A combination elf, oracle and rock star, Cambridge University physicist Stephen Hawking makes waves in physics that other people ride.
So scientists listened when Hawking proposed in a technical talk Thursday at Caltech that the universe sprang from nothing into something in the shape of a wrinkly pea, and that the universe can be both open and closed, depending on how you look at it.
Probably, in truth, few of the hundreds of Caltech techies who turned out to hear the great physicist's talk understood exactly what he was talking about, according to Hawking's longtime colleague, Caltech physicist John Preskill. But Hawking, like Einstein--to whom he is frequently compared--has a habit about making outrageous proposals that turn out to be right. "He has a feel for what is the right answer," Preskill said.
A blithe spirit trapped in a deflated body, Hawking, 56, communicates through a computer attached to a voice synthesizer. His disembodied voice booms out like the wizard of Oz. He smiles easily, if awkwardly, his mouth stretching into wide grins, his eyes brightening with delight at his own jokes and puns.
Turning Theories Inside Out
This charming juxtaposition of genius and jokester attracted 2,500 people--including Gov. Pete Wilson and media mogul Rupert Murdoch--for a Wednesday night public lecture at Caltech. Long lines of admirers snaked around the normally quiet campus. "It reminds me of the days when Einstein used to come here to speak," said Ed Stone, director of NASA's Jet Propulsion Laboratory.
On Thursday, Hawking granted a rare private interview to a few reporters--one of the handful he has done in the 25 years he has been regularly visiting Caltech.
Hawking tackles the biggest problems in physics: the nature of space, the nature of time, and the origin and fate of the universe.
Previously, he turned physics inside out when he showed that black holes, those voracious cosmic light swallowers, actually radiate energy.
Now, he seems to be saying that the long-standing controversy over whether the universe is closed--and will eventually collapse in on itself--or open, in which case it will expand forever, can be answered both ways: The universe is open and closed, depending on how you slice it.
Until recently, Hawking firmly believed that the universe was closed. In other words, the space-time fabric of the universe is something like a sphere, only in four dimensions. A spherical universe starts with a big bang, expands to a maximum point, then starts contracting again, ending with a big crunch.
Hawking likes this kind of universe because it flows smoothly from nothing to something without any sharp tears in the laws of nature. He feels it's an improvement over the standard big bang model, in which the universe blasts into being from an infinitely dense and infinitely small speck of space-time, so concentrated that known ideas of physics almost certainly break down.
Hawking's so-called no-boundary universe is finite, but has no edges. Like the surface of Earth, it has no beginning and no end. And it seemed--until now at least--that a no-boundary universe had to be closed.
But recently, Hawking said, he has been forced to reevaluate his views, based on mounting evidence for an open universe. Last week, for example, new measurements of exploding stars seemed to imply that the universe is expanding faster at its outer limits.
Such a universe would never collapse in a crunch, but rather expand infinitely. Rather than a sphere, it would unfurl like an open horn. Ultimately, it dissipates into increasing disorder, spreading forever deeper into space and time.
Ironically, the thing that powers such an expansion is the energy of the vacuum of space, which produces a repulsive force, pushing galaxies and stars farther and farther apart. Einstein proposed the existence of such a negative pressure--which he called the cosmological constant--but later dismissed it as his biggest blunder when it no longer seemed necessary to explain the expanding universe.
Now Hawking seems willing to embrace Einstein's idea for the first time. Or as he conceded, with typical whimsy, in his talk: "Negative pressure is just tension, which is a common condition in the modern world."
To understand how the universe can be open and closed at the same time, however, requires expanding space-time into new dimensions--specifically, imaginary ones. These are imaginary in a mathematical, not a fictitious, sense.
Imaginary space and time run at right angles to ordinary space and time. Combining real space-time with imaginary space and time allows for both an open and a closed universe.
"I realized there was another way of looking at a no-boundary universe that can look open," Hawking said.