If we ever hear from aliens, it likely won’t be for at least another 1,500 years, a new study suggests.
Researchers at Cornell University say they arrived at that number by combining the Fermi Paradox with the Mediocrity Principle, which they described at the June 16 meeting of the American Astronomical Society in San Diego.
The Fermi Paradox states that while there are likely billions of Earth-like planets in our galaxy, no extraterrestrial has yet to contact us. The Mediocrity Principle, which was coined in the 16th century by Copernicus, states that Earth's physical attributes are not unique, therefore it may be some time before any alien life forms are able to contact us.
“We haven’t heard from aliens yet, as space is a big place – but that doesn’t mean no one is out there,” said Cornell student Evan Solomonides, a co-author of the paper. “It’s possible to hear any time at all, but it becomes likely we will have heard around 1,500 years from now. Until then, it is possible that we appear to be alone – even if we are not; but, if we stop listening or looking, we may miss the signals. So we should keep looking.”
Television and radio signals from Earth have only been traveling for about 80 years, the researchers said, adding that those transmissions have only reached about 8,531 stars and 3,555 potential Earth-like planets. The Milky Way galaxy has around 200 billion stars.
Furthermore, if an alien civilization were to receive the transmissions, researchers said it would likely take it a long time to decipher them.
“Even our mundane, typical spiral galaxy – not exceptionally large compared to other galaxies – is vast beyond imagination,” said Solomonides. “Those numbers are what make the Fermi Paradox so counterintuitive. We have reached so many stars and planets, surely we should have reached somebody by now, and in turn been reached …this demonstrates why we appear to be alone.”
In their paper, the researchers say that in about 1,500 years, “approximately half” of the galaxy could have received Earth’s transmissions.
“This is not to say that we must be reached by then or else we are, in fact, alone. We simply claim that it is somewhat unlikely that we will not hear anything before that time,” Solomonides said. “We are on the third planet around a tediously boring star surrounded by other completely normal stars about two-thirds of the way along one of several arms of a remarkably average spiral galaxy. The mediocrity principle is the idea that because we are not in any special location in the universe, we should not be anything special in the universe.”