If not exactly in crisis, modern cosmology is at least in a state of unprecedented ferment. The past 20 years or so have seen dramatic advances in our knowledge and understanding of the universe. This is all thanks to space probes such as the Hubble space telescope, the Cosmic Background Explorer (COBE) and the Wilkinson Microwave Anisotropy Probe, together with a clutch of hugely more sensitive telescopes on earth which are able to view the heavens in every region of the electromagnetic spectrum.
These have all contributed to the prevailing wisdom that the universe originated about 14 billion years ago in an unconscionably hot fireball, the “Big Bang”. Immediately afterwards it expanded massively, a period of “inflation” driven by forces as yet unknown. Today we believe it is still expanding, driven by a mysterious “dark energy”. Just as mysterious, it now seems that only a small proportion of the universe is made up of the familiar stuff of stars, planets and asteroids. The rest is an unseen “dark matter” which seems to play a major role in stabilising the galaxies. In its absence - and unchecked by gravity - stars would spin off into deep space.
Next year, the world’s latest, largest and most expensive atom-smasher, the Large Hadron Collider, is due to go live, recreating, 100 metres beneath the Swiss Jura mountains, temperatures and pressures not experienced since the birth of the universe. (Hadron is physics-speak for the family of particles including protons and neutrons which together constitute the atomic nucleus.) By crashing subatomic particles together and analysing the debris from the collisions, it promises greatly to extend our understanding of the Big Bang. It might even, some hope, give a clue to what came before - “If anything”, one must add, since most cosmologists believe that space and time originated with the Big Bang.
The advance in our understanding of the universe has helped to spur a flourishing genre of science writing that tries to explore and explain these phenomena. The past few years have been a fertile period for books, popular and otherwise, about modern cosmology, the common ground shared by astronomy and particle physics. Last year a rash of volumes was published to commemorate the centenary of Albert Einstein’s magnificent achievements in quantum theory and special relativity. This year’s crop has benefited from the discoveries made by the new telescopes and probes, some of them capable of seeing back in time to within 300,000 years of the Big Bang. (It is worth reflecting, in passing, what an achievement that represents for an earthbound hominid species enjoying only a few hundred thousand years of intellectual evolution.)
“Before the beginning,” Pedro Ferreira concludes in The State of the Universe, “there was no time to talk about.” He goes on to argue that this concept, while difficult to grasp, makes sense when space-time is viewed as a living and evolving entity: “Time becomes part of this thing and we cannot dissociate it from the existence of the universe,” he writes. It was Einstein, of course, who at the beginning of the last century overturned conventional ideas of the topology of the universe. He argued that our visible world is defined by four dimensions - three of space and one of time - inextricably interlinked, and that gravity, far from being a force of attraction between bodies, is simply a deformation in space-time.
Theoretical cosmologists today, however, have advanced theories about the nature of matter which demand more than four dimensions. Some call for half a dozen or more; and this is where cosmology’s apparent rude good health starts to show signs of decay. Cosmology ties together the very large, the universe itself, and the very small, the particles of which everything is composed. Much of the thinking around these topics is necessarily theoretical. The principal quest is for a “Theory of Everything”, which can explain the universe in simple terms. Unfortunately, the two most important theories of the 20th century, quantum physics and relativity, are incompatible. Einstein spent most of his later years unsuccessfully attempting to solve this problem.
The most popular candidate, however, is something called “M theory” which holds that matter is made up of tiny vibrating strings. Ferreira sums it up thus: “If we were to look at sufficiently high energies, instead of seeing photons, electrons or quarks (conventional subatomic particles) we would find tiny strings that wriggle and vibrate as they propagate through space and time. There is only one type of string but the way it vibrates gives it a wide range of appearances.”
Nobody has ever seen one of these strings. They exist only in abstract mathematical formulae, yet huge tomes have been written about them, such as last year’s Warped Passages by Harvard physicist Lisa Randall. Some scientists are beginning to link emperors and new clothes. Robert Matthews, for example, visiting reader in science at Aston University and a noted exponent of scientific common sense, argues: “Strings and M theory are based on little more than fancy maths and a grab-bag of ideas expected from any theory of everything.” (Ferreira is less crushing, reasoning only that M theory could be the basis for a theory of everything but that its proponents have yet to demonstrate its relevance to ordinary physics.)
The three books reviewed here are intended, one assumes, for a general audience. While avoiding the industrial-strength mathematics which distinguished Sir Roger Penrose’s Road to Reality (2005), none could be described as a popular read, however. Ferreira, a lecturer in astrophysics at Oxford University, describes his book as a primer; it would be best suited to readers with some grounding in modern physics and astronomy. He reviews the early history of the subject, revealing that in the 3rd century BC, Aristarchus of Samos pioneered the idea that the sun, not the earth, is at the centre of the universe, anticipating Copernicus in 1497 by almost two millennia.
Ferreira takes the obligatory tour around Einstein, space/time and gravity, the origin of stars and galaxies and the light and heavy elements before tackling today’s big unresolved questions: is the universe finite or infinite? What is its topology? What is the nature of dark matter and energy? Cosmologists have only tentative answers to these puzzles and Ferreira does a good job of balancing the likely with the improbable. He writes plainly and without panache: a minor quibble is Jem Finer’s illustrations which seem curiously informal for a serious work.
While Ferreira has written a general textbook, Joseph Silk, another Oxford academic, has developed a somewhat specific theme in The Infinite Cosmos: whether the universe is finite or infinite. The title, perhaps, gives away Silk’s persuasion: “What is certain,” he writes, “is that the universe is very, very large. Even if it is not infinite, it is likely to be far, far larger than the remotest horizon visible with the world’s most powerful telescopes. At the very least, the universe is nearly infinite.”
There are powerful philosophical implications in this answer: life, we know, has originated at least once in the infinitesimally small part of the universe we inhabit. In an infinite universe, it must surely have originated many times. Silk argues, indeed, that in such a universe: “There would be identical copies of ourselves replicating every action, every word, somewhere.” At which point I feel inclined to rehearse one of the quotes with which Silk kicks off each chapter, this from Tennessee Williams: “I think that a vacuum is a hell of a lot better than some of the stuff that Nature replaces it with.”
The publisher’s blurb for The Infinite Cosmos claims that Silk weaves the ideas of famous writers, poets and philosophers into his account, but that’s going it a bit. Quotes apart, he brings the odd philosopher and theologian into a concluding essay on God and infinity, but the text is otherwise solidly scientific. Silk skips over any detailed account of early ideas about the nature of the cosmos in his eagerness to get to grips with his main thesis. Inevitably, the two books cover much of the same ground. Silk writes in short, punchy sentences (good) but often fails to develop his statements to extract the full meaning for the reader (bad). Here’s an example: “General relativity is a theory of gravity that starts with the concept that space is measureable, whatever the scale.” This sounds promising but Silk assumes too much on the part of the reader and fails to explain how this is related to more orthodox definitions.
Both Ferreira and Silk devote many pages to a discussion of the nature of dark matter. The prime suspect, they both argue, is the neutralino, a heavy, long-lived particle for which experimental evidence has yet to be found. Neither author mentions a controversial alternative explanation dating back to 1983 which could render dark matter unnecessary. Called modified Newtonian dynamics, this theory holds that Newton’s law of gravity (which has proved to be reliable for all practical calculations) may not hold in deep space. In other words, the gravitational effects which have persuaded cosmologists of the existence of dark matter may simply be the result of a flaw in Newton’s argument.
Silk believes that a convincing theory of everything will not emerge until the third millennium. Achieving this goal will, by necessity, involve quantum computing, a form of computation in which our familiar binary digits (bits) will be replaced by quantum bits or qubits. A bit in a conventional computer system represents a 0 or a 1; because of the bizarre nature of quantum mechanics, qubits represent a 0 and a 1 simultaneously. So, as Seth Lloyd claims in Programming the Universe, a quantum computer given 10 input qubits can do 1,024 things at once. One with 300 qubits of input can do more things at once than there are elementary particles in the universe. If this is hard to understand, rest assured that only a handful of physicists including Lloyd have ever created a quantum computer, however basic, and their non-quantum physicist colleagues regard them with a mixture of wonder and incomprehension.
Lloyd, a professor at the Massachusetts Institute of Technology and one of the few individuals to have built and run a quantum computer, tells the story of his early work on quantum processes at Rockefeller University. “One day in 1986, two professors and Heinz Pagels, the executive director of the New York Academy, walked into my office. ‘Lloyd,’ they said, ‘you must stop working on this crazy stuff and switch to a topic that we understand. If you do not, you must leave Rockefeller.’” - His contemporaries were working on - what do you know? - string theory: “I couldn’t for the life of me see why what I was doing was crazier than string theory,” he writes ruefully.
In this anecdotal, sometimes whimsical but good-natured book, Lloyd seeks to persuade us that the entire universe is a quantum computer, continually computing itself. “Yes,” he affirms, “the universe is a quantum computer. What is the universe computing? Everything we see and everything we don’t see is a manifestation of the universe’s quantum computation.” It helps to remember that Lloyd is one of the world’s foremost quantum physicists, a scientist with a deep knowledge of complexity (he once described 32 different varieties) - for this is a complex book. It would help even more to understand quantum physics. I have no shame in admitting I have no idea whether Lloyd is right about the universe. After all, as the late, great Richard Feynman said: “I think I can safely say that no one understands quantum mechanics.” But quantum physicists, computer experts and mathematicians will enjoy Lloyd’s idiosyncratic approach.
Perhaps everybody should enjoy these books and others like them while they can. After all, when the Large Hadron Collider comes on-stream next year, they will all have to be rewritten.
Alan Cane is senior technology correspondent for the FT.
THE STATE OF THE UNIVERSE
by Pedro G. Ferreira
Weidenfeld & Nicolson ₤18.99, 320 pages
THE INFINITE COSMOS
by Joseph Silk
Oxford University Press ₤18.99, 256 pages
PROGRAMMING THE UNIVERSE
by Seth Lloyd
Jonathan Cape ₤18.99, 240 pages
