synthesizing matter

Have you heard about solar cells?

2 photons, momentum must be conserved.
And yes, if a high enough energy photon passes through matter, it can turn into an electron-positron pair. Can't happen without the matter because, again, energy and momentum must be conserved.

>>8510291
Can momentum be conserved without matter?

>>8510357
In units where c=1, a photon has the same amount of momentum as it has energy. Any particle with mass, including positrons and electrons, has less momentum than energy. Therefore a photon cannot turn into a positron-electron pair without either transferring some of its momentum to something else or getting energy from something else.

>>8510273
yeah:
http://www.sciencealert.com/physicists-have-figured-out-how-to-create-matter-and-antimatter-using-light