Cosmic rays are incredibly powerful invisible particles, and we can’t be sure where they come from. Not much in the way of a comforting thought, but it makes for a cosmic mystery that astronomers have been trying to solve for decades.  And now they have come one step closer. Here’s what we do know.  Cosmic rays are energetic atomic nuclei travelling at near the speed of light.  They hit our atmosphere and rapidly interact with the molecules there to break into billions of smaller, less energetic particles that shower down on the life on Earth, without giving us much notice...