The ancients believed that the universe consisted of countlessworlds we could not see, and argued endlessly over the natureof these distant, invisible planets and whether they might beinhabited. Until recently many scientists thought we wouldnever discover the truth, believing that extra-solar planetswere simply too far, too small and too dim to detect. But newtechnologies have suddenly revealed thousands of distantplanets, opening up the most exciting period in astronomy indecades. Some believe we're on the verge of answering theancient question: are we alone in the universe?
