THE SEARCH FOR
Now when we think that each of these stars is prob-
ably the centre of a solar system grander than our
own, we cannot seriously take ourselves to be the
only minds in it all.
—Percival Lowell (1855–1916)
Perhaps it seems strange that I would start a chapter with a quotation from Percival Lowell, whose greatest claim to fame comes from having imagined a system of canals and a civilization on Mars that existed nowhere but within his own mind. But his story in many ways parallels the ongoing story that we now find ourselves in. Lowell saw a few real things that seemed to hint at the idea that life might be possible on Mars, such as its polar caps, its seasonal changes in coloration, and the vague surface markings that he mistook for a network of canals. He took these hints so much to heart that he lost his objectivity, and became convinced that he saw not just hints but actual proof. Lowell was a scientist, and in most respects quite a good one, but when it came to life on Mars, he abandoned science and built a case based on faith. Unfortunately for Lowell, his faith was unlike religious faith, for which science can generally say nothing about its validity. Instead, he had a faith that was set from the beginning on a collision course with science, because it was only a matter of time until improved observations would shatter the mythology he had created.
Today, we understand a great deal about the nature of our universe and the stars and planets within it, and this understanding gives us good reason to think that life—including intelligent life—might be possible on many worlds. The idea seems so eminently reasonable that it’s tempting to make the same leap of faith as did Lowell, and conclude not just that other civilizations are possible, but that they really exist. Indeed, a great many