4 8 8 D O C . 3 3 9 A N I S O T R O P I C P R E S S U R E F O R C E S streben. Die Rechnung zeigt, dass die Grösse dieser Kräfte des Faktors z eine Prü- fung des Resultates durch das Experiment bequem zulässt.[10] A. Einstein ADS. [2 091]. The document consists of three pages. Page numbers presented here in the margin in square brackets depart from those in the original, where they appear in the top right corner of the page. [1]The document was presented by Max von Laue on behalf of Einstein to the physical- mathematical class of the Prussian Academy of Sciences at its session of 23 November 1922 (Preußische Akademie der Wissenschaften [Berlin]. Physikalisch-mathematische Klasse. Sitzungsbe- richte (1922): 447). [2]See Maxwell 1879. For a detailed discussion of how Maxwell’s paper came to be written, see Brush 1976, pp. 210–230, and Brush and Everitt 1969. [3]For Einstein’s help given to his cousin Edith Einstein in the preparation of her dissertation, see Doc. 68 see also Einstein, E. 1922 for a publication based on the dissertation. In this paper Einstein presents a more complete version of the calculation published by his cousin. However, both Einsteins confine themselves to demonstrating the existence of such second-order effects, without showing that they are able to explain the radiometer effect as it is observed. [4]In Maxwell 1879, the form of the velocity distribution is simply assumed. [5]The integral below is the quantity H introduced by Ludwig Boltzmann. For systems of independent particles, its negative is proportional to the entropy. Boltzmann’s H-theorem proves that H can never increase accordingly, the entropy never decreases. An extremum of H corresponds to equilibrium. [6]In eq. (6), L is the total kinetic energy in the gas, a conserved quantity. [7]This value for h gives the Maxwell velocity distribution for the molecules in a gas. [8]The p in the denominator of the right-hand side of this equation should be ρ, the density of the gas. The quantities M, R, and T should be squared so that the whole expression reads , in agreement with eq. (40) of Einstein, E. 1922. [9]The corrected form of the equation given here agrees with the values for and given in Einstein, E. 1922, with the same corrections described in the preceding note, so that the equation would read Edith Einstein did not give values for the off-diagonal terms, such as . [10]Probably a reference to experiments of the radiometer type. For a discussion, see Loeb, L. 1934. For the historical context of the radiometer problem, see Woodruff 1968 and Brush 1976. pxx pyy – 18 25 ----- - M2 ρR2T2 --------------- - fx 2 ⋅ ⋅ = pxx, pyy, pzz pμν pδμν 18 25 ----- - M2 ρR2T2 --------------- - fμ fν 1 2 -- - δμν fα 2 ⋅ – . ⋅ ⋅ += pxy