Astronaut
Why do astronauts float in the space station?
Weightlessness in an orbiting spacecraft is physically identical to free-fall.An object that rests on the ground is subject to a normal force exerted by the ground. The normal force acts only on the boundary of the object that is in contact with the ground. This force is transferred into the body.The force of gravity on every part of the body is balanced by stress forces acting on that part. A weightless astronaut feels weightless due to the absence of these stress forces.But actually they are not weightless.It is gravity that keeps the space station, the astronauts, and their equipment in orbit around the Earth.An object in orbit around the Earth is falling with sideways motion that is so rapid that as it falls, the Earth’s surface moves away at just the right rate that it falls around the Earth.This is exactly what the Moon is doing in its orbit around the Earth. It is falling, but moving sideways so rapidly so that instead of approaching the Earth’s surface, it remains at an approximately fixed distance.Inside the station,astronauts and their equipments float because they and their equipments are falling — falling around the Earth — along with
everything inside their spacecraft.If we look at them from outside their spacecraft,we can see they are not floating and traveling in a circle around the Earth.But inside the space station,they appear to be floating,and they experience weightlessness.
