So far, no little green men have landed on earth and asked us to take them to our leaders.
But that doesn't mean aliens haven't visited earth already, according to one NASA scientist.
Silvano P. Colombano, a computer expert in NASA's Intelligent Systems Division, says alien life might be on earth right now, just not as we know it.
In a new paper, Colombano explains that "the intelligence that we might find and that might choose to find us (if it hasn't already)" could be very different from us, and nothing like the aliens we imagine in our movies and television shows.
"We need to re-visit our most cherished assumptions," he wrote, before adding that "our form of life and intelligence, may just be a tiny first step in a continuing evolution that may well produce forms of intelligence that are far superior to ours and no longer based on carbon 'machinery.'"
While carbon molecules are the building blocks of life, Colombano suggests that aliens that developed from other elements could worlds apart from humans.
Instead of imagining other carbon-based life forms that resemble humans or animals, Colombano told other scientists that alien life might resemble "extremely tiny super-intelligent" creatures, who could live for much longer than we do and therefore travel incredibly long distances.
He says it's entirely possible that such small aliens could have technology more impressive than our own, and might use it to visit earth without being noticed.
As Colombano points out, the technologies humans use to search for aliens, including radio waves, might not be up to the task of finding these space oddities.
The scientist urged his fellow experts to "consider the UFO phenomenon worthy of study," and to expand the horizons of their imagination when considering aliens by adopting a willingness "to stretch possibilities as to the nature of space time and energy."
While Colombano is not suggesting that aliens "walk among us," many still think there's life somewhere other than earth.
And a large number of true believers say they've seen proof of alien life with their own two eyes. Until we learn more, keep watching the skies, because the truth is out there...
[H/T: Fox News]