Friday, 24 February 2012

Lisa Randall interview

Poised on the Edge: An interview with Lisa Randall

New Humanist March-April 2012 issue

‘There is no question that there is an unseen world,’ Woody Allen once said. ‘The problem is how far is it from mid-town and how late is it open’. The notion of parallel realities has been a staple of science fiction ever since 1923 when H.G. Wells wrote Men Like Gods, in which there exists an alternative world with ‘no parliament, no politics, no private wealth, no business competition, no police, no prison’. The Utopians who inhibit this world had shared our past until history inexplicably branched. Yet by the late 1950s science caught up when Hugh Everett III, a graduate student at Princeton, showed that theoretically one could treat each and every possible outcome of a quantum experiment, such as measuring the position of a particle like an electron, as actually existing in an alternative parallel reality. He believed that his theory was the simplest interpretation of quantum mechanics, but accepting it was ‘a matter of taste’. At the time no one took his idea seriously. But as physics moves on, tastes change. 

‘I think multiple universes probably exist, but it's very unlikely we'll know about most of them,’ says Lisa Randall as we chat over coffee during a visit to London to promote her latest book, Knocking on Heaven’s Door.  The 49 year-old Harvard professor of theoretical physics leaves the door open to the possibility that there might be others that we can somehow glimpse. ‘The exception,’ she says ‘would be universes that affect properties of our own’. 

It’s an idea that Randall expands upon in her book, as she tries to portray what is happening today in particle physics and cosmology in terms of both experiments and theory.  For particle physicists and even cosmologists this is the era of the Large Hadron Collider, the gigantic particle accelerator under the Franco-Swiss border near Geneva that is smashing together protons at unprecedented energies in an attempt to recreate the conditions of the very early universe to test our understanding of the nature of matter and forces. ‘I wanted to convey the excitement and implications of the research taking place there,’ says Randall, ‘so when discoveries are made, anyone interested can understand what was found and what it could mean.’ And what it could mean is nothing short of mind bending. 

Theoretical physics at the cutting-edge is an exotic discipline and not much is more exotic than the notion of extra spatial dimensions in addition to the three that we are all used to. These extra dimensions could be flat, like three dimensions of our everyday existence. ‘Or they could be warped,’ says Randall ‘like reflections in a fun-house mirror’. They might be unimaginably small or infinite in size. ‘An infinite extra dimension might sound incredible,’ concedes Randall ‘yet an unseen infinite dimension and parallel universes within it are some of the possibilities for what might exist in our cosmos’.

It was in the 1980s that superstring theory emerged as the leading candidate for the ‘theory of everything’. Superstring theory says what we detect in our experiments as particles are not really particles at all but manifestations of the ‘vibrations’ of one-dimensional objects called ‘strings’. Superstrings vibrate in ten dimensions but we don’t notice these extra dimensions because they are curled up into a space that is infinitesimally small. ‘Since we don’t see them,’ explains Randall, ‘these new dimensions of space must be hidden.’ We would not notice a curled-up dimension ‘just like a tight-rope walker would view his path as one-dimensional, but a tiny ant on the wire might experience two’.

Physicists had known for years that extra dimensions could be rolled up, but it was only in 1999 that Randall and her former student Raman Sundrum discovered another reason that extra dimensions might be hidden. ‘Einstein's theory of relativity tells us that energy and matter curve space and time. We found that spacetime with extra dimensions could be so warped that even an infinite extra dimension could exist but escape detection.’ The Randall-Sundrum theory mimicked three dimensions so uncannily that evidence that supports three dimensions of space can also be regarded as supporting the idea of such warped extra-dimensional universes.
Not long afterwards Randall and another colleague discovered an even more startling theoretical possibility - the universe can have three spatial dimensions in some regions but have more or less in others. If Randall is right then we might find ourselves living in an isolated region with three spatial dimensions inside a universe with many more. Randall’s two papers soon became among the most cited of recent times.
However theoretically sound and mind blowing the idea might be, the question remains: is there any compelling reason to take extra spatial dimensions seriously? Randall argues there is, for ‘they may help solve some outstanding problems that have no convincing solutions without them.’

Why, for example, is gravity is so weak compared to the other known fundamental forces? ‘Gravity might not appear to be all that weak when you're hiking up a mountain,’ says Randall ‘but bear in mind that the gravitational force of the entire Earth is acting on you.’ However, throw in an additional warped dimension and in this new five dimensional spacetime gravity is strong in one region of a fourth dimension of space but very weak everywhere else. In this universal architecture it’s natural for gravity to be weak in our vicinity.

Randall enjoyed maths at high school in New York but chose to study physics because ‘I wanted something that could connect to the real world.’ After getting her PhD from Harvard in 1987 she returned in 2001 as its first female tenured professor of theoretical physics. ‘I do what I do’, she replies with good grace when I ask if she’s a role model for other women contemplating a life in science. ‘One of the nice side benefits is that I can potentially inspire other women, and men, and defy stereotypes.’ It was an unfair question, but it’s one that Randall doesn’t often escape especially after comparisons to Jodie Foster’s character in the film Contact (there is, it must be said, a slight resemblance).

‘Often people don’t really understand what science is and what we can expect it to tell us,’ says Randall. The book was an attempt to correct some of the misconceptions and that ‘we shouldn’t be afraid to ask big questions or to consider grand concepts’. A few days before we meet Randall appeared on Radio 4’s Start the Week to discuss her book and found herself sharing a studio with Richard Dawkins and Chief Rabbi Jonathan Sacks. ‘Finding the word “atheist” odd’, Randall says she would categorize myself as a ‘nonbeliever’.

‘Religion puts things together to see what they mean, science takes them apart,’ said Sacks during the programme. I remind Randall that at one point in the discussion she had responded by saying that it wasn’t science versus religion, but the rational versus the irrational.  ‘It's odd how often scientists get asked about religion because they really are such different enterprises. I do think however that it helps to precisely pinpoint the differences so we can have sensible conversation.’

‘The answer,’ believes Randall, ‘has to do with understanding that contradictions arise when we treat religion as something other than a social or psychological enterprise. When we believe an entity or spirit literally affects the world, or our choices today, this goes against the material mechanist view of science. That is why when the Chief Rabbi said that God is a gardener, who sets everything in motion, I asked whether he thought God keeps gardening. We don't know what happens in the beginning. Scientists won't choose a deistic interpretation but we can't show a contradiction either. But in later times or today, that would run counter to what science shows, unless we believe God just acts according to the rules of science in which case the role is rather unclear.’

Not one to shy away from the big questions, one of the things Randall is currently attempting to explain the amount of dark matter in the universe. With the biggest and most exciting experiments in particle physics and cosmology under way, what they reveal could provide clues that may ultimately change our view of the fundamental constituents of matter, and even of space itself. ‘We are,’ Randall believes, ‘poised on the edge of discovery’. 

How the Hippies Saved Physics

How the Hippies Saved Physics: Science, Counterculture, and the Quantum Revival by David Kaiser 

Financial Times, 14-15 January 2012

Quantum teleportation may sound like science fiction, but in 1997 a team led by Austrian physicist Anton Zeilinger turned it into a scientific fact. A single particle was transported, not physically but through transferring its quantum properties to a second particle, thereby effectively teleporting it from one place to another. Although not as dramatic as Captain Kirk being “beamed up”, it was nonetheless a stunning demonstration of a process deemed impossible just a decade earlier.

Even more remarkable is the fact that quantum teleportation and – for example – the ideas that underpin quantum-encrypted bank transfers have their origins in the hazy, drug-fuelled excesses of the 1970s New Age movement. As David Kaiser, a physicist at the Massachusetts Institute of Technology, explains in How the Hippies Saved Physics, many of the concepts at the heart of today’s science of quantum information can be traced back to a freewheeling circle of young physicists involved in an informal discussion group founded in May 1975 at the Lawrence Berkeley National Laboratory in California.

Calling themselves the “Fundamental Fysiks Group” (FFG), they met weekly for nearly four years as they sought to recapture the excitement and mystery that had attracted them to physics in the first place. Members came and went as the group organised workshops and conferences on everythingfrom LSD to extrasensory perception, clairvoyance, psychokinesis and eastern mysticism with a heavy dose of quantum physics – the science of the atomic and sub-atomic levels of reality where mind-bending, counterintuitive ideas are the norm. This heady cocktail was already being sipped in the very first meeting, as Fritjof Capra spoke about his then new book The Tao of Physics, in which he argued that parallels existed between quantum theory and eastern mysticism.

Kaiser, too, sees an interconnection between the FFG, quantum pioneers such as Albert Einstein and Niels Bohr, and the debate over what quantum physics reveals about the nature of reality. Einstein admitted to having spent a hundred times longer thinking about quantum physics than his theory of relativity and believed there was “a real world existing independently of perception”. Bohr, meanwhile, maintained that there was no objective reality but only an “abstract quantum description”.

By the time Capra and FFG members began studying physics in the 1960s and 1970s, the cold war imperative to find practical applications meant that such philosophical engagement had fallen out of fashion in favour of a “shut up and calculate” approach.

John Bell
What fascinates Kaiser is the mismatch between the FFG scientists’ “soaring intellectual aspirations and their modest professional platform” as they rescued Bell’s theorem – one of the great achievements of 20th-century physics – from a decade of obscurity. In 1964 John Bell managed to discover what had eluded both Einstein and Bohr: a mathematical theorem that offered a way of deciding between their opposing world views. Bell’s theorem stipulated that quantum objects that had once interacted with each other would retain a strange connection. Nudge a particle here and its partner would instantaneously dance over there – they remained “entangled” regardless of whether they were nanometres or light years apart.

Entanglement, for the likes of Capra, was akin to the eastern mystics’ emphasis on holism. Not everyone may have followed him there, but as the FFG grappled with Bell’s theorem it forced more conventionally minded physicists to pay attention. Today only the provenance of its successes would raise an eyebrow. Like so many of their peers, the hippies who “saved” physics have been absorbed by the mainstream. 

How To Build A Time Machine

How To Build A Time Machine: The Real Science of Time Travel by Brian Clegg 

New Scientist, 10 December 2011

At 10pm on Saturday May 7 2005, some 400 people waited at the Massachusetts Institute of Technology for some very special guests to arrive. Time travellers from any and every point in the future had been invited to join the party in Cambridge. “The idea was a simple one that might at first seem trivial but was, in fact rather clever,” Brian Clegg explains in How to Build a Time Machine. “If time travel is possible, why not flag up a certain place and time in history and invite time travellers to attend?” 
The organisers had tried to ensure that the relevant information seeped into the future, and hoped a combination of the internet, print media and TV coverage would do the job. How could any curious, party-loving time traveller resist?

The no-show raises a simple question about the possibility of travelling back in time: We may not yet have the technology to move freely through the ages, but if time machines are going to be built at some point in the future, why hasn't anyone come back to visit us? According to the theory of special relativity, as one moves faster and faster and approaches the speed of light, time slows down. At the speed of light, time stands still. If one could go faster than light, then in principle it is possible to travel back in time. So, Clegg asks, “Where are the time travellers?”

Accelerating beyond light speed to go back to the future requires an infinite of energy, so is practically ruled out (though a huge question mark hangs over faster-than-light neutrinos). However, general relativity does permit the construction of a time machine if space-time is twisted to create a loop, allowing a traveler heading into the future to circle back to an event in his or her own past. This is possible in curved space-time because it’s like a rollercoaster with a loop-the-loop: the cars always go forward but the track circles back to a previous point. 

If a time machine is constructed in the year 2100, for example, it means the loop in space-time starts then: the time machine can be used to go back to 2100 but not to a time before. This feature of time machines has been suggested by physicists J. Richard Gott and Kip Thorne - the former using cosmic strings and the latter, wormholes. Time travel is possible machine when strings cross or wormhole mouths are moved.

Despite its impracticality, Clegg believes it’s never too soon to consider the potential social and ethical impact of a functioning time machine. He devotes a chapter to the classic “grandfather paradox” - travelling back in time to kill your grandfather before he ever meets your grandmother, rubbing yourself out of existence. It was to handle such conundrums that Stephen Hawking suggested the chronology protection conjecture - the laws of physics conspire to prevent time travel to the past on a macroscopic scale.

H G Wells
Though 116 years have passed since H.G. Wells published his novella, The Time Machine, it is only in recent decades that time travel has leapt from the pages of science fiction to those of physics journals.  While Clegg offers an introduction to time travel, unlike the preceding How to Build a Time Machine by Paul Davies or Gott’s Time Travel in Einstein’s Universe, he doesn't offers much new understanding. In surveying the basics he does conclude – somewhat reassuringly – that,  “time travel technology is not something an amateur can cobble together in the garage”, and that when it does happen it will be down to sophisticated science, “subject to checks and safeguards”. In the end, I suppose, only time will tell.