The 100 Most Influential Scientists of All Time (32 page)

Inevitably, Einstein's fame and the great success of his theories created a backlash. The rising Nazi movement found a convenient target in relativity, branding it “Jewish physics” and sponsoring conferences and book burnings to denounce Einstein and his theories.

In December 1932 Einstein decided to leave Germany forever (he would never go back). It became obvious to Einstein that his life was in danger. Einstein settled at the newly formed Institute for Advanced Study at Princeton, N.J., which soon became a mecca for physicists from around the world.

The 1930s were hard years for Einstein. His son Eduard was diagnosed with schizophrenia and suffered a mental breakdown in 1930. His beloved wife, Elsa Löwenthal, whom he married after having divorced Mileva in 1919, died in 1936. To his horror, during the late 1930s, physicists
began seriously to consider whether his equation
E = mc
²
might make an atomic bomb possible. Then, in 1938–39, a group of physicists showed that vast amounts of energy could be unleashed by the splitting of the uranium atom.

Einstein was granted permanent residency in the United States in 1935 and became an American citizen in 1940, although he chose to retain his Swiss citizenship. During the war, Einstein's colleagues were asked to journey to the desert town of Los Alamos, N.M., to develop the first atomic bomb for the Manhattan Project. Einstein, the man whose equation had set the whole effort into motion, was never asked to participate because the U.S. government feared Einstein's lifelong association with peace and socialist organizations. Instead, during the war Einstein was asked to help the U.S. Navy evaluate designs for future weapons systems. Einstein also helped the war effort by auctioning off priceless personal manuscripts. In particular, a handwritten copy of his 1905 paper on special relativity was sold for $6.5 million. It is now located in the Library of Congress.

Einstein was on vacation when he heard the news that an atomic bomb had been dropped on Japan. Almost immediately he was part of an international effort to try to bring the atomic bomb under control, forming the Emergency Committee of Atomic Scientists.

Although Einstein continued to pioneer many key developments in the theory of general relativity—such as wormholes, higher dimensions, the possibility of time travel, the existence of black holes, and the creation of the universe—he was increasingly isolated from the rest of the physics community. Because of the huge strides made by quantum theory in unraveling the secrets of atoms and
molecules, the majority of physicists were working on the quantum theory, not relativity. Einstein tried to find logical inconsistencies in the quantum theory, particularly its lack of a deterministic mechanism. Einstein would often say that “God does not play dice with the universe.”

In 1935 Einstein's most celebrated attack on the quantum theory led to the EPR (Einstein-Podolsky-Rosen) thought experiment. According to quantum theory, under certain circumstances two electrons separated by huge distances would have their properties linked, as if by an umbilical cord. Under these circumstances, if the properties of the first electron were measured, the state of the second electron would be known instantly—faster than the speed of light. This conclusion, Einstein claimed, clearly violated relativity. (Experiments conducted since then have confirmed that the quantum theory, rather than Einstein, was correct about the EPR experiment. In essence, what Einstein had actually shown was that quantum mechanics is nonlocal; i.e., random information can travel faster than light. This does not violate relativity, because the information is random and therefore useless.)

The other reason for Einstein's increasing detachment from his colleagues was his obsession, beginning in 1925, with discovering a unified field theory—an all-embracing theory that would unify the forces of the universe, and thereby the laws of physics, into one framework. In his later years he stopped opposing the quantum theory and tried to incorporate it, along with light and gravity, into a larger unified field theory.

In some sense, Einstein, instead of being a relic, may have been too far ahead of his time. The strong force, a major piece of any unified field theory, was still a total mystery in
Einstein's lifetime. Only in the 1970s and '80s did physicists begin to unravel the secret of the strong force with the quark model.

(b. Nov. 1, 1880, Berlin, Ger.—d. Nov. 1930, Greenland)

G
erman meteorologist and geophysicist Alfred Lothar Wegener formulated the first complete statement of the continental drift hypothesis. The son of an orphanage director, Wegener earned a Ph.D. degree in astronomy from the University of Berlin in 1905. He had meanwhile become interested in paleoclimatology, and in 1906–08 he took part in an expedition to Greenland to study polar air circulation. He made three more expeditions to Greenland, in 1912–13, 1929, and 1930. He taught meteorology at Marburg and Hamburg and was a professor of meteorology and geophysics at the University of Graz from 1924 to 1930. He died during his last expedition to Greenland in 1930.

Like certain other scientists before him, Wegener became impressed with the similarity in the coastlines of eastern South America and western Africa and speculated that those lands had once been joined together. In about 1910 he began toying with the idea that in the Late Paleozoic era (about 250 million years ago) all the present-day continents had formed a single large mass, or supercontinent, which had subsequently broken apart. Wegener called this ancient continent Pangaea. Other scientists had proposed such a continent but had explained the separation of the modern world's continents as having resulted from the subsidence, or sinking, of large portions of the supercontinent to form the Atlantic and Indian oceans. Wegener, by contrast, proposed that Pangaea's constituent portions had slowly moved thousands of miles apart over long periods of geologic time. His term for this movement was
die
Verschiebung der Kontinente
(“continental displacement”), which gave rise to the term continental drift.

Wegener first presented his theory in lectures in 1912 and published it in full in 1915 in his most important work,
Die Entstehung der Kontinente und Ozeane (The Origin of Continents and Oceans)
. He searched the scientific literature for geological and paleontological evidence that would buttress his theory, and he was able to point to many closely related fossil organisms and similar rock strata that occurred on widely separated continents, particularly those found in both the Americas and in Africa. Wegener's theory of continental drift won some adherents in the ensuing decade, but his postulations of the driving forces behind the continents' movement seemed implausible. By 1930 his theory had been rejected by most geologists, and it sank into obscurity for the next few decades, only to be resurrected as part of the theory of plate tectonics during the 1960s.

(b. Aug. 6, 1881, Lochfield Farm, Darvel, Ayrshire, Scot.—d. March 11, 1955, London, Eng.)

S
cottish bacteriologist Sir Alexander Fleming was best known for his discovery of penicillin. Fleming had a genius for technical ingenuity and original observation. His work on wound infection and lysozyme, an antibacterial enzyme found in tears and saliva, guaranteed him a place in the history of bacteriology. But it was his discovery of penicillin in 1928, which started the antibiotic revolution, that sealed his lasting reputation. Fleming was recognized for this achievement in 1945, when he received the Nobel Prize for Physiology or Medicine, along with Australian pathologist Howard Walter Florey and British biochemist Ernst Boris Chain, both of whom isolated and purified penicillin.

After working as a London shipping clerk, Fleming began his medical studies at St. Mary's Hospital Medical School in 1901. At first he planned to become a surgeon, but a temporary position in the laboratories of the Inoculation Department at St. Mary's Hospital persuaded him that his future lay in the new field of bacteriology.

In November 1921 Fleming discovered lysozyme, an enzyme present in body fluids such as saliva and tears that has a mild antiseptic effect. This was the first of his major discoveries. It came about when he had a cold and a drop of his nasal mucus fell onto a culture plate of bacteria. Realizing that his mucus might have an effect on bacterial growth, he mixed the mucus into the culture and a few weeks later saw signs of the bacteria having been dissolved. Fleming's study of lysozyme, which he considered his best work as a scientist, was a significant contribution to the understanding of how the body fights infection. Unfortunately, lysozyme had no effect on the most pathogenic bacteria.

On Sept. 3, 1928, Fleming noticed that a culture plate of
Staphylococcus aureus
he had been working on had become contaminated by a fungus. A mold, later identified as
Penicillium notatum
(also called
P. chrysogenum
), had inhibited the growth of the bacteria. He at first called the substance “mould juice” and then “penicillin,” after the mold that produced it. Fleming decided to investigate further, because he thought that he had found an enzyme more potent than lysozyme. In fact, it was not an enzyme but an antibiotic—one of the first to be discovered. By the time Fleming had established this, he was interested in penicillin for itself.

Very much the lone researcher with an eye for the unusual, Fleming had the freedom to pursue anything that interested him. While this approach was ideal for taking advantage of a chance observation, the therapeutic development of penicillin required multidisciplinary teamwork. Fleming, working with two young researchers, failed to stabilize and purify penicillin. However, he did point out that penicillin had clinical potential, both as a topical antiseptic and as an injectable antibiotic, if it could be isolated and purified.

Penicillin eventually came into use during World War II as the result of the work of a team of scientists led by Howard Florey at the University of Oxford. Though Florey, his coworker Ernst Chain, and Fleming shared the
1945 Nobel Prize, their relationship was clouded due to the issue of who should gain the most credit for penicillin. Fleming's role was emphasized by the press because of the romance of his chance discovery and his greater willingness to speak to journalists.

(b. Oct. 7, 1885, Copenhagen, Den.—d. Nov. 18, 1962, Copenhagen)

D
anish physicist Niels Bohr is generally regarded as one of the foremost physicists of the 20th century. He was the first to apply the quantum concept, which restricts the energy of a system to certain discrete values, to the problem of atomic and molecular structure. For this work he received the Nobel Prize for Physics in 1922. His manifold roles in the origins and development of quantum physics may be his most important contribution, but through his long career his involvements were substantially broader, both inside and outside the world of physics.

Bohr's first contribution to the emerging new idea of quantum physics started in 1912. Only the year before, Ernest Rutherford and his collaborators at the University of Manchester had established experimentally that the atom consists of a heavy positively charged nucleus with substantially lighter negatively charged electrons circling around it at considerable distance. According to classical physics, such a system would be unstable, and Bohr felt compelled to postulate, in a substantive trilogy of articles published in
The Philosophical Magazine
in 1913, that electrons could only occupy particular orbits determined by the quantum of action and that electromagnetic radiation from an atom occurred only when an electron jumped to a lower-energy
orbit. Although radical and unacceptable to most physicists at the time, the Bohr atomic model was able to account for an ever-increasing number of experimental data, famously starting with the spectral line series emitted by hydrogen.

Already in his 1913 trilogy, Bohr had sought to apply his theory to the understanding of the periodic table of elements. At the University of Copenhagen, where Bohr had established an Institute for Theoretical Physics, he improved upon this aspect of his work, developing an elaborate scheme building up the periodic table by adding electrons one after another to the atom according to his atomic model. When Bohr was awarded the Nobel Prize for his work in 1922, the Hungarian physical chemist Georg Hevesy, together with the physicist Dirk Coster from Holland, were working at Bohr's institute to establish experimentally that the as-yet-undiscovered atomic element 72 would behave as predicted by Bohr's theory. They succeeded in 1923, thus proving both the strength of Bohr's theory and the truth in practice of Bohr's words at the institute's inauguration about the important role of experiment. The element was named hafnium (Latin for Copenhagen).