We've climbed the highest mountains, conquered the deepest oceans and crossed the widest deserts. It seems there's little left for us to see on this planet. So what's next? Space, of course. The idea of living on a space station or in a lunar city may sound like science fiction, but a hundred years ago no one even heard of an aeroplane — yet today more than 500 million people a year travel by air. We may have no choice, in any case. The world's population is growing at a rate of 97 million a year. It means that by the middle of the century there will so many people on our planet that if everyone in India jumped up and down at the same time, it would cause a tidal wave big enough to cover Europe. Greenpeace warns that if we continue to burn fossil fuels at the same rate as we do today, global warming will reach catastrophic levels. They predict sinking continents and severe drought. Add to that the problems caused by hunger, disease, war and nat­ural disasters, and you will see why space agencies across the globe are pouring mil­lions of dollars into space research. The first pieces of the International Space Station have been launched — a giant project which will allow scientists to carry out ground-breaking research in technolo­gy and medicine and see just how long people can live in space. So sometime in this century we might very well see the emergence of a space gen­eration — that means humans born and raised somewhere other than Earth.