This operation relates the external protocols in the numerator and denominator of the Crooks relation. In stochastic thermo, the entropy production is proportional to the log of the following: the probability of a trajectory, over the probability of the trajectory under this operation. In quantum mechanics, this operation is an anti-unitary operator that [emphasize] commutes with the Hamiltonian. (15[1])Spin-1/2 systems (-5[1])that are invariant under this operation (-5[1])satisfy (*) Kramers’ theorem. Magnetic (10[1])fields break symmetry under this operation, which is unified (10[1])with symmetry under charge conjugation and parity inversion. Loschmidt’s paradox (10[1])asks (-5[1])how it is possible for Newton’s laws, which (-5[1])are invariant (-5[1])under this operation, (-5[1])to give rise to a quantity like entropy that only increases. (10[1]-5[1])For 10 (-5[1])points, (10[1])name this operation analogized to playing a movie backwards. (10[2])■END■ (10[3]0[4])