How do satellites stay in orbit?

An orbit is really a state of continuous falling. A satellite is pulled toward Earth by gravity, but it is also moving forward very fast, so as it falls, the curved surface of the Earth falls away beneath it at the same rate. The result is that the satellite keeps circling the planet instead of crashing down. To achieve this in low orbit, a satellite must travel at roughly 28,000 kilometres per hour. Above the atmosphere there is almost no air resistance, so it can keep going for a long time. Higher orbits require lower speeds, and at one special altitude a satellite orbits in step with Earth rotation.