Lesson 2: What is weightlessness? What does it feel like?

It is difficult to imagine situations where we are not attracted to the Earth. Absence of gravity is known as weightlessness. It is like floating, the feeling you get when a roller coaster suddenly goes down.

Astronauts on the International Space Station are in free fall all the time. Gravity still pulls on the Station, but because it travels around the Earth at such high speed, its travelling forwards equals out the falling and the ISS stays more or less at the same height. The astronauts inside it experience weightlessness, floating around in no particular direction. There's no up or down for them... down is wherever their feet are.

The Russian space station Mir was launched in 1986. Since then, many astronauts have spent long periods of time on board Mir and the ISS. Space travellers go through a range of often unpleasant feelings: they feel dizzy, sleepy and weak, suffer from loss of appetite and stomach upsets and lose their sense of time and space. Fortunately, after few days, their bodies adapt to weightlessness and astronauts start to feel both calm and euphoric...

When they return to Earth, astronauts have to readapt to gravity and regain their balance. A Russian astronaut who had been back for several months once told the story of how he was surprised when he saw a cup fall to the ground! They also have to build up the muscles they lost because they did not use them in space.