  Using a twisted nematic liquid crystal system exhibiting planar Ising model
dynamics, we have measured the scaling exponent $\theta$ which characterizes
the time evolution, $p(t) \sim t^{-\theta}$, of the probability p(t) that the
local order parameter has not switched its state by the time t. For 0.4 seconds
to 200 seconds following the phase quench, the system exhibits scaling behavior
and, measured over this interval, $\theta = 0.19 \pm 0.031$, in good agreement
with theoretical analysis and numerical simulations.
