©
2000 American Institute of Physics, S-0031-9228-0012-240-9
D
ECEMBER
2000 P
HYSICS
T
ODAY
67
B
OOKS
Martin Rees’s Compelling,
Unified View of the Universe
Just Six Numbers:
The Deep Forces that
Shape the Universe
Ī
Martin Rees
Basic Books (Perseus Group),
New York, 2000. 173 pp. $22.00 hc
ISBN 0-465-03672-4
Reviewed by Edward W. Kolb
In the world of astrophysics, Martin
Rees is the summarizer of choice for
major international meetings. His
clear, reasoned concluding remarks
often make the most complicated and
confusing astrophysical problems seem
tractable. Rees brings the same clari-
ty of exposition to Just Six Numbers,
his most recent book. Few people see
the big picture as Rees does, and he
paints a big picture indeed.
Just Six Numbers offers much more
than just six numbers. Rees uses the
seeming “fine tuning” of six numbers,
ranging from the cosmological con-
stant to the ratio of the electric force
and gravitational force between two
electrons, as threads that weave a tale
of the shaping of our universe by a few
fundamental forces and concepts. In
explaining how our existence depends
on six numbers having values in a
surprisingly narrow range of possibil-
ities, Rees connects the nature of fun-
damental forces with the development
of the universe.
Rees’s breadth of vision and his
ability to synthesize apparently dis-
parate facts into a compelling whole
are evident throughout the book.
Among the subjects Rees touches on
are stellar nucleosynthesis, the devel-
opment of intelligence in our bio-
sphere, black holes, gravitational
entropy, the arrow of time, and the
dimensionality of space.
Many of the topics in the book are
at the leading edge of research. In a
field as active and vital as modern cos-
mology, some of the subjects in the
book are likely to evolve in funda-
mental ways in the next few years.
Where appropriate, Rees is clear
about how the picture may change. As
he notes, we have only outlined our
view of the universe; our view will
evolve as the details are developed.
Although the details may change,
many of the fundamental ideas Rees
develops undoubtedly will survive.
Throughout the book, Rees empha-
sizes that complex structures may
emerge from a simple set of laws and
initial conditions. The interplay of
simplicity and complexity is sure to
remain part of the way we understand
the universe.
Thought-provoking questions, such
as the existence of other “universes”
beyond our cosmic horizon, are dis-
cussed with confidence and flair.
Rees’s ability to present his own view-
point while still giving a fair hearing
to other viewpoints is manifest here.
For instance, the concept of “multi-
verses,” the idea that the observable
region of the universe is just one
member of a possibly infinite ensem-
ble in which even the laws of physics
may vary, often elicits a discussion of
the anthropic principle. Although he
never explicitly mentions the contro-
versial anthropic principle, Rees pres-
ents a well-balanced discussion of the
concept.
The book is accessible to a wide
audience. Although it is targeted
toward the nonspecialist, Rees never
“talks down” to his audience. Even
specialists in the field can benefit
from the book. Although it is not a
textbook, it would be ideal supple-
mentary reading for an undergradu-
ate course in “cosmology for poets.”
Concepts of Mass in
Contemporary Physics
and Philosophy
Ī
Max Jammer
Princeton U. P., Princeton, N.J.,
2000. 180 pp. $39.50 hc
ISBN 0-691-01017-X
Investigating the conceptual founda-
tions of contemporary physics is an
activity to which both philosophers
and physicists can contribute. Such
an activity is important, not only to
philosophers interested in such eso-
teric matters, but also to practicing
physicists. In particular, the concep-
tual foundations of space, time, and,
indeed, mass are important issues in
ongoing research into quantum theo-
ries of gravity. In such cutting-edge
fields, the overlap between physics and
philosophy is most evident. Max Jam-
mer’s Concepts of Mass in Contempo-
rary Physics and Philosophy contri-
butes to the widening of that overlap.
Jammer treated space and time in
his Concepts of Space (Harvard, 1957;
Dover, 1993). Now he focuses on mass.
“Next to space and time, mass is the
most fundamental notion in physics
. . .” Jammer declares in the preface of
his new book.
In one sense, the book may be
viewed as an up-to-date philosophical
and thematic supplement to his pre-
vious historical survey, Concepts of
Mass in Classical and Modern Physics
(Harper & Row, 1964; Dover, 1997).
The new book emphasizes develop-
ments since 1960, and thus provides a
needed service in assembling current
research on the subject. In a larger
sense, however, the book stands on its
own, combining historical elements of
Concepts of Mass in Classical and
Modern Physics with a thematic analy-
sis to produce a coherent whole.
The book is unique in bringing
together a number of diverse topics
concerning the concept of mass in
modern physics. These topics include
inertial mass, relativistic mass, the
mass–energy relation, gravitational
mass, and the nature and origin of
mass. Jammer begins by considering
operational definitions of inertial
mass and the related question of
whether inertial mass should be
viewed as a theoretical or an observa-
tional concept. His discussion of rela-
tivistic mass centers on the distinc-
tions between relativistic mass, rest
mass, and classical (Newtonian)
mass, and the debate over their rela-
tionships. He then considers deriva-
tions of the mass–energy relation and
its interpretations. The background
for much of this material is presented
in more detail in his Concepts of Mass
E
DWARD
W. (R
OCKY
) K
OLB
is head of
the theoretical astrophysics group at Fermi-
lab and a professor of astronomy and astro-
physics at the University of Chicago. He
wrote Blind Watchers of the Sky (Perseus,
1997), a book on the historical development
of cosmology, and, with Michael Turner, he
wrote The Early Universe (Perseus, 1993),
a graduate-level text.