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86. T heodosius D obzhansky 8 7 .
H a n t a r o N agaoka
91. R osalyn
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92. S heldon L ee G lashow ( l e f t ) and S te v en W einberg [1290] WILDT
ANDERSON [1292]
arriving from deep space, thus giving rise to the discovery of “X-ray stars.” [1290] WILDT, Rupert (vihlt) German-American astronomer Born: Munich, Germany, June 25, 1905 Died: Orleans, Massachusetts, January 9, 1976 Wildt obtained his Ph.D. at the Uni versity of Berlin in 1927. He came to the United States in 1935 and became an American citizen in 1941. Working at the University of Got tingen, and later at Yale University in the United States, Wildt specialized in atmospheres of all sorts. In 1932 he iden tified certain absorption bands, observed by Slipher [1038] in the spectra of Jupi ter and the other outer planets, as be longing to ammonia and methane. It has since been recognized that the atmo spheres of those planets are chiefly hy drogen and helium (which yield no easily observed absorption bands), but certainly ammonia and methane are important minor components. Wildt took into account this atmo spheric composition, plus the overall den sity of each planet, and the equatorial bulging due to its speed of rotation and the distribution of densities within its structure, and out of it attempted to deduce a picture of the general structure of these outer planets. Essentially, for Jupiter and the others, he pictured a deep and dense atmosphere, underneath which is a thick shell of ice overlying an interior of rock and metal. This model was approached cautiously by astrono mers, and it has since been abandoned as a result of the data sent back by the Pio neer and Voyager Jupiter probes in 1973 and thereafter. In 1937 Wildt speculated that the cloudy cover of Venus might consist of droplets of formaldehyde, since water seemed to be absent. Venus probes from 1962 onward confirmed that surface water is absent on Venus but the clouds do contain water. However, they also contain sulfur and sulfuric acid, so those clouds are anything but benign. [1291] CHARGAFF, Erwin Austrian-American biochemist Born: Czemowitz, Austria (now Chernovtsy, USSR), August 11, 1905 Chargaff obtained his Ph.D. at the University of Vienna in 1928 and worked in Berlin from 1930 to 1933. The coming of Hider was his signal to leave Germany. He spent two years in Paris, then in 1935 left for the United States, where he worked at the Columbia University College of Physicians and Surgeons. The development of paper chroma tography in 1944 by Martin [1350] and Synge [1394] was, initially, to separate the amino acids and estimate the quan tity of each in a particular protein mole cule. However, the technique could eas ily be modified to suit all sorts of mix tures and in the late 1940s Chargaff was one of those who set about determining the quantity of each of the nitrogenous bases present in a particular nucleic acid molecule. He tested a wide variety of such mole cules and showed that in general the number of adenine units in each was equivalent to the number of thymine units, while the number of guanine units was equivalent to the number of cytosine units. This was used, most fruitfully, by Crick [1406] and James Dewey Watson [1480] in working out the Watson-Crick model of DNA structure. [1292] ANDERSON, Carl David American physicist
September 3, 1905 Anderson studied at the California In stitute of Technology, obtaining his Ph.D., magna cum laude, in 1930. He remained at the Institute, working with Millikan [969] on cosmic rays, and was a member of the faculty thereafter, be coming professor of physics in 1939 and chairman of the division in 1962. In the course of his cosmic ray studies, Anderson devised a cloud chamber with 805 [1292] ANDERSON
ochoa
[1293] a lead plate dividing it. Ordinarily the particles associated with cosmic rays are so energetic that their curvature in even a strong magnetic field is not very pro nounced. The lead partition, while not stopping such particles altogether, did subtract suificient energy so that the paths on the far side assumed a distinct curvature, and more could be learned from a curved track than from a straight one. In August 1932, while studying photo graphs of tracks in such a cloud cham ber, Anderson came across some that looked exactly like the tracks of an elec tron, except that they curved the wrong way. They were precisely what one might expect from electrons carrying a positive charge rather than a negative one. Indeed, it seemed to Anderson that this must be the positively charged elec tron toward which the mathematics of Dirac [1256], two years earlier, had pointed the way. Anderson suggested the name positron for the new particle, and this was accepted. He also suggested negatron as a name for the ordinary electron, but this never caught on. In making his discovery, Anderson just nosed out Blackett [1207] and the Joliot- Curies [1204, 1227], who were also on the track of the positron. Nor was the positron the only new particle located by Anderson in the course of his cosmic ray work. In 1935, while making cloud chamber exposures on Pike’s Peak in Colorado, he observed a new track that was less curved than an electron track and more curved than a proton track. The most direct inter pretation of the track was that it belonged to a particle of intermediate mass, of a type that had been theoret ically predicted a short time before by Yukawa [1323], The observed particle proved to be 130 times as massive as an electron and therefore about V
as mas sive as a proton. Anderson suggested the name mesotron for it. The name was ac cepted but was quickly shortened to meson.
Both positron and meson, formed out of the superabundance of energy as sociated with cosmic ray particles, are short-lived indeed. The positron reacts with the first electron it approaches. The two cancel each other out, so to speak, matter being destroyed and the equiva lent amount of energy, in the form of a pair of gamma rays, being created. The change exactly matches that predicted by Einstein’s [1064] famous E=mc2 equa tion. Later it was found by Blackett that the process could be reversed; gamma rays could be converted into an electron- positron pair, destroying energy and cre ating mass in its place. As for the meson, that broke down in a matter of millionths of a second. A positively charged meson broke down to positrons and neutrinos, while a nega tively charged one broke down to elec trons and neutrinos. Anderson was awarded the 1936 Nobel Prize in physics for his discoveries, sharing it with Hess [1088], whose discovery of cosmic rays led quite directly to Anderson’s achieve ments. In 1963 it was discovered that neutrinos formed in association with An derson’s mesons (later called mu-mesons) were not quite like the neutrinos of those associated with the electron. Thus, the mysterious particle first predicted by Pauli [1228] turned out to exist in two forms, and since to each there had to correspond one of Dirac’s antiparticles, there were also two different antineu trinos—four no-charge, no-mass particles altogether. In one respect, Anderson’s meson proved a disappointment. It did not readily interact with atomic nuclei. If it was truly the particle of intermediate mass predicted by Yukawa, it should so interact. In the next decade, however, Powell [1274] discovered a slightly more massive meson, which proved to be Yu kawa’s predicted particle. Anderson’s meson, in fact, was shown in 1961 to be a duplicate of the electron in every prop erty but mass. It was nothing but a very heavy electron, so to speak. [1293] OCHOA, Severo Spanish-American biochemist
24, 1905 806
[1293] OCHOA
JANSKY [1295]
Ochoa, the youngest son of a lawyer, attended the University of Malaga, grad uating in 1921. He studied medicine at the University of Madrid and obtained his medical degree cum laude in 1929. In 1936 he left Spain, spending a year in Germany studying under Meyerhof [1095] and three in England. He went to the United States in 1940 and was natu ralized in 1956. After 1942 he served on the faculty of New York University Col lege of Medicine, where he became chairman of the department of biochem istry in 1954. Ochoa did considerable work on the chemical mechanisms of the body. In particular he studied how molecules of carbon dioxide are incorporated into compounds and how they are liberated. His work, along with that of Lipmann [1221], helped identify the “two-carbon fragment” that is one of the key com pounds in the metabolic pattern. Ochoa’s chief fame, however, arose in connection with his work on nucleic acid. Thanks to the work of Watson [1480] and Crick [1406], biochemists in the 1950s were flocking to nucleic acids as, a decade before, they had gathered round coenzymes and as, two decades before, they had swarmed over vitamins. The nucleic acid is a large and compli cated molecule made up of long chains of individual phosphate-containing units called nucleotides. Nucleic acids had been shown by Levene [980] to exist in two varieties, RNA and DNA, each being made up of four different types of nu cleotides. The body was clearly capable of build ing nucleic acids out of nucleotides and to do this, enzymes were necessary. In 1955 Ochoa isolated such an enzyme from a strain of bacteria and allowed it to react with nucleotides to which a sec ond phosphate unit had been added, nu cleotides of the variety which, if they were strung together, would be expected to form molecules of RNA. The result of incubating the nucleo tides in the presence of the enzyme was a startling rise in viscosity. The solution grew thick and jellylike, a pretty good sign that long, thin molecules of RNA had been formed. Ochoa’s synthetic RNA differed from the natural in an in teresting fashion. In natural RNA, nu cleotides of each of the four varieties existed, but Ochoa could begin with one variety of nucleotide and build up a syn thetic RNA consisting of that one vari ety endlessly repeated. In the next year Kornberg [1422] extended Ochoa’s work and synthesized DNA. As a result Ochoa and Kornberg shared the 1959 Nobel Prize in medicine and physiology. [1294] MOTT, Sir Nevill Francis English physicist
ber 30, 1905 Mott obtained his master’s degree at Cambridge in 1930, having studied under Bohr [1101] and Ernest Ruther ford [996], He gained a professorial posi tion at the University of Bristol in 1933 and in 1954 returned to Cambridge. He worked on theoretical consid erations of the scattering of beams of particles by atomic nuclei and on the transition of certain substances between states in which an electrical current was conducted and not conducted. In partic ular, he and his assistant, P. W. Ander son [1458], worked on the semiconduct ing properties of amorphous, glassy sub stances, a potentially cheaper and more convenient raw material for solid-state devices than ultra-pure metals and semi metals. For this work he and Anderson both received shares in the 1977 Nobel Prize for physics, along with Van Vleck [1219]. Mott was knighted in 1962. [1295] JANSKY, Karl Guthe American radio engineer
October 22, 1905 Died: Red Bank, New Jersey, February 14, 1950 Jansky was educated at the University of Wisconsin, where his father was on 807
[1295] JANSKY
BLOCH [1296]
the faculty. Out of college, and after a year as instructor there, he took a job in 1928 with Bell Telephone Laboratories. There in 1931 he tackled the problem of static. The noisy crackling of static inter fered chronically with radio reception (and with radio-telephony, as in ship-to- shore calls, which is where Bell Tele phone came in). Static had a number of causes, including thunderstorms, nearby electric equipment, and aircraft passing overhead. Jansky, however, detected a new kind of weak static from a source that, at first, he could not identify. It came from overhead and moved steadily. At first, it seemed to Jansky, it moved with the sun. However, it gained slightly on the sun, to the extent of four minutes a day. But this is just the amount by which the vault of the stars gains on the sun. Con sequently, the source must lie beyond the solar system. By the spring of 1932 Jansky had decided the source was in the constellation of Sagittarius, the direction in which Shapley [1102] and Oort [1229] placed the center of our galaxy. He pub lished his findings in December 1932. When Bell issued a press release on the subject, it made the front page of the New York Times. This represented the birth of radio as tronomy, in which astronomers learned to receive and interpret microwaves (the shortest radio waves) rather than light waves. Its usefulness was that micro waves penetrated dust clouds that light waves could not so that a radio telescope could detect the galactic center, which, as a result of obscuring dust clouds, ordi nary telescopes could never see. Jansky himself did not continue the development of the science. He made a few observations after his initial work, but that was all. He was more interested in his engineering and was willing to leave the universe to others. Despite the fact that his discovery was well publi cized, astronomers did not take up the challenge for several years, although Whipple [1317] presented a discussion of Jansky’s observation. An amateur astron omer, Reber [1368]r carried on actual work singlehandedly. It was the development of microwave techniques in connection with radar dur ing World War II that made radio as tronomy expand and flourish after that war. Jansky died of a heart ailment while still a young man but he lived long enough to see radio astronomy come out of the doldrums and begin to emerge as a prime tool of the new astronomy. In his honor the unit of strength of radio wave emission is now called the jansky. [1296] BLOCH, Felix Swiss-American physicist Born: Zurich, Switzerland, Octo ber 23, 1905 After an education in Zürich originally aimed at engineering, Bloch did his grad uate work at the University of Leipzig in Germany, earning his Ph.D. in 1928 and receiving his first professorial appoint ment in Leipzig in 1932. He left Ger many the next year, however, when Hitler came to power, and then worked at institutions in Holland, Denmark, and Italy, going to the United States in 1934 and making it his permanent home. He became an American citizen in 1939. He became an associate professor of physics at Stanford University in that year and during World War II worked at Los Alamos on the atomic bomb project. After the war Bloch returned to pure physics and particularly to the study of the magnetic fields of atomic nuclei. This had been investigated by Stern [1124] and Rabi [1212], but they had worked with beams of gaseous atoms or mole cules. Bloch devised a method of deter mination on liquids and solids and, with Alvarez [1363], measured the magnetic moment of the neutron. Purcell [1378] working independently also devised such a method, a slightly different one. For this work, Bloch and Purcell shared the 1952 Nobel Prize in physics. Bloch’s work on the magnetic proper ties of atomic nuclei also led to the de velopment of a subtle method of chemi cal analysis called “nuclear magnetic res onance.”
In 1954 and 1955 Bloch served as the 8 0 8
[1297] KUIPER
TOMBAUGH [1299]
first director-general of CERN, the mul tinational laboratory for nuclear science at Geneva. [1297] KUIPER, Gerard Peter (koy'- per) Dutch-American astronomer Born: Harenkarspel, Netherlands, December 7, 1905 Died: Mexico City, Mexico, December 23, 1973 Kuiper was educated at the University of Leiden, from which he graduated in 1927 and where he earned his Ph.D. in 1933. He came to the United States that year and became a naturalized citizen in 1937. After 1936 he served on the fac ulty of the University of Chicago and worked at the Yerkes Observatory. His best-known discoveries are in con nection with our solar system. In 1948, for instance, he detected carbon dioxide in the atmosphere of Mars, but also showed (by infrared studies) that the Martian polar caps were ice and not fro zen carbon dioxide as some had thought. (Recent Mars-probe data may indicate Kuiper was wrong here after all.) His search for other atmospheres led him to the discovery that Titan, the larg est satellite of Saturn, possesses an atmo sphere containing methane and ammo nia. It is the only satellite now known to possess an atmosphere. His theories led him to suspect that Triton, the satellite of Neptune, may also possess an atmo sphere, but its distance prevents that point from being settled. No other satel lite is both massive enough and cold enough for an atmosphere. Kuiper expanded the satellite picture of the solar system by discovering two new small ones in the far reaches of the system (the thirtieth and the thirty-first). In 1948 he discovered a satellite of Uranus, the smallest and closest to that planet, and its fifth. He named it Miranda. In 1949 he discovered a sec ond satellite of Neptune, a small one with an eccentric orbit. He named it Nereid.
Kuiper’s studies also brought him to the conclusion that Pluto, the outermost planet, at the very edge of the solar sys tem, is smaller than had been supposed. It is, it would seem, only 3,700 miles in diameter, about the size of Mars. He also determined its period of rotation to be about 6.4 days. In 1951 he advanced a theory in which planets were formed by conden sation of gaseous “protoplanets”; the sat ellites in this view were independent con densations. This has largely replaced George Darwin’s [777] dramatic view of the moon as bom of the earth. Kuiper’s work sparked a rebirth of interest in the astronomy of the solar system, an inter est that grew enormously as the space age dawned and seemed to bring our sister worlds within physical reach. In the mid-sixties, he was naturally deeply involved in the programs by which rocket devices explored the moon’s surface at close range. [1298] MORGAN, William Wilson American astronomer Born: Bethesda, Tennessee, Janu ary 3, 1906 Morgan studied at the University of Chicago, graduating in 1927 and obtain ing his Ph.D. in 1931. He then worked at that university’s Yerkes Observatory. In the late 1940s Morgan made a de tailed study of the large blue-white stars of the galaxy. These ionized hydrogen gas in their neighborhood and, by detect ing the spectral emissions of this gas, Morgan was able to work out portions of the actual spiral structure of our own galaxy, a structure that had till then been assumed but not demonstrated. This structure was elaborated still fur ther by means of the radio emissions of non-ionized hydrogen, predicted by Van de Hulst [1430] even as Morgan was doing his work. [1299] TOMBAUGH, Clyde William (tom'boh) American astronomer
4, 1906
Tombaugh’s family was too poor to send him to college, but young Clyde 809
[1299] TOMBAUGH
TOMONAGA [1300]
was fascinated by astronomy and worked eagerly with a 9-inch telescope built out of parts of old machinery lying about his father’s farm. In 1929 he managed to get a job as an assistant at Lowell Observatory, where the tradition of Percival Lowell [860], dead for thirteen years, still lingered, and where the search for a planet beyond Neptune, Lowell’s Planet X, still contin ued under the guidance of Slipher [1038],
Tombaugh tackled the job with vigor. If the new planet existed, it would be so dim that any telescope that would bring it into view would also bring into view floods of dim stars. The planet would be distinguishable by its motion, to be sure, but it would be so distant from the sun and from the earth that its visible motion would be only slight. Tombaugh used a technique whereby he could take two pictures of the same small part of the sky on two different days. Each of these would have from 50,000 to 400,000 stars on it. Despite all those stars, the two plates should be identical if the spots of light were stars and only stars. If the two plates were focused on a given spot on a screen in rapid alternation, none of the stars should seem to move. If one of the “stars” were really a planet, however, one that had moved against the starry background during the interval between photographs, it should shift position, and as the plates are alternately thrown upon the screen, that one star would seem to dart back and forth. On February 18, 1930, after almost a year of painstaking comparisons, Tom baugh found a “star” in the constellation Gemini that flickered. From the slowness of its motion, he was sure it was trans Neptunian. A month of observation fol lowed and then the new planet was an nounced on March 13, 1930, the sev enty-fifth anniversary of Lowell’s birth. It was named Pluto, a significant name on two counts. First, the god of the nether darkness was an appropriate title for a planet swinging farthest out from the light of the sun, and second, the first two letters of its name are the intials of Percival Lowell. Once again the solar system had been enlarged, as a century before it had been enlarged by Leverrier [564] and Adams [615] and a century and a half before by Herschel [321]. Nor has any object be yond Pluto been discovered in the gener ation since Tombaugh’s feat, though Oort [1229] has speculated as to a trans Plutonian asteroid belt that gives rise to the comets, whose composition Whipple [1317] was to clarify. Within the solar system, puzzles also remain, such as the mystery, which Wildt [1290] attempted to penetrate, of what lies below the opaque upper regions of the atmospheres of the giant outer planets. As for Pluto, it has turned out to be an odd planet, with an orbit more eccen tric and more inclined to the ecliptic than any of the other planets. It is far smaller than the other outer planets, as Kuiper [1297] showed, and there are as tronomers who now suspect it is not a true planet but was once a satellite of Neptune, which, through some cata strophic change, was jarred into an inde pendent orbit of its own. After the discovery, Tombaugh was rewarded with a scholarship to the Uni versity of Kansas and was finally able to get his college education. He obtained his bachelor’s degree in 1936 and his master’s in 1939. [1300] Download 17.33 Mb. Do'stlaringiz bilan baham: 
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