This week David Holmes talks us through the 'Hairy Ball Theorem' and gives a proof in under an hour!

For those of you who now nothing about the 'Hairy Ball Problem': imagine a sphere covered with hairs, and you want to comb the hairs so that they all lie flat. Can this be done? Will you always end up with a point where you can't comb the hair flat? On what surfaces can you solve this problem?

If this is all to theoretical for you, then consider the wind on the Earth's surface. If you consider the horizontal direction of the wind at each point, the theorem tells you that at some point on the Earth, there is no wind!