Time dependent systems do not in general conserve energy invalidating much of the
theory developed for static systems and turning our intuition on its head. This is particularly
acute in luminal space time crystals where the structure moves at or close to the velocity of
light. Conventional Bloch wave theory no longer applies, energy grows exponentially with
time, and a new perspective is required to understand the phenomenology. In this letter we
identify a new mechanism for amplification: the compression of lines of force that are
nevertheless conserved in number.