Reviews
phy sic s wor ld.com
Nicolas Gisin
CERN
Saved by Bell
Revolutionary
John Bell
commenting on the
famous Bell’s
inequalities at CERN
in 1982.
John Stewart Bell
and TwentiethCentury Physics:
Vision and Integrity
Andrew Whitaker
2016 Oxford
University Press
$44.95hb 480pp
From a scientific point of view, the
theories of relativity and quantum
mechanics are often considered the
20th century’s most renowned and
profound discoveries. But the past
100 years have also seen many other
significant advances in science: from
the discovery of penicillin to the
structure of DNA, from continental drift to the Big Bang, and even
that of information theory, which set
the basis for today’s hi-tech society.
However, there is an often forgotten
but nevertheless crucial discovery
in physics that, in my opinion, surpasses all the others. By that I mean
the pioneering work done by physicist John Bell on “local hidden variables” of quantum mechanics, which
ultimately led to his ideas of “nonlocality” or Bell’s inequalities.
In John Stewart Bell and TwentiethCentury Physics: Vision and Integrity,
fellow physicist Andrew Whitaker
tells the story of Bell’s life and his
revolutionary discovery that not everything in physics can be explained
P hy sic s Wor ld  Januar y 2017
using only local variables. Back in
1935 Albert Einstein, Boris Podolsky and Nathan Rosen realized that
two quantum particles can be in a
state such that a measurement on
one particle instantaneously affects
the other – no matter how far apart
they may be. This effect, more commonly referred to today as entanglement, upset the trio because such
“spooky action at a distance” would
require information to travel faster
than the speed of light. We now
know than entanglement emerges
thanks to correlations between
measurements made on the two
particles, and that entangled particles have much stronger correlations
than are allowed in classical physics. But it was Bell’s breakthrough
in 1964 that laid the groundwork
for this phenomenon, when the
Northern Irish physicist calculated
an upper limit on how strong these
correlations could be, if they were
caused by local physics alone. Bell
reasoned that correlations stronger
than this limit would occur only if
the particles were entangled and this
is Bell’s inequality.
Whitaker, a physics professor at
Queen’s University, Belfast, tells
the story of Bell’s main discovery,
but the book also goes beyond that.
Bell was no one-discovery-wonder
and, peculiarly, pursued quantum
mechanics as a “hobby” in his spare
time. Indeed, he was a very successful high-energy theoretical physicist,
spending most of his career at the
CERN particle-physics laboratory in
Geneva. The book sets the stage with
Bell as a student at Queen’s, and then
follows his dual career – from the
early 1950s to his “decade of great
success” in the 1960s – including the
publication of his seminal paper in
1964, which he wrote while in the US
on sabbatical from CERN.
Through the book, one reads a lot
about Bell’s character and the many
people with whom he interacted
including Alain Aspect, Abner Shimony, Reinhold Bertlmann and even
myself. Interestingly, despite the fact
that Bell seemed to discuss his ideas
with a number of fellow scientists, he
had very few joint publications on his
work on quantum foundations. It is
also remarkable how few papers Bell
published in refereed journals. It
seems he didn’t quite like the referee
reports he must have received about
his fundamental work, which was initially ignored and did not truly gain
favour until the 1970s.
Bell died unexpectedly at the relatively young age of 62, from a cerebral haemorrhage, which Whitaker
describes as the “final tragedy”. The
book continues with the far-reaching implications of Bell’s discovery, including brief descriptions of
many of today’s active researchers.
Bell’s inequalities are now experimentally testable and his concept of
non-locality is gaining momentum.
Violating a so-called Bell inequality shows that an experiment is truly
quantum in nature and there are no
“local hidden variables” at play.
Today, Bell’s non-locality is also
being exploited for futuristic applica-
43
Reviews
phy sic s wor ld.com
tions in a new field that would never
exist without Bell’s seminal discovery – namely, “device-independent
quantum information processing”.
The idea is that a quantum protocol
would be completely independent of
the internal workings of the devices
being used, which would therefore
eliminate the risk of a quantum
cryptographic system being hacked.
That is because the protocol looks
merely at the statistics of any measurement made, without the need
to understand in any detail how
the data were collected; it suffices
to know that they were produced
at separate locations that couldn’t
communicate. The National Institute for Standards and Technology in
the US has already tapped into this
idea and has created a free, public
It is remarkable
how few papers
Bell published in
refereed journals
unpredictable sampling and secure
authentication methods.
I truly enjoyed reading this very
informative book. Moreover, it is
nicely illustrated with many pictures
of John, his wife Mary and others such as Michael Horne, Daniel
Greenberger and Artur Ekert. This
is not a book to learn about physics,
but to get to know a bit about the man
who made one of the most profound,
if not the most profound, discoveries
of the 20th century.
Nicolas Gisin is a physicist and professor at
the University of Geneva. He won the first
random number generator that you biennial John Stewart Bell Prize in 2009 and
can access online. Large sets of truly is the author of Quantum Chance,
random numbers are difficult to pro- Nonlocality, Teleportation and other
duce, but they are used in a variety Quantum Marvels (Springer 2012), e-mail
of applications today, including in [email protected]
iStock/Lena_ graphics
Between the lines
Close encounters
“The truth is in here” reads a
line at the top of a new book
about – you guessed it – aliens.
In a series of 20 short, sharp
essays by a mix of extraterrestrial
scientists and experts, compiled
and edited by physicist and TV
presenter Jim Al-Khalili, Aliens
attempts to succinctly answer
Serious science
A new book of essays some big questions beginning
with “Do aliens exist?” You would
about alien life
covers all aspects of be forgiven if at first glance, you
the subject from the think this book is more fiction than
fact – the paperback cover with its
conditions
tagline of “Science Asks: Is There
necessary for life to
Anyone Out There?” and its neon
the psychology
green backing may throw off the
behind alienserious scientific reader. But do
abduction claims.
not judge this little book by its
cover, for it does pack a punch. The
book opens with an introduction
from Al-Khalili, followed by an
intriguing essay by cosmologist
Martin Rees, in which he speculates
about how future humans,
travelling across the galaxy, may be
the aliens that we seek today. The
other 19 essays are divided into
four categories: close encounters;
where to look for life elsewhere; life
as we know it; and alien hunting.
What would motivate aliens to
visit us; what are the necessary
ingredients and conditions for life
to form, evolve and flourish; what
about some form of life elsewhere
in the solar system; and what
might aliens look like – all these
themes and more are mentioned
in the book by seasoned science
writers, authors and scientists
including Monica Grady, Lewis
44
Dartnell, Louisa Preston and Paul
Davies. Thanks to the discovery
of thousands of exoplanets in the
past decade, astrobiology and the
search for life beyond our planet
has become a common topic in
the popular-science book market,
and indeed may soon saturate it.
What sets Aliens apart in some
ways is the real expanse of topics
covered. The two chapters you’ll
guiltily enjoy the most deal not with
science per se, but with the human
aspect of alien existence. Science
broadcaster Dallas Campbell’s
entertaining chapter tells the tale
of “five of the most notorious UFO
stories that have taken the flying
saucer from fringe subculture to
mainstream modern folklore”. In
a subsequent essay, psychologist
and professor of paranormal
belief Chris French looks into the
psychology behind the many people
world over who are convinced that
they have had “close encounters” or
been abducted by extraterrestrials.
Aliens is an entertaining and
educational if slightly basic read for
anyone with a scientific interest in
extraterrestrials.
●● 2016 Profile Books £8.99pb
240pp
Lively lectures
Mention the Royal Institution
and most people will know it best
for its long-running and beloved
“Christmas Lectures”. Indeed,
the lectures have been run every
year since 1825, only taking a
hiatus between 1939 and 1942 as
a result of the Second World War.
The lectures were the brainchild
of Michael Faraday, who wanted
to bring science in an engaging
manner to children and young
adults. Although the lectures
have been televised since 1936,
each year’s lecture (which takes
place over a few days) still has a
live audience of school children.
Over the years, the lectures have
been on all aspects of science, but
those mentioned in 13 Journeys
Through Space and Time: Christmas
Lectures from the Royal Institution
have a bit more of a physics thread.
Compiled by astronomer and
writer Colin Stuart, the book
features 13 chapters, each of which
is a shortened version of an actual
lecture based on the theme of
space and time. Beginning with
Sir Robert Stawell Ball’s 1881
lecture on the Sun, Moon and the
planets and finishing with Kevin
Fong’s 2015 lecture on how to
survive in space, the book spans
many decades and plots the huge
advances that science has made in
that time. Some of the more famous
lecturers include James Hopwood
Jeans and Carl Sagan. The book
also boasts an introduction from
British astronaut Tim Peake,
who (virtually) participated in
Fong’s 2015 lecture while he
was on board the International
Space Station. Grab a copy of the
book to read about the whacky
live demonstrations done by the
lecturing scientists and for some
Christmas nostalgia.
●● 2016 Michael O’Mara £9.09hb
224pp
P hy sic s Wor ld  Januar y 2017