The valentine's day symbol movie was discussed recently on the Bad Astronomy blog:Sixty Symbols is a collection of videos about physics and astronomy presented by experts from The University of Nottingham.
They aren't lessons or lectures - and this site has never tried to be an online reference book.
The films are just fun chats with men and women who love their subject and know a lot about it!
http://blogs.discovermagazine.com/badas ... 0-symbols/