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Where are the aliens?One night about 60 years ago, physicist Enrico Fermi looked up into the sky and asked, "Where is everybody?"
He was talking about aliens.
Today, scientists know that there are millions, perhaps billions of planets in the universe that could sustain life. So, in the long history of everything, why hasn't any of this life made it far enough into space to shake hands (or claws … or tentacles) with humans? It could be that the universe is just too big to traverse.
It could be that the aliens are deliberately ignoring us. It could even be that every growing civilization is irrevocably doomed to destroy itself (something to look forward to, fellow Earthlings).
Or, it could be something much, much weirder. Like what, you ask? Here are nine strange answers that scientists have proposed for Fermi's paradox.
The aliens are hiding in underground oceans.Slide 2 of 19
The aliens are hiding in underground oceans.If humans hope to converse with ET, we'll need to have a few icebreakers handy. No, seriously — alien life is probably trapped in secret oceans buried deep inside frozen planets.
Subsurface oceans of liquid water slosh beneath multiple moons in our solar system and may be common throughout the Milky Way, astronomers say. NASA physicist Alan Stern thinks clandestine water worlds like these could provide a perfect stage for evolving life, even if inhospitable surface conditions plague those plants. "Impacts and solar flares, and nearby supernovae, and what orbit you're in, and whether you have a magnetosphere, and whether there's a poisonous atmosphere — none of those things matter" for life that's underground, Stern told Space.com.
That's great for the aliens, but it also means we'll never be able to detect them just by glancing at their planets with a telescope. Can we expect them to contact us? Heck, Stern said — these critters live so deep, we can't even expect them to know that there's a sky over their heads.Slide 3 of 19
The aliens are imprisoned on "super-Earths."Slide 4 of 19
The aliens are imprisoned on "super-Earths."No, "super-Earth" is not Captain Planet's dorky cousin. In astronomy, the term refers to a type of planet with a mass up to 10 times greater than Earth's. Star surveys have turned up oodles of these worlds that could have the right conditions for liquid water. This means alien life could conceivably be evolving on super-Earths all over the universe.
Unfortunately, we'll probably never meet these aliens. According to a study published in April, a planet with 10 times Earth's mass would also be subject to 2.4 times Earth's escape velocity — and overcoming that pull could make rocket launches and space travel near impossible.
"On more-massive planets, spaceflight would be exponentially more expensive," study author Michael Hippke, a researcher affiliated with the Sonneberg Observatory in Germany, previously told Live Science. "Instead, [those aliens] would be to some extent arrested on their home planet."Slide 5 of 19
We're looking in the wrong places (because all aliens are robots).Slide 6 of 19
We're looking in the wrong places (because all aliens are robots).Humans invented the radio around 1900, built the first computer in 1945 and are now in the business of mass-producing handheld devices capable of making billions of calculations per second. Full-blown artificial intelligence may be right around the corner, and futurist Seth Shostak said that's reason enough to reframe our search for intelligent aliens. Simply put, we should be looking for machines, not little green men.
"Any [alien] society that invents radio, so we can hear them, within a few centuries, they've invented their successors," Shostak said at the Dent:Space conference in San Francisco in 2016. "And I think that's important, because the successors are machines."
A truly advanced alien society may be completely populated by super-intelligent robots, Shostak said, and that should inform our search for aliens. Instead of focusing all our resources on finding other habitable planets, perhaps we should also look to places that would be more attractive to machines — say, places with lots of energy, like the centers of galaxies. "We're looking for analogues of ourselves," Shostak said, "but I don't know that that's the majority of the intelligence in the universe."Slide 7 of 19
We've already found aliens (but are too distracted to realize it).Slide 8 of 19