Science Puzzle
Orbital Trajectory
A satellite is in orbit above a planet. Gravity is constantly pulling the satellite straight toward the planet with considerable force. Yet the satellite never falls down to the surface.
How does the satellite stay up if gravity is continuously pulling it down?
The Answer
The satellite is falling. It is in continuous free fall toward the planet. But it is also moving sideways so fast that the planet curves away beneath it just as quickly as it falls.
Think of throwing a ball horizontally. It falls in a curve and hits the ground. Throw it faster and it lands further away. Throw it fast enough and the curve of its fall matches the curve of the spherical planet beneath it: by the time the ball has fallen a metre, the ground has also curved away a metre. The ball never hits the ground. That is an orbit.
There is no centrifugal force pushing outward. Centrifugal force is a fictitious force felt in a rotating reference frame. In reality, the only force acting on an orbiting satellite is gravity, directed inward. The satellite is simply falling around the planet continuously.
The principle: Orbital mechanics. An orbit is continuous free fall. The tangential velocity is high enough that the planet curves away beneath the satellite as fast as the satellite falls toward it.