- According to NASA, there are 2,326 confirmed exoplanets -- some of which may have Earth-like characteristics.
- We have only discovered about 0.125 percent of the planar area of the Milky Way
(CNN)E.T. phone home?
Yeah, that'll have to wait another 1,500 years.
Astronomers estimate that if there are aliens out there, we won't be making contact with them for at least that long.
"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 University student Evan Solomonides.
He was presenting a paper Tuesday at the American Astronomical Society's meeting, where he -- along with his professor Yervant Terzian -- explores this topic.
"Until then, it is possible that we appear to be alone -- even if we are not."
Sixty generations is a long time to wait. Why bother?
"If we stop listening or looking, we may miss the signals," he said in a statement. "So we should keep looking."
Where is everybody?
In order to understand how Solomonides arrived at this '1,500 years' figure, we'll have to take you through a quick physics lesson. Namely, two terms:
The first, the Fermi paradox. It's the contradiction that has perplexed scientists and "Star Wars" fans alike: If the universe is filled with Earth-like planets (and it is), why haven't we made contact with aliens yet?
The second, Copernicus' principle of mediocrity. This one suggests that perhaps there's nothing exceptional or special about us.
For decades, humans have been sending out television broadcasts or radio signals into space.
The Earth's broadcast signals have touched every star within 80 light years from the Sun. According to NASA's Kepler mission, signals have reached 2,326 confirmed exoplanets.
And yet, for decades we've received nothing but static.
"We have reached so many stars and planets, surely we should have reached somebody by now, and in turn been reached," Solomonides said.
Are we there yet?
So, what gives? In one word, distance.
Solomonides thinks the reason why no one has answered our radio signals is because space is incredibly vast.
We've only been sending out signals for the last 80 years. We have only discovered about 0.125 percent of our Milky Way.
The astronomers say we should give the signals time to reach half of all the solar systems in the Milky Way in order to be picked up. And even then, there may be a small percentage of intelligent life that will have the capability of deciphering and responding to our messages.
"We simply claim that it is somewhat unlikely that we will not hear anything before that time," Solomonides said.
"You might not expect to pick up any signals until someone knows we're here," said Dr. Seth Shostak, senior astronomer at the SETI Institute, the government agency looking for extraterrestrial life. "That means the noise we make as a society has to have reached them."