The 100 Most Influential Scientists of All Time (34 page)

Soon after discovering the existence of these external galaxies, Hubble undertook the task of classifying them according to their shapes (1926) and exploring their stellar contents and brightness patterns. In studying the galaxies, Hubble made his second remarkable discovery—namely, that these galaxies are apparently receding from the Milky Way and that the further away they are, the faster they are receding (1927). The implications of this discovery were immense. The universe, long considered static, was expanding; and, even more remarkably, as Hubble discovered in 1929, the universe was expanding in such a way that the ratio of the speed of the galaxies to their distance is a constant now called Hubble's constant.

Although Hubble was correct that the universe was expanding, his calculation of the value of the constant was incorrect, implying that the Milky Way system was larger than all other galaxies and that the entire universe was younger than the surmised age of the Earth. Subsequent astronomers, however, revised Hubble's result and rescued his theory, creating a picture of a cosmos that has been expanding at a constant rate for 10 billion to 20 billion years.

For his achievements in astronomy, Hubble received many honours and awards. Among his publications were
Red Shifts in the Spectra of Nebulae
(1934) and
The Hubble Atlas of Galaxies
(published posthumously, 1961, and edited by Allan Sandage). Hubble remained an active observer of galaxies until his death.

(b. Feb. 28, 1901, Portland, Ore., U.S.—d. Aug. 19, 1994, Big Sur, Calif.)

A
merican theoretical physical chemist Linus Pauling became the only person to have won two unshared Nobel Prizes. His first prize (1954) was awarded for research into the nature of the chemical bond and its use in elucidating molecular structure; the second (1962) recognized his efforts to ban the testing of nuclear weapons.

In 1927 Pauling began a long career of teaching and research at the California Institute of Technology (Caltech). Analyzing chemical structure became the central theme of his scientific work. By using the technique of X-ray diffraction, he determined the three-dimensional arrangement of atoms in several important silicate and sulfide minerals. In 1930, during a trip to Germany, Pauling learned about electron diffraction, and upon his return to California he used this technique of scattering electrons from the nuclei of molecules to determine the structures of some important substances. This structural knowledge assisted him in developing an electronegativity scale in which he assigned a number representing a particular atom's power of attracting electrons in a covalent bond.

To complement the experimental tool that X-ray analysis provided for exploring molecular structure, Pauling turned to quantum mechanics as a theoretical tool. He used quantum mechanics to determine the equivalent
strength in each of the four bonds surrounding the carbon atom. He developed a valence bond theory in which he proposed that a molecule could be described by an intermediate structure that was a resonance combination (or hybrid) of other structures. His book
The Nature of the Chemical Bond, and the Structure of Molecules and Crystals
(1939) provided a unified summary of his vision of structural chemistry.

By the mid-1930s Pauling was performing successful magnetic studies on the protein hemoglobin. He developed further interests in protein and, together with biochemist Alfred Mirsky, Pauling published a paper in 1936 on general protein structure. In this work the authors explained that protein molecules naturally coiled into specific configurations but became “denatured” (uncoiled) and assumed some random form once certain weak bonds were broken.

On one of his trips to visit Mirsky in New York, Pauling met Karl Landsteiner, the discoverer of blood types, who became his guide into the field of immunochemistry. Pauling was fascinated by the specificity of antibody-antigen reactions, and he later developed a theory that accounted for this specificity through a unique folding of the antibody's polypeptide chain. World War II interrupted this theoretical work, and Pauling's focus shifted to more practical problems, including the preparation of an artificial substitute for blood serum useful to wounded soldiers and an oxygen detector useful in submarines and airplanes.

After the war Pauling became interested in the study of sickle-cell anemia. He perceived that the sickling of cells noted in this disease might be caused by a genetic mutation in the globin portion of the blood cell's hemoglobin. In 1949 he and his coworkers published a paper identifying the particular defect in hemoglobin's structure that was responsible for sickle-cell anemia, which
thereby made this disorder the first “molecular disease” to be discovered.

While serving as a visiting professor at the University of Oxford in 1948, Pauling returned to a problem that had intrigued him in the late 1930s—the three-dimensional structure of proteins. By folding a paper on which he had drawn a chain of linked amino acids, he discovered a cylindrical coil-like configuration, later called the alpha helix. The most significant aspect of Pauling's structure was its determination of the number of amino acids per turn of the helix. During this same period he became interested in deoxyribonucleic acid (DNA), and early in 1953 he and protein crystallographer Robert Corey published their version of DNA's structure, three strands twisted around each other in ropelike fashion. Shortly thereafter James Watson and Francis Crick published DNA's correct structure, a double helix. Pauling was awarded the 1954 Nobel Prize for Chemistry “for his research into the nature of the chemical bond and its application to the elucidation of the structure of complex substances.”

During the 1950s Pauling and his wife became well known to the public through their crusade to stop the atmospheric testing of nuclear weapons. Pauling's sentiments were also promulgated through his book
No More War!
(1958), a passionate analysis of the implications of nuclear war for humanity. In 1960 he was called upon to defend his actions regarding a test ban before a congressional subcommittee. His work on behalf of world peace was recognized with the 1962 Nobel Prize for Peace awarded on Oct. 10, 1963, the date that the Nuclear Test Ban Treaty went into effect. Pauling also later published a paper on orthomolecular psychiatry that explained how mental
health could be achieved by manipulating substances normally present in the body.

In Pauling's later career, his scientific interests centred on a particular molecule—ascorbic acid (vitamin C). He examined the published reports about this vitamin and concluded that, when taken in large enough quantities (megadoses), it would help the body fight off colds and other diseases. The outcome of his research was the book
Vitamin C and the Common Cold
(1970), which became a best-seller. Pauling's interest in vitamin C in particular and orthomolecular medicine in general led, in 1973, to his founding an institute that eventually bore his name—the Linus Pauling Institute of Science and Medicine. During his tenure at this institute, he became embroiled in controversies about the relative benefits and risks of ingesting megadoses of various vitamins. The controversy intensified when he advocated vitamin C's usefulness in the treatment of cancer. Pauling and his collaborator, the Scottish physician Ewan Cameron, published their views in
Cancer and Vitamin C
(1979).

Although he continued to receive recognition for his earlier accomplishments, Pauling's later work provoked considerable skepticism and controversy. His cluster model of the atomic nucleus was rejected by physicists, his interpretation of the newly discovered quasicrystals received little support, and his ideas on vitamin C were rejected by the medical establishment. In an effort to raise money to support his increasingly troubled institute, Pauling published
How to Live Longer and Feel Better
(1986), but the book failed to become the success that he and his associates had anticipated. Despite their personal reliance upon megadoses of vitamin C, both Pauling and his wife developed cancer.

(b. Sept. 29, 1901, Rome, Italy—d. Nov. 28, 1954, Chicago, Ill., U.S.)

I
talian-born American scientist Enrico Fermi was one of the chief architects of the nuclear age. He developed the mathematical statistics required to clarify a large class of subatomic phenomena, explored nuclear transformations caused by neutrons, and directed the first controlled chain reaction involving nuclear fission. He was awarded the 1938 Nobel Prize for Physics, and the Enrico Fermi Award of the U.S. Department of Energy is given in his honour. Fermilab, the National Accelerator Laboratory, in Illinois, is named for him, as is fermium, element number 100.

In 1924 Fermi took a position as a lecturer in mathematical physics at the University of Florence in Italy. His early research was in general relativity, statistical mechanics, and quantum mechanics. Examples of gas degeneracy (appearance of unexpected phenomena) had been known, and some cases were explained by Bose-Einstein statistics, which describes the behaviour of subatomic particles known as bosons. Between 1926 and 1927, Fermi and the English physicist P.A.M. Dirac independently developed new statistics, now known as Fermi-Dirac statistics, to handle the subatomic particles that obey the Pauli exclusion principle; these particles, which include electrons, protons, neutrons (not yet discovered), and other particles with half-integer spin, are now known as fermions.

In 1927 Fermi became a full professor at the University of Rome. In 1929 Fermi, as Italy's first professor of theoretical physics and a rising star in European science, was named by Italian Prime Minister Benito Mussolini to his new Accademia d'Italia, a position that included a substantial salary (much larger than that for any ordinary university position), a uniform, and a title (“Excellency”).

During the late 1920s, Fermi changed his focus to the more primitively developed field of nuclear physics. He began to study the neutrino, an almost undetectable particle that had been postulated a few years earlier by the Austrian-born physicist Wolfgang Pauli. This led to Fermi's recognition that beta decay from radioactive particles was a manifestation of the weak force, one of the four known universal forces (the others being gravitation, electromagnetism, and the strong force).

In the 1930s Fermi reasoned that the neutral neutron would be an ideal projectile with which to bombard charged nuclei in order to initiate such reactions. With his colleagues, Fermi subjected more than 60 elements to neutron bombardment, using a Geiger-Müller counter to detect emissions and conducting chemical analyses to determine the new radioactive isotopes produced. Along the way, they found by chance that neutrons that had been slowed in their velocity often were more effective. When testing uranium they observed several activities, but they could not interpret what occurred. Some scientists thought that they had produced transuranium elements, namely elements higher than uranium at atomic number 92. The issue was not resolved until 1938, when it was revealed that the uranium had split and the several radioactivities detected were from fission fragments.

Fermi was little interested in politics, yet he grew increasingly uncomfortable with the fascist politics of his homeland. When Italy adopted the anti-Semitic policies of its ally, Nazi Germany, a crisis occurred, for Fermi's wife, Laura, was Jewish. The award of the 1938 Nobel Prize for Physics serendipitously provided the excuse for the family to travel abroad, and the prize money helped to establish them in the United States.

Fermi began his new life at Columbia University, in New York City. Within weeks of his arrival, news that uranium could fission astounded the physics community. Scientists had known for many years that nuclei could disgorge small chunks, such as alpha particles, beta particles, protons, and neutrons, either in natural radioactivity or upon bombardment by a projectile. However, they had never seen a nucleus split almost in two. The implications were both exciting and ominous, and they were recognized widely.

When uranium fissioned, some mass was converted to energy, according to Albert Einstein's famous formula
E = mc
²
. Uranium also emitted a few neutrons in addition to the larger fragments. If these neutrons could be slowed to maximize their efficiency, they could participate in a controlled chain reaction to produce energy; that is, a nuclear reactor could be built. The same neutrons traveling at their initial high speed could also participate in an uncontrolled chain reaction, liberating an enormous amount of energy through many generations of fission events, all within a fraction of a second; that is, an atomic bomb could be built.