Curious, can this process be reversed? Also, is momentum conserved, then if it is wouldn't the positron and electron be ejecting at the speed of light (and wouldn't that violate the principle that matter cannot reach the speed of light)? If not what is slowing them down / where is the energy going? Could this be theoretically a way to power something? Either by the ricochet of the particles off something, or by using them to energize something?