I am working on a story where superheroes have started to appear. Their powers are all based on manipulation of spacetime and mass, and not on electromagnetism. One character is a speedster who can compress time. He can experience many seconds while everything around him experiences one second. What I can't wrap my head around is what physics would need to happen to make a small region of space have a faster clock rate. Slower - sure. But faster? Would the hero have a different speed of light? Would his 1g acceleration toward the Earth be modified?