IMAGINE a discussion of Darwin’s theory of natural selection, Penrose’s
twistor theory, Lovelock and Margulis’s Gaia hypothesis, Conway’s Game of Life,
Mandelbrot’s fractals and Prigogine’s non-equilibrium thermodynamics, intimately
intertwined with gauge theories in elementary particle physics, string theory,
cosmology, general relativity, quantum mechanics and topological quantum field
theory. Add philosophy, art, theology, politics and sociology, with homage to
the relational view of space and time proposed by Leibnitz in contrast to the
discredited absolute space and time of Newton.

Smolin has the ambitious goal of explaining the problems that confront the
new generation of theoretical physicists and cosmologists, and proposes his own
ideas towards their solution. He has undoubtedly made an impressive sweep across
most of the unanswered questions in fundamental physics, but it is difficult to
form a judgment about the parts of his story with which I have only a passing
familiarity. Let me look first at a part that I am very familiar
with—namely, elementary particle physics and quantum mechanics.

Curiously, in his discussion of the standard model of the weak and
electromagnetic interactions, Smolin makes no mention of Sheldon Glashow, the
first to write down such a model and who shared the Nobel prize with Steven
Weinberg and Abdus Salam. The omission of a reference to Glashow seems
significant because Glashow is a well-known opponent of the string theory
approach that Smolin embraces enthusiastically.

Smolin is honest, however, in his account of the present arbitrariness in
string theory and its inability to predict the particle masses we see around us,
along with its lack of “any realistic expectation of soon receiving guidance
from experimental physics”.

The centrepiece is a popular exposition of Smolin’s Darwinian approach to
cosmology, which he calls “cosmological natural selection”. The basis for the
theory is the apparent need for the twenty or so parameters of the standard
model to be fine-tuned to an incredible degree of accuracy over a huge range of
magnitudes, so that life, the Galaxy and the Universe can exist at all.

It is widely believed that our Universe contains a huge number of black holes
whose interiors correspond to unobservable regions. According to general
relativity, all matter inside the black hole collapses to a point singularity.
Smolin argues that quantum effects may come into play to remove this singularity
and the collapsing black hole “bounces” back into an expansion. Smolin suggests
that inside each black hole is a new expanding Universe with black holes. He
then assumes that the twenty-odd parameters of the standard model change a
little bit at each bounce and, as in Darwinian evolution, the “fitness
landscape” of all possible universes evolves until universes in which the
parameters correspond to a state of maximal black hole production
predominate.

Supposedly, the theory is testable by playing God and twiddling the set of
parameters we observe in our Universe: we can then attempt to see whether or not
such changes lead to more or less black hole production. Perhaps I am at odds
with a new, postmodernist world, but such “random assumption” physics reminds me
of the once-great University of Salamanca. In the 18th century, only one faculty
set an examination with a single question repeated every year: “What language do
the angels speak?”

I AM delighted by this book. It is without doubt the best and most
up-to-date, popular, nontechnical account I have come across of the conceptual
problems of quantum mechanics, and of the recent ideas that have gone some way
towards resolving them. I recommend it unreservedly to anyone, including
professional physicists, with an interest in how the apparently concrete world
about us arises from the shadowy abstractions of quantum mechanical
probabilities.

In Where Does the Weirdness Go? David Lindley sets out to
explain—with only one equation—the present status of attempts to
understand the most fundamental mystery of modern physics, namely, how the
familiar world of Newton’s laws and classical mechanics emerges from the quantum
world described by Schrödinger’s equation and quantum wave functions. All
the usual suspects make their appearance, from Bohr and Einstein, to David Bohm
and John Bell. As Lindley makes clear, Bell’s contribution in focusing at least
part of the great quantum mechanics debate onto an experimentally testable
question cannot be overstated.

I received most of my education in these matters from Bell himself. While at
CERN in the early 1970s, I happened to attend one of his seminars, entitled “The
Einstein-Podolsky-Rosen (EPR) paradox for accelerator physicists”. It was then
that I first appreciated what Bell had shown by his theorem: that any
deterministic, hidden variable theory that reproduced the predictions of quantum
mechanics must be nonlocal and allow just the “spooky action at a distance” that
Einstein was trying to eliminate.

Lindley devotes the first part of his book to an exceptionally clear and
careful account of the conceptual problems posed by the famous double slit
experiment. Surely the photon must go through one slit or the other, but how
then does the interference pattern arise? This leads to a discussion on the fate
of Schrödinger’s cat as an extreme example of the “measurement problem” of
quantum mechanics.

According to Werner Heisenberg, the physical world may be split into two
parts: the observed object and the observing system. The former is supposed to
be described by quantum mechanics and the latter by classical physics, with
measuring devices that display classical properties like the position of a
pointer and so on. Since everything can ultimately be regarded as being made up
of atoms obeying Schrödinger’s equation, there is clearly some ambiguity as
to where this “Heisenberg frontier” is located. The orthodoxy of Heisenberg and
Bohr claims that this ambiguity leads to no observable effects. It was just this
“shifty split” that Bell detested.

The last section of the book is devoted to recent attempts to explain how
ideas based on decoherence shed light on the measurement problem. Nobel
prizewinner Murray Gell-Mann has explained decoherence as the entanglement of
the interesting properties of a system with all the myriad other properties in
which we have no interest. We are only interested in which horse wins a race,
not what happens to the horseflies, collisions with air molecules and so on.
Advocates of the decoherence mechanism claim that the summation over all these
details for classical macroscopic objects causes all the strange quantum effects
to disappear.

Lindley gives us a beautiful discussion of the challenge to our concept of
reality posed by quantum mechanics, and is not afraid to come out with
forthright, common-sense opinions. I find his whole book a particularly
refreshing approach to an area that is often shrouded in mysticism. Only in his
last section, when Lindley talks about cosmological aspects of quantum
mechanics, does he, as he himself says, stumble “into a swamp of seemingly
circular questions and answers”.

FROM the atomic to the cosmic, stretching across the extremes of the Universe, The Search for Infinity concerns itself with structure. Clearly revealing its pedigree as a series of newspaper articles, it offers snack-
sized pieces on the exciting outer limits of physics.

Lavishly illustrated, entertainingly presented, up-to-date, accessibly priced – it is a book that should appear on many a coffee table. If a cheaper paperback version appears, it should find its way into the rucksack of many a sixth-former, where it would do the most good.

Topics are dealt with in double-page spreads generously decorated with photographs and diagrams. Many sections are augmented by a short, fascinating biography of an associated scientist – did you know that Niels Bohr, an ardent footballer, nearly became the Peter Schmeichel of the turn of the century? This style of presentation, fragmentary at first glance, will appeal to many among the generation brought up on 30-second adverts.

The subject matter of The Search for Infinity falls naturally into two parts: the microscopic and the very large. Though a coherent story builds up mas you go though the book, it would have benefited from stronger links between the two.

The first part looks inward towards the atom, the nucleus and the quark. The story begins with the first ideas of the early Greek philosophers – Thales, Pythagoras, Democritus and others – leading to the theory of the four elements of Plato and Aristotle. The beginnings of modern science are traced back to relatively obscure figures, such as Pierre Gassendi, credited with the first concept of gravity, and early “atomicists”, such as the “Mad Duchess”, Margaret Cavendish, who believed in four types of atoms – square, long, round and sharp. The authors then go on to describe the wave-particle duality of light, Maxwell’s theory of electromagnetism, and quantum mechanics, before settling down to a fascinating historical survey of nuclear and elementary particle physics.

All the heroes of modern physics make their appearance, and there are some nice anecdotes illustrating that even great physicists are human too. The authors take time out to describe some of the mighty accelerators that helped to uncover significant pieces of the jigsaw that is now described, somewhat prosaically, as the standard model. The section ends by looking at Einstein’s dream of a unified theory in the modern context of superstrings.

In the second part we are shown how the large-scale Universe was created and what its structure consists of. Several essays deal with the early Universe, blending empirical evidence (such as the COBE microwave background data and the large-scale structure work of Margaret Geller) with the inflation theories of Alan Guth and others.

Black holes and neutron stars both earn their own double-page spreads, although the discoverer of the latter, Jocelyn Bell Burnell, may not appreciate that working so close to such intense gravitational fields has
caused her to age unnaturally fast (her date of birth is given incorrectly).

It is good to see some of the exciting discoveries now coming from high energy astrophysics appearing so rapidly in a popular book. In particular, the enigmatic problem of gamma-ray bursts is given the coverage it deserves. These brief, blinding flashes of high energy radiation apparently originate from the farthest corners of the Universe, but the mechanism that produces them is currently beyond our comprehension. Even the discovery just last year of MACHOs – massive astrophysical compact halo objects, also known as brown dwarf stars (possibly) – gets in.

This wonderful book combines a lively description of the discoveries that have led to our present picture of the Universe with an intelligible survey of the theories that we use to try to make sense of it. It would be possible to quibble about the somewhat uncritical presentation of some of the ideas making up the “theory of everything”, but this would be churlish. The Search for Infinity is a marvellous read and deserves a wide audience. For an up-to-date and entertaining account of the state of cosmology and particle physics, it is hard to beat.