The universe is so big and full of stars that it seems obvious some must have evolved intelligent life. But it turns out we know so little we can’t know what’s obvious. Quite likely we are alone
Are we alone in the universe? Of all the billions of stars out there, is there none around which intelligent life has arisen, no other conscious beings who have looked at their sky and asked themselves whether there was anyone else out here? All we can know is that we don’t know of any others. But that has not stopped more or less well-informed speculation. The universe is so unthinkably enormous and old that it seems almost impossible that only one of the quintillion or so stars in the universe has actually developed intelligent life.
So where are they? So asked the physicist Enrico Fermi in 1950. If other intelligent species are out there, why haven’t we seen them yet? The mismatch between what we’d expect from the numbers, which is a universe full of spacefaring civilisations, and what we observe – nothing – is known as the Fermi paradox. Few of the explanations proposed for it are cheering. Perhaps all civilisations advanced enough to develop space travel are also technologically capable of annihilating themselves as well, and perhaps they all do. Perhaps the first culture to develop interstellar travel has already snuffed out all its rival species as they emerge, and is at this moment watching our first tentative explorations of the solar system as a cat might watch a fledgling on the ground. Or perhaps we have simply got the numbers wrong.