For a body to stay in orbit around Earth, it must travel tangentially (magenta arrow) with a velocity that lets the body fall a radial distance due to the force of gravity (black arrow) in such a way that it follows the curvature of Earth (yellow arrow). The resultant displacement can be represented as the sum of both motions (blue arrow). As an example, astronauts inside a space shuttle appear to be floating in zero gravity with an absence of gravity, but actually they are continuously falling around Earth.