Why can we see through glass but not other solids? Let this awesome video explain

It seems like a simple enough question - why are some materials transparent while others are opaque? But, as this video from the University of Nottingham's Sixty Symbols project explains, a lot of the most common explanations you get are fundamentally wrong. Watch a professional scientist recoil in horror at the… » 2/20/11 7:30pm 2/20/11 7:30pm