Sunday, November 25, 2012
Rutherford used his 11 and 1/4 inch telescope to take pictures of the moon, the planets and stars. Then using a diffraction grating of his own manufacture he began taking spectra of planets and stars. In 1863 he published a paper which was the first attempt to classify stars according to their spectra, dividing stars into three categories. Today, most stars are classified using the system developed by Annie Jump Cannon that classifies stars by their color. In order of decreasing surface temperature, O are blue stars, B white/blue stars, A white stars, F yellow/white stars, G yellow stars, K orange stars, and M red stars.
Rutherford served as an trustee of Columbia University from from 1858 to 1884. He was an active participant in the International Meridian Conference which established the prime meridian as the line of longitude that runs through Greenwich, England. In 1867 he served as president of the American Photographical Society. He was an associate of the Royal Astronomical Society and a member of the National Academy of Sciences since its founding in 1863.
In his later years he was in delicate health and he died from the complications of a cold he contracted while traveling to his winter residence in Florida on May 30, 1892.
Anon; "A Sketch of Lewis Morris Rutherford", Popular Science (1893) Vol. 42
Gould, B.A.; "Memoir of Lewis Morris Rutherford: 1816-1892"; National Academy Press; 1895
Lewis Morris Rutherford Wikipedia Entry
Sunday, November 18, 2012
Blackett graduated from Magdalene College with a B.A. in 1921 and continued working for Rutherford for another ten years. In 1923 he became a fellow at Kings College and in 1924 he used a cloud chamber to record the transmutation of nitrogen into oxygen. A cloud chamber is a closed chamber saturated with water or alcohol vapor. When ionizing particles (alpha particles for example) are introduced they create ions. The vapor in the chamber condenses on these ions and the condensed liquid shows the path of the particle through the chamber. While in the Cavendish Laboratory Blackett used a cloud chamber to do experiements involving cosmic rays. From 1924 to 1925 he worked in the laboratories of James Franck in Gottingen, Germany studying atomic spectra. In 1932, working with Italian physicist Giuseppe Occhialini, he developed a cloud chamber with a geiger counter to trigger the camera.
In 1933 he became professor at Birkback College, at the University of London. Also in 1933 he confirmed Carl David Anderson's discovery of the positron. A positron is a positively charged electron, an anti-matter particle. Blackett also worked on annihilation, the collision of matter and anti-matter that produces gamma radiation. In 1937 he became the Longworthy professor at Victoria University in Manchester. While there he worked on a theory of the earth magnetism, hoping to use it to unify the forces of gravity and magnetism. Although he was unsuccessful his work led to the development of paleomagnetism, which was used to prove the existence of continental drift.
In 1935 he was invited to serve on the Tizard Committee, which recommended the installation of radar for air defense. During World War II he served on various defense committees and contributed to the invention of the Mark XIV bomb sight. In 1940 he was awarded the Royal Medal by the Royal Society. In 1948 he was awarded the Nobel Prize for his work on particle physics using cloud chambers. He was appointed chairman of the physics department of Imperial College at London in 1953 and he retired in 1963. Blackett served as an adviser to the post war Labor government and in 1964, at his advice, set up the Ministry of Science and Technology. Blackett was outspoken politically and frequently came under criticism for his socialist and anti-nuclear weapon views.
He died on July 13, 1974.
Brown, Matt; "Patrick Blackett: From Cosmic Rays to International Development"; November 18, 2007; London Blog at blogs.nature.com
Nye, Mary Jo; Blackett: Physics, War and Politics in the 20th Century; Harvard University Press; 2004
Patrick Blackett Nobel Biography
Patrick Blackett Wikipedia Entry
Sunday, November 11, 2012
Slipher's first project, at the direction of Lowell, writing from his Boston office, was mounting and using the new spectrograph on Lowell's 24-inch refracting telescope. Slipher used it to record the spectra of Mars, Jupiter, and Saturn. Using the spectra that Slipher produced the confirmed the visually known periods of the planets. Using spectra taken of Mars, he attempted to prove there was water in the Martian atmosphere and he attempted to find the rotational period of Venus. He then turned the telescope to the gas giants and determined that the rotational period of Uranus was 10.75 hrs (it was later determined to be 25 hrs.).
Slipher is remembered chiefly for the work that he did determining the velocity of what at the time where called spiral nebula. Today we know these spiral shaped clouds are galaxies, just like our Milky Way. Slipher determined that these spiral nebula were moving much faster (three times) the velocity of any object observed at that time. Edwin Hubble later used this data to show the universe was expanding and the farther an object was away from Earth, the faster it would be moving away. Slipher is also responsible for hiring Clyde Tombaugh and was responsible for overseeing the work involved in the discovery of Pluto.
Awards won by Slipher include the Bruce Medal (1935), the Lalande Prize (1919), a Gold Medal from the Royal Society (1932), the Henry Draper Prize from the National Academy of Sciences (1932) and a gold medal from the Paris Academy of Sciences (1919). Slipher also has a crater on the moon named after him. In addition to his scientific work Slipher was also active in the community of Flagstaff, Arizona, where he was one of the founders of its first high school.
Slipher died on November 8, 1969, in Flagstaff, Arizona.
Hoyt, Willliam Graves, "Vesto Melvin Slipher: 1875-1969"; National Academy Press, 1980
Trimble, Virginia; Williams, Thomas; Bracher, Katherine; Jarrell, Richard; Marche, Jordan; and Ragep, F. Jamil; "Vesto Slipher" in Biographical Encyclopedia of Astronomers; Springer; 2006
Vesto Sipher Wikipedia Entry