Artificial Gravity
Astronauts in orbit experience weightlessness. They are in free fall in the Earth's gravity field, just as is the craft in which they live. Inside the craft, they are free to float around subject to no force RELATIVE to the craft. This can make everyday activities difficult. Astronauts cannot drink a normal cup of tea or use a toilet in the normal way. Food will not stay on a plate, and astronauts cannot use their muscles in a natural way, which means that over a period of time, their muscles waste away. Artificial gravity would be extremely useful on a spacecraft in orbit. We cannot make gravity artificially in the way the writers of Star Trek would have us believe, but we can create forces to mimic the effect of gravity by setting a spacecraft spinning.
Anybody inside the craft will experience a force W – an artificial weight – acting away from the centre of the craft. This force is called a centrifugal force, as opposed to the centripetal force supplied by the floor of the space, which exerts a reaction force towards the centre of the craft to keep people moving around the centre.
