EINSTEIN 1905: THE STANDARD

OF GREATNESS

By John S. Rigden

Harvard, $21.95, 192 pages

EINSTEIN’S COSMOS: HOW ALBERT EINSTEIN’S VISION TRANSFORMED OUR UNDERSTANDING OF SPACE AND TIME

By Michio Kaku

Atlas, $22.95, 251 pages

REVIEWED BY JEFFREY MARSH

Fifty years after his death, Albert Einstein is still probably the only scientist whose visage is instantly recognized by the general public. Biographies and new exegeses of his work continue to be published every year, but 2005 has produced a bumper crop because it is the centennial of the year of his greatest achievements.

In “Einstein 1905,” John Rigden, a Washington University physics professor and historian of science, focuses on five papers that Einstein wrote that year, when he was an unknown 26-year-old clerk in the Swiss patent office. He explains why those papers “make 1905 one of the most memorable years in the history of science and make the six months from March 17 to September 27 the most productive six months any scientist ever enjoyed … . In 1905, the outpouring of one man’s genius changed forever our understanding of nature.”

Setting the stage for his discussion of the five landmark papers, Mr. Rigden mentions a famous book by the French mathematical physicist Henri Poincare, “La Science et l’Hypothese” which cited three fundamental problems in physics that nobody had been able to solve. One was an explanation of the photoelectric effect — the ejection of electrons from a metal surface illuminated by ultraviolet light. The second was Brownian motion — the zig-zag motion of pollen (or other microscopic particles) suspended in a liquid, a phenomenon first observed by the Scottish botanist Robert Brown in 1827. The third problem was the failure of experiments to detect any evidence of the earth’s motion through the ether, the mysterious substance that was believed to be the medium whose vibrations were manifested as light and other electromagnetic waves. Einstein’s papers conclusively answered all three problems.

The first paper, written in March, the only one of the five that Einstein himself called “revolutionary,” explained the photoelectric effect by exploring the idea that light consists of particles. This idea starkly contradicted one of the greatest triumphs of 19th century physics, the wave theory of light, which was necessary to explain such optical phenomena as diffraction and interference.

However, one phenomenon the wave theory could not explain, the spectrum of light emitted by a so-called “black body,” had been explained by Max Planck in 1900 by treating light as if it were emitted and absorbed only in discrete packets (or “quanta”), but Planck was at pains to emphasize that this was only a calculational device. Einstein used the quantum idea to explain aspects of the photoelectric effect that contradicted the wave theory, and made several predictions that were later verified experimentally.

Mr. Rigden shows how radical Einstein’s step was by quoting remarks made up to 20 years later by leading physicists including not only Planck and Niels Bohr, the man who used the quantum theory to explain the spectrum of the hydrogen atom, but even Robert Millikan, who confirmed Einstein’s predictions experimentally, who all said that Einstein had gone too far. Firmly confident in his understanding of the laws of nature, though, Einstein was unshaken.

The second paper was Einstein’s doctoral dissertation. It used the atomic theory, which was generally but not yet universally accepted, to calculate the size of molecules of a dissolved substance from experimentally measured properties of the solution.

Einstein had previously had several dissertations on different subjects rejected, and had thought of abandoning his academic ambitions. This successful dissertation, Mr. Rigden tells us, was unusual for Einstein in its detailed calculations and the practical applications it had, which led to its still being frequently cited in papers written by other scientists over half a century later. The third paper used the atomic theory to explain Brownian motion as the result of constant random bombardment of the suspended pollen particles by sub-microscopic molecules of the surrounding liquid. Using thermodynamic and statistical reasoning, he calculated how far the particles should move on average in a minute, in terms of the size of the particles, the liquid’s temperature, and several constants of nature. After experiments confirmed his formula, virtually every scientist had been convinced that atoms really exist.

The fourth paper introduced the special theory of relativity. In the words of one scholar quoted by Mr. Rigden, this paper “is unparalleled in the history of science in its depth, breadth, and sheer intellectual virtuosity … in thirty pages … it is … as complete as Newton’s book-length Principia.” Using two principles — that the laws of physics are the same to observers moving at a constant velocity with respect to each other, and the surprising fact that the speed of light appears the same to all such observers — he showed that time and space were not independent of each other, a radical insight that produced such surprising conclusions as the fact that identical clocks moving with respect to each other run at different rates. In his fifth paper, he used his relativity theory to calculate the energy of moving objects, and derived the result E = mc2, the most famous equation of physics.

Mr. Rigden’s book provides a clearly written account of these papers. It places each one in the context of the physics of the time, and explains the unique contribution Einstein made by his unerring vision for the key principles involved and his convincing solutions to the problems he tackled. In a brief epilogue, he summarized Einstein’s achievements in the remaining 50 years of his career, which included his development of the general theory of relativity, completed in 1916, and his further development of the quantum theory. He points out several examples of how far many of Einstein’s insights were far ahead of their time. These include his 1917 paper that led to the development of the laser in the early 1960s and his 1925 prediction of a new state of matter, the Bose-Einstein condensate, first produced in 1995.

In “Einstein’s Cosmos,” Michio Kaku, a professor of theoretical physics at the City University of New York, surveys Einstein’s life, enlivening the basic biographical material with many anecdotes and samples of the witticisms which helped to humanize the popular image of the genius. He tells us, for example, about the execrable quality of the cigars the young Einstein smoked. When he gave one to fellow physicist Max von Laue, von Laue discreetly tossed it into the river as he and Einstein crossed a bridge. And he tells us the reaction of Einstein’s second wife, Elsa, when astronomers at Mount Wilson observatory told the touring Einsteins that their 100-inch telescope could determine the structure of the universe, Elsa replied, “My husband does that on the back of an old envelope.”

The book’s basic aim, though, is to provide a very accessible account of Einstein’s achievements: the special and general theories of relativity, his contributions to quantum mechanics, and his 40-year search for a unified field theory that took Einstein out of the mainstream of physics. This quest, together with his continued belief that quantum mechanics, with its assertion that nature was irreducibly statistical in nature, meant that for the second half of his long career he was regarded by many as a quixotic figure, but Mr. Kaku tells us that it is only now that physics is beginning to catch up with many of Einstein’s ideas. In his words, “crumbs that tumbled off Einstein’s plate are now winning Nobel Prizes for other scientists.”

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Jeffrey Marsh has written widely on scientific topics and public issues ranging from nuclear strategy to social policy.

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