BOOK REVIEW
Events of 1905
Peter Galison
Secrets of the Old One: Einstein, 1905. Jeremy Bernstein.
vii + 200 pp. Copernicus Books, 2006. $25.
It's About Time: Understanding Einstein's Relativity. N.
David Mermin. xvi + 192 pp. Princeton University Press, 2005. $35.
Every generation rewrites Shakespeare, finding new meanings in his
tragic heroes, his plays within plays, his depictions of love and
betrayal. So it has been—and will remain—for Einstein,
as physicists continue to explore the depths of his work in quantum
theory and general relativity. Einstein's reasoning is very much
with us, from the laboratory production of Bose-Einstein
condensates, through the observatory's glimpses of gravitational
lensing, to the abstractions of string theory and the outer reaches
of cosmology. For historians and philosophers of science, Einstein
remains a figure of endless fascination—what he thought about
the real and the objective in science, how he sorted out the
shifting politics of his very long day: pacifism, militancy against
Nazism, the atomic bomb, McCarthyism. No doubt our current concerns
weigh on us as we try over and over to discern how this
extraordinary figure fit into the changing culture that surrounded
his life, which spanned the years from 1879 to 1955. A hundred years
after his staggering series of papers in 1905, Einstein's works also
remain points of departure for many architects, artists and musicians.
A wide public with various levels of technical background would like
to know what it was that Einstein did in his physics. Over the
course of 2005, we had dozens of books about Einstein and
relativity. Just out are new ones by two of our most engaging
physicist-writers, Jeremy Bernstein and N. David Mermin. Bound by a
common interest in relativity (in the works reviewed here, mainly
special relativity), they have aimed their books at different
audiences. Both are excellent—for very different reasons.
Before continuing, I should confess that I think most
popularizations of science actually do more harm than good. Why?
Because in my view the single most important feature of scientific
work is not this or that specific result. Instead, what physics in
particular does so beautifully—and what science more generally
accomplishes—is the linking of diverse phenomena, the binding
together of a myriad of predictions and explanations.
What nearly all popularizations do is systematically undermine the
progressive reasoning that links principles, conventions,
experiments and laws. Bad science writing splinters the most
interesting feature of science, its long run of connected
argumentation, into isolated metaphors that last just long enough to
evoke a particular result. Black holes are said to be like huge
funnels; quantum electron orbits, to resemble diffuse clouds. This
problem of shattered connectedness is bad enough. Adding to the
difficulty is that many science writers (or scientists writing for
the broad public) feel caught: Either insert a new metaphor or two
per sentence, or introduce a mathematical apparatus that loses the
vast majority of the audience from the first page.
Is there any passage between these twin dangers? There are at least
two, but both are formidably difficult to navigate. One way to
proceed is to find a felicitous metaphor and stick with
it—using the conceit to display the interconnectedness of the
phenomena that at first glance appear scattered within a scientific
domain. The best popular physics book written in the last half
century, in my view, is of this kind—Richard Feynman's
QED: The Strange Theory of Light and Matter, which has
an absolute minimum of mathematics and a single guiding image.
Feynman is nonetheless able to lead the reader through the
connections between reflection, refraction and a dozen more
complex physical phenomena. On my short list of other really good
popular science books that actually let you follow reasoning from
one sector of the world to another are Steven Weinberg's 1977 book
The First Three Minutes and Brian Greene's much more
recent The Elegant Universe (1999). Such ventures
(and the list beyond these is not very long) give up the
disconnected-metaphor approach and so require real concentration to
read. It is not accidental but instead exactly the point of a good
systematic popularization of physics that one cannot just
dip in and read sections in an arbitrary order.
A second kind of wide-angle science writing that I also quite
like—when it too avoids the metaphor-a-minute
approach—embeds the science in a larger picture. Richard
Rhodes does this nicely in his remarkable history of the Manhattan
Project. James Gleick does it beautifully in his biography of
Feynman and in his study of chaos. In other words, the effort in
this second kind of writing is to situate specific, illustrative
pieces of the science rather than to focus on the interconnections
worked out in detail. Let's call this an embedded rather
than a systematic approach.
Jeremy Bernstein shines at this strategy of embedment, particularly
in his biographical sketches—the striking series of portraits
of physicists he has given us over the years in The New
Yorker, in which he humanizes figures like Hans Bethe while
keeping their ideas lucid and central. My favorite work of
Bernstein's may be less widely known: his hard-hitting analysis of
the infamous tapes of the captured German nuclear scientists at Farm
Hall. Slicing through their vacuous claims to have understood the
physics of nuclear weapons from the get-go, Bernstein dissects the
conversations, skewering apologetics and obfuscations. For example,
he shows that the captured scientists often conflated fast and slow
fission neutrons and that anyone who confuses the two has not
understood the sine qua non of explosive chain reactions.
When wearing his research hat, Cornell's David Mermin is a
theoretical physicist, but his ferocious drive to find the simplest
explanations of physical concepts has echoed far beyond work in his
research specialty. For example, it was Mermin's extraordinarily
simple explanation of Bell's inequality that taught several
generations of physicists and philosophers of science the range and
depth of what John Bell had done. In particular, Mermin made the
depth of Bell's contribution transparent: The results of quantum
observations that ground the inequality could be grasped in their
entirety without the details of the theory of quantum
mechanics; the correlations between distant effects simply make it
necessary that any theory, canonical quantum mechanics or
any putative alternative, would have to be nonlocal.
Bernstein's and Mermin's styles differ too. If you have read even a
single one of Bernstein's sketches, you will recognize his style
immediately: a mixture of conceptual presentation, telling anecdote
and personal reminiscence. In his new book, Secrets of the Old
One, he uses this approach to good effect. Einstein himself
stands just outside—or, more precisely,
before—Bernstein's story. But stories, including some I've
never heard, appear right and left, many based on Bernstein's
discussions with leading physicists who knew Einstein well
(especially the physicist-philosopher Philipp Frank), and others
based on Einstein's letters and other writings.
Secrets of the Old One truly is a book aimed at a wide
audience. It should be no trouble to read for anyone who enjoys
sophisticated, often witty writing about science. There are a few
moments when more technical comments will fly by—a beautiful
side remark about the relative dimensions of the magnetic and
electric fields is pregnant with meaning. When a point is central,
Bernstein slows to explain it with enormous clarity: the random
walk, the Doppler shift, ether experiments, the twin paradox. Then,
around these scientific explorations, Bernstein wanders in the best
essay style through relevant stories of Viennese cafes and American
basement laboratories. (Mermin's text—more on this in a
moment—is a step up the ladder of demands that can be made on
an audience.)
Bernstein aims to cover the basics of Einstein's theory of special
relativity, Brownian motion and the quantum of light, and he treats
each neatly. Beginning with relativity has advantages for Bernstein:
In a way, at least in the retelling, it requires the least technical
background to understand—and Bernstein uses this physical
simplicity to advantage by beginning with explanations even of the
Pythagorean Theorem, which Einstein so admired as a child. Bernstein
discusses the Lorentz transformations, making them plausible in
their Einsteinian form, and introduces to good effect the space-time
diagrams of the great mathematician and mathematical physicist
Hermann Minkowski. Bernstein has a nice and simple discussion of how
Einstein used the random walk to treat the erratic movements of
colloidal particles as evidence for the physical reality of atoms.
And he cleanly introduces Einstein's notions about the quantum of
light, the only one of his ideas that Einstein himself called "revolutionary."
Within Bernstein's reasonable and self-imposed constraints of target
audience, emphasis and level, I wished for one last chapter: a
discussion of connections among Einstein's great works of 1905. The
papers have an intense stylistic unity, a feature Gerald Holton has
long emphasized. They generally begin with an asymmetry that deeply
troubled Einstein (and practically no one else). For example, it
bothered him tremendously that Maxwell's equations ("as they
are usually understood") gave two different explanations for
the generation of a current in a coil as it approached a
magnet—one explanation if the magnet was "at rest"
and the coil in motion; another explanation if the reverse were the
case. Einstein's papers ended with a resolution of the asymmetry
and, inevitably, a suggestion of very concrete experimental
predictions (such as the photoelectric effect, the motion of
electrons in electromagnetic fields or a quantitative account of the
wanderings of suspended Brownian particles).
But my imaginary last chapter could go even further. Einstein has
long been seen as an heir to Ernst Mach—to Mach's razor-sharp
critique of "metaphysical" notions such as "absolute
space" and "absolute time." Less philosophically well
known was Einstein's fascination with the program of Ludwig
Boltzmann's development of statistical mechanics. It was toward
Boltzmann's intellectual world of the statistical study of atoms and
molecules that Einstein first turned his theoretical
research—in 1902, three years before the "miracle
year." My imaginary last chapter could explore how Einstein's
fascination with statistical fluctuations joined the light-quantum
paper to the Brownian-motion paper; and it could explain how the
quantum of light helped carve out a thinkable way in which light
could move without an underlying ether. On this reading, Einstein's
light-quantum paper is the leading vertex of an arrow, joined on one
side via fluctuations to Brownian motion and on the other to an
etherless electrodynamics of moving bodies. But maybe I'm gilding
the lily—Bernstein has gone far in brief, accessible style.
That is more than enough.
Now let's move on to Mermin's It's About Time. From the
title forward, Mermin's exposition heads for only a portion of
Einstein's 1905 year. As his title suggests, Mermin's argument is
that Einstein's contribution to special relativity revolves around
his reformation of time. Light quanta and Brownian motion do not
enter into his discussion—nor does the long experimental
history of ether-drift experiments or the complex theoretical
inquiry by Hendrik Lorentz, Henri Poincaré and others into
the physics of the electron.
There are two things remarkable about Mermin's book. First, it
consistently switches back and forth between different frames of
reference. This way the reader really understands how extraordinary
the theory is—that different points of view can capture one
and the same phenomenon while giving it different descriptions. Now,
the uninitiated might think this was an obvious thing to do. After
all, the theory of relativity, as its name advertises, is precisely
designed to give an account of the world that is not
dependent on a particular choice of inertial reference frame. But in
fact I can't think of another account (other than one remarkable
place where Einstein himself does it) where the view from multiple
reference-frame perspectives is so consistently kept front and
center. Second, the book starts and finishes with
collisions—looked at from different frames of reference. As a
start, this very clever stratagem conveys the fecundity of
switching reference frames. As a finish, it leaves the reader with a
clear understanding of the most famous equation in all of modern
science, E = mc
^{2}.
Back in 1905—in his first relativity article—Einstein
used the more-than-metaphor of coordinated clocks along train
tracks. It served him well for a lifetime. Mermin too uses trains,
clocks and light signals to enormously good effect, constantly
switching between points of view, explaining real physics clearly.
My only regret is that I was never lucky enough to watch Mermin do
this at the board. I imagine some of the more complex diagrams gain
in force by watching their elements laid down in sequence. Then
there's a second approach—introduced by Minkowski in his
eponymous diagrams. About midway through the book, having conveyed
crucial ideas, Mermin introduces the idea of space-time geometry:
how the x and t axes look in different frames of
reference, and how this new geometry alters the way we define
simultaneity, length and much else. Indeed, Mermin pursues spacetime
with diligence all the way through a myriad of results and resolved "paradoxes."
It's About Time is a book that should join the very best
systematic popular expositions of science written in the last 50
years. Secrets of the Old One is one of the best
scientist-sketches and adds to Bernstein's long list of such
successes. Hats off—Bernstein and Mermin. They have written
excellent popular books, in very different styles, ones that stand
out on a subject, Albert Einstein, about whom there is no shortage
of excellent writing.