Is there anybody out there?【T1】For centuries human beings have wondered, although the ways in which we have gone about this have varied, encompassing spiritual and metaphysical questions as well as scientific ones. As we have gained greater understanding of the universe, however, our searches have taken on more concrete form. Questions about extraterrestrials have become a subject for science rather than science fiction and philosophy.

Now a new collaboration between the Very Large Array observatory in New Mexico and the privately funded Seti Institute in California, could mean that our curiosity about aliens is closer than ever before to being satisfied. Data from the VLA’s 28 giant radio telescopes, configured so as to scan a vast expanse of sky, will be fed through a special supercomputer that will search for distant signals.【T2】Scientists who work at the Seti Institute said the announcement means their research, for a long time confined to the eccentric margins of respectable science, are now “almost mainstream”.

How likely it is that a signal will be found, and what this might mean, are hard questions to answer. Seti’s existing projects have not detected any transmissions from other planets so far.【T3】But recent discoveries in space and Earth sciences have provided some encouragement to those who are enthusiastic about the prospect, however remote, of detecting other civilisations.

While once it was thought that our solar system could be unique, since the discovery of the first exoplanet (a planet in another solar system) in the 1990s, thousands more have been located.【T4】Around one in five stars are now thought to have a planet in their orbit in a so-called “habitable zone”—that is, at a distance from the star where the temperature (neither too hot nor too cold) means that life is theoretically feasible.

At the same time, the date at which life on Earth is thought to have started has been pushed back.【T5】Whereas once it was thought that the deep oceans could have sat dead and empty for billions of years before a freak chemical reaction produced the primitive cells that were the first form of life, recent science suggests that this could have happened much more quickly after the planet formed 4.5bn years ago. If it happened here, why not elsewhere?

【T4】