  We consider experimental evidence for the hypothesis that the Planck energy,
$E_p \approx 10^{19}GeV$, sets the scale $\epsilon$ at which wave function
collapse causes deviations from linear Schr\"{o}dinger evolution. With a few
plausible assumptions about the collapse process, we first show that the
observed CP violation in $K_L$ decay implies a lower bound on $\epsilon$
remarkably close to $E_p$. If the bound is saturated, the entire CP violation
is due to collapse and a prediction made that the branching ratio for CP
violation in the B meson decay will be $\gamma \approx 10^{-5}$. We then show
that the assumptions are consequences of a simple non-linear, stochastic
modification of the Schr\"{o}dinger equation with $\epsilon$ setting the scale
of the non-linearity.
