August Ferdinand Möbius (1790–1868) was a German mathematician and astronomer with a genius for spotting simple, surprising structures hiding in plain sight. He was a quiet, unhurried professor at Leipzig — but his name is attached to one of the most famous shapes in the world, a loop of paper that has delighted and baffled schoolchildren for generations.

The famous work

Möbius pops up in two very different rooms of mathematics. In geometry there are the elegant Möbius transformations, which glide the complex plane around, turning lines and circles into other lines and circles. And in number theory there's the mysterious Möbius function, which tags each number with +1, -1, or 0 depending on its prime factors and powers a clever trick called Möbius inversion.