Will humanity find intelligent alien life anytime soon? Probably not, according to theoretical physicist Stephen Hawking.

Hawking made the prediction yesterday (April 12) during the Breakthrough Starshot announcement in New York City. At the news conference, Hawking, along with Russian billionaire investor Yuri Milner and a group of scientists, detailed a new project that aims to send a multitude of tiny, wafer-size spaceships into space to the neighboring star system Alpha Centauri.

If these tiny spaceships travel at 20 percent the speed of light, they'll be able to reach Alpha Centauri in just 20 years, Milner said. Once there, the spacecraft will be able to do a 1-hour flyby of Alpha Centauri and collect data that's impossible to gather from Earth, such as taking close-up photos of the star system, probing space dust molecules and measuring magnetic fields, said Avi Loeb, chairman of the Breakthrough Starshot Advisory Committee and a professor of science at Harvard University. [8 Shocking Things We Learned From Stephen Hawking's Book]

In addition to learning about space technology, the audience wanted to hear about aliens — specifically, when scientists might find them.

Hawking took questions from reporters in advance so that he would have time to prepare his answers. (Hawking, who has amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is paralyzed but "speaks" with the assistance of a computer.)

Hawking said it's not likely that scientists will find intelligent alien life in the next 20 years. "The probability is low, probably," he said.

But the cosmologist did mention one caveat.

"The discoveries of the [NASA] Kepler mission suggest that there are billions of habitable planets in our galaxy alone," Hawking said. "There are at least a hundred billion galaxies in the visible universe, so it seems likely that there are others out there."

Hawking has famously predicted that intelligent aliens might threaten humankind. Indeed, when asked yesterday about what Earthlings should do if we come across intelligent alien life, he said, "We should hope that they don't find us."

Other researchers on the panel offered a more optimistic view of extraterrestrial life.

Ann Druyan, an author, TV producer and wife of the late astronomer and astrophysicist Carl Sagan, said that, in her view, "extraterrestrials are beautiful until proven ugly, because of the great feat and demonstration of maturity that's required to learn how to be a space-bearing civilization."

She added, "It puzzles me that we always imagine the punitive extraterrestrials to be technically so far ahead of us, and yet every bit as stunted, emotionally and spiritually, as we are at this moment."

In fact, Hawking agreed that humans might not be all that great. When asked what he thought alien life might look like, he joked, "Judging by the election campaign, definitely not like us."