An award-winning, respected scientist claims space aliens may not be something out of science fiction -- they may be living all around us. But they are not in the form of little green men.
Arizona State University physicist Paul Davies says alien life, in the form of tiny microbes, could be hanging around "right under our noses -- or even in our noses."
"How do we know all descended from a single origin?" he told a conference at London's prestigious , which serves as Britain's academy of sciences. "We've just scratched the surface of the microbial world."
Davies points out that there are unusual organisms all over the world, such as chemical-eating bacteria that hide out deep in the ocean and organisms that thrive in boiling-hot springs. Who knows where they came from?
"How weird do they have to be suggest a second genesis as opposed to just an obscure branch of the family tree?" he said. Davies suggested that the only way to prove an organism wasn't "life as we know it" was if it were built using exotic elements which no other form of life had.
No such organism has yet to be found. Davies also noted that less than 1 percent of all the world's bacteria has been comprehensively studied, so there's still lots of unexamined stuff out there.
"You cannot tell just by looking that a microbe has some radically different inner chemistry," he said.
The conference also dealt with the increased difficulty in contacting other life that might be out there somewhere.
Frank Drake, who conducted the first organized search for alien radio signals in 1960, said that the Earth used to pump out a loud mess of radio waves, television signals and other radiation. But now with advanced digital technology, satellites and fiber optics, space is getting quieter, making it harder for someone -- or something -- else to hear us.
"Very soon we will become very undetectable," he said. If similar processes were taking place in other technologically advanced societies, then the search for them "will be much more difficult than we imagined."
Drake is excited by the possibility of using lasers to send super-bright flashes of light into space for a tiny fraction of a second. The flashes could theoretically be seen by an advanced civilization up to 1,000 light years away.
But Drake noted that the interstellar equivalent to turning a flashlight on and off only works if a prospective alien civilization wants to get in touch to begin with.
"For this to work, there has to be altruism in the universe," he said.