Friday, May 15, 2015

Ross Andersen - In the beginning: Crisis in cosmology

The science of cosmology has achieved wonders in recent centuries. It has enlarged the world we can see and think about by ontological orders of magnitude. Cosmology wrenched the Earth from the centre of the Universe, and heaved it, like a discus, into its whirling orbit around one unremarkable star among the billions that speed around the black-hole centre of our galaxy, a galaxy that floats in deep space with billions of others, all of them colliding and combining, before they fly apart from each other for all eternity. Art, literature, religion and philosophy ignore cosmology at their peril.

But cosmology’s hot streak has stalled. Cosmologists have looked deep into time, almost all the way back to the Big Bang itself, but they don’t know what came before it. They don’t know whether the Big Bang was the beginning, or merely one of many beginnings. Something entirely unimaginable might have preceded it. Cosmologists don’t know if the world we see around us is spatially infinite, or if there are other kinds of worlds beyond our horizon, or in other dimensions. And then the big mystery, the one that keeps the priests and the physicists up at night: no cosmologist has a clue why there is something rather than nothing.

Last November, I spent a week with Paul Steinhardt, the director of the Princeton Center for Theoretical Sciences. Steinhardt was one of the first high-profile physicists to question BICEP2’s findings in public. In a column for Nature last June, he said that the team’s analysis was seriously flawed. Few cosmologists were surprised. Steinhardt is inflationary theory’s most vocal critic, and has been for years. But perhaps critic is the wrong word. Apostate might be better, for Steinhardt was present at inflation’s birth. You might even say he midwifed it.

Steinhardt learned the art of theory at Caltech, at the feet of Richard Feynman, the charismatic Nobel Prize-winner and Manhattan Project veteran. As an evangelist for science, Feynman was second only to Carl Sagan and, even then, it’s a matter of taste. Feynman took Steinhardt under his wing, serving as his student thesis advisor, and his personal mentor. The two of them created a course together, a weekly meeting called Physics X where students would propose a question or some unexplained phenomenon, and then watch as Feynman riffed, hopping back and forth between disciplines with ease. The meetings were held in an old lecture hall with creaky wood benches, which is now named for Feynman. Steinhardt makes it sound like a grove outside Athens.

Steinhardt didn’t give much thought to cosmology until his postdoc days at Harvard, when he attended a talk by Guth. This was back in 1982, when Guth was a postdoc at Stanford, a ‘struggling postdoc’, according to Steinhardt.

‘Guth gave the most wonderful talk,’ Steinhardt told me. ‘He detailed his new theory of inflation from the ground up, including the basics of Big Bang cosmology, which I had never been exposed to.’ Guth explained that there were problems with Big Bang cosmology. For one, the Universe is mysteriously uniform in all directions. If you position telescopes at the North and South poles, and point each of them at a dark patch of sky, you can catch light from opposite ends of the Universe. If you measure the temperature of light from these regions, all the way out to eight digits, you’ll see the same number. This is mysterious because the two regions are separated by more than 20 billion light years, too far to have ever interacted in a way that would lead to such extraordinary equilibrium. It’s possible to generate a uniform universe such as ours within the standard Big Bang framework, but you have to carefully calibrate its initial conditions. You have to ‘fine-tune’ it.

Guth said the Big Bang’s problems could be avoided if the early universe had expanded, exponentially, so that its structure stretched and smoothed. He also said particle physics provided a mechanism for this expansion. But there was a catch: Guth couldn’t figure out how the expansion would end.

Within a few years, ‘eternal inflation’ was ascendant. A decade later, it was the sexiest idea in cosmology. Today, it is virtually a paradigm

‘It was the most exciting and most depressing talk I had ever been to,’ Steinhardt told me. ‘I couldn’t believe that such a sweet idea would have such a sour ending.’

Steinhardt decided to take a few weeks off, to brush up on astrophysics and cosmology, and to see if he could come up with a workaround for Guth’s problem. Weeks turned into months. In the meantime, Steinhardt landed a professorship at the University of Pennsylvania, where he picked up a talented grad student named Andreas Albrecht. Together, the two men developed an inflationary model that allowed inflation to continue forever, generating an infinite, bubbly multiverse as it went along. Linde hit upon a similar idea a few months before, but he was in Moscow at the time. His work was still hidden behind the Iron Curtain. When Guth debuted the theory of inflation, it was widely seen as stillborn, but Linde, Albrecht and Steinhardt breathed new life into it. Within a few years, ‘eternal inflation’ was ascendant. A decade later, it was the sexiest idea in cosmology. Today, it is virtually a paradigm.

Steinhardt had everything to gain by continuing to champion inflation, but before long, the theory’s flaws began to nag at him. ‘I made the first eternal inflation model, but I left the problems for someone else to solve,’ he told me. When decades passed with no solutions, Steinhardt’s doubts grew. He began to wonder whether there might be another way to fix Big Bang cosmology. He wondered if there were previous Big Bangs before our Big Bang. He began working on a new theory. So far, the work has been lonely.

‘The last 30 years is a very unusual period in the history of fundamental physics and cosmology,’ Steinhardt told me. ‘There’s confusion, and maybe even a certain amount of fear. People are wedded to these ideas, because they grew up with them. Scientists don’t like to change ideas unless they’re forced to. They get involved with a theory. They get emotionally attached to it. When an idea is looking shaky, they go into defensive mode. If you’re working on something besides inflation, you find yourself outside the social network, and you don’t get many citations. Only a few brave souls are willing to risk that.’

I teased Steinhardt, pointing out that he hadn’t exactly been hauled before the Inquisition. Steinhardt is fully tenured, a lion of Princeton’s storied physics department. He walks the same leafy streets that Albert Einstein walked. Indeed, his official title at Princeton is Albert Einstein Professor in Science. Still, he feels overmatched. He told me he has asked for help from outside the field.

‘The outside community isn’t recognising the problem,’ he said. ‘This whole BICEP2 thing has made some people more aware of it. It’s been nice to have that aired out. But most people give us too much respect. They think we know what we’re doing. They take too seriously these voices that say inflation is established theory.’

I asked him who might help. What cavalry was he calling for?

‘I wish the philosophers would get involved,’ he said.

Last October, John Kovac boarded an 18-hour flight from the United States to New Zealand, as he has every year since 1990. After touching down in Christchurch, he drove to a large warehouse, to be fitted with a fluffy red parka, military-grade snow boots, mittens, goggles and other extreme-cold weather gear. The next morning, he crossed the Southern Ocean in a military transport plane, before landing at McMurdo research station on the coast of Antarctica. The Southern Ocean is the violent, iceberg-strewn moat that encircles Antarctica. It is the only latitudinal band on Earth where there is no land to stop ocean winds from whipping furiously around the planet, stirring up storms as they go. These storms had waylaid Kovac at McMurdo before, but this year the weather was mild. He was cleared to leave the next morning, to complete the last leg of his trip.

No matter how jetlagged, Kovac always makes it a point to stay awake for this final flight. During the first two hours, the plane passes over hundreds of miles of blocky, blue-veined glaciers, before cresting over the Transantarctic Mountains, whose barren peaks once played host to thick forests and, during the early Jurassic, some of the first large dinosaurs.

The final hour is more monotonous, because Central Antarctica is an enormous plateau, blanketed by ice so thick, it conceals whole mountain ranges. Few microorganisms can survive there. Birds fly over only if they are blown off-course by a Southern Ocean storm. Human beings are the only resident land animals. Kovac told me the plateau’s featureless terrain makes him feel like he’s flying over a frozen white sea that seems to stretch forever. At the end of the flight, the plane dips and a long building on stilts appears in the porthole window, a building whose slate grey exterior and sleek Scandinavian angles make it look like a villain’s lair in a spy thriller. That’s when Kovac knows he’s reached South Pole Station.

The politics that govern land use on Antarctica are radical, relative to Earth’s other six continents. The first human visitors to Antarctica came to claim territory for crown or country but, in 1959, 12 nations signed a treaty that demilitarised Antarctica indefinitely, in order to preserve it for peaceful, scientific purposes. One of the finest achievements of Cold War diplomacy, the treaty transformed an object of imperial conquest into a commons for the collective human mind... read more: