According to many widely respected estimates, our galaxy should be dotted with technologically advanced alien civilizations capable of contacting us. And yet, as we turn our ears to the cosmos, we hear nothing from them. This puzzle is known as the Fermi paradox, the apparent contradiction between the relatively high probability of alien contact and the complete lack of evidence for it.
A group of researchers at Oxford University's Future of Humanity Institute recently confirmed this paradox: We are "in fact" alone in this universe.
"We find a substantial probability of there being no other intelligent life in our observable universe, and thus that there should be little surprise when we fail to detect any signs of it. This result dissolves the Fermi paradox, and in doing so removes any need to invoke speculative mechanisms by which civilizations would inevitably fail to have observable effects upon the universe," researchers stated in their paper.
Not giving up hope
However back in 2013, Cornell student Evan Solomonides offered a solution. In fact, Solomonides even made a prediction as to when E.T. should be expected to phone, reported Phys.org.
"We haven't heard from aliens yet, as space is a big place — but that doesn't mean no one is out there," said Solomonides. "It's possible to hear any time at all, but it becomes likely we will have heard around 1,500 years from now."
Why 1,500 years? Solomonides' calculation rests on the idea that most other alien civilizations are as mediocre as we are, and that it takes a long time for any civilization to become advanced enough to broadcast proof of their existence to the galaxy. If it's true that most aliens have, like us, barely scratched the surface as it pertains to long-distance communication or space travel, then we can use our own progress as a benchmark.
The 1936 Berlin Olympic Games broadcast was the first radio signal that was sent into space from Earth, and even though that signal is traveling at the speed of light, it has only made it as far as 80 light-years away. This is a minuscule distance compared to the size of the Milky Way. So if it's assumed that the vast majority of alien civilizations are on our pace, it means only about one-tenth of 1 percent of the Milky Way would be blanketed by signals, even if we're being fairly liberal about the numbers of alien civilizations out there.
The 1,500 years comes from this model. That's about how long it will take for all the projected bubbles of signals to expand into enough of the galaxy to make contact more likely than not. Of course, that doesn't mean a signal can't come before that, or after. We could hear from aliens tomorrow, or it could be another 3,000 years before we do. But if Solomonides is right, we really shouldn't start to worry about the Fermi paradox until roughly the year 3500.
That's a relief, sort of. It means that the galaxy, not to mention the universe as a whole, could be teeming with aliens even if we haven't heard from them yet. So there's no reason to feel lonely. Yet at the same time, it means that we're all probably so far away from one another that communication between civilizations is a rare occurrence, which is kind of a lonely realization in its own right. As it's said: Loneliness is not alone.
"It is possible that we appear to be alone — even if we are not. But if we stop listening or looking, we may miss the signals. So we should keep looking," reassured Solomonides.
Editor's note: This article has been updated since it was originally published in June 2016.