Two lectures on the direction of time

O. C. de Beauregard

pp. 341-366

in: Wesley C. Salmon (ed), Hans Reichenbach, Berlin, Springer, 1979

Abstract

Since long ago theoretical physicists and/or philosophers of science have been trying to get at the knot of a truly puzzling enigma situated at the very heart of the problem of physical irreversibility. Poincare [1], for instance, remarks that if the arrow of the Zeroth and Second Laws were reversed, if heat flowed from cooler towards warmer sources, and if viscosity were an accelerating rather than a damping force, no prediction would be possible. It would be, as Griinbaum [4] comments, dangerous to get into a lukewarm bathtub, because one could never know which end is going to boil and which to freeze; and it would be dangerous to play at bowls, because bodies would get in motion by themselves, in unpredictable directions and with unforeseeable velocities. Such a world would be a law-less world, insofar as our thinking conforms to the familiar experience of causes developing after effects. In our familiar world it is "blind statistical retrodiction", in Watanabe's [2] words, which is impossible. As no records have been preserved, we cannot "retrotell" the chain of events having generated the quasi-homogeneous swarm of the Little Planets. Neither can we retrotell at which point has been deposited the ink drop now completely diluted inside a glassful of water