  A scenario for measuring the predicted processes of vacuum elastic and
inelastic photon-photon scattering with modern lasers is investigated. Numbers
of measurable scattered photons are calculated for the collision of two,
Gaussian-focused, pulsed lasers. We show that a single 10PW optical laser beam
split into two counter-propagating pulses is sufficient for measuring the
elastic process. Moreover, when these pulses are sub-cycle, our results suggest
the inelastic process should be measurable too.
