Important historic dates in science

March 31: Sir Lawrence Bragg
(Born March 31, 1890: Died July 1, 1971)
Australian-born British physicist and X-ray crystallographer, who at the early age of 25, shared the Nobel Prize for Physics in 1915 (with his father, Sir William Bragg). Lawrence Bragg formulated the Bragg law of X-ray diffraction, which is basic for the determination of crystal structure: n[lambda] = 2dsin[theta] which relates the wavelength of x-rays [lambda], the angle of incidence on a crystal [theta], and the spacing of crystal planes d, for x-ray diffraction, where n is an integer (1, 2, 3, etc.). Together, the Braggs worked out the crystal structures of a number of substances. Early in this work, they showed that sodium chloride does not have individual molecules in the solid, but is an array of sodium and chloride ions.

March 30: Auguste Bravais
(March 30, 1863: Born August 23, 1863)
French physicist and mineralogist, best remembered for his work on the lattice theory of crystals. Bravais lattices are named for him. In 1850, he showed that crystals could be divided into 14 unit cells for which: (a) the unit cell is the simplest repeating unit in the crystal; (b) opposite faces of a unit cell are parallel; and (c) the edge of the unit cell connects equivalent points. These unit cells fall into seven geometrical categories, which differ in their relative edge lengths and internal angles. In 1866, he elaborated the relationships between the ideal lattice and the material crystal. Sixty years later, Bravais' work provided the mathematical and conceptual basis for the determination of crystal structures after Laue's discovery of X-ray diffraction in 1911.

March 29: Test ban treaty
In 1960, British Prime Minister Harold Macmillan reached agreement with U.S. leaders in Washington, D.C., on a nuclear test ban treaty to be put to the U.S.S.R.

March 28: Nuclear accident
In 1979, a nuclear accident occured at the Three Mile Island nuclear power plant outside Harrisburg, Pennsylvania, USA. Caused by human and mechanical errors, a cooling system malfunctioned and permitted a partial meltdown of the reactor's core. Some radioactivity leaked into the atmosphere. Although it is the worst U.S. nuclear accident, disaster was avoided.

March 27: Wilhelm Conrad Röntgen
(Born March 27, 1845: Died February 10, 1923)
German physicist who was a recipient of the first Nobel Prize for Physics, in 1901, for his discovery of X rays, which heralded the age of modern physics and revolutionized diagnostic medicine.

March 26: Max Abraham
(Born March 26, 1875: Died November 16, 1922)
German physicist whose life work was almost all related to Maxwell's theory. The text he wrote was the standard work on electrodynamics in Germany for a long time. Throughout his life, he remained strongly opposed to Einstein's Theory of Relativity, objecting to its postulates which he felt were contrary to classical common sense. He further held that the experimental evidence did not support that theory. In 1902, he had developed a theory of the electron in which he held that an electron was a perfectly rigid sphere with a charge distributed evenly over its surface. He also believed in the ether theory, thought that future astronomical data would validate it, and thus relativity was not in fact a good description of the real world.

March 25: Radium
In 1903, The Times newspaper reported that the French physicist, Pierre Curie assisted by Mme Curie, communicated to the Academy of Sciences that the recently discovered Radium "possesses the extraordinary property of continuously emitting heat, without combustion, without chemical change of any kind, and without any change to its molecular structure, which remains spectroscopically identical after many months of continuous emission of heat ... such that the pure Radium salt would melt more than its own weight of ice every hour ... A small tube containing Radium, if kept in contact with the skin for some hours ... produces an open sore, by destroying the epidermis and the true skin beneath ... and cause the death of living things whose nerve centres do not lie deep enough to be shielded from their influence.

March 24: Peter Debye
(Born March 24, 1884: Died November 2, 1966)
Petrus (Peter) Josephus Wilhelmus Debye was a Dutch physical chemist whose investigations of dipole moments, X rays, and light scattering in gases brought him the 1936 Nobel Prize for Chemistry. Most of his work was in chemical-physics with special interest in electrolytes and dipolar momentum analysis. He established a theory of specific heat with some improvements on that proposed by Einstein. Debye performed important work in the analysis of crystalline powders using X-ray diffraction techniques. He also determined the dimensions of gaseous molecules and the interatomic distances using X-rays.

March 23: Cold fusion
In 1989, two Utah scientists claimed they have produced fusion at room temperature. Martin Fleischmann and Stan Pons announced in Utah how they had sustained a controlled nuclear fusion reaction in a test-tube that generated up to 100 per cent more energy than they put in. Then followed efforts to replicate the work. Leading scientists failed. There were sporadic sightings of excess heat, which Fleischmann said cannot be accounted for by chemistry alone. Crucially, there were no tell-tale signs of nuclear processes, notably subatomic particles called neutrons. Thus, the idea of cold fusion has been discredited.

March 22: Burton Richter
(Born March 22, 1931)
American physicist who was jointly awarded the 1976 Nobel Prize for Physics with Samuel C.C. Ting for the discovery of a new subatomic particle, the J/psi particle.

March 21: Plutonium named
In 1942, a secret report was submitted suggesting the name "plutonium" for artificial element 94 since it followed neptunium and uranium (elements 93 and 92). The symbols Pu and Np were also suggestions. The paper was held secret until after WW II, when it was published by the Journal of the American Chemical Society in 1948. The authors were Glenn Seaborg and Arthur C. Wahl. Since McMillan and Abelson had named neptunium after the planet that lies outside of the orbit of Uranus, the name for the next element in the periodic table was named after the next planet, Pluto. But instead of "plutium," the authors decided on the name "plutonium." Seaborg said, " It just sounded better." They also liked "Pu" instead of "Pl."

March 20: Polykarp Kusch
(Born January 26, 1911: Died March 20, 1993)
German-American physicist who, with Willis E. Lamb, Jr., was awarded the Nobel Prize for Physics in 1955 for his accurate determination that the magnetic moment of the electron is greater than its theoretical value, a vital determination that led to revised theories about the interactions of electrons with electromagnetic radiation.

March 19: Frédéric Joliot-Curie
(Born March 19, 1900: Died August 14, 1958)
French physical chemist, husband of Irène Joliot-Curie, who were jointly awarded the 1935 Nobel Prize for Chemistry for their discovery of artificially prepared, radioactive isotopes of new elements. They were the son-in-law and daughter of Nobel Prize winners Pierre and Marie Curie.

March 18: First spacewalk
In 1965, Voskhod 2 was launched into space carrying Aleksey Leonov and Pavel Belyayev aboard. On the second orbit Leonov left the spacecraft through the air lock while still tethered to the vessel. He was the first man to climb out of a spacecraft in space. While outside, he took motion pictures and practiced moving outside of the spacecraft for 10 minutes. Voskhod 2 made 17 orbits at about 110 miles above earth.

March 17: Irène Joliot-Curie
(Born September 12, 1897: Died March 17, 1956)
French physical chemist, wife of Frédéric Joliot-Curie, who were jointly awarded the 1935 Nobel Prize for Chemistry for their discovery of new radioactive isotopes prepared artificially. She was the daughter of Nobel Prize winners Pierre and Marie Curie.

March 16: Yves-André Rocard
(Born: May 22, 1903: Died: March 16, 1992)
French mathematician and physicist who contributed to the development of the French atomic bomb and to the understanding of such diverse fields of research as semiconductors, seismology, and radio astronomy. During WW II, as Head of the Research Department of the Free French Naval Forces in England, he learnt about radars in England and interference from strong radio emission from the Sun. After the war, Rocard returned to France and proposed that France started a project to conduct radio astronomy. In the last part of his life he studied biomagnetism and dowsing which reduced his standing in the eyes of many of his colleagues.

March 15: Arthur Holly Compton
(Born: September 10, 1892: Died: March 15, 1962)
American physicist and engineer. He was a joint winner, with C.T.R. Wilson of England, of the Nobel Prize for Physics (1927) for his discovery and explanation of the change in the wavelength of X rays when they collide with electrons in metals. This so-called Compton effect is caused by the transfer of energy from a photon to a single electron, then a quantum of radiation is re-emitted in a definite direction by the electron, which in so doing must recoil in a direction forming an acute angle with that of the incident radiation. During WW II, in 1941, he was appointed Chairman of the National Academy of Sciences Committee to Evaluate Use of Atomic Energy in War, assisting in the development of the atomic bomb. (Image: Compton (left) with his assistant Richard L. Doan, 1936.)

March 14: Albert Einstein
(Born March 14, 1879: Died April 18, 1955)
German-American physicist who developed the special and general theories of relativity and won the Nobel Prize for Physics in 1921 for his explanation of the photoelectric effect. Recognized in his own time as one of the most creative intellects in human history, in the first 15 years of the 20th century Einstein advanced a series of theories that proposed entirely new ways of thinking about space, time, and gravitation. His theories of relativity and gravitation were a profound advance over the old Newtonian physics and revolutionized scientific and philosophic inquiry.

March 13: Sir Federico Cesi
(Born March 13, 1585: Died August 1, 1630)
Italian scientist who founded the Accademia dei Lincei (1603, Academy of Linceans or Lynxes), often cited as the first modern scientific society, and of which Galileo was the sixth member (1611). Cesi first announced the word telescope for Galileo's instrument. At an early age, while being privately educated, Cesi became interested in natural history and that believed it should be studied directly, not philosophically. The name of the Academy, which he founded at age 18, was taken from Lynceus of Greek mythology, the animal Lynx with sharp sight. He devoted the rest of his life to recording, illustrating and an early classification of nature, especially botany. The Academy was dissolved when its funding by Cesi ceased upon his sudden death.

March 12: Sir William Henry 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.

March 11: Arthur Jeffrey Dempster
(Born August 14, 1886: Died March 11, 1950)
American physicist who built the first mass spectrometer, a device used to separate and measure the quantities of different charged particles, such as atomic nuclei or molecular fragments. He used a magnetic analyzer that focused ions into an electrical collector. His mass spectrography studies of uranium samples revealed the isotope uranium-235 (1935), the primary fuel in atomic bombs and reactors.

March 10: Val Logsdon Fitch
(Born March 10, 1923)
American particle physicist who was corecipient with James Watson Cronin of the Nobel Prize for Physics in 1980 for an experiment conducted in 1964 that disproved the long-held theory that particle interaction should be indifferent to the direction of time. Working with Leo James Rainwater, Fitch had been the first to observe radiation from muonic atoms; i.e., from species in which a muon is orbiting a nucleus rather than an electron. This work indicated that the sizes of atomic nuclei were smaller than had been supposed. He went on to study kaons and in 1964 began his collaboration with James Cronin, James Christenson, and René Turley which led to the discovery of violations of fundamental symmetry principles in the decay of neutral K-mesons.

March 9: Mesons
In 1948, the University of California at Berkeley and the Atomic Energy Commission officially announced the artificial production of mesons using the 184-inch cyclotron at the university's Radiation Laboratory. Time reported the discovery and hinted that the study of mesons might "lead in the direction of a vastly better source of atomic energy than the fission of uranium."

March 8: 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.

March 7: William Draper Harkins
(Born December 28, 1873: Died March 7, 1951)
American nuclear chemist who was one of the first to investigate the structure and fusion reactions of the nucleus. In 1920, Harkins predicted the existence of the neutron, subsequently discovered by Chadwick's experiment. He made pioneering studies of nuclear reactions with Wilson cloud chambers. In the early 1930's, (with M. D.Kamen) he built a cyclotron. Harkins demonstrated that in neutron bombardment reactions the first step in neutron capture is the formation of an "excited nucleus" of measurable lifetime, which subsequently splits into fragments. He also suggested that subatomic energy might provide enough energy to power the Sun over its lifetime.

March 6: Bohr's model of the atom
In 1913, this date was written by Niels Bohr on his first paper describing his new ideas on atomic structure, and mailed to his mentor, Ernest Rutherford. It was one of three historic papers he wrote on this subject.

March 5: Coperian theory decreed false
In 1616, Copernican theory is declared "false and erroneous" in a decree written by Cardinal Robert Bellarmine, and issued by the Catholic Church in Rome. Further, no person was to be permitted to hold or teach the theory that the earth revolves around the sun. When Galileo subsequently violated the decree, he was put on trial and held under house arrest for the final eight years of his life.

March 4: Richard C. Tolman
(Born March 4, 1881: Died September 5, 1948)
Richard Chace Tolman was an American physicist and chemist who demonstrated that electrons are the charge-carrying entities in the flow of electricity, and also made a measurement of its mass. During the Manhattan Project of WW II, he was the chief scientific adviser to Brig. General Leslie Groves, the head of military affairs overseeing the development of the atomic bomb. After the war he was adviser to the U.S. representative to the United Nations Atomic Energy Commission.

March 3: William Penney
(Born June 24, 1909: Died March 3, 1991)
(Baron Penney of East Hendred) British nuclear physicist who led Britain's development of the atomic bomb. Penney was to Britain as Oppenheimer was to the U.S. He was a prominent part of the British Mission at Los Alamos during WW II, where his principal assignment was studying the damage effects from the blast wave of the atomic bomb, but he became involved in implosion studies as well. Penney's combination of expertise, analytical skill, effective communication, and the ability to translate them into practical application soon made him one of the five members of the Los Alamos "brain trust" that made key decisions. He was the only Briton to be part of the ten man Target Committee that drew up the list of targets for the atomic bombing of Japan.

March 2: Radioacitvity reported
In 1896, Henri Becquerel reported his discovery of the penetrating rays of a uranium compound to the French Academy of Sciences. The photographic plate, fogged by these rays, showing the outline of a metal cross lying between the compound and the plate, is the first recognition of the effects later known as radioactivity.

March 1: Radioactivity discovered
In 1896, Henri Becquerel discovered radioactivity when he developed the photographic plate he left in a desk drawer and found it had fogged with the image of the uranium compound crystals resting on it. Thus, the discovery was in fact the result of a chance occurrence. He had originally stored objects together on February 26, after postponing his intended experiment on phosphorescent emissions stimulated by the sun. Instead he now found spontaneous and penetrating rays, independent of any input of energy. The mysterious nucleus of the atom had been revealed, but realizing that took more years of research by other scientists. He received a share of the 1903 Nobel Prize with Pierre and Marie Curie for their work on radioactivity.

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