If you're hoping to see the day when earthlings finally make formal contact with an extraterrestrial civilization, don't hold your breath. You may have to wait about 1,500 years, two Cornell University astronomy researchers say.
"Space is so immensely, mindbogglingly big that, even at the speed of light, it takes an incredible amount of time for a communication to reach anywhere -- to any significant portion of the galaxy," Evan Solomonides, a Cornell physics and math major, told The Huffington Post.
Solomonides and Yervant Terzian, a Cornell astronomy professor, co-authored a paper that Solomonides presented last week at the American Astronomical Society in San Diego, California. Their research focuses on something called the Fermi paradox, named after physicist Enrico Fermi. In the 1950s, Fermi raised the question that if, as many scientists believe, there are huge numbers of technological civilizations out there, why haven't earthlings seen tangible evidence?
In their paper, the Cornell researchers wrote:
"We clearly show that human communication has reached a sphere with a radius of roughly 80 light years, and has not reached a number of stars and planets adequate to expect an answer.
"It is actually unlikely that the Earth would have been reached at all thus far, and we do not anticipate to be reached until approximately 50 percent of stars/planets have been reached. We offer a prediction that we should not expect this until at least 1,500 years in the future.
"Thus, the Fermi paradox is not a shocking observation -- or lack thereof -- and humanity may very well be contacted within our species' lifespan."
Solomonides and Terzian also consider something known as the mediocrity principle, which suggests that earthlings -- compared with life that may exist in the Milky Way galaxy in which we live -- aren't that special.
"Whatever natural processes gave rise to life on our planet should be extraordinarily common, and should have happened in enumerable places throughout the galaxy," the scientists wrote. "Yet, we are, to the best of our knowledge thus far, utterly alone. How can this be?"
Solomonides said the search for extraterrestrial intelligence by the California-based SETI Institute, which is trying to locate a definitive ET signal from outer space, is the best chance to find alien neighbors.
"I think what SETI has been doing is exactly what we should be doing, because if we stop looking and listening for a second, we could miss it when it finally comes," Solomonides said. "If we stopped paying attention for a year, a month or a week -- if that is when we finally get a signal, the one powerful signal from a civilization that indicates that they're there -- we've missed it and there's no way to ever get that back, so we have to keep looking and trying."
Seth Shostak, a senior astronomer at the SETI Institute in Mountain View, California, said searchers look for definitive ET signs.
"Our experiments listen for alien signals that are relentless -- you can find them repeatedly," Shostak told HuffPost in an email. "Otherwise, who knows what you've picked up?"
"Perhaps the extraterrestrials aren't going to spend the money to broadcast our way until they've heard from us, and know of our existence," he said. "If so, it could be a long time before such a targeted signal is transmitted to Earth.
"But you know what? We could pick up the signal from a powerful alien radar transmitter tomorrow -- just the radio noise from an advanced society," Shostak said.
"Given that possibility, I'm not inclined to sit on my hands for a few centuries to await a deliberate response to 'I Love Lucy.'"
Shostak, for one, isn't waiting 1,500 years for that conclusive alien signature to arrive.