BOOKS & ARTS NATURE|Vol 445|25 January 2007 secretary for fish and wildlife and parks, once not the job of public-affairs officers to alter, usually told by cosmologists and astronomers, stated: “If we are saying that the loss of spe- filter or adjust engineering or scientific mat- energy plays the central role. First there was cies in and of itself is inherently bad — I don’t erial produced by NASA’s technical staff.” a singularity and there was no past for it to think we know enough about how the world But the damage caused by the Bush admin- emerge from. Then expansion. As the Universe works to say that.” In 2004, on the day after istration’s contempt for scientific facts is no expanded, it cooled down and various forms of Bush’s re-election, the Fish and Wildlife Serv- laughing matter. In the two years since Bush matter condensed out because the disruptive ice, which Manson oversees, fired the biologist was re-elected, “reality” — especially the reality thermal energy gradually dropped below the Andy Eller, who had charged that the service of Iraq, which, Shulman points out, the United binding energies that hold constituent parts was not fulfilling its mandate of protecting the States invaded on the basis of erroneous techni- of protons, nuclei and atoms together. Tiny Florida panther, an endangered species. The cal claims — has humbled his administration. quantum fluctuations made some regions of agency was forced to re-hire Eller after a court In November, as the death toll in Iraq surged, the Universe slightly denser, and gravity ampli- ruled in his favour. voters handed the reins of power in Congress fied this effect, which resulted in gas clouds, Some of the Bush administration’s actions to the Democrats. In December, the Iraq Study stars and galaxies. Stars exploding to super- have been almost comically incompetent. Last Group, headed by the Bush family friend James novae produced heavier elements, then our January, for example, George Deutsch, a public- Baker, issued a scathing critique of the US Sun and Solar System formed, and about 4 bil- affairs officer at NASA, tried to prevent the occupation of Iraq. Bush’s approval rating has lion years ago, life emerged on Earth. But this space agency’s James Hansen from speaking sunk to one of the lowest levels ever recorded. story leaves many questions unanswered. How to the press about the dangers of global warm- The declaration of that Bush official — “We did life arise? Why is the Universe so complex? ing. Andrew Revkin of The New York Times create our own reality” — has now taken on a Could such complexities have arisen from total quickly exposed the attempt to censor Hansen, tragic irony. ■ randomness? and it was soon revealed that Deutsch, contrary John Horgan is director of the Center for Science Now, enter computer science. Algorithmic to what it said on his CV, had never graduated Writings at the Stevens Institute of Technology, information theory shows that there are short, from university. Deutsch resigned and NASA Hoboken, New Jersey. His most recent book is random-looking programs that can cause a administrator Michael Griffin declared: “It is Rational Mysticism. computer to produce complex-looking out- puts. Lloyd illustrates this with a popular story attributed to the French mathematician Émile Borel. Imagine a bunch of monkeys typing ran- domly into typewriters. Given enough time, it The Universe’s quantum monkeys is certainly possible that one of these monkeys will type the first million digits of π or the first physics, complexity, sex, life, the Universe and act of Hamlet. Possible, but very unlikely. Now, Programming the Universe: A Quantum all that, and he does it well. Despite this pro- take the typewriters away and give the mon- Computer Scientist Takes On the Cosmos by Seth Lloyd liferation of topics, the main message stands keys computers that recognize any random Alfred A. Knopf/Jonathan Cape: 2006. out and is reiterated several times — the Uni- inputs not as text but as a computer program. 240 pp. $25.95/£18.99 verse is a quantum computer programmed by When the computers try to execute random quantum fluctuations, and the computational programs, most of the time they will crash or Artur Ekert capability of the Universe explains how com- generate garbage, but every now and then just A little less than 14 billion years ago, a huge plex systems can arise from fundamentally a few lines of random code typed by monkeys explosion gave birth to the Universe, and once simple physical laws. will give interesting outputs — for example, the it sprang into existence, the Universe began Lloyd tells the story of the evolving Universe successive digits of π, or intricate fractals. Or computing. The positions, velocities and in terms of interplay between energy and infor- perhaps much more interesting patterns if the internal states of every elementary particle, mation. In the conventional history of the ori- computer is the Universe itself. every atom and molecule, indeed every single gin and the evolution of the Universe, the story This vision of a computational Universe is physical entity register bits of information. Those bits are continually altered by physical interactions that act like sequences of logic gates — given a sufficient supply of bits and M. KULYK/SPL enough time, they can compute just about any- thing that is computable. Thus, the Universe is a computer. It is not a metaphor, it really is. More than that, the fundamental laws of phys- ics that govern any interaction are quantum; hence, the Universe is a huge quantum compu- ter that computes its own behaviour. It started in a very simple state initially, but in time, as the number of computational steps increased, the computing quantum Universe spun out more complex patterns, including galaxies, stars and planets, and then life, humans, you and me, and Seth Lloyd and his book Programming the Universe. Like many other good stories of this type, Lloyd’s book will puzzle and even irritate as much as it persuades. Lloyd writes in a lively style, weaving jokes and personal anecdotes into more technical narrative. He shares his views on cosmology, computation, quantum Get with the program: the Universe, it turns out, is actually a giant quantum computer.

366 NATURE|Vol 445|25 January 2007 BOOKS & ARTS not new: it was proposed in the 1960s by Kon- Richard Feynman and David Deutsch pointed parts are patchy and many details are brushed rad Zuse and Ed Fredkin, and revived more out this opportunity in the 1980s, the hunt has under the carpet. For example, anyone try- recently by Stephen Wolfram. However, unlike been on for interesting things for quantum ing to work out numerical estimates of the his predecessors, Lloyd stresses the quantum computers to do, and at the same time, for the physical limits to computation or the computa- nature of computation. This distinction is scientific and technological advances that could tional capacity of the Universe is much better important because, to the best of our knowl- allow us to build quantum computers. The field off consulting Lloyd’s original paper on the edge, it seems impossible to simulate the evo- is flourishing, and Lloyd provides a good pop- subject (see Nature 406, 1047–1054; 2000). It lution of a quantum system in an efficient way ular introduction to the subject. However, he is clear that Lloyd has forsaken accuracy for on a classical computer. does not stop at the level of building quantum snappiness in several places, but then this is a A classical computer simulation of quantum computers, he takes on the biggest quantum popular exposition. evolution typically involves an exponential computer there is — the Universe. Seth Lloyd is a good storyteller, but is the slowdown in time. This is because the amount The Universe is a quantum computer, and story convincing? Well, I was convinced, but of classical information needed to describe the quantum mechanics supplies the Universe with when I tried a nice line from the book — evolving quantum state is exponentially larger ‘monkeys’ in the form of ubiquitous random “programmed by quanta, physics gave rise to than that needed to describe the correspond- quantum fluctuations — the same fluctuations chemistry and then to life, programmed by ing classical system with similar accuracy. that provided the seeds of galaxy formation mutation and recombination, life gave rise to However, instead of viewing this intractability and of all that followed. The Universe has Shakespeare, programmed by experience and as an obstacle, today we regard it as an oppor- pockets of complex behaviour because, Lloyd imagination, Shakespeare gave rise to Hamlet” tunity — if that much computation is needed claims, the monkeys have been working very — on a colleague of mine, an English literature to work out what will happen in a quantum hard. He estimates that the visible Universe, fellow, he only shook his head in disbelief and multi-particle interference experiment, then programmed by quantum fluctuations, has walked away. ■ the very act of setting up such an experiment performed about 10122 operations on 1092 quan- Artur Ekert is at the Mathematical Institute, and measuring the outcome is equivalent to tum bits. No wonder we are here! University of Oxford, UK, and the National performing a complex computation. Since I think this is a delightful book, but some University of Singapore.

botox, body piercing and ‘nipping and tucking’, there is someone making money out of it. And Cover story it does not necessarily have to stop just because someone is dead, as some enterprising Ancient Skin: A Natural History Egyptian undertaker realized. by Nina G. Jablonski Some forms of personal make-over and University of California Press: 2006. disguise teach a salutory lesson: that culture 290 pp. $24.95, £15.95 comes at a biological price, paid from the genetic legacy bequeathed you by evolution. John Galloway You are, let’s say for the sake of argument, a Biology is a historical science. Ask a ‘why?’ fair-skinned northern European. But it has question about biology, as Nina Jablonski become the thing to show off a nice tan (Jab- keeps doing in her book Skin, and you invite lonski fingers fashionista Coco Chanel as the an evolutionary answer. She also tells us every- perpetrator of this particular vanity), and that thing we might want to know about skin; means lying about without clothes in hot sun in perhaps more than some people want to know. latitudes rather nearer the Equator. The trouble She then goes on to take informed guesses as is, the reason you are fair is a good historical to why skin is the way it is and, by implication, one, indeed a matter of life and death for your why it is not like something else. Skin’s appear- ancestors in the Europe of 50,000 or so years ance, its form and function, questions of how ago. And that fact has implications for modern and why it works, and sometimes doesn’t, have day Sun-worshippers, some of whom discover been thrashed out over a billion or so years that mortality still starts with the skin. at — to borrow her words — the “negotiating At the core of Jablonski’s theme is the skin’s table of evolution”. ability to multi-task: it protects, controls tem- For Alexander Pope, the “proper study of perature, senses the world around you, and mankind” may have been “man”, but Jablonski, shows people how you really feel, as opposed as befits a modern biologist, thinks otherwise. to what you choose to tell them. But skin is Understanding starts, and possibly finishes, also a chemical factory, fuelled in part by solar with comparisons, between humans and our radiation. It manufactures vitamin D, without biological relatives and neighbours, both near The skin’s characteristics have been thrashed out which you can neither extract calcium from and not-so-near. We may share virtually all at “the negotiating table of evolution”. your diet nor incorporate it in your bones — our genes with chimpanzees, but those we posing something of a challenge to survival. don’t share are responsible for a lot of differ- way we live. Our skin is the visible, immediate Here’s an evolutionary conundrum. Ultra- ences, reproductive, linguistic and cognitive. personal territory where biology most obviously violet light, which damages DNA directly and Skin genes, for example, which are responsible gives way to culture. Jablonski quotes Franz also destroys the folic acid essential for its syn- among other things for colour, body hair and Kafka, who had the right idea, viewing the thesis, is, ironically, the energy source needed the number of sweat glands, may well explain skin as “not only a garment but also a strait- to make vitamin D. In equatorial Africa, our why chimps are still confined to African jun- jacket and fate”. People go to a lot of trouble and ancestral home, evolution engineered a nice gles, whereas we, their closest relatives, have expense to alter their appearance and change compromise that allowed humans to leave already been to the Moon. their fate. From war-paint and cosmetics to the sheltering forest canopy and begin global Skin is not just about biology, but also the tanning, bleaching, tattooing, ritual scarring, colonization. Melanins that absorb ultraviolet

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