Galison, Peter. Einstein’s Clocks, Poincare’s Maps:
Empires in Time.
Contrary to popular belief in the United States, Einstein
did not operate in a scientific vacuum, and his time as a patent “clerk” in
Bern was not a dead-end that was a complete waste of his talents and abilities.
At least that is the opinion of Peter Galison’s Einstein’s Clocks,
Poincare’s Maps. Focusing on the
time period between 1890 and 1910, Galison examines the role of developments in
coordinated time theory, the impact of France’s Ecole Polytechnique on
research methods, and the training Einstein received in the patent office in
the development of his theory of special relativity. At the same time, Galison places both the
adoption of standard measurements for time, space and geography in the context
of late 19th century international politics and traditions of
European scientific thought.
Although it is disguised in biographical studies of Henry
Poincare and Albert Einstein, Galison’s real target seems to be the development
of the theory of special relativity, which he ultimately attributes to
Einstein. Although he credits Einstein
with the discovery, Galison repeatedly states that the theory was the outgrowth
of physics research involving electromagnetic fields and time coordination efforts
of cities, railroads, and nations. In
this respect, the biographical treatment of Einstein and Poincare is merely a
tool that provides understanding of the main topic. This is not to imply that Einstein and
Poincare are an afterthought, rather they are the main characters in a story
that involves them, but is not about them.
The reason Galison takes this tack is that it provides the
most accessible method for discussing the development of the theory of
relativity in the greater context of scientific inquiry and the pressures of
international competition over weights and measures, universal time standards,
and the location of the prime meridian.
However, at times, Galison focuses so much on these issues that it is
easy to lose sight of Einstein, Poincare, and relativity. It can be argued that Galison provides so
much background and historical context that it overwhelms the reader with
excessive amounts of detail.
Galison chooses Einstein as one of his two speakers on the
topic of coordinated time and relativity simply because it was Einstein’s 1905
paper “On the Electrodynamics of Moving Bodies” that signaled the change from
an emphasis on classical mechanics in the study of physics to a new
theoretical-practical model. Poincare,
on the other hand, is chosen as the foremost practitioner of the practical
mechanical philosophy, and a product of the foremost school of engineering in
Europe. (14) The contrast between the scientific philosophies of the two men
allows Galison to illustrate the profound significance of the change
represented by Einstein’s theory of special relativity, and is easiest to
illustrate biographically.
Before leaping into the intricacies of international
relations, the training of engineers, or the workings of Swiss patent offices,
Galison takes the time to explain Einstein’s theory of special relativity and
how it was different from prevailing thought on how electromagnetic fields
work. In 1905, when Einstein introduced
the theory of special relativity, most physicists believed that light waves
moved through some unknown substance as waves in the ocean or sound waves
through the air. Unable to quantify the
unknown media light moved through, 19th century physicists dubbed it
ether, and hoped that eventually they would be able to identify it empirically.
The problem with using ether to explain physical phenomena went beyond merely
being unable to quantify it or study its effects; it required that identical
events require multiple explanations depending on minimal changes in the
experiment. The example Einstein used to
introduce his theory was that under the old classical mechanics methodology
using ether, the electricity generated in a coil when near a magnet was
explained differently depending on whether the coil moved toward the magnet, or
the magnet moved closer to the coil.
Einstein believed that there should be a single explanation for the
electrical field generated regardless of whether the coil or magnet moved, and
he blamed the requirement for separate explanations on physicist’s insistence
that ether existed.
Einstein’s solution was to dispose of the ether
entirely. He did this for two
reasons. First, he believed that there
should be a single explanation for what he saw as a single problem, and second,
because the existence of ether could not be demonstrated empirically. Without any proof of ether’s existence,
Einstein saw no reason to jump through scientifically questionable hoops to
account for it. This led him to the
postulate that there was “no way to tell which unaccelerated reference frame
was at rest”, which meant that physical objects that were not accelerating
behaved independently of the reference frame they occupied. This new principle
of relativity is interesting not only in the impact it had on 20th
century scientific understanding, but that Galileo had noted that when at sea
in smooth waters, experiments, such as ball drops, behaved in the same manner
they did on land. As Galison puts it, “
There was simply was no way to use any part of mechanics to tell whether a room
was ‘really’ at rest or ‘really’ moving.” The general idea behind the theory of
relativity was understood for at least three hundred years before Einstein
published his paper.
Relativity enters into Galison’s broader topic due to
Einstein’s extension of it to the speed of light. Einstein contended that the speed of light
was always exactly the same, regardless of the speed of the source relative to
the observer. What this meant was that
rather than light moving at 300,000 kilometers per second + the speed of the
source, light always moved at exactly 300,000 kilometers per second. This impacted physicists’ conception of
simultaneity, which in turn affected ideas of how the coordination of
disparately located clocks should be done.
Einstein insisted that the concept of simultaneity be defined
procedurally, saying that just because he received to signals at the same
moment did not mean they were sent at the same moment if the signals traveled
different distances. Einstein demonstrated
the solution using a clock coordination scenario, which was particularly apt
given the importance of clock coordination for the running of trains and the
prestige of governments. Einstein’s procedure for clock coordination said that
users should have, “one observer at the origin A send a light signal when his
clock says 12:00 to B at a distance d from A; the light signal reflects
off B and returns to A. Einstein has B
set her clock to noon plus half the round trip time.” If the speed of light
remained the same in any direction, then it could be used to determine trip
time so that clocks could be easily coordinated over large distances.
In isolation, Einstein’s theory, even with its deliberate
inclusion of a procedure for time coordination, could have been significant
only to scientists. However, Galison
points out that it had an almost immediate impact on time coordination, which
stretched along rail lines and across oceans, due to the research of James
Clerk Maxwell. A Cambridge physicist,
Maxwell developed a theory that “showed light to be nothing more than electric
waves.” This allowed Einstein’s theory of relativity to have an immediate
impact as railroads and telegraph stations used electricity to coordinate their
clocks.
The immediate applicability of the theory of relativity to
clock coordination highlights two issues of international concern at the turn
of the 20th century, which Galison concentrates heavily on. The first issue was the development of
standard units of measure for both weight and distance. After diplomatic maneuvering the honor of
creating, distributing, and storing the standard meter and kilogram fell to
France, which painstakingly created the copies to be held by other nations and
kept the originals and “witnesses” in carefully protected vaults. The second issue was of standardized,
universal time, and it was much more difficult to resolve.
Galison discusses in detail the task of laying undersea
telegraph cables, which were used both for communication, but also for mapping
and time coordination. While the use of
the cables for time coordination is an immediately obvious use of the cables
given Einstein and Maxwell’s work, their use for mapping is not so intuitive. Both mapping and time coordination were pre-requisites
for the adoption of universal time standards.
Mapping comes into the equation because of the difficulty of
mapping accurate longitude lines.
Longitudinal calculation requires extremely precise measurement of time,
a task that was near impossible with the chronometers available for rail and
shipboard use. Laying undersea telegraph
cables, which could be used for time coordination, also allowed cartographers
to determine extremely precise calculation of the longitude of the receiving
stations. While this solved the problem
of determining exactly where any geographic location was in relation to
another, it did not solve the issue of where to start counting longitude from,
which was a political issue.
For every day people, the solution to the international
political dispute over where the prime meridian should be located is what makes
Einstein’s theory of special relativity relevant. This dispute, which focused on whether the
prime meridian, or longitude of zero degrees, should be at Greenwich, England,
or Paris, France, was ultimately decide by the United States’ adoption of
standardized time zones based on Greenwich as the zero line and England’s
dominant role in overseas shipping. Of
course, Galison does not immediately leap to this conclusion, and continues to
discuss the lives and training of both Poincare and Einstein after discussing
it, but this is the essence of Einstein’s Clocks, Poincare’s Maps. As he says himself, his work is the story of
the development time coordination, and the adoption of a universal time
standard represents the ultimate in time coordination, which is ultimately the
legacy of Henri Poincare and Albert Einstein.
