The universe is shrouded in mystery—a shroud so dark, in fact, that 27 percent of the matter in it is “dark.” Dark matter does not interact with photons and electromagnetic waves, so it’s invisible to our eyes and to every kind of telescope. Basically, it’s the darkness that surrounds every celestial body, and we only know that it’s there because astronomers observe its gravitational pull on everything else. Read more about The Missing Universe: CERN Has Started Searching for Dark Photons