What is the ‘Fermi Paradox’ – and how long do we have until we find aliens?

Among the endless stars and galaxies whizzing through the black vastness of space, it may seem impossible that there isn’t life out there somewhere.

So where is it?

One scientist from Imperial College London says that alien life could be much closer than we think — and that we could find it in the next “decade or two.”

It comes in a new paper, which has been selected for publication in the Journal of the British Interplanetary Society.

“Until recently, detecting signs of life elsewhere has been so technically challenging as to seem almost impossible. However, new observational insights and other developments mean that signs of life elsewhere might realistically be uncovered in the next decade or two,” David Clements wrote in the paper.

The heart of the matter is something called the “Fermi Paradox.” First thought up by Enrico Fermi in the 1950s, the paradox boils down to this: It seems as if life should be out there. But it’s not. So where the heck is it?

Scientists have struggled with this problem for years. The Drake Equation, a famous mathematical formula for estimating the number of probably intelligent civilizations, seems to suggest that intelligent life should be all over the place. In fact, for humans to be alone in the universe would be a one in 10 billion trillion chance, scientist Adam Frank said, according to NASA.

There have been many theories — some outlandish, some practical — about why the paradox exists, according to The Atlantic. Perhaps there simply is no life, and the incredibly slim odds just made us incredibly lucky. Perhaps life is out there, but it’s not intelligent: It’s little bugs, or single-celled creatures.

On a more chilling level, maybe there is intelligent life but it is purposefully silent. Maybe they are silently observing us (the “zoo” hypothesis), or they don’t believe we’re worth bothering with, or they are fearful of colonization. Maybe they did exist but are now dead.

This latter, grim hypothesis is known as the “Great Filter,” which suggests that at some point in a civilization’s evolution, some sort of catastrophe wipes them out before they can make contact, the Australian Broadcasting Corp. reported.

In his paper, Clements is less pessimistic. He believes life could actually be common — but is trapped miles underwater beneath the thick, icy shells that surround moons in our own solar system.

Some moons around gas giants like Jupiter are believed to by full of such water, deep below a think crust of ice, Clements writes — and that could be a habitat that sustains life.

He writes that because scientists have already found faraway planets that could have similar moons, it could be that underwater moon life is “in fact the dominant home for life in the Galaxy, with life on Earthlike, terrestrial planets, being the exception rather than the rule.”

They could even have developed high intelligence or technology, he said, according to Newsweek.

“Intelligent sub-ice life would certainly be very different, but I’ve seen no evidence that it would be impossible. Indeed the capabilities of octopuses… are quite surprising. Technology in a water environment, if developed, could be quite different from what we’re familiar with,” he said, according to the magazine.

“We are left with the rather chilling prospect that the galaxy may be filled with life, but that any intelligence within it is locked away beneath impenetrable ice barriers, unable to communicate with, or even comprehend the existence of, the universe outside,” Clements writes in his paper.

That is, unless we can discover it.