Leaping the Abyss: Stephen Hawking on black holes, unified field theory, and Marilyn Monroe.

• Author: Benford, Gregory
• Position: Interview

STEPHEN HAWKING SEEMED slightly worse, as always. It is a miracle that he has clung to life for over 20 years with Lou Gehrig's disease. Each time I see him I feel that this will be the last, that he cannot hold on to such a thin thread for much longer.

Hawking turned 60 in January. Over the course of his brilliant career, he has worked out many of the basics of black hole physics, including, most strikingly, his prediction that black holes aren't entirely black. Instead, if they have masses equivalent to a mountain's, they radiate particles of all kinds. Smaller holes would disappear in a fizz of radiation--a signature that astronomers have searched for but so far not found.

The enormous success of Hawking's 1988 book, A Brief History of Time, has made him a curious kind of cultural icon. He wonders how many of the starlets and rock stars who mentioned the book on talk shows actually read it.

With his latest book, The Universe in a Nutshell (Bantam), he aims to remedy the situation with a plethora of friendly illustrations to help readers decipher such complex topics as superstring theory and the nature of time. The trick is translating equations into sentences, no mean feat. The pictures help enormously, though purists deplore them as oversimplified. I feel that any device is justified to span such an abyss of incomprehension.

When I entered Stephen's office at the University of Cambridge, his staff was wary of me, plainly suspecting I was a "civilian" harboring a crank theory of the universe. But I'd called beforehand, and then his secretary recognized me from years past. (I am an astrophysicist and have known Stephen since the 1970s.) When I entered the familiar office his shrunken form lolled in his motorized chair as he stared out, rendered goggle-eyed by his thick glasses--but a strong spirit animated all he said.

Hawking lost his vocal cords years ago, to an emergency tracheotomy. His gnarled, feeble hands could not hold a pen. For a while after the operation he was completely cut off from the world, an unsettling parallel to those mathematical observers who plunge into black holes, their signals to the outside red-shifted and slowed by gravity's grip to dim, whispering oblivion.

A Silicon Valley firm came to the rescue. Engineers devised tailored, user-friendly software and a special keyboard for Hawking. Now his frail hand moved across it with crablike speed. The software is deft, and he could build sentences quickly. I watched him flit through the menu of often-used words on his liquid crystal display, which hung before him in his wheelchair. The invention has been such a success that the Silicon Valley folk now supply units to similarly afflicted people worldwide.

"Please excuse my American accent," the speaker mounted behind the wheelchair said with a California inflection. He coded this entire remark with two keystrokes.

Although I had been here before, I was again struck that a man who had suffered such an agonizing physical decline had on his walls several large posters of a person very nearly his opposite: Marilyn Monroe. I mentioned her, and Stephen responded instantly, tapping one-handed on his keyboard, so that soon his transduced voice replied, "Yes, she's wonderful. Cosmological. I wanted to put a picture of her in my latest book, as a celestial object." I remarked that to me the book was like a French Impressionist painting of a cow, meant to give a glancing essence, not the real, smelly animal. Few would care to savor the details. Stephen took off from this to discuss some ideas currently booting around the physics community about the origin of the universe, the moment just after the Big Bang.

Stephen's great politeness paradoxically made me ill at ease; I was acutely aware of the many demands on his time, and, after all, I had just stopped by to talk shop.

"For years my early work with Roger Penrose seemed to be a disaster for science," Stephen said. "It showed that the universe must have begun with a singularity, if Einstein's general theory of relativity is correct. That appeared to indicate that science could not predict how the universe would begin. The laws would break down at the point of singularity, of infinite density." Mathematics cannot handle physical quantities like density that literally go to infinity. Indeed, the history of 20th century physics was in large measure about how to avoid the infinities that crop up in particle theory and cosmology. The idea of point particles is convenient but leads to profound, puzzling troubles.

I recalled that had spoken to Stephen about mathematical methods of getting around this problem one evening at a party in King's College. There were analogies to methods in elementary quantum mechanics, methods he was trying to carry over into this surrealistic terrain.

"It now appears that the way the universe began can indeed be determined, using imaginary time," Stephen said. We discussed this a bit. Stephen had been...