People have speculated about the existence of extraterrestrial life for thousands of years. Today we know that within our solar system the earth is almost certainly unique in supporting intelligent life. But our solar system is only a tiny part of the universe: there are millions of stars in our galaxy, and around some may circle planets with life – even intelligent life.

No matter where we look in the universe, we find that everything is composed of the same chemical elements in much the same proportions. And stars, nebulae, star clusters, and galaxies are found throughout. The same chemical and physical processes operate. The “sameness” of the universe implies that life elsewhere could be similar to life on earth. The sheer size of the universe makes it likely that the same conditions that produced life on earth could be present elsewhere.

Scientists believe that in the depths of space millions of earth-type planets are revolving around sun-type stars at a distance that provides the right conditions for life. However, obtaining proof of the existence of such planets presents immense practical problems. Any planet would be visible only from the faint reflected light from its parent star – and this would be lost because of the glare from the star itself. The difficulty has been compared with trying to distinguish between a candle and a searchlight when the two are side by side and being observed from many miles away.