"For many millennia, humans have gazed up in wonder at the night-time sky. The full panoply of the Milky Way is an awesome sight. The scale of space is immense. Is there life out there somewhere? If so, where, and what form does it take? In the space of a couple of sentences, we've already gone from generalized wonder to specific questions. The next step is from questions to hypotheses, or, in other words, proposed answers. Here are two such hypotheses that I'll flesh out as the book progresses: life exists on trillions of planets in the universe; it usually follows evolutionary pathways that are broadly similar to - though different in detail from - those taken on Earth. Going from cosmic wonder to questions about alien life and on to hypothetical answers has been possible for a long time. But the final steps - from hypothetical answers to testing the hypotheses to arriving at an understanding of reality - have so far proved beyond humanity's grasp. That may be about to change. We may be on the threshold of being able to answer the age-old question 'are we alone in the universe?' with a resounding 'no'. But what is the basis of this claim? The short answer is advancing technology, and in particular advancing design of telescopes. We'll get to that topic soon. But first, let me reassure you that I'm not alone in my optimism about the imminent discovery of evidence for alien life"--