Important historic dates in science

July 31: Hendrik Christoffel van de Hulst
(Born November 19, 1918: Died July 31, 2000)
Dutch astronomer who predicted theoretically (1944) that in interstellar space the amount of neutral atomic hydrogen, which in its hyperfine transition radiates and absorbs at a wavelength of 21 cm, might be expected to occur at such high column densities as to provide a spectral line sufficiently strong as to be measurable. Shortly after the end of the war several groups set about to test this prediction. The 21-cm line of atomic hydrogen was detected in 1951, first at Harvard University followed within a few weeks by others. The discovery demonstrated that astronomical research, which at that time was limited to conventional light, could be complemented with observations at radio wavelengths, revealing a range of new physical processes.

July 30: Atomic energy
On this day in 1957 the International Atomic Energy Agency was established by the United Nations.

July 29: I. I. Rabi
(Born July 29, 1898: Died January 11, 1988)
Isidor Isaac Rabi was an American physicist who was awarded the Nobel Prize for Physics in 1944 for his invention (in 1937) of the atomic and molecular beam magnetic resonance method of measuring magnetic properties of atoms, molecules, and atomic nuclei. He spent most of his life at Columbia University (1929-67), where he performed most of his pioneering research in radar and the magnetic moment associated with electron spin in the 1930s and 1940s. His Nobel-winning work led to the invention of the laser, the atomic clock, and diagnostic uses of nuclear magnetic resonance. He originated the idea for the CERN nuclear research center in Geneva (founded 1954).

July 28: Otto Hahn
(Born March 8, 1879: Died July 28, 1968)
German chemist who, with the radiochemist Fritz Strassmann, is credited with the discovery of nuclear fission. He was awarded the Nobel Prize for Chemistry in 1944 and shared the Enrico Fermi Award in 1966 with Strassmann and Lise Meitner. Element 105 carries the name hahnium in recognition of his work.

July 27: Bertram Borden Boltwood
(Born July 27, 1870)
Bertram Borden Boltwood was an American chemist and physicist whose work on the radioactive decay of uranium and thorium was important in the development of the theory of isotopes. Boltwood studied the "radioactive series" whereby radioactive elements sequentially decay into other isotopes or elements. Since lead was always present in such ores, he concluded (1905) that lead must be the stable end product from their radioactive decay. Each decay proceeds at a characteristic rate. In 1907, he proposed that the ratio of original radioactive material to its decay products measured how long the process had been taking place. Thus the ore in the earth's crust could be dated, and give the age of the earth as 2.2 billion years.

July 26: Underwater nuclear test
In 1946, the United States detonated the "Baker" atomic bomb at Bikini Atoll in the Pacific in the first underwater test of the device during "Operation Crossroads." The test was made to record the effect of a nuclear explosion on naval vessels. The targets brought into Bikini Lagoon were outdated U.S. Navy ships and German and Japanese vessels captured during WW II.The bomb was encased in a watertight steel caisson, suspended 90 feet below the landing ship LSM-60. Radio signals from a command ship closed circuits that armed and then detonated the bomb at 8:45 am. A massive column of steam and water erupted from the lagoon, and the explosion created a series of huge waves. The target ship Carrier Saratoga was struck by the first wave, less than a second later, was swept 800 yards from its mooring point and sank eight hours after the explosion. The 90-foot wave also crashed into Battleship Arkansas which sank almost immediately, as did the submarines Pilotfish, Apogon, Shipjack and the fuel barge YO-160.

July 25: Underwater nuclear test
In 1946, the United States detonated the "Baker" atomic bomb at Bikini Atoll in the Pacific in the first underwater test of the device during "Operation Crossroads." The test was made to record the effect of a nuclear explosion on naval vessels. The targets brought into Bikini Lagoon were outdated U.S. Navy ships and German and Japanese vessels captured during WW II.The bomb was encased in a watertight steel caisson, suspended 90 feet below the landing ship LSM-60. Radio signals from a command ship closed circuits that armed and then detonated the bomb at 8:45 am. A massive column of steam and water erupted from the lagoon, and the explosion created a series of huge waves. The target ship Carrier Saratoga was struck by the first wave, less than a second later, was swept 800 yards from its mooring point and sank eight hours after the explosion. The 90-foot wave also crashed into Battleship Arkansas which sank almost immediately, as did the submarines Pilotfish, Apogon, Shipjack and the fuel barge YO-160.

July 24: Sir James Chadwick
(Born October 20, 1891: Died July 24, 1974)
English physicist who received the Nobel Prize for Physics (1935) for his discovery of the neutron. He studied at Cambridge, and in Berlin under Geiger, then worked at the Cavendish Laboratory with Rutherford, where he investigated the structure of the atom. He worked on the scattering of alpha particles and on nuclear disintegration. By bombarding beryllium with alpha particles, Chadwick discovered the neutron - a neutral particle in the atom's nucleus - for which he received the Nobel Prize for Physics in 1935. In 1932, Chadwick coined the name "neutron," which he described in an article in the journal Nature. He led the UK's work on the atomic bomb in WW II, and was knighted in 1945.

July 23: Three Mile Island Unit 2 re-entered
In 1980, the first human re-entry was made into the Three Mile Island Unit-2 containment building since shutdown after the March 28, 1979 accident, when the core of the nuclear power plant lost water coolant and began a partial melt-down incident.

July 22: Gustav Hertz
(Born July 22, 1887: Died October 30, 1975)
German quantum physicist who, with James Franck, received the Nobel Prize for Physics in 1925 for the Franck-Hertz experiment, which confirmed the quantum theory that energy can be absorbed by an atom only in definite amounts and provided an important confirmation of the Bohr atomic model. He was a nephew of Heinrich Hertz. Although he fought on the German side in World War I, being of Jewish descent, he was forced to resign his professorship (1934) when Hitler took power. From 1945 he worked in the Soviet Union, and then in 1955 was a professor of physics in Leipzig, East Germany.

July 21: Atomic nucleus recoil
In 1904, a letter in the journal Nature, Harriet Brooks pointed out a peculiar type of volatility shown by an active deposit of radium immediately after its removal from the emanation. Hahn and Russ and Markower later showed (1909) that "the effect was due to the recoil of radium B from the active surface accompanying the expulsion of an alpha-particle from Radium A. This method of the separation of the elements by recoils ultimately proved of much importance in disentangling the complicated series of changes in the radioactive bodies," according to Rutherford (1933). Thus, Harriet Brooks was probably the first person to observe the recoil of the atomic nucleus as nuclear particles were emitted during radioactive decay.

July 20: Polaris missile test
On July 20, 1960 the submerged USS George Washington off the coast of Cape Canaveral, Fla., executed the first test launch of a pair of Polaris missile from a submarine at sea. The target was more than 1,100 miles away. The Polaris has a designed range of 1,500 nautical miles and is capable of being launched when the submarine is hidden far below the surface. The George Washington was the first Fleet Balistic Missile submarine. Fitted with 16 tubes for Polaris A1 missile, the submarine was commissioned December 30, 1959, and de-commissioned January 24, 1985. The "Georgefish" and her crews made 55 deterrence patrols in both the Atlantic and Pacific oceans in her 25 year career.

July 19: Edward Pickering
(Born July 19, 1846: Died February 3, 1919)
Edward Charles Pickering, was born Boston, Mass., U.S. physicist and astronomer. After graduating from Harvard, he taught physics for ten years at MIT where he built the first instructional physics laboratory in the United States. At age 30, he directed the Harvard College Observatory for 42 years. His observations were assisted by a staff of women, including Annie Jump Cannon. He introduced the use of the meridian photometer to measure the magnitude of stars, and established the Harvard Photometry (1884), the first great photometric catalog. By establishing a station in Peru (1891) to make the southern photographs, he published the first all-sky photographic map (1903).

July 18: Pierre-Louis Dulong
(Born July 18, 1838: Died February 12, 1785)
Chemist and physicist who helped formulate the Dulong-Petit law of specific heats (1819), which proved useful in determining atomic weights.

July 17: Gordon Gould
(Born July 17, 1920)
Physicist, coined the word "laser": acronym for Light Amplification by Stimulated Emission of Radiation. Even before high school, thinking of Marconi, Bell, and Edison, Gould intended to be an inventor. During WWII, Gould worked with the Manhattan Project on the separation of uranium isotopes. By the 50's, he was a graduate student at Columbia University. On 9 Nov 1957, during a Saturday night without sleep, he had the inventor's inspiration and began to write down the principles of what he called a laser in his notebook Although Charles Townes and Arthur Schawlow, also successfully developed the laser, eventually Gould gained his long-denied patent rights.

July 16: Atomic bomb
In 1945, the first atomic bomb was exploded at Los Alamos, New Mexico. The atomic bomb was invented by two refugee German scientists in Britain, Professor Rudolph Peierls and Otto Frisch, of Birmingham University. They designed a "blue-print" for making an atom bomb in 1940. It actually began when the Italian-born physicist Enrico Fermi, working in the United States, invented an apparatus which produced the first atomic chain reactions. In 1940 both the Americans and British were researching the atom bomb and when the United States entered WW2, the British joined the American "Manhattan Project" and production of the bomb went on ahead in the US.

July 15: Pavel Alekseyevich Cherenkov
(Born July 15, 1904: Died January 6, 1990.)
Soviet physicist who discovered Cherenkov radiation (1934), a faint blue light emitted by electrons passing through a transparent medium when their speed exceeds the speed of light in that medium. Fellow Soviet scientists Igor Y. Tamm and Ilya M. Frank investigated the phenomenon from which the Cherenkov counter was developed. Extensive use of this Cherenkov detector was later made in applications of experimental nuclear and particle physics. For their work, the trio shared the 1958 Nobel Prize for Physics.

July 14: Maurice de Broglie
(Born April 27, 1875: Died July 14, 1960)
(6th duke) (Louis-César-Victor-) Maurice de Broglie was a French physicist who made many contributions to the study of X rays. While in the navy (1895-1908), he first distinguished himself by installing the first French shipboard wireless. From 1912, his chief interest was X-ray spectroscopy. His "method of the rotating crystal" was an application of Bragg's "focussing effect" to eliminate spurious spectral lines. De Broglie discovered the third L absorption edge (1916), which led to the exploration of "corpuscular spectra." During 1921-22, he worked with his brother Louis to refine Bohr's specification of the substructure of the various atomic shells. He also did pioneer work in nuclear physics and cosmic radiation.

July 13: First atomic bomb
In 1945, the first atomic bomb arrived partly assembled at its test site in the New Mexico desert. It is a Friday the 13th. By Sunday, it is completed and set at the top of a tower waiting for the first atomic bomb test.

July 12: Jean Picard
(Born July 21, 1620: Died July 12, 1682)
French Jesuit, active astronomer, cartographer, hydraulics engineer, Jean Picard devised a movable-wire micrometer to measure the diameters of celestial objects such as the Sun, Moon and planets. For land surveying and leveling, he designed instruments that incorporated the astronomical telescope. He greatly increased the accuracy of measurements of the Earth, using Snell's method of triangulation (Mesure de la Terre, 1671). This data was used by Newton in his gravitational theory. Picard was one of the first to apply scientific methods to the making of maps.

July 11: Aleksandr Prokhorov
(Born July 11, 1916)
Aleksandr Mikhaylovich Prokhorov is the Soviet physicist who received, (with Nikolay G. Basov, USSR and Charles H. Townes, US), the Nobel Prize for Physics in 1964 "for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser-laser principle." "Maser" stands for "microwave amplification by stimulated emission of radiation." An amplification can occur only if the stimulated emission is larger than the absorption, requiring that there should be more atoms in a high energy state than in a lower one. This state is called an inverted population. Prokhorov had researched the maser independently but simultaneously with the other prize recipients.

July 10: Frank Schlesinger
(Born May 11, 1871: Died July 10, 1943)
American astronomer who pioneered in the use of photography to map stellar positions and to measure stellar parallaxes, which could give more precise determinations of distance than visual ones, and with less than one hundredth as much time at the telescope. He designed instruments and mathematical and numerical techniques to improve parallax measurements. He published ten volumes of zone catalogs, including some 150,000 stars. He compiled positions, magnitudes, proper motions, radial velocities, and other data to produce the first edition and, with Louise Jenkins, the second, of the widely-used Bright Star Catalogues, making Yale a leading institution in astrometry. He established a second Yale observatory in South Africa.

July 9: John Wheeler
(Born July 9, 1911)
John Archibald Wheeler was the first American physicist involved in the theoretical development of the atomic bomb. He also originated a novel approach to the unified field theory. Wheeler was awarded the 1997 Wolf Prize "for his seminal contributions to black hole physics, to quantum gravity, and to the theories of nuclear scattering and nuclear fission." After recognizing that any large collection of cold matter has no choice but to yield to the pull of gravity and undergo total collapse, Wheeler first coined the term "black hole" in 1967.

July 8: Igor Yevgenyevich Tamm
(Born July 8, 1895: Died April 12, 1971)
Soviet physicist who shared the 1958 Nobel Prize for Physics with Pavel A. Cherenkov and Ilya M. Frank for his efforts in explaining Cherenkov radiation. Tamm was an outstanding theoretical physicist, after early researches in crystallo-optics, he evolved a method for interpreting the interaction of nuclear particles. Together with I. M. Frank, he developed the theoretical interpretation of the radiation of electrons moving through matter faster than the speed of light (the Cerenkov effect), and the theory of showers in cosmic rays. He has also contributed towards methods for the control of thermonuclear reactions.

July 7: Isaac Newton receives degree
In 1668, Sir Isaac Newton received his M.A. from Trinity College in Cambridge.

July 6: J. Carson Mark
(Born July 6, 1913: Died March 2, 1997)
Canadian-born American scientist who, as head of the theoretical division at the Los Alamos (N.M.) Scientific Laboratory, was instrumental in the development of the hydrogen bomb. He began at Los Alamos in 1945 as a collaborator on the Manhattan Project. He joined the staff in 1946 and became leader of T Division the following year until his retirement in 1973. At the Laboratory, he was involved in the development of various weapons systems, including thermonuclear bombs. He had a broad range of research interests, including hydrodynamics, neutron physics and transport theory. By the 1960s, much of the weapons work had been relocated and the T division diversified into working with outside agencies and private industry.

July 5: Georg Charles von Hevesy
(Born August 1, 1885: Died July 5, 1966)
Hungarian-Danish-Swedish chemist who earned him the 1943 Nobel Prize for the development of isotopic tracer techniques which greatly advanced understanding of the chemical nature of life processes. An example of a tracer is an isotope of radioactive phosphorus, which in solutions of sodium phosphate can be injected into animals and humans. Blood samples showed that the radio-phosphorus content in human blood falls after only 2 hours to a mere 2% of its initial value and gradually changes places with the phosphorus atoms of the tissues, organs and skeleton. He also discovered, with Dirk Coster, the element hafnium (1923).

July 4: Marie Curie
(Born Nobember l7, 1867: Died July 4, 1934)
Marie Marja Sklodowska Curie was a Polish-born French chemist and physicist. In 1898, her celebrated experiments on uranium minerals led to discovery of two new elements. First she separated polonium, and then radium a few months later. The quantity of radon in radioactive equilibrium with a gram of radium was named a curie. With Henri Becquerel and her husband, Pierre Curie, she was awarded the 1903 Nobel Prize for Physics. She was then sole winner of a second Nobel Prize in 1911, this time in Chemistry. Her family won five Nobel awards in two generations. She died of radiation poisoning from her pioneeing work before the need for protection was known.

July 3: Pluto
In 1841, John Couch Adams decided to determine the position of an unknown planet by the irregularities it causes in the motion of Uranus. He entered in his journal; "Formed a design in the beginning of this week in investigating, as soon as possible after taking my degree, the irregularities in the motion of Uranus... in orderto find out whether they may be attributed to the action of an undiscovered planet beyond it..." In September 1845 he gave James Challis, director of the Cambridge Observatory, accurate information on where the new planet, as yet unobserved, could be found; but unfortunately the planet was not recognized at Cambridge until much later, after its discovery at the Berlin Observatory on September 23, 1846.

July 2: Sir William Bragg
(Born July 2, 1862: Died March 12, 1942)
Sir William Henry Bragg was a pioneer British scientist in solid-state physics who was a joint winner (with his son Sir Lawrence Bragg) of the Nobel Prize for Physics in 1915 for research on the determination of crystal structures. During the WW I, Bragg was put in charge of research on the detection and measurement of underwater sounds in connection with the location of submarines. He also constructed an X-ray spectrometer for measuring the wavelengths of X-rays. In the 1920s, while director of the Royal Institution in London, he initiated X-ray diffraction studies of organic molecules. Bragg was knighted in 1920.

July 1: X-ray
In 1934, the first X-ray photograph of the whole body taken in a one-second exposure, using ordinary clinical conditions such as would exist at an average hospital, was made at Rochester, N.Y. The one-piece radiograph was made by Arthur W. Fuchs of the Eastman Kodak Company. A selective filter was used for the first time, and the film size was 32"x72". It was exhibited by the Chicago Roentgen Society at the Century of Progress Exhibition in Chicago, Illinois.

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Photos courtsey of Today in Science