12 strange reasons humans haven't found alien life yet [View all]

Scientists have been searching for evidence of extraterrestrial life for decades. So, where are all the aliens? Here are 12 intriguing theories ...


Scientists have discovered thousands of planets beyond our solar system. So where are all the aliens? (Image credit: Getty Images / Anton Petrus)

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 12 unusual answers that scientists have proposed for the Fermi paradox.

We're looking in the wrong universe
Maybe we haven't found aliens because our universe isn't particularly conducive to life. Maybe Earth is an anomaly — a lucky blue dot adrift in a vast ocean of darkness and dead worlds. Maybe we'd have better luck looking for life in the next universe over. That last idea is the premise of a 2024 study that assumes our cosmos is just one possible universe within an endless "multiverse" of realities, each one slightly different from the rest. To test whether our universe has the optimal conditions for life to emerge, the researchers compared star formation rates here to star formation rates in a host of hypothetical, parallel universes with different concentrations of matter and energy. The main factor the team considered was a universe's density of dark energy — a mysterious force that drives the constant, accelerating expansion of the cosmos. A universe with too much dark energy would expand too quickly, scattering star-forming material and stunting the growth of large-scale structures like galaxy clusters. But in a universe with too little dark energy, gravity might become overwhelming, causing large structures to collapse before habitable planets had the chance to form. The team's models revealed that the optimal density of dark energy within a universe would enable up to 27% of ordinary matter to turn into stars. But in our universe, only an estimated 23% of matter turns into stars — meaning there are fewer stars here than there could be and, as a result, fewer places for alien life to emerge. Better luck in the next universe!

Aliens don't live on planets
Every alien species needs a habitable planet to live on, right? Surprisingly, a 2024 study argues that may not always be the case. In a paper accepted for publication in the journal Astrobiology, researchers proposed a scenario in which an alien colony could survive by floating freely in space, no planet required. It may sound wild, but it's not without real-world precedent; humans, for example, can live for hundreds of days without a planet while residing on the International Space Station (albeit with constant deliveries of crucial resources from their planet), and hardy tardigrades can survive the vacuum of space. A theoretical planet-free alien colony would have to overcome many challenges, including a lack of resources, exposure to cosmic radiation and the vacuum of space, and access to enough sunlight. With this in mind, the researchers paint the picture of a species that could survive these trials: a free-floating colony of organisms measuring up to 330 feet (100 meters) across, encased in a thin, hard, transparent shell that could maintain a livable temperature and pressure through the greenhouse effect. Finding such a species is a long shot, but it's not impossible. A free-floating alien colony could also explain why no intelligent aliens are answering our calls: They don't have a landline to use.

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. Fortunately, NASA's Europa Clipper spacecraft is on the way to one such moon to look for evidence of life up-close. The Clipper will arrive at Jupiter's frozen moon Europa in 2030.

https://www.livescience.com/space/extraterrestrial-life/12-strange-reasons-humans-havent-found-alien-life-yet


Fascinating theories. The more I read of this article, the more I thought--what species in its right mind would send living individuals out to find what they could in their lifetimes? Send robots.....
It kind of touches on that by saying all aliens could be robots.

Another fascinating, (and profound,) theory is the Fermi paradox:
"Advanced forms of intelligence have the tendency to destroy others. Another solution to the Fermi paradox that has been proposed is that intelligent life beyond a certain point of technological development will destroy other intelligent forms of life once they appear."