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Hello there.

This is Numberphile. We mainly post videos about mathematics and just numbers in general.

Pi and the size of the Universe

Pi and the size of the Universe

Our Pi Playlist (more videos): http://bit.ly/PiPlaylist

Pi is famously calculated to trillions of digits - but Dr James Grime says 39 is probably enough.

An extra note from Dr Grime: "Since pi39 ends in 0, you may think we could use pi38 instead - which has even fewer digits. Unfortunately, the rounding errors of pi38 are ten times larger than the rounding errors of pi39 - more than a hyrdogen atom. So that extra decimal place makes a difference, even if it's 0."

Synesthesia

Synesthesia

Zequals and Estimation

Zequals and Estimation