The 100 Most Influential Scientists of All Time (40 page)

After working at the University of Copenhagen, where he first determined to investigate DNA, he did research at the Cavendish Laboratories (1951–53). There Watson learned X-ray diffraction techniques and worked with Crick on the problem of DNA structure. In 1952 he
determined the structure of the protein coat surrounding the tobacco mosaic virus but made no dramatic progress with DNA. Suddenly, in the spring of 1953, Watson saw that the essential DNA components—four organic bases—must be linked in definite pairs.

This discovery was the key factor that enabled Watson and Crick to formulate a molecular model for DNA—a double helix, which can be likened to a spiraling staircase or a twisting ladder. The DNA double helix consists of two intertwined sugar-phosphate chains, with the flat base pairs forming the steps between them. Watson and Crick's model also showed how the DNA molecule could duplicate itself. Thus it became known how genes, and eventually chromosomes, duplicate themselves. Watson and Crick published their epochal discovery in two papers in the British journal
Nature
in April–May 1953. Their research answered one of the fundamental questions in genetics.

Watson subsequently taught at Harvard University (1955–76), where he served as professor of biology (1961–76). He conducted research on the role of nucleic acids in the synthesis of proteins. In 1965 he published
Molecular Biology of the Gene
, one of the most extensively used modern biology texts. He later wrote
The Double Helix
(1968), an informal and personal account of the DNA discovery and the roles of the people involved in it, which aroused some controversy.

In 1968 Watson assumed the leadership of the Laboratory of Quantitative Biology at Cold Spring Harbor, Long Island, N.Y., and made it a world centre for research in molecular biology. He concentrated its efforts on cancer research. In 1981 his
The DNA Story
(written with John Tooze) was published. From 1988 to 1992 at the National Institutes of Health, Watson helped direct the Human
Genome Project, a project to map and decipher all the genes in the human chromosomes, but he eventually resigned because of alleged conflicts of interests involving his investments in private biotechnology companies.

In early 2007 Watson's own genome was sequenced and made publicly available on the Internet. He was the second person in history to have a personal genome sequenced in its entirety. In October of the same year, he sparked controversy by making a public statement alluding to the idea that the intelligence of Africans might not be the same as that of other peoples and that intellectual differences among geographically separated peoples might arise over time as a result of genetic divergence. Watson's remarks were immediately denounced as racist. Though he denied this charge, he resigned from his position at Cold Spring Harbor and formally announced his retirement less than two weeks later.

(b. May 11, 1918, New York, N.Y., U.S.—d. Feb. 15, 1988, Los Angeles, Calif.)

A
merican theoretical physicist Richard Phillips Feynman was widely regarded as the most brilliant, influential, and iconoclastic figure in his field in the post-World War II era. Feynman remade quantum electrodynamics—the theory of the interaction between light and matter—and thus altered the way science understands the nature of waves and particles. He was co-awarded the Nobel Prize for Physics in 1965 for this work, which tied together in an experimentally perfect package all the varied phenomena at work in light, radio, electricity, and magnetism. The other cowinners of the Nobel Prize, Julian S. Schwinger of the United States and Tomonaga Shin'ichirō of Japan, had
independently created equivalent theories, but it was Feynman's that proved the most original and far-reaching. The problem-solving tools that he invented—including pictorial representations of particle interactions known as Feynman diagrams—permeated many areas of theoretical physics in the second half of the 20th century.

Feynman studied physics as an undergraduate at the Massachusetts Institute of Technology and received his doctorate at Princeton University in 1942. At Princeton, with his adviser, John Archibald Wheeler, he developed an approach to quantum mechanics governed by the principle of least action. This approach replaced the wave-oriented electromagnetic picture developed by James Clerk Maxwell with one based entirely on particle interactions mapped in space and time. In effect, Feynman's method calculated the probabilities of all the possible paths a particle could take in going from one point to another.

During World War II Feynman was recruited to serve as a staff member of the U.S. atomic bomb project at Princeton University (1941–42) and then at the new secret laboratory at Los Alamos, New Mexico (1943–45). At Los Alamos he became the youngest group leader in the theoretical division of the Manhattan Project. With the head of that division, Hans Bethe, he devised the formula for predicting the energy yield of a nuclear explosive. Feynman also took charge of the project's primitive computing effort, using a hybrid of new calculating machines and human workers to try to process the vast amounts of numerical computation required by the project. He observed the first detonation of an atomic bomb on July 16, 1945, near Alamogordo, New Mexico, and, though his initial reaction was euphoric, he later felt anxiety about the force he and his colleagues had helped unleash on the world.

At war's end Feynman became an associate professor at Cornell University (1945–50) and returned to studying the fundamental issues of quantum electrodynamics. In 1950 he became professor of theoretical physics at the California Institute of Technology (Caltech), where he remained the rest of his career.

Five particular achievements of Feynman stand out as crucial to the development of modern physics. First, and most important, is his work in correcting the inaccuracies of earlier formulations of quantum electrodynamics, the theory that explains the interactions between electromagnetic radiation (photons) and charged subatomic particles such as electrons and positrons (antielectrons).

By 1948 Feynman completed this reconstruction of a large part of quantum mechanics and electrodynamics and resolved the meaningless results that the old quantum electrodynamic theory sometimes produced. Second, he introduced simple diagrams, now called Feynman diagrams, that are easily visualized graphic analogues of the complicated mathematical expressions needed to describe the behaviour of systems of interacting particles. This work greatly simplified some of the calculations used to observe and predict such interactions.

In the early 1950s Feynman provided a quantum-mechanical explanation for the Soviet physicist Lev D. Landau's theory of superfluidity—i.e., the strange, frictionless behaviour of liquid helium at temperatures near absolute zero. In 1958 he and the American physicist Murray Gell-Mann devised a theory that accounted for most of the phenomena associated with the weak force, which is the force at work in radioactive decay. Their theory, which turns on the asymmetrical “handedness” of particle spin, proved particularly fruitful in modern particle physics. And finally, in 1968, while working with
experimenters at the Stanford Linear Accelerator on the scattering of high-energy electrons by protons, Feynman invented a theory of “partons,” or hypothetical hard particles inside the nucleus of the atom, that helped lead to the modern understanding of quarks.

Feynman's lectures at Caltech evolved into the books
Quantum Electrodynamics
(1961) and
The Theory of Fundamental Processes
(1961). In 1961 he began reorganizing and teaching the introductory physics course at Caltech; the result, published as
The Feynman Lectures on Physics
, 3 vol. (1963–65), became a classic textbook. Feynman's views on quantum mechanics, scientific method, the relations between science and religion, and the role of beauty and uncertainty in scientific knowledge are expressed in two models of science writing, again distilled from lectures:
The Character of Physical Law
(1965) and
QED: The Strange Theory of Light and Matter
(1985).

(b. July 25, 1920, London, Eng.—d. April 16, 1958, London)

B
ritish scientist Rosalind Franklin contributed to the discovery of the molecular structure of deoxyribonucleic acid (DNA), a constituent of chromosomes that serves to encode genetic information.

Franklin attended St. Paul's Girls' School before studying physical chemistry at Newnham College, Cambridge. After graduating in 1941, she received a fellowship to conduct research in physical chemistry at Cambridge. But the advance of World War II changed her course of action: not only did she serve as a London air raid warden, but in 1942 she gave up her fellowship in order to work for the British Coal Utilisation Research Association, where she investigated the physical
chemistry of carbon and coal for the war effort. Nevertheless, she was able to use this research for her doctoral thesis, and in 1945 she received a doctorate from Cambridge. From 1947 to 1950 she worked with Jacques Méring at the State Chemical Laboratory in Paris, studying X-ray diffraction technology. That work led to her research on the structural changes caused by the formation of graphite in heated carbons—work that proved valuable for the coking industry.

In 1951 Franklin joined the Biophysical Laboratory at King's College, London, as a research fellow. There she applied X-ray diffraction methods to the study of DNA. When she began her research at King's College, very little was known about the chemical makeup or structure of DNA. However, she soon discovered the density of DNA and, more importantly, established that the molecule existed in a helical conformation. Her work to make clearer X-ray patterns of DNA molecules laid the foundation for James Watson and Francis Crick to suggest in 1953 that the structure of DNA is a double-helix polymer, a spiral consisting of two DNA strands wound around each other.

From 1953 to 1958 Franklin worked in the Crystallography Laboratory at Birkbeck College, London. While there she completed her work on coals and on DNA and began a project on the molecular structure of the tobacco mosaic virus. She collaborated on studies showing that the ribonucleic acid (RNA) in that virus was embedded in its protein rather than in its central cavity and that this RNA was a single-strand helix, rather than the double helix found in the DNA of bacterial viruses and higher organisms. Franklin's involvement in cutting-edge DNA research was halted by her untimely death from cancer in 1958.

(b. June 10, 1929, Birmingham, Ala., U.S.)

A
merican biologist Edward Osborne Wilson was recognized as the world's leading authority on ants. He was also the foremost proponent of sociobiology, the study of the genetic basis of the social behaviour of all animals, including humans.

Wilson received his early training at the University of Alabama (B.S., 1949; M.S., 1950). After receiving his doctorate in biology at Harvard University in 1955, he was a member of Harvard's biology and zoology faculties from 1956 to 1976. At Harvard he was later Frank B. Baird Professor of Science (1976–94), Mellon Professor of the Sciences (1990–93), and Pellegrino University Professor (1994–97). He was professor emeritus from 1997. In addition, Wilson served as curator in entomology at Harvard's Museum of Comparative Zoology (1973–97).

In 1955 Wilson completed an exhaustive taxonomic analysis of the ant genus
Lasius
. In collaboration with W.L. Brown, he developed the concept of “character displacement,” a process in which populations of two closely related species, after first coming into contact with each other, undergo rapid evolutionary differentiation in order to minimize the chances of both competition and hybridization between them.

After his appointment to Harvard in 1956, Wilson made a series of important discoveries, including the determination that ants communicate primarily through the transmission of chemical substances known as pheromones. In the course of revising the classification of ants native to the South Pacific, he formulated the concept of the “taxon cycle,” in which speciation and species dispersal are linked to the varying habitats that organisms encounter as their populations expand. In 1971 he published
The Insect Societies
, his definitive work on ants and other social insects. The book provided a comprehensive picture of the ecology, population dynamics, and social behaviour of thousands of species.

In Wilson's second major work,
Sociobiology: The New Synthesis
(1975), a treatment of the biological basis of social behaviour, he proposed that the essentially biological principles on which animal societies are based also apply to humans. This thesis provoked condemnation from prominent researchers and scholars in a broad range of disciplines, who regarded it as an attempt to justify harmful or destructive behaviour and unjust social relations in human societies. In fact, however, Wilson maintained that as little as 10 percent of human behaviour is genetically induced, the rest being attributable to environment.