Happy Tau Day…

28th of June (6-28 as the Yanks would put it) is Tau day…

What is Tau I hear you ask???

We all know about pi… that number that links the diameter and circumference of a circle. But since we rarely use diameter (we use radius again) we need to add a factor of 2 to all our maths…


circumference = 2 x pi x radius

Anything else we do with circles has this extra 2 in it. E.g. Angles in radians – a whole rotation is 2 pi radians.

So along comes Tau where tau = 2 pi

That 2 disappears.

  • curcumference = tau x radius
  • 1 rotation is tau radians
  • Think of the difference that would make to Unit 4 A-level Physics
It’s not taken off yet – but it might… It would not be the first time we changed maths to make it more sensible – like when we went decimal or even the invention of zero.
Have a look at this BBC article for more details
Mr G
Source: BBC News