The search for extraterrestrial intelligence

Abstract

There is one way in which we could discover extraterrestrial life now, with no more than the instruments we already have, and this is by life telling us that it is there. This could be by transmitting radio or laser signals that we receive, or by sending probes into the Solar System that we find, or in any other way that a technological intelligence could make its existence known. And indeed it is technological intelligence that we will have discovered. Regardless of the likelihood of such a discovery, it would be an astonishing finding. We would have learned not only that there is life in at least one other place in the Universe, not only that it had evolved into multicellular species, not only that one of these species had evolved intelligence, but also that the intelligence was technological. We would have discovered what is usually called extraterrestrial intelligence (ETI). Whatever they looked like, these creatures would be thinking like us — they would be trying to understand the Universe and manipulate their environment in the same way that we do. What are the chances of such a discovery, and how might it be made?