Member

Born in Nottingham in 1908, Essen studied at University College Nottingham and earned his physics degree in 1928 from the University of London. He started work at the National Physics Laboratory (NPL) the following year, under D. W. Dye, investigating the potential of tuning forks and quartz crystal oscillators for precise time measurement. His research led to his development of the quartz ring clock in 1938, the clock soon becoming a standard for time measurement at observatories throughout the world.

Essen earned his Ph.D. (1941) and D.Sc. (1948) in physics from the University of London. During World War II, Essen worked on radar and developed a number of instruments, including the cavity resonance wavemeter. This work led to Essen's 1946 measurement of the speed of light by comparing the geometry of resonant cavities with normal mode wavelengths. His interest in the frequency of atomic spectra led Essen to propose a more precise measure of time through the atomic oscillations of caesium. In 1955, he developed, in collaboration with Jack Perry, the first practical atomic clock by integrating the caesium atomic standard with conventional quartz crystal oscillators to allow calibration of existing time-keeping. Soon after the caesium spectrum became the international time standard.

With the track record and authority Essen commanded, especially regarding time, one would think his was a voice to be heard. Yet his late-in-life objections to special relativity met with a cold reception, especially from his employers at NPL. The publication of his 1971 book, The Special Theory of Relativity: A Critical Analysis, led to a strongly encouraged retirement in 1972. Essen continued to publish papers against Einstein's theories and supported the dissident movement in the years prior to his death in 1997.

Articles:

• Proc. Roy. Soc. A194, 348 (1948). (with Gordon Smith)
• Proc. Roy. Soc. A204, 260 (1950).
• Nature 167, 258 (1951).
• Nature 167, 512 (1951). (with K. D. Froome)
• "An Atomic Standard of Frequency and Time Keeping," Nature V176, p. 280-282 (Aug 1955). (with J. V. L. Perry)
• Nature 177, 744 (1956). (with J. V. L. Perry)
• Nature 178, 34 (1956).
• "The Clock Paradox of Relativity," Nature V180, N4594, pp. 1061-1062 (1957).
• Phil. Trans. A250, 45 (1957). (with J. V. L. Perry)
• Nature 180, 137 (1957).
• Nature 180, 526 (1957). (with J. V. L. Perry and J. A. Pierce)
• Research 10, 217 (1957).
• L. ESSEN, J. V. L. PARRY, W. MABKOWITZ and R. G. HALL, Nature 181, 1054 (1958).
• L. ESSEN, J. V. L. PARRY, J. H. HOLLOWAY, W. A. MAINBERGER, F. H. REDER and G. M. R. WINXLER, Nature 182, 41 (1958).
• W. MARXOWITZ, R. G. HALL, L. ESSEN and J. V. L. PARRY, Phys. Rev. Letters 1, 105 (1958).
• Proceedings of the Royal Society of London, S-A, V270, pp. 312-314 (1962).