From io9: Links to some images from the 2009 Crazy 4 Cult art show. Includes two Ghostbusters and two Back To The Future references. (hat tip: calliopes_pen)

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The Tau Manifesto, or why 2π is more important than π. As a trig teacher, I'm one of the culprits here. And while I don't think the half-turn/full turn distinction makes that much of a difference, mathematically - twos are a dime a dozen in formulae, anyway, and I prefer Euler's formula with the negative sign - I agree that getting kids to remember that π radians is half a circle can be tricksy.