Squaring the Circle

Alex Bellos discusses how the Incans used knots in string (Quipu) to record numbers.Check out Brilliant (get 20% off their premium service): https://brillian...

Why squaring the circle - the old-fashioned way - was found to be impossible?

Numblr: http://numberphile.tumblr.com/

This video featuring Dr James Grime: https://twitter.com/jamesgrime

The paper from this video on ebay - http://bit.ly/brownpapers