Inertia is the tendency of all objects and matter in the universe to stay still, or, if moving, to continue moving in the same direction unless acted on by some outside force. This forms the first law of motion formulated by Isaac Newton (1642–1727). To move a body at rest, enough external force must be used to overcome the object’s inertia; the larger the object is, the more force is required to move it. In his *Philosophae Naturalis Principia Mathematica,* published in 1687, Newton sets forth all three laws of motion. Newton’s second law is that the force to move a body is equal to its mass times its acceleration (F = MA), and the third law states that for every action there is an equal and opposite reaction.