaxies. Everything in space moves at certain speed based upon strength of the gravitational field at that point. Very massive objects like planets, stars, and black holes can cause big changes in an objects motion.

The equation that is used to calculate the strength of the gravitational attraction between two objects was developed by Sir Isaac Newton. For more information, scroll over the variables in the equation.