Scientists

Berzelius

This 19th century Swedish chemist was one of the founders of modern chemistry. He is especially noted for his determination of atomic weights, the development of modern chemical symbols, his electrochemical theory, the discovery and isolation of several elements, the development of classical analytical techniques, and his investigation of isomerism and catalysis, phenomena that owe their names to him. He was a strict empiricist and insisted that any new theory be consistent with the sum of chemical knowledge. He is best known for his system of electrochemical dualism. The electrical battery, invented in 1800 by Alessandro Volta and known as the voltaic pile, provided the first experimental source of current electricity. In 1803 he demonstrated, as did the English chemist Humphry Davy at a slightly later date, the power of the voltaic pile to decompose chemicals into pairs of electrically opposite constituents. In addition to his qualitative specification of chemicals, he investigated their quantitative relationships as well. As early as 1806, he began to prepare an up-to-date Swedish chemistry textbook and read widely on the subject of chemical combination. Finding little information on the subject, he decided to undertake further investigations. His teaching interests focused his attention upon inorganic chemistry. Around 1808 he launched what became a vast and enduring program in the laboratory analysis of inorganic matter. To this end, he created most of his apparatuses, prepared his own reagents, and established the atomic weights of the elements, the formulas of their oxides, sulfides, and salts, and the formulas of virtually all known inorganic compounds. His experiments led to a more complete depiction of the principles of chemical combining proportions, an area of investigation that the German chemist Jeremias Benjamin Richter named "stoichiometry". Among his other accomplishments were his improvements of laboratory apparatuses and techniques used for chemical and mineral analysis, especially solvent extraction, elemental analysis, quantitative wet chemistry, and qualitative mineral analysis. he also characterizedand named two new concepts: "isomerism," in which chemically diverse substances possess the same composition; and "catalysis".

Agassiz

This 19th century Swiss-born U.S. naturalist, geologist, and teacher made revolutionary contributions to the study of natural science with landmark work on glacier activity and extinct fishes. He achieved lasting fame through his innovative teaching methods, which altered the character of natural science education in the United States. His epoch-making work, Recherches sur les poissons fossiles, appeared in parts from 1833 to 1843. In it, the number of named fossil fishes was raised to more than 1,700. The great importance of this fundamental work rests on the impetus it gave to the study of extinct life itself. Turning his attention to other extinct animals found with the fishes, he published in 1838-42 two volumes.

Wallace

This 19th century scientist was a British humanist, naturalist, geographer, and social critic. He became a public figure in England during the second half of the 19th century, known for his courageous views on scientific, social, and spiritualist subjects. His formulation of the theory of evolution by natural selection, which predated Charles Darwin's published contributions, is his most outstanding legacy, but it was just one of many controversial issues he studied and wrote about during his lifetime. His wide-ranging interests—from socialism to spiritualism, from island biogeography to life on Mars, from evolution to land nationalization—stemmed from his profound concern with the moral, social, and political values of human life. In early 1858 he sent a paper outlining these ideas to Darwin, who saw such a striking coincidence to his own theory that he consulted his closest colleagues, the geologist Charles Lyell and the botanist Joseph Dalton Hooker. The three men decided to present two extracts of Darwin's previous writings, along with Wallace's paper, to the Linnean Society. The resulting set of papers, with both Darwin's and his names, was published as a single article entitled "On the Tendency of Species to Form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection" in the Proceedings of the Linnean Society in 1858.

Stevens

This 19th/20th century American biologist and geneticist was one of the first scientists to find that sex is determined by a particular configuration of chromosomes. In 1905, after experiments with the yellow mealworm, she published a paper in which she announced her finding that a particular combination of the chromosomes known as X and Y was responsible for the determination of the sex of an individual. She continued her research on the chromosome makeup of various insects, discovering supernumerary chromosomes in certain insects and the paired state of chromosomes in flies and mosquitoes.

Michelson

This 19th/20th century German-born American physicist established the speed of light as a fundamental constant and pursued other spectroscopic and metrological investigations. He received the 1907 Nobel Prize for Physics. In 1881, upon his return to the United States from Europe, he determined the velocity of light to be 299,853 kilometres (186,329 miles) per second, a value that remained the best for a generation, until Michelson bettered it. By 1887, with the help of his colleague, American chemist Edward Williams Morley, he was ready to announce the results of what has since come to be called the namesake-Morley experiment. Those results were still negative; there were no interference fringes and apparently no motion of the Earth relative to the ether (this was then thought to make up the basic substratum of the universe). It was perhaps the most significant negative experiment in the history of science. In terms of classical Newtonian physics, the results were paradoxical. Evidently, the speed of light plus any other added velocity was still equal only to the speed of light. To explain the result of the namesake-Morley experiment, physics had to be recast on a new and more refined foundation, something that resulted, eventually, in Albert Einstein's formulation of the theory of relativity in 1905.

Aristotle

This 4th century Greek philosopher is most famous for perpetuating false ideals until the Renaissance. Among inaccuracies from other "scientists" were the existence of 4 elements in the universe (earth, wind, fire, and water), 4 elementary qualities (wet, dry, hot, cold), and that the earth is the center of the universe.

Borlaug

This American agricultural scientist and plant pathologist helped to lay the groundwork of the so-called Green Revolution, the agricultural technological advance that promised to alleviate world hunger. For his achievements he was awarded the Nobel Prize for Peace in 1970. The Green Revolution resulted in increased production of food grains (especially wheat and rice) and was due in large part from the introduction into developing countries of new, high-yielding varieties, beginning in the mid-20th century with Borlaug's work. Its early dramatic successes were in Mexico and the Indian subcontinent. Wheat production in Mexico multiplied threefold in the time that Borlaug worked with the Mexican government.

Mead

This American anthropologist was noted for the force of her personality, her outspokenness, and the quality of her scientific work. In 1925, during the first of her many field trips to the South Seas, she gathered material for the first of her 23 books, Coming of Age in Samoa (1928; new ed., 1968), a perennial best-seller and a characteristic example of her reliance on observation rather than statistics for data. The book clearly indicates her belief in cultural determinism, a position that caused some later 20th-century anthropologists to question both the accuracy of her observations and the soundness of her conclusions. Her other works include Growing Up in New Guinea (1930; new ed., 1975), Sex and Temperament in Three Primitive Societies (1935; reprinted, 1968). As an anthropologist, she was best known for her studies of the nonliterate peoples of Oceania, especially with regard to various aspects of psychology and culture, the cultural conditioning of sexual behaviour, natural character, and culture change. As a celebrity, she was most notable for her forays into such far-ranging topics as women's rights, childrearing, sexual morality, nuclear proliferation, race relations, drug abuse, population control, environmental pollution, and world hunger.

Hubble

This American astronomer is considered the founder of extragalactic astronomy. He provided the first evidence of the expansion of the universe. While at Mount Wilson, Hubble discovered (1922-24) that not all nebulae in the sky are part of the Milky Way. He found that certain nebulae contain stars called Cepheid variables, for which a correlation was already known to exist between periodicity and absolute magnitude. Using the further relationship among distance, apparent magnitude, and absolute magnitude, Hubble determined that these Cepheids are several hundred thousand light-years away and thus outside the Milky Way system and that the nebulae in which they are located are actually galaxies distinct from the Milky Way. This discovery, announced in 1924, forced astronomers to revise their ideas about the cosmos.

Leavitt

This American astronomer was known for her discovery of the relationship between period and luminosity in Cepheid variables, pulsating stars that vary regularly in brightness in periods ranging from a few days to several months. One result of her work on stellar magnitudes was her discovery of 4 novas and some 2,400 variable stars, the latter figure comprising more than half of all those known even by 1930. She continued her work at the Harvard Observatory until her death. Leavitt's outstanding achievement was her discovery in 1912 that in a certain class of variable stars, the Cepheid variables, the period of the cycle of fluctuation in brightness is highly regular and is determined by the actual luminosity of the star. The subsequent calibration of the period-luminosity curve allowed American astronomers Edwin Hubble, Harlow Shapley, and others to determine the distances of many Cepheid stars and consequently of the star clusters and galaxies in which they were observed. The most dramatic application was Hubble's use in 1924 of a Cepheid variable to determine the distance to the great nebula in Andromeda, which was the first distance measurement for a galaxy outside the Milky Way.

Wilson

This American 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. He 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 On Human Nature (1978), for which he was awarded a Pulitzer Prize in 1979, Wilson discussed the application of sociobiology to human aggression, sexuality, and ethics. His book The Ants (1990) was a monumental summary of contemporary knowledge of those insects.

Carson

This American biologist was well known for her writings on environmental pollution and the natural history of the sea. An article in The Atlantic Monthly in 1937 served as the basis for her first book, Under the Sea-Wind , published in 1941. It was widely praised, as were all her books, for its remarkable combination of scientific accuracy and thoroughness with an elegant and lyrical prose style. The Sea Around Us (1951) became a national best-seller, won a National Book Award, and was eventually translated into 30 languages. Her third book, The Edge of the Sea, was published in 1955. Carson's prophetic Silent Spring (1962) was first serialized in The New Yorker and then became a best-seller, creating worldwide awareness of the dangers of environmental pollution. The vision of the environmental movement of the 1960s and early '70s was generally pessimistic, reflecting a pervasive sense of "civilization malaise" and a conviction that the Earth's long-term prospects were bleak. Her Silent Spring suggested that the planetary ecosystem was reaching the limits of what it could sustain. She stood behind her warnings of the consequences of indiscriminate pesticide use, despite the threat of lawsuits from the chemical industry and accusations that she engaged in "emotionalism" and "gross distortion."

Curl

This American chemist , with Richard E. Smalley and Sir Harold W. Kroto discovered the first fullerene, a spherical cluster of carbon atoms, in 1985. The discovery opened a new branch of chemistry, and all three men were awarded the 1996 Nobel Prize for Chemistry for their work. In the 1990s a method was announced for producing buckyballs in large quantities and practical applications appeared likely. In 1991 Science magazine named buckminsterfullerene their "molecule of the year." his later research focused on quartz tuning forks and the development of trace gas sensors. This research was aimed at creating sensors that could be used to generate arrays of quartz tuning forks. These arrays could then be used for the photoacoustic detection of gases. He also was developing improved technology to sequence DNA that employed high-powered lasers and fluorescent dyes.

Smalley

This American chemist and physicist shared the 1996 Nobel Prize for Chemistry with Robert F. Curl, Jr., and Sir Harold W. Kroto for their joint discovery of carbon60 (C60, or buckminsterfullerene, or buckyball) and the fullerenes. On a visit to his lab, Kroto realized that the technique might be used to simulate the chemical conditions in the atmosphere of carbon stars and so provide compelling evidence for his conjecture that the chains originated in stars. A leading supporter of nanotechnology, he played a key role in the establishment in 2000 of the National Nanotechnology Initiative, a federal research and development program.

Alvarez

This American experimental physicist was awarded the Nobel Prize for Physics in 1968 for work that included the discovery of many resonance particles (subatomic particles having extremely short lifetimes and occurring only in high-energy nuclear collisions). After World War II he helped construct the first proton linear accelerator. In this accelerator, electric fields are set up as standing waves within a cylindrical metal "resonant cavity," with drift tubes suspended along the central axis. In about 1980 he helped his son, Walter , publicize Walter's discovery of a worldwide layer of clay that has a high iridium content and which occupies rock strata at the geochronological boundary between the Mesozoic and Cenozoic eras; i.e., about 66.4 million years ago. They postulated that the iridium had been deposited following the impact on Earth of an asteroid or comet and that the catastrophic climatic effects of this massive impact caused the extinction of the dinosaurs .

Watson

This American geneticist and biophysicist James Dewey Watson played a crucial role in the discovery of the molecular structure of deoxyribonucleic acid (DNA), the substance that is the basis of heredity. For this accomplishment he was awarded the 1962 Nobel Prize for Physiology or Medicine with Francis Crick and Maurice Wilkins. 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.

Collins

This American geneticist discovered genes causing genetic diseases and led the U.S. National Institutes of Health (NIH) public research consortium in the Human Genome Project (HGP). . Headed by American geneticist and businessman J. Craig Venter, a former NIH scientist, Celera had devised its own, quicker method—though some scientists, this geneticist among them, questioned the accuracy of the work. However, in the end the public and private endeavours came together. On June 26, 2000, she, Venter, and U.S. Pres. Bill Clinton gathered in Washington, D.C., to announce that the rough draft sequence of the DNA in the human genetic map had been completed through the combined effort of Collins's public research consortium and Venter's private company. The breakthrough was hailed as the first step toward helping doctors diagnose, treat, and even prevent thousands of illnesses caused by genetic disorders. In April 2003, following further analysis of the sequence, the HGP came to a close. The announcement of the completion of the HGP coincided with the 50th anniversary of American geneticist and biophysicist James D. Watson and British biophysicist Francis Crick's publication on the structure of DNA.

Venter

This American geneticist, biochemist, and businessman pioneered new techniques in genetics and genomics research and headed the private-sector enterprise, Celera Genomics, in the Human Genome Project (HGP). While at the NIH, Venter became frustrated with traditional methods of gene identification, which were slow and time-consuming. He developed an alternative technique using expressed sequence tags (ESTs), small segments of deoxyribonucleic acid (DNA) found in expressed genes that are used as "tags" to identify unknown genes in other organisms, cells, or tissues. Venter used ESTs to rapidly identify thousands of human genes. Although first received with skepticism, the approach later gained increased acceptance; in 1993 it was used to identify the gene responsible for a type of colon cancer. His attempts to patent the gene fragments that he identified, however, created a furor among those in the scientific community who believed that such information belonged in the public domain.

Gould

This American paleontologist, evolutionary biologist, and science writer focused on the evolution and speciation of West Indian land snails. With Niles Eldredge, he developed in 1972 the theory of punctuated equilibrium, a revision of Darwinian theory proposing that the creation of new species through evolutionary change occurs not at slow, constant rates over millions of years but rather in rapid bursts over periods as short as thousands of years, which are then followed by long periods of stability during which organisms undergo little further change. He also argued that population genetics is useful—indeed, all-important—for understanding relatively small-scale or short-term evolutionary changes but that it is incapable of yielding insight into large-scale or longterm ones, such as the Cambrian explosion. One must turn to paleontology in its own right to explain these changes, which might well involve extinctions brought about by extraterrestrial forces (e.g., comets) or new kinds of selection operating only at levels higher than the individual organism.

Salk

This American physician and medical researcher Jonas Edward Salk developed the first safe and effective vaccine for polio. Working with scientists from other universities in a program to classify the various strains of poliovirus, he corroborated other studies in identifying three separate strains. He then demonstrated that killed virus of each of the three, although incapable of producing the disease, could induce antibody formation in monkeys. In 1952 he conducted field tests of his killed-virus vaccine, first on children who had recovered from polio and then on subjects who had not had the disease; both tests were successful in that the children's antibody levels rose significantly and no subjects contracted polio from the vaccine.

McClintock

This American scientist discovered mobile genetic elements, or "jumping genes," which won her the Nobel Prize for Physiology or Medicine in 1983. In the 1940s, by observing and experimenting with variations in the coloration of kernels of corn, she discovered that genetic information is not stationary. By tracing pigmentation changes in corn and using a microscope to examine that plant's large chromosomes, she isolated two genes that she called "controlling elements." These genes controlled the genes that were actually responsible for pigmentation. She found that the controlling elements could move along the chromosome to a different site, and that these changes affected the behaviour of neighbouring genes. She suggested that these transposable elements were responsible for new mutations in pigmentation or other characteristics. Her work was ahead of its time and was for many years considered too radical—or was simply ignored—by her fellow scientists.

Pauling

This American theoretical physical chemist 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 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. 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. 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.

Oppenheimer

This American theoretical physicist and science administrator was director of the Los Alamos laboratory during development of the atomic bomb (1943-45) and director of the Institute for Advanced Study, Princeton (1947-66). Accusations of disloyalty led to a government hearing that resulted in the loss of his security clearance and of his position as adviser to the highest echelons of the U.S. government. The joint effort of outstanding scientists at Los Alamos culminated in the first nuclear explosion on July 16, 1945, at the Trinity Site near Alamogordo, New Mexico, after the surrender of Germany. In October of the same year, he resigned his post. In 1947 he became head of the Institute for Advanced Study and served from 1947 until 1952 as chairman of the General Advisory Committee of the Atomic Energy Commission, which in October 1949 opposed development of the hydrogen bomb.

Feynman

This American theoretical physicist 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. 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. By 1948 he 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 his namesake 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.

Freud

This Austrian neurologist Sigmund Freud was the founder of psychoanalysis. Freud may justly be called the most influential intellectual legislator of his age. His creation of psychoanalysis was at once a theory of the human psyche, a therapy for the relief of its ills, and an optic for the interpretation of culture and society. Despite repeated criticisms, attempted refutations, and qualifications of his work, its spell remained powerful well after his death and in fields far removed from psychology as it is narrowly defined. In what many commentators consider Freud's master work, Die Traumdeutung (The Interpretation of Dreams), published in 1899, but given the date of the dawning century to emphasize its epochal character, he interspersed evidence from his own dreams with evidence from those recounted in his clinical practice. Freud contended that dreams played a fundamental role in the psychic economy. The mind's energy—which he called libido and identified principally, but not exclusively, with the sexual drive—was a fluid and malleable force capable of excessive and disturbing power. Needing to be discharged to ensure pleasure and prevent pain, it sought whatever outlet it might find. If denied the gratification provided by direct motor action, libidinal energy could seek its release through mental channels. The Interpretation of Dreams provides a hermeneutic (interpretation) for the unmasking of the dream's disguise, or dreamwork, as he called it. He later attempted to clarify the relationship between his earlier topographical division of the psyche into the unconscious, preconscious, and conscious and his subsequent structural categorization into id, ego, and superego. The id was defined in terms of the most primitive urges for gratification in the infant, urges dominated by the desire for pleasure through the release of tension and the cathexis of energy. The id is ruled by what he called the primary process directly expressing somatically generated instincts. The secondary process that results leads to the growth of the ego, which follows what Freud called the reality principle in contradistinction to the pleasure principle dominating the id. The last component in Freud's trichotomy, the superego, develops from the internalization of society's moral commands through identification with parental dictates.

Schrödinger

This Austrian theoretical physicist contributed to the wave theory of matter and to other fundamentals of quantum mechanics. He shared the 1933 Nobel Prize for Physics with the British physicist P.A.M. Dirac. Adopting a proposal made by Louis de Broglie in 1924 that particles of matter have a dual nature and in some situations act like waves, he introduced a theory describing the behaviour of such a system by a wave equation that is now known as his namesake equation. The solutions to this equation, unlike the solutions to Newton's equations, are wave functions that can only be related to the probable occurrence of physical events. In 1935, he developed a thought experiment involving his cat.

Bateson

This British biologist founded and named the science of genetics. His experiments provided evidence basic to the modern understanding of heredity. A dedicated evolutionist, he cited embryo studies to support this contention in 1885 that chordates evolved from primitive echinoderms, a view now widely accepted. In 1894 he published his conclusion (Materials for the Study of Variation) that evolution could not occur through a continuous variation of species, since distinct features often appeared or disappeared suddenly in plants and animals. Realizing that discontinuous variation could be understood only after something was known about the inheritance of traits, he began work on the experimental breeding of plants and animals. In 1900, he discovered an article, "Experiments with Plant Hybrids," written by Gregor Mendel, an Austrian monk, 34 years earlier. The paper, found in the same year by Hugo de Vries, Carl Correns, and Erich Tschermak von Seysenegg, dealt with the appearance of certain features in successive generations of garden peas. Bateson noted that his breeding results were explained perfectly by Mendel's paper and that the monk had succinctly described the transmission of elements governing heritable traits in his plants.

Crick

This British biophysicist received the 1962Nobel Prize for Physiology or Medicine, along with James Watson and Maurice Wilkins, for determining the molecular structure of deoxyribonucleic acid (DNA), the chemical substance ultimately responsible for hereditary control of life functions. This accomplishment became a cornerstone of genetics and was widely regarded as one of the most important discoveries of 20th-century biology. Using the X-ray diffraction studies of DNA done by Wilkins and X-ray diffraction pictures produced by Rosalind Franklin, Watson and he were able to construct a molecular model consistent with the known physical and chemical properties of DNA. By 1961 he had evidence to show that each group of three bases (a codon) on a single DNA strand designates the position of a specific amino acid on the backbone of a protein molecule. He also helped to determine which codons code for each of the 20 amino acids normally found in protein and thus helped clarify the way in which the cell eventually uses the DNA "message" to build proteins.

Goodall

This British ethologist Jane Goodall is known for her exceptionally detailed and long-term research on the chimpanzees of Gombe Stream National Park in Tanzania. Interested in animal behaviour from an early age, she left school at age 18. She worked as a secretary and as a film production assistant until she gained passage to Africa. Once there, she began assisting paleontologist and anthropologist Louis Leakey. Over the years Goodall was able to correct a number of misunderstandings about chimpanzees. She found, for example, that the animals are omnivorous, not vegetarian; that they are capable of making and using tools; and, in short, that they have a set of hitherto unrecognized complex and highly developed social behaviours. Her work served as a classic example of aggressive behavior in chimpanzees; she observed one of the animals intimidating rivals by banging two oilcans together. She wrote a number of books and articles about various aspects of her work, notably In the Shadow of Man (1971). She summarized her years of observation in The Chimpanzees of Gombe: Patterns of Behavior (1986).

Hoyle

This British mathematician and astronomer was best known as the foremost proponent and defender of the steady-state theory of the universe. This theory holds both that the universe is expanding and that matter is being continuously created to keep the mean density of matter in space constant. The notion that the universe on average is not only homogeneous and isotropic in space but also constantin time was philosophically attractive. He, Hermann Bondi, and Thomas Gold called it the perfect cosmological principle. In the late 1950s and early '60s, controversy about the steady-state theory grew. New observations of distant galaxies and other phenomena, supporting the big-bang theory (a phrase that he had coined in derision in the 1940s), weakened the steady-state theory, and it has since fallen out of favour with most cosmologists.

Turing

This British mathematician and logician made major contributions to mathematics, cryptanalysis, logic, philosophy, and biology and to the new areas later named computer science, cognitive science, artificial intelligence, and artificial life. In 1936 his seminal paper On Computable Numbers, with an Application to the Entscheidungsproblem [Decision Problem] was recommended for publication by the American mathematician-logician Alonzo Church, who had himself just published a paper that reached the same conclusion as this scientist/mathematician. In the summer of 1938 Turing returned from the United States to his fellowship at King's College. At the outbreak of hostilities with Germany in September 1939, he joined the wartime headquarters of the Government Code and Cypher School at Bletchley Park, Buckinghamshire. During 1939 and the spring of 1940, he and others designed a radically different code-breaking machine known as the Bombe. His ingenious Bombes kept the Allies supplied with intelligence for the remainder of the war.

Boyle

This British natural philosopher and theological writer was best known as a natural philosopher, particularly in the field of chemistry, but his scientific work covered many areas including hydrostatics, physics, medicine, earth sciences, natural history, and alchemy. In 1659 he and Robert Hooke, the clever inventor and subsequent curator of experiments for the Royal Society, completed the construction of their famous air pump and used it to study pneumatics. Their resultant discoveries regarding air pressure and the vacuum appeared in Boyle's first scientific publication, New Experiments PhysicoMechanicall, Touching the Spring of the Air and its Effects (1660). The findings of this experiment led to his namesake law dealing with pressure and volume.

Franklin

This British 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. 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. 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.

Pinker

This Canadian-born American experimental psychologist was known for his evolutionary interpretation of language acquisition in humans. His early studies on the linguistic behaviour of children led him to endorse noted linguist Noam Chomsky's assertion that humans possess an innate facility for understanding language. Eventually Pinker concluded that this facility arose as an evolutionary adaptation. He expressed this conclusion in his first popular book, The Language Instinct, which became a runaway best-seller. In Words and Rules: The Ingredients of Language (1999), he focused on the human faculty for language, offering an analysis of the cognitive mechanisms that make language possible. Exhibiting a lively sense of humour and a talent for explaining diffi cult scientifi c concepts clearly, he argued that the phenomenon of language depended essentially on two distinct "ingredients," or mental processes—the memorization of words and the manipulation of them with rules of grammar.

Bohr

This Danish physicist 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. He worked with Ernest Rutherford to establish experimentally that the atom consists of a heavy positively charged nucleus with substantially lighter negatively charged electrons circling around it at considerable distance.

Kroto

This English chemist, with Richard E. Smalley and Robert F. Curl, Jr., was awarded the 1996 Nobel Prize for Chemistry for their joint discovery of the carbon compounds called fullerenes. In the course of his research, Kroto used microwave spectroscopy to discover long, chainlike carbon molecules in the atmospheres of stars and gas clouds. Wishing to study the vaporization of carbon in order to find out how these carbon chains formed, he went to Rice University (Houston, Texas), where Smalley had designed an instrument, the laser-supersonic cluster beam apparatus, that could vaporize almost any known material and then be used to study the resulting clusters of atoms or molecules. He generated clusters of carbon atoms by vaporizing graphite in an atmosphere of helium. Some of the spectra they obtained from the vaporization corresponded to previously unknown forms of carbon containing even numbers of carbon atoms ranging from 40 to more than 100 atoms. Most of the new carbon molecules had a structure of C60. The researchers recognized that this molecule's atoms are bonded together into a highly symmetrical, hollow structure that resembles a sphere or ball. C60 is a polygon with 60 vertices and 32 faces, 12 of which are pentagons and 20 of which are hexagons—the same geometry as that of a soccer ball. In the 1985 paper describing their work, the discoverers chose the whimsical name buckminsterfullerene for C60, after the American architect R. Buckminster Fuller, whose geodesic dome designs have a structure similar to that atom. The discovery of the unique structure of fullerenes, or buckyballs, as this class of carbon compounds came to be known, opened up an entirely new branch of chemistry

Priestley

This English clergyman, political theorist, and physical scientist contributed to advances in liberal political and religious thought and in experimental chemistry. He is best remembered for his contribution to the chemistry of gases. He discovered 10 new gases: nitric oxide (nitrous air), nitrogen dioxide (red nitrous vapour), nitrous oxide (inflammable nitrous air, later called "laughing gas"), hydrogen chloride (marine acid air), ammonia (alkaline air), sulfur dioxide (vitriolic acid air), silicon tetrafluoride (fluor acid air), nitrogen (phlogisticated air), oxygen (dephlogisticated air, independently codiscovered by Carl Wilhelm Scheele), and a gas later identified as carbon monoxide. Priestley's experimental success resulted predominantly from his ability to design ingenious apparatuses and his skill in their manipulation. He gained particular renown for an improved pneumatic trough in which, by collecting gases over mercury instead of in water, he was able to isolate and examine gases that were soluble in water.

Dalton

This English meteorologist and chemist was a pioneer in the development of modern atomic theory. He upheld the view, against contemporary opinion, that the atmosphere was a physical mixture of approximately 80 percent nitrogen and 20 percent oxygen rather than being a specific compound of elements. He measured the capacity of the air to absorb water vapor and the variation of its partial pressure with temperature. He defined partial pressure in terms of a physical law whereby every constituent in a mixture of gases exerted the same pressure it would have if it had been the only gas present. One of Dalton's contemporaries, later hailed him as the "father of meteorology." In a memoir read to the Manchester Literary and Philosophical Society on Oct. 21, 1803, he claimed: "An inquiry into the relative weights of the ultimate particles of bodies is a subject, as far as I know, entirely new; I have lately been prosecuting this inquiry with remarkable success."He described his method of measuring the masses of various elements, including hydrogen, oxygen, carbon, and nitrogen, according to the way they combined with fixed masses of each other. If such measurements were to be meaningful, the elements had to combine in fixed proportions. His measurements, crude as they were, allowed him to formulate the Law of Multiple Proportions

Faraday

This English physicist and chemist is known for his many experiments that contributed greatly to the understanding of electromagnetism. Faraday, who became one of the greatest scientists of the 19th century, began his career as a chemist. He wrote a manual of practical chemistry that reveals his mastery of the technical aspects of his art, discovered a number of new organic compounds, among them benzene, and was the fi rst to liquefy a "permanent" gas (i.e., one that was believed to be incapable of liquefaction). His major contribution, however, was in the field of electricity and magnetism . He was the first to produce an electric current from a magnetic field, invented the first electric motor and dynamo, demonstrated the relation between electricity and chemical bonding, discovered the effect of magnetism on light, and discovered and named diamagnetism, the peculiar behavior of certain substances in strong magnetic fields. He provided the experimental, and a good deal of the theoretical, foundation upon which James Clerk Maxwell erected classical electromagnetic field theory. He has a constant named after him that equates one mole of electrons equal to 96,500 Coulombs.

Newton

This English physicist and mathematician was the culminating figure of the scientific revolution of the 17th century. In optics, his discovery of the composition of white light integrated the phenomena of colors into the science of light and laid the foundation for modern physical optics. In mechanics, his three laws of motion, the basic principles of modern physics, resulted in the formulation of the law of universal gravitation. In mathematics, he was the original discoverer of the infinitesimal calculus. Newton's Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), 1687, was one of the most important single works in the history of modern science.

Hawking

This English theoretical physicist developed a theory of exploding black holes that drew upon both relativity theory and quantum mechanics. He also worked with space-time singularities. He worked primarily in the field of general relativity and particularly on the physics of black holes. In 1971 he suggested the formation, following the big bang, of numerous objects containing as much as 1,000,000,000 tons of mass but occupying only the space of a proton. These objects, called mini black holes, are unique in that their immense mass and gravity require that they be ruled by the laws of relativity, while their minute size requires that the laws of quantum mechanics apply to them also. In 1974 Hawking proposed that, in accordance with the predictions of quantum theory, black holes emit subatomic particles until they exhaust their energy and finally explode. Hawking's work greatly spurred efforts to theoretically delineate the properties of black holes, objects about which it was previously thought that nothing could be known. His work was also important because it showed these properties' relationship to the laws of classical thermodynamics and quantum mechanics.

Cousteau

This French naval officer and ocean explorer Jacques-Yves Cousteau was known for his extensive underseas investigations. Not formally trained as a scientist, Cousteau was drawn to undersea exploration by his love both of the ocean and of diving. In 1943 he and the French engineer Émile Gagnan developed the first fully automatic compressedair Aqua-Lung. He helped to invent many other tools useful to oceanographers, including the diving saucer, a small, easily maneuverable submarine for seafloor exploration, and a number of underwater cameras. In 1950 he converted a British minesweeper into the Calypso, an oceanographic research ship aboard which he and his crew carried out numerous expeditions. He eventually popularized oceanographic research and the sport of scuba diving in the book Le Monde du silence (1952; The Silent World), written with Frédéric Dumas. Two years later he adapted the book into a documentary film that won both the Palme d'Or at the 1956 Cannes International Film Festival and an Academy Award in 1957, one of three Oscars his films received.

Audubon

This Frenchman born in Haiti , whose original name was Fougère Rabin, or Jean Rabin, was an ornithologist, artist, and naturalist who became particularly well known for his drawings and paintings of North American birds. Critics of his work have pointed to certain fanciful (or even impossible) poses and inaccurate details, but few argue with their excellence as art. To many, his work far surpasses that of his contemporary (and more scientific) fellow ornithologist, Alexander Wilson.

Wegener

This German meteorologist and geophysicist formulated the first complete statement of the continental drift hypothesis. He first presented his theory in lectures in 1912 and published it in full in 1915 in his most important work,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. His 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.

Koch

This German physician was one of the founders of bacteriology. He discovered the anthrax disease cycle (1876) and the bacteria responsible for tuberculosis (1882) and cholera (1883). For his discoveries in regard to tuberculosis, he received the Nobel Prize for Physiology or Medicine in 1905. In 1878 Koch summarized his experiments on the etiology of wound infection. By inoculating animals with material from various sources, he produced six types of infection, each caused by a specific microorganism. He then transferred these infections by inoculation through several kinds of animals, reproducing the original six types. In that study, he observed differences in pathogenicity for different species of hosts and demonstrated that the animal body is an excellent apparatus for the cultivation of bacteria. He determined guidelines to prove that a disease is caused by a specific organism. These four basic criteria, called Koch's postulates, are: • A specific microorganism is always associated with a given disease. • The microorganism can be isolated from the diseased animal and grown in pure culture in the laboratory. • The cultured microbe will cause disease when transferred to a healthy animal. • The same type of microorganism can be isolated from the newly infected animal.

Planck

This German theoretical physicist originated the quantum theory, which won him the Nobel Prize for Physics in 1918. Planck made many contributions to theoretical physics, but his fame rests primarily on his role as originator of the quantum theory. This theory revolutionized modern understanding of atomic and subatomic processes, just as Albert Einstein's theory of relativity revolutionized the understanding of space and time. Together they constitute the fundamental theories of 20th-century physics. Both have forced humans to revise some of their most cherished philosophical beliefs, and both have led to industrial and military applications that affect every aspect of modern life. One of the first problems that Planck attempted to solve concerned blackbody radiation. By the 1890s various experimental and theoretical attempts had been made to determine the spectral energy distribution—the curve displaying how much radiant energy is emitted at different frequencies for a given temperature of the blackbody. He had to assume that the oscillators comprising the blackbody and re-emitting the radiant energy incident upon them could not absorb this energy continuously but only in discrete amounts, in quanta of energy; only by statistically distributing these quanta, each containing an amount of energy hv proportional to its frequency, over all of the oscillators present in the blackbody could he derive the formula he had hit upon. He adduced additional evidence for the importance of his formula by using it to evaluate the constant h (his value was 6.55 × 10-27 erg-second, close to the modern value), as well as the so-called Boltzmann constant (the fundamental constant in kinetic theory and statistical mechanics), Avogadro's number, and the charge of the electron.

Mayer

This German-born American physicist shared one-half of the 1963 Nobel Prize for Physics with J. Hans D. Jensen of West Germany for their proposal of the shell nuclear model. At the University of Chicago, she received a regular appointment as full professor in 1959. From 1948 to 1949 Mayer published several papers concerning the stability and configuration of protons and neutrons that constitute the atomic nucleus. She developed a theory that the nucleus consists of several shells, or orbital levels, and that the distribution of protons and neutrons among these shells produces the characteristic degree of stability of each species of nucleus.

Bethe

This German-born American theoretical physicist helped shape quantum physics and increased the understanding of the atomic processes responsible for the properties of matter and of the forces governing the structures of atomic nuclei. He received the Nobel Prize for Physics in 1967 for his work on the production of energy in stars. Moreover, he was a leader in emphasizing the social responsibility of science. In 1943 he joined the Los Alamos Laboratory (now the Los Alamos National Laboratory) in New Mexico as the head of its theoretical division. He and the division were part of the Manhattan Project, and they made crucial contributions to the feasibility and design of the uranium and the plutonium atomic bombs. The years at Los Alamos changed his life. In the aftermath of the development of these fission weapons, he became deeply involved with investigating the feasibility of developing fusion bombs, hoping to prove that no terrestrial mechanism could accomplish the task. He believed their development to be immoral.

Einstein

This German-born physicist developed the special and general theories of relativity. He won the Nobel Prize for Physics in 1921 for his explanation of the photoelectric effect. He is generally considered the most influential physicist of the 20th century. During 1905, often called his "miracle year," he published four papers in the Annalen der Physik, each of which would alter the course of modern physics. At first his 1905 papers were ignored by the physics community. This began to change after he received the attention of just one physicist, perhaps the most influential physicist of his generation, Max Planck, the founder of the quantum theory. Soon, owing to Planck's laudatory comments and to experiments that gradually confirmed his theories, he rose rapidly in the academic world. One of the deep thoughts that consumed Einstein from 1905 to 1915 was a crucial flaw in his own theory: it made no mention of gravitation or acceleration. For the next 10 years, he would be absorbed with formulating a theory of gravity in terms of the curvature of space-time. To him, Newton's gravitational force was actually a by-product of a deeper reality: the bending of the fabric of space and time. In November 1915 he finally completed the general theory of relativity, which he considered to be his masterpiece.

Hippocrates

This Greek is known as the "Father of Medicine." Technical medical science developed in the Hellenistic period under his influence and after. Surgery, pharmacy, and anatomy advanced; physiology became the subject of serious speculation; and philosophic criticism improved the logic of medical theories. His oath is the basis of all medical aspirations.

Ptolemy

This Greek-Egyptian Muslim scientist incorrectly pushed his geocentric views,but his greatest claim to fame is the mathematical relationships and movements of heavenly bodies in the sky, which he categorized in his book, The Mathematical Collection. HIs 141 BCE treatise Planetary Hypothesis and his Almagest established the European and Muslim communities to embracing this idea until the Renaissance.

Fermi

This Italian-born American scientist 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, andan award of the U.S. Department of Energy is given in his honour. A National Accelerator Laboratory, in Illinois, is named for him, as is element number 100. He moved to the University of Chicago, where he continued to construct piles in a space under the stands of the football field. The final structure, a flattened sphere about 7.5 metres (25 feet) in diameter, contained 380 tons of graphite blocks as the moderator and 6 tons of uranium metal and 40 tons of uranium oxide as the fuel, distributed in a careful pattern. The pile went "critical" on Dec. 2, 1942, proving that a nuclear reaction could be initiated, controlled, and stopped. Chicago Pile 1, as it was called, was the first prototype for several large nuclear reactors constructed at Hanford, Wash., where plutonium, a man-made element heavier than uranium, was produced. In 1944 he became an American citizen and moved to Los Alamos, N.M., where physicist J. Robert Oppenheimer led the Manhattan Project's laboratory.

Rutherford

This New Zealand-born British physicist was considered the greatest experimentalist since Michael Faraday. He was the central figure in the study of radioactivity, and with his concept of the nuclear atom he led the exploration of nuclear physics. He won the Nobel Prize for Chemistry in 1908. He accepted Thomson's invitation to collaborate on an investigation of the way in which X-rays changed the conductivity of gases. This yielded a classic paper on ionization—the breaking of atoms or molecules into positive and negative parts (ions)—and the charged particles' attraction to electrodes of the opposite polarity. He then pursued other radiations that produced ions, looking first at ultraviolet radiation and then at radiation emitted by uranium. Placement of uranium near thin foils revealed to Rutherford that the radiation was more complex than previously thought: one type was easily absorbed or blocked by a very thin foil, but another type often penetrated the same thin foils. He named these radiation types alpha and beta, respectively, for simplicity. With the German physicist Hans Geiger, Rutherford developed an electrical counter for ionized particles; when perfected by Geiger, the Geiger counter became the universal tool for measuring radioactivity. In 1911, Rutherford disproved William Thomson's model of the atom as a uniformly distributed substance. Because a few of the alpha particles in his beam were scattered by large angles after striking the gold foil, Rutherford knew that the gold atom's mass must be concentrated in a tiny, dense nucleus.

Pavlov

This Russian physiologist was known chiefly for his development of the concept of the conditioned reflex. In a now-classic experiment, he trained a hungry dog to salivate at the sound of a bell, which was previously associated with the sight of food. He developed a similar conceptual approach, emphasizing the importance of conditioning, in his pioneering studies relating human behaviour to the nervous system. He was awarded the Nobel Prize for Physiology or Medicine in 1904 for his work on digestive secretions.

Gamow

This Russian-born American nuclear physicist and cosmologist was one of the foremost advocates of the big-bang theory, according to which the universe was formed in a colossal explosion that took place billions of years ago. In addition, his work on deoxyribonucleic acid (DNA) made a basic contribution to modern genetic theory. In 1928, he traveled to Göttingen, where he developed his quantum theory of radioactivity, the first successful explanation of the behaviour of radioactive elements, some of which decay in seconds while others decay over thousands of years. His paper called "The Origin of Chemical Elements" (1948) attempted to explain the distribution of chemical elements throughout the universe, posits a primeval thermonuclear explosion, the big bang that began the universe. According to the theory, after the big bang, atomic nuclei were built up by the successive capture of neutrons by the initially formed pairs and triplets. In 1954 his scientific interests grew to encompass biochemistry. He proposed the concept of a genetic code and maintained that the code was determined by the order of recurring triplets of nucleotides, the basic components of DNA. His proposal was vindicated during the rapid development of genetic theory that followed.

Thomson

This Scottish engineer, mathematician, and physicist William Thomson, also known as Baron Kelvin, profoundly influenced the scientific thought of his generation. Thomson, who was knighted and raised to the peerage in recognition of his work in engineering and physics, was foremost among the small group of British scientists who helped to lay the foundations of modern physics. His contributions to science included a major role in the development of the second law of thermodynamics; the absolute temperature scale (measured in Kelvins); the dynamical theory of heat; the mathematical analysis of electricity and magnetism, including the basic ideas for the electromagnetic theory of light; the geophysical determination of the age of the Earth; and fundamental work in hydrodynamics. His theoretical work on submarine telegraphy and his inventions for use on submarine cables aided Britain in capturing a preeminent place in world communication during the 19th century.

Lyell

This Scottish geologist was largely responsible for the general acceptance of the view that all features of the Earth's surface are produced by physical, chemical, and biological processes through long periods of geological time. The concept was called uniformitarianism. his achievements laid the foundations for evolutionary biology as well as for an understanding of the Earth's development. In 1859 publication of Darwin's Origin of Species gave new impetus to his work. Although Darwin drew heavily on his Principles of Geology both for style and content, He had never shared Darwin's belief in evolution. But reading the Origin of Species triggered studies that culminated in publication of The Geological Evidence of the Antiquity of Man in 1863, in which he tentatively accepted evolution by natural selection. Only during completion of a major revision of the Principles of Geology in 1865 did he fully adopt Darwin's conclusions, however, adding powerful arguments of his own that won new adherents to Darwin's theory

Linnaeus

This Swedish naturalist and explorer was the first to frame principles for defining natural genera and species of organisms and to create a uniform system for naming them (binomial nomenclature). In 1735 he published Systema Naturae ("The System of Nature"), a folio volume of only 11 pages, which presented a hierarchical classification, or taxonomy, of the three kingdoms of nature: stones, plants, and animals. Each kingdom was subdivided into classes, orders, genera, species, and varieties. This hierarchy of taxonomic ranks replaced traditional systems of biological classification that were based on mutually exclusive divisions, or dichotomies. His studies of plant hybridization influenced the experimental tradition that led directly to the pea plant experiments of Austrian botanist Gregor Mendel.

Jung

This Swiss psychologist and psychiatrist founded analytic psychology, in some aspects a response to Sigmund Freud's psychoanalysis. He proposed and developed the concepts of the extraverted and the introverted personality, archetypes, and the collective unconscious. His early researches led him to understand Freud's investigations; his findings confirmed many of Freud's ideas, and, for a period of five years (between 1907 and 1912), he was Freud's close collaborator. A serious disagreement came in 1912,with the publication of his Psychology of the Unconscious (1916), which ran counter to many of Freud's ideas. He devoted the rest of his life to developing his ideas, especially those on the relation between psychology and religion. In his view, obscure and often neglected texts of writers in the past shed unexpected light not only on his own dreams and fantasies but also on those of his patients; he thought it necessary for the successful practice of their art that psychotherapists become familiar with writings of the old masters.

Fleming

This UK scientist did 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. He 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.

Waksman

This Ukrainian-born American biochemist was one of the world's foremost authorities on soil microbiology. After the discovery of penicillin, he played a major role in initiating a calculated, systematic search for antibiotics among microbes. His consequent codiscovery of the antibiotic streptomycin, the first specific agent effective in the treatment of tuberculosis, brought him the 1952 Nobel Prize for Physiology or Medicine.

Pliny, the Elder

This first century CE scientist wrote the 37-volume encyclopedic work known as Natural History. The topics included cosmology and astronomy, zoology, botany, medicine and drugs, and minerals (including precious stones) and metals.

Galen of Pergamum

This second century CE Greek physician, writer, and philosopher exercised a dominant influence on medical theory and practice in Europe from the Middle Ages until the mid-17th century. His authority in the Byzantine world and the Muslim Middle East was similarly long-lived. He advocated dissection of animals for knowledge and practice for surgery. Unfortunately, he was not allowed to dissect human cadavers; so, he incorrectly supposed human processes by using animal processes. He incorrectly believed that human health requires an equilibrium between the four main bodily fluids, or humours—blood, yellow bile, black bile, and phlegm. His incorrect assumptions on blood flow were corrected in the 17th century by William Harvey.

Humboldt

18th/19th German naturalist and explorer was a major figure in the classical period of physical geography and biogeography—areas of science now included in the earth sciences and ecology. With his book Kosmos he made a valuable contribution to the popularization of science. A current off the west coast of South America was named after him. He did an investigation of a phenomenon that had aroused his interest in South America: the sudden fluctuations of the Earth's geomagnetic field—the so-called magnetic storms. With the help of assistants, he carried out observations of the movement of a magnetometer in a quiet garden pavilion in Berlin; but it had been clear to him for a number of years that, to discover whether these magnetic storms were of terrestrial or extraterrestrial origin, it would be necessary to set up a worldwide net of magnetic observatories.

Snake

Because it was supposed that Asclepius effected cures of the sick in dreams, the practice of sleeping in his temples in Epidaurus in South Greece became common. This practice is often described as Asclepian incubation. In 293 BCE his cult spread to Rome, where he was worshiped as Aesculapius. Asclepius was frequently represented standing, dressed in a long cloak, with bare breast; his usual attribute was a staff with what coiled around it? This staff is the only true symbol of medicine.

Laplace

He was a French mathematician, astronomer, and physicist and is best known for his investigations into the stability of the solar system. In the 1780's Laplace successfully accounted for all the observed deviations of the planets from their theoretical orbits by applying Sir Isaac Newton's theory of gravitation to the solar system, and he developed a conceptual view of evolutionary change in the structure of the solar system. He also demonstrated the usefulness of probability for interpreting scientific data. He was not executed during the French Revolution because he was not rich nor political. He went on to publish A Philosophical Essay on Probability in 1814, a follow-up to his 1812 Analytic Theory of Probability.

Pierre Curie

He was a French physical chemist and cowinner of the Nobel Prize for Physics in 1903. He and his wife, Marie, discovered radium and polonium in their investigation of radioactivity. An exceptional physicist, he was one of the main founders of modern physics. The phenomenon of radioactivity, discovered in 1896 by Henri Becquerel, had attracted Marie's attention.He and his wife determined to study a mineral, pitchblende, the specific activity of which is superior to that of pure uranium. While working with Marie to extract pure substances from ores, an undertaking that really required industrial resources but that they achieved in relatively primitive conditions, he concentrated on the physical study (including luminous and chemical effects) of the new radiations. Through the action of magnetic fields on the rays given out by the radium, he proved the existence of particles electrically positive, negative, and neutral; these Ernest Rutherford was afterward to call alpha, beta, and gamma rays. He then studied these radiations by calorimetry and also observed the physiological effects of radium, thus opening the way to radium therapy. Give both first and last name.

Ray

He was a leading 17th century English naturalist and botanist who contributed significantly to progress in taxonomy. His enduring legacy to botany was the establishment of species as the ultimate unit of taxonomy. He had never interrupted his research in botany. In 1682 he had published a Methodus Plantarum Nova (revised in 1703 as the Methodus Plantarum Emendata . . . ), his contribution to classification, which insisted on the taxonomic importance of the distinction between monocotyledons and dicotyledons, plants whose seeds germinate with one leaf and those with two, respectively. Ray's enduring legacy to botany was the establishment of species as the ultimate unit of taxonomy

LaVoisier

He was a prominent French chemist and leading figure in the 18th-century chemical revolution who developed an experimentally based theory of the chemical reactivity of oxygen and coauthored the modern system for naming chemical substances. Having also served as a leading financier and public administrator before the French Revolution, he was executed with other financiers during the revolutionary terror. The assertion that mass is conserved in chemical reactions was an assumption of Enlightenment investigators rather than a discovery revealed by their experiments. Lavoisier believed that matter was neither created nor destroyed in chemical reactions, and in his experiments he sought to demonstrate that this belief was not violated. Still he had difficulty proving that his view was universally valid. His insistence that chemists accepted this assumption as a law was part of his larger program for raising chemistry to the investigative standards and causal explanation found in contemporary experimental physics. The oxygen theory of combustion resulted from a demanding and sustained campaign to construct an experimentally grounded chemical theory of combustion, respiration, and calcination, in which a loss of weight occurs. The phlogiston theory that then-scientists believed in did not account for these weight changes, for fire itself could not be isolated and weighed. Lavoisier hypothesized that it was probably the fixation and release of air, rather than fire, that caused the observed gains and losses in weight. This idea set the course of his research for the next decade.

Galvani

He was an Italian physician and physicist who investigated the nature and effects of what he conceived to be electricity in animal tissue. His discoveries led to the invention of the voltaic pile, a kind of battery that makes possible a constant source of current electricity. His developing interest was indicated by his lectures on the anatomy of the frog in 1773 and in electrophysiology in the late 1770s, when, following the acquisition of an electrostatic machine (a large device for making sparks) and a Leyden jar (a device used to store static electricity), he began to experiment with muscular stimulation by electrical means. In 1786, for example, he obtained muscular contraction in a frog by touching its nerves with a pair of scissors during an electrical storm. He also observed the legs of a skinned frog kick when a scalpel touched a lumbar nerve of the animal while an electrical machine was activated. He provided the major stimulus for Alessandro Volta to discover a source of constant current electricity

Asclepius

He was honoured as a hero, and eventually worshiped as a god. The legend made him the son of Apollo (god of healing, truth, and prophecy) and the mortal princess Coronis, he became the Greco-Roman god of medicine. Legend has it that the Centaur Chiron, who was famous for his wisdom and knowledge of medicine, taught him the art of healing. At length Zeus was afraid that he might render all men immortal and slew him with a thunderbolt.

Leaky Family

Louis , Mary, and their son, Richard, respectively, heavily influenced modern archaeology and paleoanthropology. They are known for their discoveries of hominin and other fossil remains in eastern Africa. In addition to their discoveries, the family inspired several now well-known zoologists and ethologists, who have themselves made groundbreaking discoveries concerning humans and their ancestors. Louis was a Kenyan archaeologist and anthropologist and was known for his fossil discoveries in East Africa, which proved that humans were far older than had previously been believed and that human evolution was centred in Africa, rather than in Asia, as earlier discoveries had suggested. He was also noted for his controversial interpretations of these archaeological finds. In 1948, on Rusinga Island in Lake Victoria, Mary discovered the skull of Proconsul africanus, an ancestor of both apes and early humans that lived about 25 million years ago. In 1959 at Olduvai Gorge, Tanzania, she discovered the skull of an early hominin (member of the human lineage) that her husband named Zinjanthropus, or "eastern man," though it is now regarded as Paranthropus, a type of australopith, or "southern ape." Their son, Richard, and his fellow workers uncovered some 400 hominin fossils representing perhaps 230 individuals, making Koobi Fora the site of the richest and most varied assemblage of early human remains found to date anywhere in the world.

Marie Curie

Polish-born French physicist Marie Curie was famous for her work on radioactivity. She was the first woman to win a Nobel Prize, and she is the only woman to win the award in two different fields. With Henri Becquerel and her husband, Pierre, she was awarded the 1903 Nobel Prize for Physics. She was the sole winner of the 1911 Nobel Prize for Chemistry. The sudden death of her husband (April 19, 1906) was a bitter blow to her, but it was also a decisive turning point in her career. Henceforth, she was to devote all her energy to completing alone the scientific work that they had undertaken. On May 13, 1906, she was appointed to the professorship that had been left vacant on her husband's death; she was the first woman to teach in the Sorbonne. In 1908 she became titular professor, and in 1910 her fundamental treatise on radioactivity was published. After being awarded a second Nobel Prize, for the isolation of pure radium, she saw the completion of the building of the laboratories of the Radium Institute at the University of Paris. She died of leukemia because of her research. Give both first and last name.

Avicenna

This 11th century CE Iranian physician and the most famous and influential of the philosopher-scientists of Islam. He was particularly noted for his contributions in the fields of Aristotelian philosophy and medicine. He composed the Book of Healing, a vast philosophical and scientific encyclopaedia and the largest of its kind written by one man, and The Canon of Medicine, which is among the most famous books in the history of medicine.

Bacon

This 13th century scientist was known as Doctor Mirabilis (Latin for "Wonderful Teacher"), was an English Franciscan philosopher and educational reformer, as well as a major medieval proponent of experimental science. Bacon studied mathematics, astronomy, optics, alchemy, and languages. He was the first European to describe in detail the process of making gunpowder, and he proposed flying machines and motorized ships and carriages. He irritated his fellow Franciscans but got permission by Pope Clement IV to continue his work on optics, languages, alchemy, flying machines, principles of reflection and refraction, and cameras.

da Vinci

This 15th/16th century literal Renaissance man did everything, including science. He dissected 30 corpses in his time to understand how to draw the human body on canvas/plaster. Working with the mathematician Luca Pacioli, he considered the proportional theories of Vitruvius, the 1st-century BCE Roman architect, as presented in his treatise On Architecture. In his illustration of this theory, the so-called Vitruvian Man, Leonardo demonstrated that when a man places his feet firmly on the ground and stretches out his arms, he can be contained within the four lines of a square, but when in a spreadeagle position, he can be inscribed in a circle. He presented drawings of screw threads, gears, hydraulic jacks, swiveling devices, transmission gears, tanks, a flying machine, and a helicopter.

Brahe

This 16th century Danish astronomer developing astronomical instruments and in measuring and fixing the positions of stars paved the way for future discoveries. His observations—the most accurate possible before the invention of the telescope—included a comprehensive study of the solar system and accurate positions of more than 777 fixed stars. He proved that the nova of 1572 was a star, added a comprehensive study of the solar system, andproved that the orbit of the comet of 1577 lay beyond the Moon. Perhaps his greatest achievement was training and teaching Johannes Kepler. He is best known for his silver nose, replacing what he lost in a duel.

Vesalius

This 16th century Flemish scientist was a Renaissance physician who revolutionized the study of biology and the practice of medicine by his careful description of the anatomy of the human body. Basing his observations on dissections he made himself, he wrote and illustrated the first comprehensive textbook of anatomy. In 1543, he wrote The Seven Books on the Structure of the Human Body, commonly known as the Fabrica.

Bruno

This 16th century Italian philosopher, astronomer, mathematician, and occultist whose theories anticipated modern science is probably best known for his strong belief in the heliocentric theory that led to his being burned at the stake by the Catholic church. In the Cena de le Ceneri (1584; "The Ash Wednesday Supper"), he not only reaffirmed the reality of the heliocentric theory but also suggested that the universe is infinite, constituted of innumerable worlds substantially similar to those of the solar system. In the same dialogue he anticipated his fellow Italian astronomer Galileo Galilei by maintaining that the Bible should be followed for its moral teaching but not for its astronomical implications. He also strongly criticized the manners of English society and the pedantry of the Oxford doctors. As a symbol of the freedom of thought, he inspired the European liberal movements of the 19th century, particularly the Italian Risorgimento (the movement for national political unity).

Copernicus

This 16th century Polish astronomer established a heliocentric (sun-centered) system, disrupting the long-held belief that the earth was the center of the universe. In the treatise Commentariolus, Copernicus postulated that, if the Sun is assumed to be at rest and if the Earth is assumed to be in motion, then the remaining planets fall into an orderly relationship whereby their sidereal periods increase from the Sun as follows: Mercury (88 days), Venus (225days), Earth (1 year), Mars (1.9 years), Jupiter (12 years), and Saturn (30 years).

Paracelsus

This 16th century Swiss-Austrian established the role of chemistry in medicine. After graduating from college, he set fire to books by Galen and Avicenna and proceeded to look at metals as the cause and cure for many diseases. He found a cure for syphillis by using salts of mercury. He cured a village of the plague. He was the first to develop the field of psychiatry.

Kepler

This 16th/17th century German astronomer discovered three major laws of planetary motion. He did not call these discoveries "laws," as would become customary after Isaac Newton derived them from a new and quite different set of general physical principles. He provided a new and correct account of how vision occurs; he developed a novel explanation for the behaviour of light in the newly invented telescope; and he discovered several new, semiregular polyhedrons. His greatest influence was on Newton.

Galileo

This 16th/17th century Italian natural philosopher, astronomer, and mathematician who made fundamental contributions to the sciences of motion, astronomy, and strength of materials and to the development of the scientific method. His formulation of (circular) inertia, the law of falling bodies, and parabolic trajectories marked the beginning of a fundamental change in the study of motion. His insistence that the book of nature was written in the language of mathematics changed natural philosophy from a verbal, qualitative account to a mathematical one in which experimentation became a recognized method for discovering the facts of nature. Finally, his discoveries with the telescope revolutionized astronomy and paved the way for the acceptance of the Copernican heliocentric system, but his advocacy of that system eventually resulted in an Inquisition process against him.

Harvey

This 17th century English physician was the first to recognize the full circulation of the blood in the human body and to provide experiments and arguments to support this idea. His key work was Anatomical Exercise on the Motion of the Heart and Blood in Animals), published in 1628. Harvey's greatest achievement was to recognize that the blood flows rapidly around the human body, being pumped through a single system of arteries and veins, and to support this hypothesis with experiments and arguments. It is likely that Harvey actually made his discovery of the circulation about 1618-19. Such a major shift in thinking about the body needed to be very well supported by experiment and argument to avoid immediate ridicule and dismissal; hence the delay before the publication of his central work. In 1649 Harvey published Two Anatomical Exercises on the Circulation of the Blood in response to criticism of the circulation theory by French anatomist Jean Riolan.

Hooke

This 17th century English physicist discovered the law of elasticity, known as his namesake law. He also conducted research in a remarkable variety of fields. In the 1650's he used his newly made telescope in finding stars in Orion and rotation axis of planets. He was the first to use the word "cell" in describing the microscopic honeycomb cavities in cork. In 1672 he discovered the phenomenon of diffraction (the bending of light rays around corners); to explain it, he offered the wave theory of light. He was the first man to state in general that all matter expands when heated and that air is made up of particles separated from each other by relatively large distances. He worked with Robert Boyle in his studies of pressure and had a bitter feud with Newton.

van Leeuwenhoek

This 17th/18th Dutch microscopist was the first to observe bacteria and protozoa. His researches on lower animals refuted the doctrine of spontaneous generation, and his observations helped lay the foundations for the sciences of bacteriology and protozoology. The dramatic nature of his discoveries made him world famous. He made microscopes consisting of a single, high-quality lens of very short focal length; at the time, such simple microscopes were preferable to the compound microscope, which increased the problem of chromatic aberration. In 1677 he described for the first time the spermatozoa from insects, dogs, and man. He extended Marcello Malpighi's demonstration in 1660 of the blood capillaries by giving (in 1684) the first accurate description of red blood cells. In his observations on rotifers in 1702, Leeuwenhoek remarked that "in all falling rain, carried from gutters into water-butts, animalcules are to be found; and that in all kinds of water, standing in the open air, animalcules can turn up. For these animalcules can be carried over by the wind, along with the bits of dust floating in the air."

Cavendish

This 18th century scientist was a natural philosopher and is considered to be the greatest experimental and theoretical English chemist and physicist of his age. He was distinguished for great accuracy and precision in researches into the composition of atmospheric air, the properties of different gases, the synthesis of water, the law governing electrical attraction and repulsion, a mechanical theory of heat, and calculations of the density (and hence the weight) of the Earth. His experiment to weigh the Earth has come to be known as his namesake experiment. His first publication (1766) was a combination of three short chemistry papers on "factitious airs," or gases produced in the laboratory. He produced "inflammable air" (hydrogen) by dissolving metals in acids and "fixed air" (carbon dioxide) by dissolving alkalis in acids, and he collected these and other gases in bottles inverted over water or mercury. He then measured their solubility in water and their specific gravity and noted their combustibility. He used the language of the old phlogiston theory in chemistry. In 1787 he became one of the earliest outside France to convert to the new antiphlogistic theory of Lavoisier, though he remained skeptical about the nomenclature of the new theory.

Herschel

This 18th/19th centurey German-born British astronomer Sir William Herschel was the founder of sidereal astronomy for the systematic observation of the heavens. He discovered the planet Uranus, hypothesized that nebulae are composed of stars, and developed a theory of stellar evolution. He also cataloged 848 double stars—pairs of stars that appear close together in space, and measurements of the comparative brightness of stars. He observed that double stars did not occur by chance as a result of random scattering of stars in space but that they actually revolved about each other. His 70 published papers include not only studies of the motion of the solar system through space and the announcement in 1800 of the discovery of infrared rays but also a succession of detailed investigations of the planets and other members of the solar system.

Ampere

This 18th/19th century French physicist André-Marie Ampère founded and named the science of electrodynamics, now known as electromagnetism . His name endures in everyday since the unit for measuring electric current is named for him. He worked on developing a mathematical and physical theory to understand the relationship between electricity and magnetism. Extending Hans Christiaan Ørsted's experimental work, he showed that two parallel wires carrying electric currents repel or attract each other, depending on whether the currents flow in the same or opposite directions, respectively. He also applied mathematics in generalizing physical laws from these experimental results. Most important was the principle that came to be his namesake law, which states that the mutual action of two lengths of current-carrying wire is proportional to their lengths and to the intensities of their currents. He also applied this same principle to magnetism, showing the harmony between his law and French physicist Charles Augustin de Coulomb's law of magnetic action. Ampère's devotion to, and skill with, experimental techniques anchored his science within the emerging fields of experimental physics.

Cuvier

This 18th/19th century French zoologist and statesman established the sciences of comparative anatomy and paleontology.

Jenner

This 18th/19th century physician is best known for his discovery of the vaccination of smallpox. The story of the great breakthrough is well known. In May 1796 Jenner found a young dairymaid, Sarah Nelmes, who had fresh cowpox lesions on her hand. On May 14, using matter from Sarah's lesions, he inoculated an eightyear-old boy, James Phipps, who had never had smallpox. Phipps became slightly ill over the course of the next 9 days but was well on the 10th. On July 1 Jenner inoculated the boy again, this time with smallpox matter. No disease developed; protection was complete. In 1798 Jenner, having added further cases, published privately a slender book entitled An Inquiry into the Causes and Effects of the Variolae Vaccinae.The procedure spread rapidly to America and the rest of Europe and soon was carried around the world.

Mendel

This 19th century Austrian botanist, teacher, and Augustinian prelate was the first to lay the mathematical foundation of the science of genetics, in what came to be named after him. He chose to conduct his studies with the edible pea (Pisum sativum) because of the numerous distinct varieties, the ease of culture and control of pollination, and the high proportion of successful seed germinations. From 1854 to 1856 he tested 34 varieties for constancy of their traits. In order to trace the transmission of characters, he chose seven traits that were expressed in a distinctive manner, such as plant height (short or tall) and seed color (green or yellow). His approach to experimentation came from his training in physics and mathematics, especially combinatorial mathematics. The latter served him ideally to represent his result. If A represents the dominant characteristic and a the recessive, then the 1:2:1 ratio recalls the terms in the expansion of the binomial equation: (A + a)^2 = A^2 + 2Aa + a^2.

Lister

This 19th century British surgeon and medical scientist was the founder of antiseptic medicine and a pioneer in preventive medicine. While his method, based on the use of antiseptics, is no longer employed, his principle—that bacteria must never gain entry to an operation wound—remains the basis of surgery to this day. He began his experiments with antisepsis. Much of his earlier published work had dealt with the mechanism of coagulation of the blood and role of the blood vessels in the first stages of inflammation. Both researches depended upon the microscope and were directly connected with the healing of wounds. He had already tried out methods to encourage clean healing and had formed theories to account for the prevalence of sepsis. Discarding the popular concept of miasma—direct infection by bad air—he postulated that sepsis might be caused by a pollen-like dust. There is no evidence that he believed this dust to be living matter, but he had come close to the truth. It is therefore all the more surprisingthat he became acquainted with the work of the bacteriologist Louis Pasteur only in 1865. He unintentionally had an effect on American history when President James Garfield was shot. He was touring the US pushing his antiseptic ideas when Garfield's physicians were wearing stained coats from previous surgeries, thus infecting the President to a horrible death.

Davy

This 19th century English chemist discovered several chemical elements (including sodium and potassium) and compounds, invented the miner's safety lamp, and became one of the greatest exponents of the scientific method. Davy early concluded that the production of electricity in simple electrolytic cells resulted from chemical action and that chemical combination occurred between substances of opposite charge. He therefore reasoned that electrolysis, the interactions of electric currents with chemical compounds, offered the most likely means of decomposing all substances to their elements. He conducted a number of other studies as well. He investigated the substance "X" (later called iodine), whose properties and similarity to chlorine he quickly discovered, and he analyzed many specimens of classical pigments and proved that diamond is a form of carbon. Davy also investigated the conditions under which mixtures of firedamp and air explode. This led to the invention of the miner's safety lamp and to subsequent researches on flame.

Galton

This 19th century English explorer, anthropologist, and eugenicist was known for his pioneering studies of human intelligence. Although he made contributions to many fields of knowledge, eugenics remained his fundamental interest, and he devoted the latter part of his life chiefly to propagating the idea of improving the physical and mental makeup of the human species by selective parenthood.He, being a cousin of Charles Darwin, was among the first to recognize the implications for mankind of Darwin's theory of evolution. He saw that it invalidated much of contemporary theology and that it also opened possibilities for planned human betterment. He coined the word eugenics to denote scientific endeavors to increase the proportion of persons with better than average genetic endowment through selective mating of marriage partners.In his Hereditary Genius (1869), in which he used the word genius to denote "an ability that was exceptionally high and at the same time inborn," his main argument was that mental and physical features are equally inherited—a proposition that was not accepted at the time.

Darwin

This 19th century English naturalist developed the theory of evolution by natural selection, which became the foundation of modern evolutionary studies. An affable country gentleman, Darwin at first shocked religious Victorian society by suggesting that animals and humans shared a common ancestry. However, his nonreligious biology appealed to the rising class of professional scientists, and by the time of his death evolutionary imagery had spread through all of science, literature, and politics. embarked on the Beagle voyage on Dec. 27, 1831. The circumnavigation of the globe would be the making of him. Five years of physical hardship and mental rigor, imprisoned within a ship's walls, offset by wide open opportunities in the Brazilian jungles and the Andes Mountains, were to give him a new seriousness. As a gentleman naturalist, he could leave the ship for extended periods, pursuing his own interests. As a result, he spent only 18 months of the voyage aboard the ship. Among the places Darwin visited on the voyage were the Cape Verde Islands, coastal regions of Brazil, Uruguay, and Argentina, and the Galapagos Islands. On the last leg of the voyage Darwin finished his 770-page diary, wrapped up 1,750 pages of notes, drew up 12 catalogs of his 5,436 skins, bones, and carcasses—and still he wondered: Was each Galapagos mockingbird a naturally produced variety? Why did ground sloths become extinct? He sailed home with problems enough to last him a lifetime. He hastily began an "abstract" of Natural Selection, which grew into a more accessible book, On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life.

Pasteur

This 19th century French chemist and microbiologist made some of the most varied and valuable discoveries in the history of science and industry. It was he who proved that microorganisms cause fermentation and disease; he who pioneered the use of vaccines for rabies, anthrax, and chicken cholera; he who saved the beer, wine, and silk industries of France and other countries; he who performed important pioneer work in stereochemistry. From studying the fermentation of alcohol he went on to the problem of lactic fermentation, showing yeast to be an organism capable of reproducing itself, even in artificial media, without free oxygen—a concept that became known as his namesake effect. He later announced that fermentation was the result of the activity of minute organisms and that when fermentation failed, either the necessary organism was absent or was unable to grow properly. He showed that milk could be soured by injecting a number of organisms from buttermilk or beer but could be kept unchanged if such organisms were excluded. By 1881 Pasteur had perfected a technique for reducing the virulence of various disease-producing microorganisms, and he had succeeded in vaccinating a herd of sheep against the disease known as anthrax. Likewise, he was able to protect fowl from chicken cholera, for he had observed that once animals stricken with certain diseases had recovered they were later immune to a fresh attack. Thus, by isolating the germ of the disease and by cultivating an attenuated, or weakened, form of the germ and inoculating fowl with the culture, he could immunize the animals against the malady.

Gay-Lussac

This 19th century French chemist and physicist pioneered investigations into the behaviour of gases, established new techniques for analysis, and made notable advances in applied chemistry. His first publication (1802), however, was on the thermal expansion of gases. To ensure more accurate experimental results, he used dry gases and pure mercury. He concluded from his experiments that all gases expand equally over the temperature range 0-100 °C (32-212 °F). This law, usually (and mistakenly) attributed to French physicist J.-A.-C. Charles as "Charles's law," was the first of several regularities in the behavior of matter that he established. In 1807 he published an important study of the heating and cooling produced by the compression and expansion of gases, resulting in his namesake law. This was later to have significance for the law of conservation of energy.

Avogadro

This 19th century Italian mathematical physicist showed in what became known as his namesake law that, under controlled conditions of temperature and pressure, equal volumes of gases contain an equal number of molecules. In 1811 he provided the correct molecular formula for water, nitric and nitrous oxides, ammonia, carbon monoxide, and hydrogen chloride. Three years later he described the formulas for carbon dioxide, carbon disulfide, sulfur dioxide, and hydrogen sulfide at a time when the difference between atoms and molecules was not well defined. In 1824 he calculated the "true affinity for heat" of a gas by dividing the square of its specific heat by its density. The results ranged from 0.8595 for oxygen to 10.2672 for hydrogen, and the numerical order of the affinities coincided with the electrochemical series, which listed the elements in the order of their chemical reactivities. The value known as his namesake number (6.02214179 × 1023), the number of molecules in a gram molecule, or mole, of any substance, has become a fundamental constant of physical science

Mendeleev

This 19th century Russian chemist developed the periodic classification of the elements. He found that, when all the known chemical elements were arranged in order of increasing atomic weight, the resulting table displayed a recurring pattern, or periodicity, of properties within groups of elements. In his version of the periodic table of 1871, he left gaps in places where he believed unknown elements would find their place. He even predicted the likely properties of three of the potential elements. The subsequent proof of many of his predictions within his lifetime brought fame to him as the founder of the periodic law. In 1871, as he published the final volume of the first edition of his Principles of Chemistry, he was investigating the elasticity of gases and gave a formula for their deviation from Boyle's law (now also known as the Boyle-Mariotte law, the principle that the volume of a gas varies inversely with its pressure).

Maxwell

This 19th century Scottish physicist was best known for his formulation of electromagnetic theory. He is regarded by most modern physicists as the scientist of the 19th century who had the greatest influence on 20th century physics, and he is ranked with Sir Isaac Newton and Albert Einstein for the fundamental nature of his contributions. In 1931, on the 100th anniversary of his birth, Einstein described the change in the conception of reality in physics that resulted from Maxwell's work as "the most profound and the most fruitful that physics has experienced since the time of Newton." The concept of electromagnetic radiation originated with him, and his field equations, based on Michael Faraday's observations of the electric and magnetic lines of force, paved the way for Einstein's special theory of relativity, which established the equivalence of mass and energy.