Hugo Tetrode
Hugo Martin Tetrode (7 March 1895, in Amsterdam – 18 January 1931, in Amstelveen) was a Dutch theoretical physicist who contributed to statistical physics, early quantum theory and quantum mechanics.
In 1912, Tetrode developed the Sackur–Tetrode equation, a quantum mechanical expression of the entropy of an ideal gas. Otto Sackur derived this equation independently around the same time. The Sackur–Tetrode constant, S0/R, is a fundamental physical constant representing the translational contribution to the entropy of an ideal gas at a temperature of 1 K and pressure of 100 kPa, where R is the gas constant.
From Amsterdam, Tetrode corresponded with Albert Einstein, Hendrik Lorentz and Paul Ehrenfest on quantum mechanics and wrote several influential papers on quantum mechanics which were published in the German physics journal Zeitschrift für Physik.
In (Tetrode 1922), he proposed that electromagnetic interactions are direct, time-symmetric actions between particles along lightlike intervals, not mediated by independent fields. An isolated charge does not radiate, because radiation is an interaction between an emitting particle and an absorbing particle. As an example, he suggested that if the sun were the only object in the universe, then it will not radiate. Mathematically, this corresponds to using the symmetric Green function (½ retarded + ½ advanced) for the interaction. Later, Wheeler and Feynman followed his idea in the Wheeler–Feynman time-symmetric theory.
The sun would not radiate if it were alone in space and no other bodies could absorb its radiation. ... If for example I observed through my telescope yesterday evening that star which let us say is 100 light years away, then not only did I know that the light which it allowed to reach my eye was emitted 100 years ago, but also the star or individual atoms of it knew already 100 years ago that I, who then did not even exist, would view it yesterday evening at such and such a time. ... One might accordingly adopt the opinion that the amount of material in the universe determines the rate of emission. Still this is not necessarily so, for two competing absorption centers will not collaborate but will presumably interfere with each other. If only the amount of matter is great enough and is distributed to some extent in all directions, further additions to it may well be without influence. (Tetrode 1922), translated in (Wheeler & Feynman 1945)
In 1928, he published two papers on mathematical extensions to Dirac's quantum theory.