A fog of gamma rays permeates the sky. Now we know why.

The Universe glows softly in gamma radiation.

This isn’t anything to be concerned about; we’re not all about to Hulk out. Well, to be more clear, this is nothing to be concerned about unless a) you’re an astronomer, and/or 2) you find the Universe a pretty interesting place and want to know more about it.

Lucky you: I’m #1 (and #2), and if you’re #2 then read on.

The Universe glows in lots of different flavors of light. For example, the Cosmic Background Radiation is a glow all over the entir...