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Physicist Alan Guth, the father of cosmic inflation theory, describes emerging ideas about where our universe comes from, what else is out there, and what caused it to exist in the first place.
He decided that the risks of death-by-bubble should no longer be ignored, and he teamed up with Vilenkin and Jaume Garriga of the University of Barcelona in Spain to investigate. The team assumed that bubble collisions would be deadly and set out to calculate the odds of such a lethal run-in. Guth’s calculations showed that the likelihood of a fatal collision in our part of the multiverse is ...
Alan Guth came up with a solution. He envisioned a period of “inflation,” when a small region of the universe, which was all at the same temperature, suddenly (in some tiny fraction of a second) expanded so much so fast that it became the entire observable universe (and then some). So all of the parts of the universe were in contact.
- Overview
- Cosmic Ripples
- Pride of Highland Park
- Small World
- Expanding Universe
- Swedish Lessons
- Gravitational Waves
Three decades ago, the innovative physicist had a eureka moment that explained the universe.
At the end of a quiet, carpeted hallway in MIT's physics department, a display case stands empty outside the office of physicist Alan Guth.
Framed in blond wood and clear glass, the empty cube waits for the world to fill nothing with something.
"It would be nice if it happens," says Guth, a rumpled 67-year-old, who sits in his respectably cluttered office, sunlight brightening piles of papers scattered over a desk and table.
"It" is not just any prize but one thing in particular: a citation for the Nobel Prize in physics. Ever since his remarkable work analyzing the gravitational ripples after the big bang, Guth's perhaps inevitable acceptance of a Swedish-accented phone call from the Nobel committee is now the talk of the physics world.
All for explaining how something small—an apple-size blip in an otherwise empty eternity—inflated almost instantaneously, becoming something much bigger, perhaps endless, a universe. Ours.
In March, Guth sat in the auditorium of the Harvard-Smithsonian Center for Astrophysics, a storied center of astronomy on the other side of Cambridge, Massachusetts, from MIT.
He waited in the audience, along with Stanford's Andrei Linde, 66, another inflation theorist, to hear from the BICEP2 astrophysics team that had spent three years looking with an unblinking telescope at one small patch of sky above the frozen waste of Antarctica.
They had looked inside that patch at the most distant thing observable in the cosmos, the so-called cosmic microwave background, or CMB. The CMB emanates from every corner of the sky—leftover heat from the first 380,000 years of the universe's history after the big bang.
On the podium that day, the BICEP2 team, led by Harvard's John Kovac, presented the results of their CMB observations: detection of gravitational wave signals of "precisely" the size that Guth's inflationary theory predicted.
These gravitational waves are "ripples" in matter triggered by inflation stretching the boundaries of the early universe faster than the speed of light. (While nothing can travel faster than light, the dimensions of space aren't a solid thing, so the waves can exceed this speed limit when they shift, according to Einstein's explanation of gravity.) A particular "curl" in the BICEP2 team's observed gravitational waves marked them as inflationary relics.
At the event, Johns Hopkins University physicist Marc Kamionkowski called the result "the smoking gun for inflation."
Guth's story begins in Highland Park, New Jersey, where he grew up and attended public school. "Neither of my parents went to college," he says. His father was a grocer and, after a fire destroyed the store, ran a dry-cleaners.
"It was sort of assumed, from the time I was born, really, that I would go to college," he says. "That's sort of the way that Jewish families in New Jersey handled things; that was the norm."
In the early 1960s, when he was in high school, physics was at the height of its Cold War prestige. A precocious student, he left high school a year early for MIT. "The chemistry teacher I would have had the following year suggested that they get rid of me."
He already had an older sister attending Lesley College in Cambridge, Massachusetts, when he arrived there in 1964. "She was dating guys from MIT and not Harvard, so I didn't end up at Harvard," he says.
"I think I always wanted to go into physics," Guth says, gesturing at the papers in his room. "What always fascinated me about science was the desire to understand what underlies it all, and I think physics is basically the study of that."
The Vietnam War was under way at the time, and a five-year degree leading to a master's degree in physics added a year to Guth's draft deferment status. "I found the transition [to college] very easy," he says. Physics students, he found, largely study both the impossibly small, or the doings of subatomic particles, and the impossibly large, or gravity's construction of space and time.
The answer that Guth and Tye found that year, however, was still crazy: The universe should be swimming with cosmic defects.
In fact, these defects should have been so numerous and so massive that if they actually existed, the age of the universe "would turn out to be about 10,000 years," Guth says, with a laugh. "This doesn't turn out to be the case, scientifically."
So, they turned to exploring whether the early universe (we are still in its first trillionth of a trillionth of a second) "supercooled" as it expanded. A 100,000-fold drop in temperature might have given the forces inside the early universe a bit more time to line up nicely with each other, essentially producing fewer defective cracks in creation.
"Once you write down the equations, it is not a hard problem at all. It is really kind of obvious," Guth says. The supercooling does dramatically affect the expansion rate of the universe. "It drives the universe into a period of exponential expansion," he says, now called cosmological inflation.
Sitting at a desk in a study in his rented home on the same night he made this discovery, Guth realized this exponential expansion would solve the "flatness" problem of the Goldilocks-perfect universe that neither collapsed nor exploded in its first instant. This relentless expansion drove the initial conditions of the universe inevitably toward its present state, a realm of vast emptiness filled with stars.
"This was a eureka moment," Guth says, with amusement and utter certainty. "On that notebook page, I wrote 'spectacular realization' in a double box."
Guth was suddenly in high demand, which was good because he needed a job. "That was very much on my mind," he says.
He had two problems, however. "I'm pretty slow at writing papers," Guth says. Plus, he could explain how inflation started, but couldn't explain how it ended.
So beginning in January 1980 at SLAC, he gave talks on inflation for months at universities around the country. At the same time, he was preparing a paper on his finding, looking for a job, and wrestling with how inflation ends. Sidney Coleman, a prominent Harvard physicist, heard the talk at SLAC, got excited, and began spreading the news to others in the field—"incredibly valuable help," Guth says.
Inflation compelled the interest of physicists because it kept all the advantages of the big bang as an explanation for the origin of the universe while filling in a uncharted spot in explaining how it actually started—in other words, what put the bang in the big bang.
"And then the job offers started to come in," he says. On a trip in April 1980 to the University of Maryland, he ate the traditional meal offered to aspiring physics professors at the end of a day of job interviews—dinner at a Chinese restaurant. His fortune cookie read:
An exciting opportunity awaits you if you are not too timid.
Despite the current hoopla over inflation, the idea enjoyed a somewhat lonely existence for more than a decade, Guth explained at a recent symposium on inflation at MIT, where he has enjoyed teaching since 1980.
Onstage, Guth's slouched demeanor gives way to that of a speaker fully engaged with his topic, one hand held behind his back as he paces. He pauses only to raise both hands to make a point as he explains his discovery to a packed audience.
The reason for those lonely decades was that other astronomers did not see the exact kind of "flatness" in the universe predicted by the theory. When others tallied up the weight of observable galaxies and cosmic dust clouds, our cosmos looked a little on the light side.
Tentative observations of the CMB, however, pointed to inflation being on the right track. "Each time they found better and better evidence," Guth says, of this time. "I was ecstatic and impressed they could even make the measurements."
In 1998, researchers discovered that the universe was expanding at an accelerating rate, revealed by observations of distant exploding stars flinging themselves farther and farther away from us at an always increasing rate. They found that the accelerating expansion of the universe was driven by "dark energy," a seeming anti-gravity force pulling the cosmos apart.
Confirmed by other observations, the discovery later earned Saul Perlmutter, Brian Schmidt, and Adam Riess a Nobel Prize in physics.
Back in his office, Guth smiles and shrugs. "My career got off to a slow start." His thesis was a bust, he wandered (studying cosmic defects, no less) in positions short of a professorship for almost a decade, and his job search led him—the man who seems to have figured out where the universe came from—to take career advice from a cookie.
Now, he bicycles to work in the morning to an office overlooking the university where his career took wing. With his just-married son a full professor in mathematics in a nearby building, and his daughter living at home with him and his wife, he says, "I feel enormously lucky. And blessed."
"He was a tremendously fun, supportive father," says his son, Larry, who chimed in at the April symposium to clarify a technical question about inflation asked from the audience. "He did like to talk about physics, no doubt. Maybe not your typical dad."
While counting his blessings, Guth waits a little longer for inflation to be validated. Both an earlier indirect look at the CMB by Europe's Planck satellite and the new BICEP2 gravitational wave results support inflation. However, they don't agree on the details.
Guth pronounces himself agnostic on what flavor of inflation emerges from the face-off between Planck and the successor to BICEP2, with more observations expected this fall. "Meanwhile, people have fun with the models," he says. (In June, after this interview, Guth expressed some doubts about the BICEP2 results after the questions about its treatment of cosmic dust. "I hope that the result will hold up, but I think we will need more data before the question is settled," he says.)
The prize cabinet outside his office may not have to wait too long, regardless. In May, the one-million-dollar Kavli Prize, a Norwegian rival to the Nobel, was awarded to Guth, Linde, and Alexei Starobinsky of the Russian Academy of Sciences, who earlier in the 1970s had worked on theories of universal expansion that informed Linde's later work on inflation. The King of Norway will award the prize to the theorists in September.
American physicist Alan Guth was best known for proposing the theory of an inflationary universe, a variation of the big-bang model that was highly influential in guiding modern cosmological thought. Guth, who taught at the Massachusetts Institute of Technology, earned several scientific awards for his work, including the Benjamin Franklin Medal (2001), the Dirac Medal (2002), and the Kavli ...
ALAN GUTH (Massachusetts Institute of Technology): When one studies the properties of atoms one found that the reality is far stranger than anybody would have invented in the form of fiction.
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Alan Harvey Guth (/ ɡuːθ /; born February 27, 1947) is an American theoretical physicist and cosmologist who is the Victor Weisskopf Professor of Physics at the Massachusetts Institute of Technology. Along with Alexei Starobinsky and Andrei Linde, he won the 2014 Kavli Prize "for pioneering the theory of cosmic inflation." [ 1 ]
