By Erik Derr ( | First Posted: Apr 18, 2013 07:13 AM EDT

Theoretical physicist Stephen Hawking spoke at Caltech about the nature of the universe, dark matter and the origin of human life. (Photo : Reuters)

The future of human discovery is in the dark --- dark matter, that is.

So says renowned theoretical physicist Stephen Hawking, who spoke about the nature of the known and unknown universe Wednesday at Pasadena-based California institute of Technology, better known as Caltech.

Hawking, the author of "A Brief History of Time," a book on the origins of the universe, made his name studying black holes, mysterious, massive phenomena that anchor galaxies, swallow stars and have gravity so strong that not even light can escape.

But, he told the packed audience, "the missing link in cosmology is the nature of dark matter and dark energy...There have been searches for dark matter, but so far no results."

Dark matter can't be seen or felt directly, but scientists say they are confident it exists because there's no other explanation for the way distant light appears to be pulled in certain ways or the fact spiral galaxies seem to be held together by something, instead of pulling apart.

Physicists believe dark matter is why it appears the universe is continuing to expand, instead of being pulled back together by its own gravity.

Hawking noted recent data generated from the European Space Agency's Planck space telescope suggest "that normal matter is only 5 percent of the energy density of the known universe, 27 percent is dark matter, 68 percent is dark energy," he said.

During his talk, Hawking recounted his decades-long career in science, his successes as well as mistakes.

He also discussed the merits of past and present cosmological theories.

An old Russian theory that the universe collapsed because of gravity and then more or less "bounced" back into the into the expansion --- or inflation, a physicists actually call it --- that's happening today was an "article of faith" by Marxists, Hawking said.

Hawking said he couldn't agree with the theory by theoretical physicist Joseph Polchinski from the University of California, Santa Barbara, which speculated about the existence of a firewall of sorts at a black hole's event horizon --- the point where the gravity of the black hole conquers everything else.

The esteemed professor also said he disagreed with another suggestion that black holes are actually trap doors to another universe and when things are pulled in --- they're spit out on the other dimensional side.

Human existence, Hawking said, is the product of chance and considering the size of the universe and variety of all the matter in it, it was just a matter of time before human life showed up.

"We are the product of quantum fluctuations in the very early universe," he said. "God really does play dice."

Hawking concluded his presentation with a Q&A session, and the the last question he answered earned one of the night's biggest laughs.

"We're in an era where we can control machines with our thoughts," began the questioner, so besides Hawking's motorized wheelchair, what else would he like to use that for?

"What I'd really like to control is not machines, but people," the professor responded.

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