A Reason Why Astronomers Think There Should be some Dark Matter

Dark Matter is one of those terms we hear a lot about in the news. It is the mysterious, hypothetical 'matter' that helps hold galaxies together. Originally, it was proposed to exist to help explain how galaxies rotate, when the observable amount of 'normal' matter is not sufficient to cause the observed rotation. This video explains a similar idea with another method, which looks at the bullet cluster.

Dark Matter - Interactive Forum from Scientific American

Check out the interactive discussion about dark matter, a favorite topic in modern physics, particularly in the astrophysics and particle physics fields. Dark matter is a generic term for anything that cannot be seen in the electromagnetic spectrum, but affects other objects gravitationally. This could be known matter such as neutrinos, neutron stars, brown dwarfs, or just unseen stars and galaxies. Or, it could be new forms of matter outside of the standard model in particle physics. There are names like WIMPS, MACHOS, axions, and others. Always a good time checking into cutting-edge ideas!