Sir Edward Sabine

Edward Sabine was born on October 14, 1788 in Dublin, Ireland. He was the fifth son and ninth child of Joseph Sabine and Sarah Sabine nee Hunt. Sabine's mother died one month after his birth. He obtained a military education first at Marlowe and then at Royal Military Academy at Woolrich. He was commissioned as an artillery officer in 1803, becoming a captain ten years later, and he rose to the rank of general in 1870. Sabine was stationed at Gibraltar during the Peninsular War and saw his first action during the War of 1812. On his voyage to Canada the ship he was on was captured by an American privateer. The ship was eventually recaptured by a British frigate and he made his way to Quebec. Sabine served in the Niagara campaign and took part in the siege and assault on Fort Eire, serving with distinction.

He returned to England in 1816 and began doing research in astronomy, terrestrial magnetism, and ornithology. He became a member of the Royal Society in 1818. Also in 1818 Sabine served as astronomer during the Ross expedition looking for the Northwest Passage. During the expedition Sabine took magnetic readings of the Earth and studied birds, identifying a new species (Larus sabini). The following year Sabine took part in another Northwest Passage expedition, this time under William Perry. The expedition was the first to make it north of the arctic circle, returning in 1820. In 1921 Sabine received the Copley Medal for his various researches during this expedition.

For the next couple years Sabine toured the world taking measurements with his pendulum. The period of a pendulum depends on its length and the force of gravity on the bob at the end of the string or arm. Because Earth is not a perfect sphere (it is an oblate sphere which bulges at the equator) the distance to the center of the Earth is not uniform at different latitudes. This causes the gravity at the earth surface to vary at different latitudes with the acceleration of gravity rising as you move toward the poles. The period of Sabine's pendulum, swung at different latitudes, differed due to the differences in gravity caused by the differences in the distance to the center of the Earth. With this experiment Sabine demonstrated that the earth is not perfectly spherical. For this work Sabine was honored with the Lalande Medal of the Institute of France in 1826

When the British Board of Longitude was abolished in 1828, Sabine, with Michael Farady and Thomas Young, was appointed as a scientific adviser to the Admiralty. In this position Sabine advocated for the creation of magnetic measuring stations throughout the British Empire. Because changes in the Earth's magnetic field, which at the time were believed to be the result of weather patterns, affected compass readings these magnetic observatories were built. The observations from these observatories were collated by Sabine in London and he discovered that changes in the Earth's magnetic field were due to sunspot activity and the influence of the moon.

Sabine won a gold medal from the Royal Society in 1849 and served as its president from 1861 to 1871. Sabine was knighted in 1864 and has a crater on the moon named after him. The California grey pine (Pinus sabineana) is also named after him.

He died on June 26, 1883 and was buried in his family vault in Tewin, Hertfordshire.


References:

Anon.; "Sir Edward Sabine"; The Observatory (1883)6:232-233

Vetch, Robert Hamilton; "Sabine, sir Edward"; Dictionary of National Biography, 1885-1900, Volume 50;

Edward Sabine Wikipedia Entry

John van Vleck

John Hasbrouck van Vleck was born on March 13, 1899 in Middletown, Connecticut. Both his father and grandfather were university professors. Van Vleck, an only child, moved with his parents to Wisconsin when he was seven when his father became a professor at the University of Wisconsin. He was educated in the Madison, Wisconsin public schools and went on to the University of Wisconsin, where he played in the band. His undergraduate education included courses on railroads and French literature, in addition to physics. Although not an athlete, he was a fan of American football, remembering the scores of games years after they had been played. He graduated in 1920 with a degree in physics. He entered the graduate program at Harvard University and graduated with a Ph.D. in 1922 completing a thesis on the binding energy of a helium atom.

After his doctorate he stayed at Harvard for a year teaching, before taking a job at the University of Minnesota, where he taught graduate physics courses from 1923-1928 He returned to teach at his alma mater, the University of Wisconsin from 1928-1934 and he taught at Harvard from 1934-1969. During World War II he worked on radar at the MIT Radiation Laboratory and participated in the Manhattan Project as part of a committee, with J. Robert Oppenheimer, that studied the feasibility of and designed the first atomic bombs. He also served on the Los Alamos Review Committee, which designed the firing mechanism for "Little Boy", the first atomic bomb used on Hiroshima, Japan.

Van Vleck's early research delt with diamagnetic and paramagnetic materials, and how their behavior could be understood when the new (at the time) field of quantum mechanics was applied. Paramagnetic materials, when exposed to an external magnetic field, are attracted to it, diamagnetic materials are slightly repelled. Neither of the materials retain a magnetic field when the external field is removed. The reason for these behaviors is the electron structures of the different materials, paramagnetic materials have unpaired electrons and diamagnetic do not. Van Vleck also worked on crystal field theory, a branch of chemistry that has to do with the complexes formed by transition metals. He showed that ligands (the atoms or groups of atoms that bond to transition metals) form covalent bonds, not just ionic bonds, with the central metal atom.

In 1977 van Vleck, along with Philip Anderson and Sir Nevil Mott, was awarded the Nobel Prize for Physics "for their fundamental theoretical investigations of the electronic structure of magnetic and disordered systems". Other awards won by van Vleck include the National Medal of Science in 1966 and the Lorentz Medal from the Royal Netherlands Academy of Arts and Sciences in 1974.

Van Vleck retired in 1969 and died in his Cambridge, Massachusetts home on October, 27 1980.


References:

Anderson, P.W.; "John Hasbrouk Van Vleck"; in Biographical Memoirs Vol. 56; National Academy Press; 1987

Carey, Charles W.; American Scientists; Infobase Publishing; 2006

John H. Van Vleck Nobel Autobiography

John Hasbrouck Van Veck Wikipedia Entry