Hawking’s Universe Is Open and Shut
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.
It’s actually not so difficult to imagine how the universe can be two contrary things at the same time. Such thinking has a long and established history in physics. For example, long-standing controversies over whether light was a wave or a particle were resolved through the discovery that light is both, wave and particle, depending on how you look at it.
In the same way, a higher-dimensional universe could be shaped something like an ice cream cone. If you slice it horizontally, it looks like a circle--a closed universe. But if you sliced it vertically, you would get a parabola--an open universe.
And where does the pea come in?
Hawking proposed that this open and shut universe comes into being from nothingness in the form of a pea instanton--a particle of space and time. An instanton is not so much a thing as an event.
Hawking called it a pea because it would not be perfectly spherical, but rather distorted. This pea instanton, he said, could evolve into either an open or a closed universe.
In fact, he said, “there is a whole family of pea instantons.”
Choosing From Many Possible Universes
So why does it appear that our universe is open? Here, Hawking invoked another principle he has previously shunned: According to the so-called anthropic principle, the universe is the way it is to some extent because if it were otherwise, intelligent beings would not be here to ask such questions.
“Physicists don’t like the anthropic principle,” he said, conceding that they might need to accept some weak version of it to choose among multiple possible universes.
Hawking seemed most pleased with his pea instanton, however, because it’s the kind of idea that can be falsified by observation. “It’s real science,” he said.
No idea in science is worth its salt if it can’t be proved wrong. If the universe really did appear in the form of a pea, then it will have left fingerprints in the microwave background--the faint afterglow of the big bang that still pervades the universe. Someday, telescopes now on the drawing boards will be able to find it. Or not.
Meanwhile, Hawking seems ready to go on making the kinds of breakthroughs that have made him almost as famous as has his courage in the face of Lou Gehrig’s disease. During the inauguration of Caltech President David Baltimore, several professors said, Hawking danced around the room in his wheelchair while a young woman struggled to keep up.
In the same way, other physicists struggle to keep up with the impish fellow who can’t even write equations with his hands.
“He translates mathematics into geometry, and turns around geometrical shapes in his head,” said another longtime Caltech colleague, Kip Thorne. “He’s turned adversity into an advantage over us poor mortals.”
