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541 [835] MICHELSON SCHAEBERLE
their points of origin are. In this way he measured the angular width of the large satellites of Jupiter. This was no more than a neat trick, however, for that width can be measured by direct obser vation. However, in 1920, with better telescopes, he turned his efforts to the measurement of the diameter of stars that cannot be measured by direct obser vation even today. Using a twenty-foot interferometer attached to the 100-inch telescope, he was able to measure the di ameter of the giant star Betelgeuse in this fashion, a startling first in astronomy which made the front page of the New York Times (a rare feat for a scientific advance in those days). Meanwhile he had suggested the use of light waves as a standard of length in place of the platinum-iridium bar pre served in a Paris suburb as the Interna tional Prototype Meter. At first he thought the bright yellow line of sodium would do, but later his studies showed that the red light radiated by heated cad mium would make a better standard. In 1893 he measured the meter in terms of cadmium-red wavelength. (The use of light waves as a length standard was finally accepted in 1960, though light radiated by the rare gas krypton, un known in 1893, was accepted as the standard, in place of cadmium red.) In 1892 Michelson became head of the de partment of physics at the University of Chicago, a position he held till his retire ment. From 1923 to 1927 he served as president of the National Academy of Sciences. In 1923 Michelson returned to the problem of the accurate measurement of the velocity of light. In the California mountains he surveyed a twenty-two- mile pathway between two mountain peaks to an accuracy of less than an inch. He made use of a special, eight sided revolving mirror, prepared for him by his friend Sperry [907], and by 1927 he had the value 299,798 kilometers per second. He tried again, this time using a long tube that could be evacuated so that the velocity of light in a vacuum could be measured. Light was reflected and re reflected until it traveled ten miles in that vacuum. Michelson was a sick man now and did not live to make the final measurements, but in 1933, after his death, the final figure was announced. It was 299,774 kilometers per second (186,271 miles per second). A generation after Michelson’s death, the accepted value of the speed of light is 299,792.5 kilometers per second (186,282 miles per second), which lies between the values obtained by Michel son’s last two sets of experiments. As an example of experiments not in volving the speed of light, consider Mi chelson’s microscopic observations of the water level in an iron pipe. The tidal changes in level amounted to four mi crons (less than a six-millionth of an inch) but this sufficed to make it possible to calculate the intensity of the attraction of the sun and moon on the earth as eas ily as though the tides of the ocean itself were being studied. He showed that the solid earth rose and fell in response to sun and moon, changing its level by thirty-five centimeters, or a little over a foot.
[836] SCHAEBERLE, John Martin (sha/ber-lee) Germ an-American astronomer
January 10, 1853 Died: Ann Arbor, Michigan, Sep tember 17, 1924 Schaeberle was taken to the United States by his family when he was still an infant. His career revolved about astro nomic instruments after he graduated from the University of Michigan in 1876.
His best-remembered feat was that of detecting the dim companion (13th mag nitude) of Procyon in 1896, duplicating the work of Clark [696] in detecting the dim companion of Sirius. This was an in dication that such dim stars might not be rare, and by the time W. S. Adams [1045] showed the dim companion of Sirius to be what came to be called a “white dwarf,” these were seen to make up a numerous class.
[837] THOMSON
LORENTZ [839] [837] THOMSON, Elihu English-American inventor
March 29, 1853 Died: Swampscott, Massachusetts, March 13, 1937 Thomson was taken to the United States by his family when he was five years old and was educated at Central High School (an elite school) in 1870. He proved a talented inventor who ended with something like seven hundred patents, chiefly in the fields of electricity and radiology. His inventions led to the development of successful alternating- current motors, and in 1890 he devised a high-frequency electrical generator. He founded an electrical company that merged with Edison’s [788] company in 1892 to form General Electric. Outside the field of electricity, he was the first to suggest the use of helium oxygen mixtures in place of the atmo spheric nitrogen-oxygen mixtures to mini mize the danger of bends in high-pres sure work. [838] PETRIE, Sir (William Matthew) Flinders (pee'tree) English archaeologist
June 3, 1853 Died: Jerusalem, Palestine, July 28, 1942 Petrie’s maternal grandfather, Matthew Flinders, had been a renowned explorer of Australia and Tasmania. Petrie was a sickly child, privately educated. He early became interested in ancient civil izations, particularly that of Egypt and most particularly in the nature of the measurement units used by the ancient Egyptians. He felt that one could deduce what those units had been by studying the an cient monuments. He began with Stone henge, concerning which he published a book in 1880, then went on to the love of his fife, the Egyptians. In the course of his archaeological researches in Egypt, he uncovered many interesting relics, including most particularly a stele of the time of Merneptah, the successor of Rameses II, which contains the ear liest known mention of Israel outside the Bible. He also excavated Akhetaten, the capital city of Egypt’s monotheist pharaoh, Ikhnaton. In addition, he did important work in correlating Mycenean history with that of Egypt by his digs in Crete and in Greece. In 1892 he became professor of Egyp tology at University College, London University, and in 1923 he was knighted. [839] LORENTZ, Hendrik Antoon (loh'rents) Dutch physicist
Lorentz attended Leiden University, obtaining his doctor’s degree, summa
years later as professor of theoretical physics, a post he held until his death. Lorentz’s doctoral thesis dealt with the theory of electromagnetic radiation, which Maxwell [692] had advanced a lit tle over a decade before. Lorentz refined the theory to take account of the manner of the reflection and refraction of light, points concerning which Maxwell’s own work had been somewhat unsatisfactory. He went further in his search into the implications of Maxwell’s work. According to Maxwell, electromag netic radiation was produced by the os cillation of electric charges. Hertz [873] showed this to be true for radio waves, which in 1887 he formed by causing electric charges to oscillate. But if light was an electromagnetic radiation after the fashion of radio waves, where were the electric charges that did the oscil lating? By 1890 it seemed quite likely that the electric current was made up of charged particles, and Lorentz thought it quite possible that the atoms of matter might also consist of charged particles. (The theories of Arrhenius [894] on the sub ject of ionization, which had just been advanced, pointed in that direction.) Lorentz suggested then that it was the charged particles within the atom that
[839] LORENTZ
OSTWALD [840] oscillated, producing visible light. (To be sure, this vision of oscillating particles was made much more subtle—and hard to picture—by the theoretical work of men like Bohr [1101] and Schrodinger [1117].) If this was so, then placing a light in a strong magnetic field ought to affect the nature of the oscillations and therefore of the wavelength of the light emitted. This was demonstrated experimentally in 1896 by Zeeman [945], a pupil of Lorentz. By that time the discovery of the electron by J. J. Thomson [869] and of radioactivity by Becquerel [834] made it seem more than ever likely that the atom did indeed contain a structure made up of charged particles, and by 1902, when there seemed no longer doubt of this, Lorentz and Zeeman shared the Nobel Prize in physics. Lorentz also tackled the negative re sults of the experiment conducted by Michelson [835] and Morley [730] and came to the same conclusion as Fitz Gerald [821], He too postulated that there are contractions of length with mo tion. It seemed to him, further, that the mass of a charged particle such as the electron depends on its volume; the smaller the volume, the greater the mass. Since the Lorentz-FitzGerald contraction reduced the volume of an electron as it sped along and reduced it the more as it moved more rapidly, it must also in crease its mass with velocity. At 161,000 miles a second, the mass of an electron is twice its “rest-mass,” according to the Lorentz formulation, and at 186,282 miles a second, the velocity of light, the mass must be infinite since the volume becomes zero. This was another indica tion that the velocity of light in a vac uum is the greatest velocity at which any material object can travel. By 1900, mass measurements on speeding subatomic particles did indeed show that Lorentz’s equation describing how mass varied with velocity was fol lowed exactly. And in 1905 Einstein [1064] advanced his special theory of Relativity from which the Lorentz-Fitz Gerald contraction could be deduced and from which it could be shown that the Lorentz mass-increase with velocity held not only for charged particles, but for all objects, charged and uncharged. In later life Lorentz ably supervised the enclosure of the Zuider Zee, an am bitious Dutch project to make more agri cultural land out of a shallow basin of the sea. [840] OSTWALD, Friedrich Wilhelm (ohst'vahlt) Russian-German physical chemist Born: Riga, Latvia, September 2, 1853
Died: Leipzig, Saxony, April 4, 1932
Ostwald, the son of a master cooper, was bom and educated in the Baltic provinces of the Russian Empire, where the ruling classes were descendants of the German immigrants who had moved in during early modem times. In his scientific training, he spent seven years on a five-year course because his agile mind was deflected here and there instead of driving steadily forward toward graduation. At the University of Dorpat (in what is now the Estonian SSR) he grew inter ested in H.PJ.J. Thomsen’s [665] work on thermochemistry. He began studying other physical properties of chemical substances, obtaining his doctor’s degree on the subject in 1878. He was ap pointed professor of chemistry at the University of Riga in 1881, but in 1887 he accepted a professorship at Leipzig and remained in Germany the rest of his life. Ostwald is considered one of the chief founders of modem physical chemistry and his interest in this field was further stimulated by reading the dissertation of Arrhenius [894]. Arrhenius’ views were not popular then but in Ostwald he found a firm friend and helper. Recog nizing the importance of Gibbs’s [740] work, Ostwald translated the American’s papers into German so that they might receive general European appreciation. (Ostwald’s grasp of the importance of American research led him in 1905 to accept the invitation to lecture for a year at Harvard as part of a program, then 544 [840] OSTWALD
GRAM [841] just starting, of a German-American ex change of professors. It was a clear sign that the United States was taking its rightful place, at last, on the research map.)
In 1887 Ostwald, in collaboration with his close friend Van’t Hoff [829], had es tablished the first learned journal to be devoted exclusively to physical chemis try. He himself did important work in many branches of physical chemistry, most notably in the field of catalysis. Thus, in 1894 he prepared an abstract of someone else’s paper on the heat of com bustion of foods, this abstract to appear in his own journal. He disagreed strongly with the conclusions of the man who wrote the paper and therefore casually added comments of his own. In this way he pointed out that the theories of Gibbs made it necessary to assume that cata lysts hastened reaction without altering the energy relationships of the sub stances involved. Catalysts performed their functions, instead, by lowering the energy of activation, the latter being Arrhenius’ concept. Ostwald further rec ognized that the ions, postulated by Ar rhenius as electrically charged atoms, could also serve as catalysts. This was particularly true of the hydrogen ions liberated by acids in solution, thus ac counting for the acid catalysis of starch breakdown to sugar. This view of catalysis, still held today, made it useful in industry and in the ap plications soon to be made to the chemi cal phenomena in living tissue. (Even biochemistry was bending to the new physical chemical outlook, and Rubner [848], for instance, spent much time measuring the energy relationship in volved in the chemical activity of living organisms.) In 1909 Ostwald was awarded the Nobel Prize in chemistry for his work on catalysis, and he congratulated the com mittee for selecting that part of his work which he himself thought the best. Ostwald was firm in his belief that chemists ought to confine their studies to measurable phenomena such as energy changes. In this respect he was a firm follower and admirer of Mach [733]. He believed that thermodynamics was the centrally important facet of chemistry and objected to theories that involved objects that could not be measured. For that reason he refused for a long time to accept the atomic theory as anything more than a convenient fiction; he was one of the last holdouts. It was the anal ysis by Perrin [990] of the phenomenon of Brownian motion that finally forced him to admit that atoms were respon sible for a clearly visible phenomenon that could be easily measured. In later life he wrote on the philoso phy of science and in 1902 founded a journal devoted to that subject. He also tried to work out a new system for mix ing and harmonizing colors. After he died, his home was converted into a mu seum in his memory. [841] GRAM, Hans Christian Joachim (grahm) Danish bacteriologist Born: Copenhagen, September 13, 1853
Died: Copenhagen, November 14, 1938
Gram, the son of a professor of law, obtained his M.D. at die University of Copenhagen in 1878. His great contribution came in 1884, when he stained bacteria by one of Ehr lich’s [845] methods and then treated the stained bacteria with iodine solution and an alcohol wash, which removed the stain from some and not from others. Those bacteria that retained the stain have been called Gram-positive ever since, while those that lost it are Gram negative. This distinction was used as an important means of classifying bacteria and in recent years has shown interesting correlation with antibiotic activity. For instance, penicillin is active against Gram-positive bacteria for the most part, while streptomycin will attack Gram negative. In 1900 Gram was appointed profes sor of pathology at the University of Copenhagen, retaining the post till his retirement in 1923. 545 [842] KOSSEL
KAMERLINGH ONNES [843] [842] KOSSEL, (Karl Martin Leonhard) Albrecht (kohs'ul) German biochemist Born: Rostock, Mecklenburg, September 16, 1853 Died: Heidelberg, July 5, 1927 It was Kossel’s intention to study bot any. His father, a merchant, saw no fu ture in that, however, so Kossel studied medicine, obtaining his degree in 1878. At the University of Strasbourg, he came under the influence of Hoppe-Seyler [663], a leading light of the then infant science of biochemistry, and in 1877 he began four years as his assistant. This made a biochemist of him. Later, he worked under Du Bois-Reymond [611]. In 1879 he began to investigate a sub stance called nuclein, which had been isolated ten years earlier by Miescher [770], one of Hoppe-Seyler’s students, and which the master had worked on himself. Until it entered Kossel’s hands, however, it remained a poorly defined substance. Kossel’s studies began by showing that nuclein contained a protein portion and a nonprotein portion so that in place of the vague nuclein, one could speak of nucleoprotein, in which the prosthetic group (the nonprotein portion) was “nucleic acid.” The protein was much like other proteins, but the nucleic acid was quite unlike any other natural prod uct known until that time. When the nucleic acids were broken down, Kossel found that among the breakdown prod ucts were purines and pyrimidines, ni trogen-containing compounds with the atoms arranged in two rings and one ring respectively. (Fischer [833] had worked on the purines.) Kossel isolated two different purines, adenine and guanine, and a total of three different pyrimidines, thymine (which he was the first to isolate), cytosine, and uracil. He also recognized the existence of a carbohydrate among the breakdown products, but the identification of that portion had to wait another generation for Levene [980], Spermatozoa have a high content of nucleic acids, and Kossel went on to study the proteins in those cells. They proved to be considerably simpler than proteins in ordinary cells, and Kossel evolved quite an elaborate theory for the build-up of ordinary proteins out of the simple cores present in spermatozoa. In this he had entered a blind alley, for he did not realize (nor did anyone for nearly half a century more) that the cru cial compounds in the spermatozoa and in all cells were the nucleic acids rather than the proteins and that the nucleic acids were present in sperm cells in full complexity. His work, even without his having re alized the full importance of nucleic acids, was impressive. He discovered the essential amino acid, histidine, for in stance. He was appointed professor of physi ology at the University of Marburg in 1895, and in 1901 he succeeded Kühne [725] as professor of physiology at Hei delberg where he remained till his retire ment in 1924. In 1910 he received the Nobel Prize in physiology and medicine for his work on proteins and nucleic acids.
[843] KAMERLINGH ONNES, Heike (ka'mer-ling ohn'es) Dutch physicist
1853
Died: Leiden, February 21, 1926 Kamerlingh Onnes, the son of a pros perous manufacturer, had his early schooling in his hometown. He entered the University of Groningen in 1870. The next year he went to Heidelberg, where he studied under Bunsen [565] and Kirchhoff [648]. He returned to Groningen for his doctorate (awarded in 1879 summa cum laude for studies on new proofs of the rotation of the earth) and in 1882 was appointed professor of experimental physics at Leiden Univer sity. Here he established the Cryogenic Laboratory (now known by his name) at which new depths of temperature were plumbed and which made Leiden famous as the cold-research center of the world. Kamerlingh Onnes chose low-tempera ture work because of his interest in the Download 17.33 Mb. Do'stlaringiz bilan baham: 
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