Robert Henry Dicke

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Robert Henry Dicke ( May 6, 1916 in St. Louis , Missouri , † March 4, 1997 in Princeton ) was an American physicist and astrophysicist .

Life

Dick was the son of a patent examiner and patent attorney. He studied at Princeton University (Bachelor in 1939) and received his doctorate in 1941 from the University of Rochester in nuclear physics. He then worked from 1941 to 1946 at the Radiation Laboratory of the Massachusetts Institute of Technology (MIT) (where he followed his teacher Lee DuBridge), where he worked on radar technologies (including a microwave detector, the fat radiometer). From 1946 he was first assistant professor and from 1957 Cyrus Fogg Brackett professor of physics at Princeton University. In 1975 he became Albert Einstein Professor of Science there . In 1984 he retired. From 1967 to 1970 he was Princeton Head of Physics Faculty. In 1946 he became a Fellow of the American Physical Society . 1954/55 he was visiting professor at Harvard.

Robert H. Dicke concluded in 1964 (with James Peebles and others) that if a Big Bang is assumed, a cosmic residual radiation ( cosmic microwave background ) would still have to be present today, which would have to correspond to the radiation of a black body at a temperature of around 3 Kelvin. George Gamow , Ralph Alpher and Robert Herman had already suspected this in the 1940s, but their prediction had been forgotten. Dick wanted to look for it experimentally, but others got ahead of him. In 1965 Arno Penzias and Robert W. Wilson in Holmdel / New Jersey detected such radiation (by chance when checking the sensitivity of their antenna), which comes to us uniformly and from all directions, i.e. could not be assigned to any cosmic object.

Dick developed a circuit for quickly switching a receiver input between an antenna and a reference resistor. This arrangement, called thickness switch after its inventor , enables reference measurements to eliminate noise sources in receiving circuits. Dicke is also considered to be the inventor of the lock-in amplifier , which he marketed in his company Princeton Applied Research. In the 1940s he was a leader in the development of a modern analysis of microwave electronics using symmetry relations, reciprocity relations and scattering matrices. Dicke held around 50 patents. He also had early ideas about adaptive optics and played a role in the development phase of the measles and laser , with a patent from 1956 and suggestions in an influential paper from 1954. In it he suggested methods for the transition of the measles from the microwave range (as originally developed by Charles Townes ) into the infrared range using a Fabry-Pérot interferometer (i.e. two parallel mirrors as an optical resonator). Next, he developed in his work of 1954, a simple model (model thickness) for the generation of coherent radiation (from him Superradiant called) in a maser (N two-state atoms in a cavity, interact with the radiation in the dipole approximation).

With Carl H. Brans, Dicke developed a scalar tensor theory of gravitation named after them ( Brans Dicke theory ) as an alternative to Einstein's general theory of relativity (ART). The motivation were also the cosmological ideas of Paul Dirac (Large Number Hypothesis) and Mach's principle . The theory violates the principle of equivalence that Dicke tested in succession with P. Roll and R. Krotkov. In connection with his theories of gravity, he formulated a weak form of the anthropic principle early on . Dick was also active on other questions of the general relativity test, for example measuring the flattening of the sun, which may contribute to the perihelion of Mercury, one of the classic GTR tests. He also tested the equivalence principle using distance measurements to the moon.

With the Dicke-Fix principle in 1960 he succeeded in improving a method for suppressing short interference signals in radar devices.

In the 1980s he dealt with helioseismology , among other things .

In spectroscopy, he described the thickness narrowing of line widths if the mean free path is much shorter than the emitted wavelength. The effect is used in the atomic clocks of the Global Positioning System , for example , and enabled more precise measurements in atomic physics at that time.

From 1963 to 1966 he was a member of the NASA Physics Committee , of which he was a member until 1970. Since 1963 he was a member of the American Academy of Arts and Sciences , since 1967 of the National Academy of Sciences and since 1978 of the American Philosophical Society .

He was married to the British Annie Currie since 1942, with whom he had a daughter and two sons.

Fonts

  • Gravitation and the Universe. In: American Philosophical Society. 1970.
  • with Peebles: The big bang cosmology - enigmas and nostrums. In: Israel Hawking: General relativity- an Einstein centenary survey. Cambridge University Press, 1979.
  • with Carol Gray Montgomery, Edward Mills Purcell : Principles of Microwave Circuits. Office of Scientific and Research Development, National Defense Research Committee, McGraw Hill 1948, Dover 1965.
  • with James P. Wittke: Introduction to Quantum Mechanics. Addison-Wesley 1960.
  • The theoretical significance of experimental relativity. Gordon and Breach 1964.

Awards

Web links

Individual evidence

  1. ^ Biographical Memoirs National Academy
  2. ↑ Dicke, Peebles, Roll, Wilkinson Cosmic Black Body Radiation , Astrophysical Journal, Vol. 142, 1965, pp. 414-419
  3. ↑ Misner, Thorne, Wheeler Gravitation , Freeman 1973, p. 1053, Box zu Dicke
  4. ↑ Dicke Coherence in spontaneous radiation processes , Physical Review, Vol. 93, 1954, p. 99
  5. ↑ This is why, for example, Laser at 50 , Photonics , is one of the “almost pioneers” of the laser
  6. ↑ Brans, Dicke Mach's Principle and a relativistic theory of gravitation , Physical Review, Vol. 124, 1961, p. 925
  7. ↑ Dicke, Roll, Krotkov The equivalence of inertial and gravitational mass , Annals of Physics, Vol. 26, 1964, pp. 442-517
  8. ↑ Dicke Dirac's Cosmology and Mach's Principle , Nature, Vol. 192, 1961, p. 441
  9. ↑ Dicke, H. Goldenberg Solar oblateness and general relativity , Physical Review Letters, Vol. 18, 1967, p. 313. Another motive was that the Brans-Dicke theory of GTR made different predictions about perihelion rotation.
  10. ↑ Williams, Dicke et al. a. New test of the equivalence principle from lunar laser ranging , Phys. Rev. Letters, Vol. 36, 1976, p. 551
  11. ↑ Dicke The effect of collisions upon the Doppler width of spectral lines , Physical Review, Vol. 89, 1953, p. 472
personal data
SURNAME Fat Robert Henry
BRIEF DESCRIPTION American physicist and astrophysicist
DATE OF BIRTH May 6, 1916
PLACE OF BIRTH St. Louis , Missouri
DATE OF DEATH March 4, 1997
Place of death Princeton