Earth orbiting the Sun. Illustration showing the Earth moving around the Sun, its orbit determined by a balance of gravitational attraction and centrifugal force. Newton's first law of motion states that a body remains at rest or in motion with a constant velocity unless an external force acts on the body. The gravitational force of attraction between the Earth and the Sun pulls the Earth into orbit around the Sun, constantly overcoming centrifugal 'force', its tendency to move in a straight line out of orbit. The inertia of the Earth, its tendency to maintain its direction and speed , prevents it from crashing into the Sun.