|
Robert Henry Dicke (May 6 1916 – March 4 1997) was an American experimental physicist, who made important contributions to the fields of astrophysics, atomic physics, cosmology and gravity.
Biography Born in St. Louis, Missouri, Dicke completed his bachelor's degree at Princeton University and his doctorate, in 1939, from the University of Rochester in nuclear physics. During the second world war he worked in the radiation laboratory at the Massachusetts Institute of Technology where he worked on the development of radar and designed the Dicke radiometer, a microwave receiver. He used this to set a limit on the temperature of the cosmic microwave background radiation, from the roof of the radiation laboratory, of less than 20 kelvins. In 1946, he returned to Princeton University, where he remained for the rest of his career. He did some work in atomic physics, particularly on the laser and measuring the gyromagnetic ratio of the electron. He was instrumental in early measurements of the cosmic microwave background radiation, whose physics he worked out with Philip James Edwin Peebles, David Todd Wilkinson and Peter G. Roll (having forgotten the earlier prediction of George Gamow). The Dicke radiometer has been used for many measurements of the background radiation, including that of Arno Penzias and Robert Woodrow Wilson. He spent the remainder of his career developing a program of precision tests of general relativity using the framework of the equivalence principle. With Carl H. Brans, he developed Brans-Dicke theory, an equivalence-principle violating modification of general relativity inspired by Paul Dirac's large numbers hypothesis and Mach's principle. He made measurements of solar oblateness which were useful in understanding the perihelion precession of Mercury's orbit, one of the classical tests of general relativity. Together with Philip James Edwin Peebles he was instrumental in transforming cosmology into a respectable field of inquiry in physics. Robert Dicke is also responsible for developing the lock-in amplifier, which is an indispensable tool in the area of applied science and engineering. Some believe that Robert Dicke deserved a Nobel prize just for the invention of such a powerful and ubiquitous device. Robert Dicke contibuted also notably contributed to the field of Spectroscopy and Radiative Transfer by means of predicting the phenomenon called Dicke narrowing (aka collisional narrowing): When the mean free path of an atom is much smaller than the wavelength of one of its radiation transitions, the atom changes velocity and direction many times during the emission or absorption of a photon. This causes an averaging over different Doppler states and results in an atomic linewidth that is much narrower than the Doppler width. Dicke narrowing occurs at relatively low pressures in the millimeter wave and microwave regions (where it is used in atomic clocks to improve precision). Dicke narrowing is analogous to the Mossbauer effect for gamma rays. | ||||||||
|
| |||||||||
 |
|
| |