Greg Neill replied to Jeff Root:
>> > photons are practically oblivious to electric and
>> > magnetic fields; photon-photon interactions have an
>> > incredibly small cross section. The interaction,
>> > according to quantum theory is, if memory serves, a
>> > third order effect which is practically nil.
>> How might I coax two photons to interact?
> The simplest way is to have them do so in the
> presence of a particle. Alone, two photons very
> rarely interact.
What maximizes the probability of two photons interacting
without a particle? They both have to exist at the same
time. What else? Should they collide perpendicularly?
Head-on? With the fields aligned? Or opposed? Or...?
-- Jeff, in Minneapolis