For more than 100 years astronomers, cosmologists and philosophers have debated whether intelligent life other than our own exists in the universe. Those that fell on the side against intelligent life argued that life itself is exceedingly rare. They looked at the data and proclaimed that too many things had to happen in the right order at the right time for any life—let alone intelligent life—to exist.

The opposite camp thought the possibility remained that, given the age of the cosmos, the number of galaxies, stars in those galaxies and probable planets around those stars, life was inevitable, even intelligent life.


Hawking jumps into the fray

After decades of self-imposed silence on the subject, world-renowned theoretical physicist, Stephen Hawking, decided to throw his metaphorical hat into the debate.

He came down on the side of intelligent life.

But the sometimes quirky scientist went farther than that. He also attached a warning aimed at all those scientists eager for contact with aliens from another star system: be careful what you wish for.

Hawking sees contact with intelligent aliens as not only dangerous, but foolhardy.

Could fleets of alien ships really invade Earth, subjugate us, convert us or turn us into food? Hawking thinks anything is possible and much of it could be bad.

His warning made world headlines and it's still reverberating to such a degree in some colleges and universities that the ivy has shaken right off the walls.

Now the 68 year old has passed judgment on another scientific debate. Time travel.

Admitting he kept quiet for many years out of fear of accusations of heresy by colleagues and other established physicists, he finally decided to throw caution to the wind. Now that he has, the wind threatens to become a hurricane.


Really getting away from it all

Hawking, referring to Einstein's relativity theory on the compression of time as mass approaches the speed of light, extrapolates that achieving speeds of 650 million miles per hour (98% the speed of light) will be achievable in the far off future. One day—on board a spaceship traveling at that speed—will equal the passage of a year on Earth. He points out that attaining such a velocity makes it possible to reach the outskirts of the Milky Way in about 80 years.

Such a space time vessel might travel a million-even millions of years into the future. The scientist thinks that when the time travelers return, if they discover the human race has disappeared, they can repopulate the Earth.

Such bold prognostication raises eyebrows-and not just amongst colleagues. Hawking only laughs, claiming he held back for years fearing being labeled a crank. "These days I'm not so cautious," he admits.

Although effectively time travel, the traveling would only be in one direction: forward. No erstwhile chrononaut could fulfill his or her fantasy of walking the streets of ancient Rome or attending the inaugural ceremonies of George Washington.

While the concept of compressing time and skipping ahead millions of years is fascinating, being unable to go backwards throws cold water on some people's personal dream … traveling back in time to the 1970s and picking up several thousand shares of Apple stock.