The truth is out there.
Unfortunately, it might also be dead.
Scientists have long questioned the absence of evidence for intelligent alien life. The Fermi paradox, for example, ponders the strange contradiction between the lack of evidence for alien civilizations and the seemingly high probability of their existence. So many habitable planets, so many stars, and yet not a single trace of alien life.
How do we explain this?
Aditya Chopra and Charles H. Lineweaver, astrobiologists from the Australian National University, have put forward their own hypothesis: The aliens are silent because they’re dead.
Their reasoning is that, while the emergence of life may very well be common throughout the universe, it’s fragile and simply does not evolve quickly enough to survive, leading to early extinction.
Most of the fossils we’ll find (if any) during our search for life, they say, will likely be from “extinct microbial life, not from multicellular species such as dinosaurs or humanoids.” They call this solution to the Fermi paradox the “Gaian Bottleneck.”
You can read their full paper here (PDF).
But that’s not all.
One of the first posts I ever wrote on this website asked the very same question: Where are all the aliens? And to me, it’s not only a question of whether or not they exist, it’s also a question of time. After all, humans represent only a handful of seconds on Earth’s clock, so to speak.
Who’s to say aliens haven’t already visited our planet, long before life existed here? Who’s to say they won’t visit long after we’re gone? And vice versa. Given how big the universe is, we’d be very lucky to run into intelligent extraterrestrial life at this particular location at this particular time. And the target is always moving.
Another group of scientists, meanwhile, are suggesting that some aliens might actually be out there, right now – but they’re hiding beneath their planets’ surfaces, in subsurface oceans or underground.
These would be the only places, they say, where life could have evolved in the face of dangerous cosmic radiation, particularly in the early universe.
“It’s possible that alien societies could exist beneath the oceans of other planets, although finding signs of them with today’s technology would be extremely difficult.” – Where Are All the Aliens? Taking Shelter From the Universe’s Radiation, Smithsonian
All of this said, one thing seems clear: Earth is a very lucky place.