Andrei Linde on the Big Bang and the biggest discovery of all time
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The past few weeks have been the most exciting in the professional life of Andrei Linde since the Russian émigré cosmologist came to California’s Stanford University in 1990.
On March 17 US astronomers working at the BICEP2 radio-telescope at the South Pole published the first observations of gravitational waves. These ripples in the fabric of space, generated just after the Big Bang, provide the best evidence so far to support the theory of cosmic inflation, which Linde played a key role in formulating in the Soviet Union in the 1980s and which still preoccupies him today.
Linde’s reaction when a colleague brought him news of the BICEP2 discovery – first stunned and then celebratory – entertained millions when Stanford posted a video of it on YouTube. Although still celebrating internally, he realises that, like all scientific findings, it must be confirmed by other observations – something he expects to happen within a year or two.
“I’m trying to be agnostic, I’m trying to be cold-blooded,” he tells the Financial Times in a rich Russian accent. “It’s a very, very hard exercise. Everything is just boiling inside me from this happiness of discovery.”
Linde, 66, realises how hard it is to explain inflationary cosmology – the exponentially rapid expansion lasting a tiny fraction of a second that sowed the seeds of everything in our universe. As you can hear in an interview on FT.com, he presents the theory as the best way to account for the way everything was created from nothing in a gigantic explosion, without invoking a divine creator. “We may start with less than a milligram of matter or maybe even literally from nothing, and then all the universe appears as result of the process which is called inflation,” he says. “This is a bit tricky. If anyone had tried to describe it to me maybe 35 years ago, I would answer: ‘This is weird, go home and tomorrow when you are not drunk come to me and tell me the story again.’ I am telling this story for more than 30 years so I got used to it but nevertheless at first glance it looks almost like cheating.”
Cosmic inflation has come a long way since Linde and colleagues had the first inklings of the concept when he was a young scientist at the Lebedev Physical Institute in Moscow in the 1970s. The most important point is that the vacuum of empty space is never empty. It contains an energy field that changes as the universe grows. At the beginning this was an “inflation field” of unimaginable intensity, which blew up the infant universe at an exponential rate for an infinitesimal fraction of a second before it underwent a “phase change” to a less explosive but still expansive state. The whole structure of today’s universe can be extrapolated from that first inflationary phase, when tiny irregularities resulting from initial quantum fluctuations were blown up perhaps a trillion, trillion, trillion times. The outcome is astonishing homogeneity on the largest scale across billions of light years but great complexity and variety on shorter scales within galaxies, stars, planets and people.
During the 1980s, as Linde’s career thrived in Moscow, he worked in parallel with US inflation theorists, notably Alan Guth, but international communications in those Soviet days did not facilitate east-west scientific collaboration. “I was working in a wonderful scientific institution with great scientific traditions and very good people,” he says. “On the other hand, when I wanted to communicate with our colleagues abroad it was a headache. For example, when I sent a letter to the US or England I must get several signatures.” Submitting a scientific paper to a foreign journal took two or three months to get permission. Attending conferences abroad was a nightmare.
One of the biggest theoretical advances during this difficult period was Linde’s work on the “multiverse”, an idea that seemed fantastic to many scientists at the time but is now close to the cosmological mainstream. He proposed that our universe is one of a vast – and perhaps infinite – number of inflationary universes that sprout off an eternal cosmic tree, without beginning and without end.
Asked whether the multiverse theory could be proved within his lifetime, Linde turns the question on its head. “Can you really prove that it is just universe?” he asks. “Why would you think the concept of universe is more natural? Why should multiplicity be forbidden? The insistence that we have just one universe has to be proved.”
Linde left Moscow in 1989, when Mikhail Gorbachev’s perestroika made it possible for him to travel with his family. He left with his wife Renata Kallosh, also a physicist, and their two sons to spend what they intended to be a year at Cern, the European physics centre outside Geneva.
While in Switzerland, however, tempting offers started to come in from western universities, including a double offer from Stanford of professorships for Linde and Kallosh. She asked a Cern physicist about Stanford, recalls Linde. “This colleague answered: ‘Do you seriously consider moving into this cultural desert [California]?’ Then in the same breath he continued, ‘But many people would die to get an offer like that, especially two offers – that is practically never’.” So the family moved to the US.
“I must attest that this is not in the slightest a cultural desert,” says Linde of Stanford. “It’s a very alive place with great people. The people here have the same mentality as our colleagues at Lebedev Physical Institute. They live like one big family.”
Linde still visits Moscow at least once a year to visit his former colleagues and his 94-year-old mother, who worked until the age of 86 as a physics professor at Moscow State University, and his brother, a psychology professor.
At Stanford, Linde has continued to push forward his thinking about cosmic inflation, melding it with string theory, one of the leading explanations of the particles and forces underlying the laws of physics. This has further strengthened his faith in the multiverse because it provides a mechanism for the laws of physics to vary in each new universe as it arises. Indeed, he says, it explains why everything in our universe, from the mass of subatomic particles to the vacuum energy of empty space, is very finely tuned to produce the conditions in which life could evolve on Earth – and almost certainly elsewhere too.
While Linde is happy to talk about any aspect of cosmology, there is one question that he surprisingly rejects: what does he make of the Californian lifestyle? “I live on campus; it’s called professors’ ghetto,” he says. “I have never experienced this ‘Californian lifestyle’. I have a full life here. This is our culture, not necessarily Californian culture.”
Clive Cookson is the FT’s science editor
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