Dark Matter is one of those things you hear about, but you’re not quite sure what it is.  Supposedly, there is a bunch of this stuff that we can’t see, but somehow it makes up most of the universe--more stuff than the stars and the planets combined can account for.  For folks of a certain age, Dark Matter wasn’t taught in school because no one had proved its existence.
Thinking up Dark Matter is one thing, proving it exists is another.  Scientists have tried experiments in the Large Hadron Colider, where things spin around and smash into each other, but so far, no Dark Matter has flown out of these collisions.

Which is why recent discoveries by the Fermi space telescope are very exciting.  Wouldn’t you like to know what makes up most of the universe? I would.

The Fermi telescope detected Gamma Radiation coming from the center of our galaxy (the Milky Way).  Objects and events like supernova explosions, neutron stars and black holes produce Gamma Rays.  Radioactive decay--the breakdown of atomic objects--also makes Gamma Rays.  (Side note:  In the Marvel comic books, Gamma Radiation turned Bruce Banner into the Hulk.  Nuclear explosions do produce Gamma Rays, but not Hulks.  Most times.)

So when the Fermi telescope looked at our galaxy’s center it found Gamma Rays, which makes sense because of the neutron stars, pulsars, radioactive decay, etc.  But when you subtract all these known sources of the rays out, there was still a lot more Gamma Radiation.

What made this extra radiation? One explanation is that there is a dense concentration of Dark Matter at the center of our galaxy.  And when two Dark Matter particles collide, they produce debris in the form of Gamma Radiation.

At this point, we don’t have a Dark Matter Detector we can switch on and use to prove the existence of Dark Matter.  But courtesy of the Fermi telescope and some smart scientists, we have growing evidence that Dark Matter exists.  And that’s pretty darn interesting to think about.

1.  Here’s a Wired UK article titled “Telescope finds signal that could be destroying dark matter” by John Timmer.

2.  If you want to read more about Gamma Rays, try National Aeronautics and Space Administration, Science Mission Directorate. (2010). Gamma Rays.

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