The universe is a big place. In the 6th century BC Anaximander suggested that other worlds were endlessly forming and disintegrating in a universe of infinite size. In the 5th century BC Democritus, a Greek philosopher argued that there were countless other worlds containing countless other lives. Into the medieval ages and beyond, telescopes became more and more powerful, yet still the edge of the universe could not be found.
Today we can watch stars forming in the nebulae of dust and gas, and from the Hubble telescope a snapshot of 10,000 galaxies- each containing billions of stars. And the theory is we are still only seeing 95% of what there is out there. Statistical extrapolations for the 1000 potentially “Goldilocks planets already identified lead to the conclusion that there are about 20 billion earth-like planets in our galaxy.
Yet… we have never found evidence of extraterrestrial activity. It was eloquently put by Enrico Fermi in his book “5 billion years of solitude: “Where the hell are they?!”
If we assume that there are many planets capable of having intelligent life spawn on them, and that those planets will allow civilisations to develop for at least as long as our human ones, then why indeed have we not had any contact from them? One theory is that the distances between earth and other earth-like planets are simply to vast to be traversed. If we can never travel faster than the speed of light, and there aren’t thinks like wormholes in space, then we should resign ourselves to the fact that even if we are not alone, we will never meet another extra-terrestrial species.
The other theory is more interesting. They are avoiding us. For whatever reasons (and maybe we don’t look very nice as a species from our history) intelligent life out there has no wish to contact us. Perhaps they consider that species should rise and fall without any foreign intervention. Perhaps they are afraid of us. Perhaps they just wish to make us remain in splendid isolation, less we taint others with our warlike tendencies. Maybe they have evolved to another level of life where physical bodies have been dispensed with and we would not be able to see or understand them even if they were skimming past earth.
Whatever the reasons, we still spend a lot of time, money and effort in trying to see if there is intelligent life beyond earth. Perhaps as science develops apace in the next few hundred years we will have made some progress towards extra-terrestrial contact. Or perhaps we are just doomed to having another 5 billion years of solitude.