The assumption that humanity is not alone is not a new one – in fact, the first clear depiction of fictional aliens was written in the second century AD, in Lucian’s “True History”, who described a war between people living on the Moon and people living on the sun attempting to colonize “the morning star”. As time went on, as Earth began to seem less and less special in the grand scheme of the cosmos, the idea that life might exist on other planets – or even around other stars – began to seem less and less fanciful. By 1686, the idea was widespread enough to be seriously described in one of the first books of popular science, intended to teach the heliocentric model and it’s implications. The idea gained steam during the Enligtenment and on into the 19th century, where there was a period from about 1877 to 1907 where it was widely believed even by scientists that the surface of Mars was marked by canals and hosted life, likely intelligent life. Later findings proved that these “canals” were optical illusions made worse by poor telescopes – and since then, humanity has failed to find any significant signs of and any life that didn’t originate on Earth.
And yet, the concept of extraterrestrial life is a serious idea, still under investigation by scientists. Everything scientists have discovered about the universe suggests that Earth is not particularly special or unique – and therefore that life must exist out there, somewhere. This is particularly highlighted by a famous piece of math known as the Drake Equation, which attempts to calculate the likeliness of finding intelligent extraterrestrial species. Based on factors like the number of planets that could support life, the amount of life that goes on to be intelligent, and so on, it’s possible to get a ballpark estimate of how many intelligent aliens we would expect to have run across by now. Unfortunately, we don’t know enough about how life and civilizations develop to be able to calculate the results – at least not as any more than a wild guess.
So, the question remains: where are all the aliens? Are there even any out there? You see, the thing is that the Galaxy is very, very big and very, very old. It might seem like this means that we’re less likely to encounter any intelligent life that might arise, but the truth is just the opposite. You see, scientists can pretty easily calculate how long it would take to colonize a galaxy, or at least fill it with probes. In October of 2012, a paper came out in which they’d done just that – and they found that even a slow-moving, not-very-expansionist species could colonize our galaxy in less than 50 million years. That sounds like a long time until you realize that the Milky Way Galaxy has been around for some 14 billion years – or long enough to have been completely colonized 280 times over.
Basically, either we’ll be the very first intelligent beings to have arisen in our galaxy, or something weird is going on that’s keeping us from seeing, talking to, or finding artifacts from whatever intelligent spacefaring aliens are out there. After all, it would only take one piece of solid data to prove that aliens exist – one monolith floating in space, one species that decided to stop hiding, one transmission we could decode.