Sarah Lee / Science Museum via Reuters

Physicist Stephen Hawking has decorated his office at the University of Cambridge with "Simpsons" memorabilia - and a prominent portrait of Marilyn Monroe.

As famed physicist Stephen Hawking turns 70, the subject that most occupies his thoughts is not how the universe arose from nothing, or how he's been able to live with neurodegenerative disease for so long. Here's what he thinks about most: "Women. They are a complete mystery."

That's the bottom line from New Scientist's interview with Hawking, timed to coincide with this weekend's birthday celebration at Cambridge. The theorist is almost completely paralyzed due to his decades-long struggle with amyotrophic lateral sclerosis, or Lou Gehrig's disease, and had to provide his answers by laboriously twitching his cheek to operate a computerized speech-translation system.

Hawking also listed what he saw as his "biggest blunder in science" (his now-repudiated insistence that information was destroyed in black holes), the most exciting development in physics during his career (the discovery of the big bang's imprint in cosmic microwave radiation) and the potential discovery that would do the most to revolutionize our understanding of the cosmos (discovery of supersymmetric particles at the Large Hadron Collider).

But it's his brief comment on women that attracted the most attention: How could it be that a scientist who has plumbed the deepest mysteries of the cosmos finds himself mystified by women?

Based on the view most folks have of geniuses, how could it not be?

The saga of the super-smart professor who is flummoxed by interpersonal relations, particularly with the opposite sex, is at least as old as Sigmund Freud (who famously wondered, "What does a woman want?"), Jerry Lewis' fictional "Nutty Professor" and the stereotype we have of Albert Einstein. It's as up to date as the TV astrophysicist on "The Big Bang Theory" who can't say a word to women unless he's under the influence.

Somehow, folks get a satisfying sense of karma from the idea that geniuses are socially stupid. But the stereotype doesn't really hold true, particularly in Hawking's case.

Like the real-life Einstein, Hawking has had an active romantic life, marked by two marriages. (Einstein's second marriage ended with the death of his wife and cousin Elsa; Hawking's ended in an ugly divorce.) Hawking's disease does not affect his sexual ability or his potency, and the fact that he's fathered three children is evidence of that. 

"The disease only affects voluntary muscle," Hawking's been quoted as saying.

He's been called an "incorrigible flirt" and a "party animal who likes to dance in his wheelchair." Having seen Hawking playfully chase his grandson around a backstage room in his wheelchair after a Seattle lecture, I can readily believe the "party animal" part. And having seen the way his expressive eyes light up a room, I know he can turn on the charm despite his disability.

Through the years, Hawking has had a special thing for Marilyn Monroe. A picture of the enigmatic blonde hangs in his Cambridge office, and Hawking once told The Guardian that if he could travel back in time, he'd rather meet Monroe than the great physicist Isaac Newton, who "seems to have been an unpleasant character."

Even as he approaches the age of 70, Hawking seems to have kept his playful, pleasant, mischievous character. That may help explain his latest comment about the mystique surrounding women, as well as his own mystique.

Here's a classic example: Actress Jane Fonda was clearly won over last year when Hawking came backstage after her performance in a play about a woman musicologist in the early stages of neurodegenerative disease. "I took his hand and carefully uncurled the fingers one by one, wanting to see how they felt and looked ... soft, pale, safe," she recalled in a blog posting.

When Fonda asked Hawking what he thought of her performance, Hawking typed out a short response: "You were my heartthrob" — which got a big laugh. Fonda came away starstruck. "This man who cannot move or speak, can, nonetheless, comprehend the incomprehensible," she wrote.

Hmm ... Maybe women aren't such a complete mystery to Hawking after all.

More about Stephen Hawking:

• Hawking is turning 70, and defying disease
• Hawking seeks a helper to make his voice heard
• 'There is no heaven,' Stephen Hawking says
• Hawking: Aliens may pose risks to Earth

Where in the Cosmos?

This year we'll be experimenting with a Cosmic Log Facebook series called "Where in the Cosmos?" WITCo will offer pictures from cosmic locales and ask you to figure out where the pictures came from. But our first WITCo picture poses a slightly different challenge: In honor of Stephen Hawking's 70th birthday, the Science Museum has commissioned a series of pictures showing the physicist in his office, surrounded by knick-knacks and pictures. One of the pictures is at the top of this item. We've posted another picture to the Cosmic Log Facebook page, but we need your help to figure out what the knick-knacks are, what the pictures on Hawking's wall show, and what the equations on his blackboard refer to. Head on over to Facebook, "like" the Cosmic Log page, and help us solve the puzzle by adding your comments.

Hawking's birthday will be marked on Sunday at Cambridge University with a symposium on "The State of the Universe," featuring talks from 27 leading scientists, including Hawking himself. The public sessions on Sunday will be streamed live over the Internet. There's also a scientific symposium that got under way today. Those sessions, which continue on Friday and Saturday, are also being streamed.

Hawking retired from his post as a mathematics professor at Cambridge in 2009 and is now director of research at the university's Center for Theoretical Cosmology. He also holds a distinguished research chair at Canada's Perimeter Institute for Theoretical Physics. For an in-depth look at his life, his work and his mystique, check out "Stephen Hawking: An Unfettered Mind," a new biography by Kitty Ferguson.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.