Scientists today remain engaged in the age-old search for extraterrestrial life, hoping that modern technologies will help them detect and possibly communicate with whatever they find.
Just this week, NASA beamed the Beatles song "Across the Universe" into space. The radio signals will take more than 2 million years to reach our nearest galaxy, Andromedea.
"I don't think the human race has a future unless we go into space. We need to expand our horizons beyond planet Earth," says legendary astronomist and physicist Stephen Hawking.
But don't look to Hollywood's versions in such movies as "Alien" or "ET" to recognize extraterrestrial life, astrophysicist and author of "Death by Black Hole," Neil DeGrasse Tyson warns.
"They've got two legs, arms, fingers, maybe three fingers, not five. They have faces. We have other life forms on Earth with whom we have DNA in common that look less like humans than Hollywood aliens do!" he said.
Tyson, who serves as director of the Hayden Planetarium at the Rose Space Center in New York City, says there's more variety among our DNA cousins on Earth, e.g., a jellyfish, a horse, a yeast cell or an oak tree.
"I think the best alien ever, ever, ever, ever was the Blob. Didn't look like anything here on Earth, did it? It was creepy and scary. And it was clearly alive," Tyson said.
Listening, Waiting, Hoping
Scientists are listening every day for signals from another galaxy.
Recently, in Australia, they got excited picking up an odd radio pulse they couldn't explain, at frequencies the human ear can't hear.
"We don't know what this mysterious radio pulse is. I doubt that's extraterrestrial. I think it's more likely a natural phenomenon," explained Dan Werthimer, a physicist at the University of California at Berkeley.
Scientists have asked millions of amateur researchers around the world to get involved by downloading a program that allows personal computers to process data from the skies.
"Everybody gets a different part of the sky to analyze. … It shows you the most interesting signal that it's found so far," Werthimer said.
Though scientific consensus remains that life on Earth is the earliest living form, many expect that bacteria found in space could be the remnants of life that started on Mars.
"We have good evidence that Mars was wet and fertile before Earth was wet and fertile. We also know that certain strains of bacteria can survive long periods of time without water," Tyson said.
"It is possible that life may have formed on Mars before Earth, gotten thrust into space with bacteria stowing away in the nooks and crannies of these castaway rocks. One of those may have then landed on Earth, thereby seeding the formation of life on earth. That is entirely possible," he said.
No End to Search
If intelligent life existed somewhere else in the universe right now, it would still take tens of thousands of years before we might know about it. That is because it takes light roughly 70,000 years to reach Earth from the next nearest star.
As Stephen Hawking once joked, "There can't be any near us; we would have seen their television programs."
Despite the enormity of the challenge, scientists and amateurs' curiosity is undiminished, and their search will continue.
"It's actually profound either way. If we find out that the universe is teeming with life and other civilizations, and we can learn about them, that would be spectacular; maybe it's like the archaeology of our future," Tyson said. "If we found out that we're all alone, that is also profound. It means life is extremely precious, and we better take care of life on this planet."
Looking up and wondering about our place in the universe, and how it all began, is an ancient and constant preoccupation of mankind. Tyson, who has devoted his life to that search, says, "It may be fundamental to what it is to be alive. To what it is to be human."