Llewellyn Thomas

from Wikipedia, the free encyclopedia
Llewellyn Thomas, Copenhagen 1926

Llewellyn Hilleth Thomas (born October 31, 1903 in London , † April 20, 1992 in Raleigh (North Carolina) ), usually simply quoted LH Thomas, was a British theoretical physicist and applied mathematician.

life and work

Thomas studied at Cambridge University (Trinity College), where he studied mathematics with Bromwich and John Edensor Littlewood and physics a. a. with Arthur Eddington and Ralph Fowler . He received his bachelor's degrees in 1924 and master's degrees in 1928, and received his doctorate in Cambridge in 1927 .

Yoshio Nishina, Llewellyn Thomas and Friedrich Hund (Copenhagen 1926)

In 1925 and 1926 he stayed in Copenhagen, where he met Yoshio Nishina and Friedrich Hund . Thomas was at Ohio State University from 1929 to 1943 (and 1945/6) and at the US Army's Aberdeen Proving Ground (the ballistic research center) during World War II . From 1945 he was at the Watson Scientific Computing Laboratory (donated by IBM ) at Columbia University , where he worked with Wallace John Eckert on the programming of the computing systems. In 1946 he became professor of physics at Columbia University, but also gave lectures, for example. B. on numerics of differential equations. In 1963 he became an IBM Fellow . In 1968 he retired from IBM and Columbia University and went to North Carolina State University . In 1976 he retired .

Thomas is known for the Thomas precession of the electron in the atom (1926) and the Thomas Fermi model (1927) with Enrico Fermi , a statistical theory of the atom. The Thomas precession is a relativistic correction in the spin-orbit interaction of an electron in an atom (or a top in an orbit). It provided a previously missing factor ½ in the fine structure splitting of the hydrogen atom.

In the Watson computer laboratory at Columbia University, he invented the magnetic core memory before An Wang . He is also said to have been responsible for the format of the instructions of the IBM NORC ( Naval Ordonance Research Computer ) used at the laboratory with three addresses.

In 1954, Thomas made the headlines of Time Magazine with an argument against Wernher von Braun's use of satellites in orbit for military purposes to promote space travel. Thomas pointed out that it would be far cheaper to detonate a bomb in orbit to turn off the satellite.

From 1958 he was a member of the National Academy of Sciences .

Thomas mostly worked for himself and had few students, including Leonard Schiff .

In 1938 Thomas developed a method of dividing the cyclotron magnet into sectors in order to solve the defocusing problem of cyclotrons at higher energies, where the relativistic increase in mass becomes noticeable (Thomas cyclotron). However, it was difficult to implement and ahead of its time and was only realized in Berkeley in 1950 by John Reginald Richardson and others.

In 1934 he became a Fellow of the American Physical Society . In 1958 he was elected a member of the National Academy of Sciences .

literature

Web links

Commons : Llewellyn Thomas  - collection of images, videos and audio files

Remarks

  1. ↑ Quantum Theory: The Schools and Their Students . tape 32 , no. 1 , 2001, p. 7–8 ( PDF ).
  2. ↑ According to Andrew Sessler, Edmund Wilson: Engines of Discovery, World Scientific, 2007, p. 20, he was frequently asked for advice by members of the physics faculty in Columbia and was nicknamed The Sage of 116th Street , The Sage of 116th Street
  3. ↑ Thomas: Motion of spinning electrons . In: Nature . Volume 117, 1926, p. 514
  4. ^ LH Thomas: The Calculation of Atomic Fields . In: Mathematical Proceedings of the Cambridge Philosophical Society . tape 23 , no. 5 , 1927, pp. 542-548 , doi : 10.1017 / S0305004100011683 . The work of Fermi is: E. Fermi: A statistical method for determining some properties of the atom and its application to the theory of the periodic table of elements . In: Journal of Physics . tape 48 , no. 1-2 , 1928, pp. 73-79 , doi : 10.1007 / BF01351576 . See also the Italian first publication by E. Fermi: Un metodo statistico per la determinazione di alcune priorieta dell'atome . In: Rendicondi Accademia Nazionale de Lincei . tape
     6 , no. 32 , 1927, pp. 602-607 .
  5. ↑ Later expanded by Paul Dirac and Carl Friedrich von Weizsäcker , hence sometimes also called the Thomas-Fermi-Dirac theory
  6. ↑ Already in L. Silberstein: The Theory of Relativity . MacMillan treated in 1914. Thomas was known through Arthur Eddington's textbook The Mathematical Theory of Relativity (1924), a corresponding work by Willem de Sitter on the relativistic correction of the precession of the moon .
  7. ^ How to shoot down a satellite . In: Time Magazine . May 3, 1954.
  8. ↑ To evaluate the effect of the mass increase collect the magnetic field needed to radially outwardly expand, resulting in defocus, which by azimuthal was corrected variation of the magnetic field
  9. ^ LH Thomas: The Paths of Ions in the Cyclotron I. Orbits in the Magnetic Field . In: Physical Review . tape 54 , no. 8 , 1938, pp. 580-588 , doi : 10.1103 / PhysRev.54.580 .
personal data
SURNAME Thomas, Llewellyn
ALTERNATIVE NAMES Thomas, LH; Thomas, Llewellyn Hilleth (full name)
BRIEF DESCRIPTION British physicist
DATE OF BIRTH October 31, 1903
PLACE OF BIRTH London
DATE OF DEATH April 20, 1992
Place of death Raleigh, North Carolina