A non-trivial exponent beta characterising non-equilibrium coarsening
processes is calculated in a soluble model. For a spin model, the expo
nent describes how the fraction p0 of spins which have never flipped (
or, equivalently, the fraction of space which has never been traversed
by a domain wall) depends on the characteristic domain scale L: p0 is
-similar-to L(beta-1). For the one-dimensional time-dependent Ginzburg
-Landau equation at zero temperature we show that the critical exponen
t beta is the zero of a transcendental equation, and find beta = 0.824
924 12....