These are very bright flashes of light - of gamma-ray light. When they occur, they're
much brighter than any other gamma-ray source in the sky. And so the fact that
they're occuring throughout the sky is telling us that they're probably not
associated with our own galaxy but coming from the distant regions of the universe.
That's our best guess right now. And if that's indeed true, since they're so bright,
that means there's a tremendous amount of energy that's being liberated from these
bursts but we still have no idea what causes them.