(Gyulavári, July 24th, 1900 – Washington, October 4th, 1992)
His name is well-known for people interested in the history of science and technology. Though he was not awarded the Nobel Prize, Zoltán Bay has become one of the most significant physicists in basic research of the natural sciences in the 20th century. He was a participant and organiser of technological development and realised industrial applications, as well. He is most famous for the lunar radar echo experiment after the 2nd World War. However, few people know about his definition of the metre based on the velocity of light and his results in the development of photoelectron multiplier tubes.
He has taken his final examination at the famous Reformed (Calvinist) College's secondary school in Debrecen in 1918, then he enrolled at the Faculty of Arts at the Royal Hungarian University of Sciences in Budapest and at the same time he was admitted to the József Eötvös College. In 1923, he was awarded a secondary school teacher's diploma, and in 1926 received his doctorate in physics.
From 1926 to 1930, he worked on a scholarship in Germany, became the member of the Collegium Hungaricum in Berlin and worked at the Physical-Chemical Institute of the University of Science in Berlin. He developed a new method of spectroscopy (1929), by means of which he was able to study the excited emission spectrum of gases and proved the existence of free N-atoms in active nitrogen. He became acquainted with John von Neumann, who later became one of his friends.
After returning home, he was appointed as senior lecturer at the Ferencz József University of Sciences of Szeged and, in 1935, as professor of the Department of Theoretical Physics. He studied of Compton scattering; paid special attention to the relationship between quantum mechanics and biology; and measured the current and voltage of the heart and created the idea of pacemakers. In this research Albert Szent-Györgyi, who was the head of the Biochemical Department of the University of Science of Szeged, played an important role.
In 1936, Lipót Aschner, General Manager of United Incandescent Lamp and Electrical Co. Ltd. invited Bay to be the head of the Tungsram Research Laboratory, following Ignác Pfeifer.
Here he improved the detection of the photon-electron coincidence of the Compton effect in the ultraviolet and visible domains. The idea of the development of a particle counter based on electron multiplication arose in 1937. At that time a sensitive multiplier was already available, the dark current of which corresponded to flow of 40 electrons per minute. In 1938, the sensitivity was improved by means of dinodes of high emission capability and in this way the detection of a and b particles also became possible.
A fast operating coincidence circuit had to be developed for the electron multiplier. Bay and his colleagues developed a device having a resolution of 1...10 ns, with which they were ahead of laboratories all over the world.
He became a correspondent member of the Hungarian Academy of Sciences in 1937 and an ordinary member in 1945. In 1938 he undertook the direction of the Nuclear Physics Department established in the József Palatine Technical and Economic University and supported by Lipót Aschner.
In 1942, radar experiments of military purpose started inTungsram for direction finding and distance measurement aiming the production of domestic active microwave devices and using them to accomplish microwave terrestrial connections and the development a radiolocator for anti-aircraft defence. The Bay research team obtained experience in the so-called pulse echo method.
The Moon echo experiment started in 1944 and the measurement were successful in 1946.
Leaving Hungary in 1948 owing to the worsened political conditions, he continued his research of fast coincidence as a professor at the George Washington University in the United States.His most important achievement here was to complete work on development of the electron multiplier, which he had begun in Hungary in 1938.
In 1955, he was appointed as the head of the Nuclear Physics Department at the American National Bureau of Standards, where he measured the frequency and velocity of light by a previously unknown method. On the basis of the of his research, the conference of the International Weights and Measures Bureau held in 1983 accepted as a standard the definition of the metre as recommended by Bay. It became possible to use the velocity of light as base unit of length measurement and to create the light measured metre.
From 1972, he was a researcher as a retired professor at the Physics Department of the American University (Washington DC). From the eighties he often visited Hungary.
His return with his friend, Albert Szent-Györgyi was a remarkable event in Hungary.
Memberships: Associate (1937) and ordinary (1945) member of the Hungarian Academy of Sciences, honorary doctor of the University of Edinburgh (1978), honorary member of the Hungarian Academy of Sciences (1981), honorary member of the Roland Eötvös Physical Society (1981), honorary doctor of the Technical University of Budapest (1986), honorary citizen of the town of Gyula (1989), honorary doctor of Lajos Kossuth University of Sciences (Debrecen) (1990), honorary President for life of Hungarian Electrotechnical Association (1990), honorary doctor of the József Attila University (Szeged) (1991).
Honours: Order of Service (Ministry of Commerce, United States) (1970), Boyden Prize (1980), Flag Order of Rubies of the Hungarian Republic (1990), Kálmán Szily Commemorative Medal, (Természet Világa - The World of the Nature, periodical, 1991)
- Bay, Z.: Electron-Multiplier as an Electron-Counting Device. In: Nature, 1938, vol. 141, p. 284.
- Bay, Z.: Electron-Multiplier as an Electron-Counting Device. In: Nature, 1938, vol. 141, p. 1011.
- Bay, Z., Szepesi, Z.: Über die Intensitätsverteilung der Compton-Streuung von ă Strahlen. In: Zeitschrift für Physik, 1939, Bd. 112, p. 20.
- Bay, Z., Papp, G.: Über den Kerneffekt bei der Streuung von ă Strahlen. In: Zeitschrift für Physik, 1939, Bd. 112, p. 86.
- Bay, Z.: Electron-Multiplier as an Electron-Counting Device. In: Reviews of Scientific Instruments, 1941, vol. 12, no. 3, p. 127133.
- Bay, Z., Papp, G.: Coincidence Device of 10-810-9 Second Resolving Power. In: Reviews of Scientific Instruments, 1948, vol. 19, p. 565.; In: Nature, 1948, vol. 161, p. 59.
- Bay, Z.: New Type of High Speed Coincidence Circuit. In: Physical Review, 1950, vol. 79, p. 233.
- Bay, Z., Meijer, R. R., Papp, G.: On Measuring Very Short Half-Lives. In: Physical Review, 1951, vol. 82, p. 754.
- Bay, Z.: Differential Coincidence Counting Method. In: Physical Review, 1951, vol. 83, p. 242.
- Bay, Z., Meijer, R. R., Papp, G.: Differential Coincidence Counting Method. In: Nucleonics, 1952, vol. 10, no. 3, p. 39.
- Bay, Z., Szent-Györgyi, A.: Window Field in Muscle. In: Nature, 1951, vol. 167, p. 482.
- Bay, Z.: Determination of the Resolving Time of Coincidences. In: Physical Review, 1952, vol. 87, p. 194.
- Bay, Z., Cleland, M. R., McLernon, F.: Coincidences with Cerenkov Counters. In: Physical Review, 1952, vol. 87, p. 901.
- Bay, Z., Goddall, M.C., Szent-Györgyi, A.: Transmission of Excitation from the Membrane to Actomyosin. In: Bull. Math. Biophysics, 1953, vol. 15, p. 1.
- Bay, Z., Henri, V. P., McLernon, F.: Simultaneity in the Compton Effect. In: Physical Review, 1955, vol. 97, p. 1710.
- Bay, Z.: Millimicrosecond Coincidence Circuits. In: Nucleonics, 1956, vol. 14, no. 5, p. 56.
- Bay, Z.: Techniques and Theory of Fast Coincidence Experiments. (Invited Paper, Scintillation Counter Symposium, Washington, D.C. 1956) In: I.R.E. Transactions on Nuclear Science, Nov. 1956, vol. 125, P12.
- Bay, Z., Farago, P. S.: Remarks on Coincidence Experiments with Visible Light. In: Proceedings of the Roy. Soc Edinburgh, 1963, Part II., vol. 66, no. 1, p. 111115.
- Avery, J., Bay, Z., Szent-Györgyi, A.: On the Energy Transfer in Biological Systems. In: Proc. Nat. Acad. of Sci., 1961, vol. 47, no. 11, p. 1742.
- Bay, Z., Boyne, H. S.: The Use of Terahertz Photobeats for Precise Velocity-of-Light Measurements. In: Rendiconti Scuola Intern. di Fisica, E. Fermi, 1964, XXXI. Corso, p. 352.
- Bay, Z., Luther, G. G.: Locking a Laser Frequency to the Time Standard. In: Applied Physics Letters, 1968, vol. 13, no. 3, p. 303.
- Bay, Z.: The Use of Microwave Modulation of Lasers for Length Measurement. Precision Measurement and Fundamental Constanst. In: Langenberger, D. N., Taylor, B. N. (Ed. by): National Bureau of Standard Special Publication 343, (US GPO, Washington, D.C. 1971) p. 59.
- Bay, Z., Luther, G. G.: The Measuring of Optical Frequencies and the Velocity of Light. Precision Measurements and Fundamental Constants. In: Langerberg, D. N., Taylor, B. N. (Ed. by): National Bureau of Standard Special Publication 343, (US GPO, Washington, D.C. 1971) p. 63.
- Bay, Z.: The Constancy of the Velocity of Light and Prospects for a Unified Standardization of Time, Frequency and Length. Proceeding of the Fourth Internat. Conf. on Atomic Mases and Fundamental Constants. Teddington, England (ed.): Sanders, J. H., Wapstra, A. H. New York: Plenum Press, 1972. p. 334.
- Bay, Z., White, J. A.: Frequency Dependence of the Speed of Light in Space. In: Physical Review, 1972, D5, no. 4, p. 796.
- Bay, Z., Luther, G. G., White, J. A.: Measurement of an Optical Frequency and the Speed of Light. In: Physical Review Letters, 1972, vol. 29, no. 3, p. 189.
- Bay, Z., White, J. A.: The Speed of Light and the New Meter. In: Physics Today, April 1974, p. 9.
- Bay, Z., White, J. A.: Radar Astronomy and the Special Theory of Relativity. In: Acta Physica Hung., 1981, vol. 51, p. 273.
- Bay, Z.: Az élet erősebb. (Life is stronger, in Hungarian) Budapest: Püski, 1990.
- Bay, Z.: Differencial Coincidence Circuit. In: Physical Review, vol. 83, 242. Part A: Precision Measurement of the Speed of Light; Part B: Proposal for a New Length Standard. In: Internal NBS Report (by Bay, Z.).
- Wagner, Francis, S.: Zoltan Bay atomic physicist. A pioneer of space research. Foreword by Albert Szent-Györgyi. Budapest, 1985.
- Butrica, Andrew J.: To See the Unseen. A History of Planetary Radar Astronomy. Washington, 1996.