Aliens likely haven't visited because humanity's technological signature is very limited
Now that more and more scientists are actively searching for signs of extraterrestrial life, whether in our solar system or in the far reaches of space, more attention has been brought to the Fermi paradox.
The Fermi paradox posits that we should have detected intelligent alien life by now, given the fact there are billions of planets in the habitable zone of their solar system in the Milky Way alone. So where are they?
A new study in preprint server arXiv suggests that we might not have encountered intelligent extraterrestrials because they may not find humanity very interesting.
Where are the aliens? A new Fermi paradox solution
Study author Amri Wandel, an astrophysicist at The Hebrew University of Jerusalem, writes in his paper that aliens are likely drawn to planets that show signs of biological life and incredibly advanced technology.
That's assuming that life is, in fact, abundant throughout the universe and the intelligent alien species in question has the technology to locate and travel to other civilizations.
Experts have offered several explanations for the Fermi paradox over the years. Some had suggested aliens visited Earth in the distant past, long before humans evolved, or could record information regarding the visit in any meaningful way.
In Wandel's new paper, the astrophysicist suggests intelligent life is abundant throughout the Milky Way, meaning we're just not very special. This solution to the Fermi paradox is based on the theory that intelligent alien civilizations have an abundance of other lifeforms to visit, many of which will be much more technologically advanced than we are.
So, in other words, Earthlings aren't that big a deal, in the context of this theory, at least. Another famous Fermi paradox solution suggests the opposite. The Great Filter theory posits that it's exceedingly difficult for a species to become multi-planetary and that most advanced civilizations will ultimately make themselves extinct.
Our technological signature hasn't reached very far
Wandel's theory is based on the fact that it is exceedingly difficult to detect signs of technology on a distant planet. Humans have been beaming radio waves out into the cosmos since the 1930s. However, the universe is so vast that these signals are estimated to have reached 15,000 stars and their orbiting planets. That is a tiny fraction of the 400 billion stars in the Milky Way alone.
What's more, it wasn't until 1974, with the Arecibo message, that humans purposefully beamed a high-power broadcast into space with the intention of communicating with intelligent extraterrestrial life. Earlier radio waves will likely have become distorted the farther they travel into the cosmos.
Wandel does write that the more time passes, the farther our technological footprint (in the form of radio waves) travels out into space. So every year, it is more likely that we will be detected by a distant alien life form, for better or for worse.
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