"I tell my students that if this formula doesn't completely blow them away then they simply have no soul," says Chris Budd of the University of Bath in the UK.
Many readers will have heard of this famous equation. It simply describes how the circumference of a circle varies with its diameter. The ratio of the two is a number called pi. It is roughly 3.14, but not exactly: pi is an irrational number, meaning the digits go on forever without repeating.
"Pi is an incredibly important number," says Budd. "We have to calculate it to very high precision for modern technology such as GPS to work at all… It can be used to describe the geometry of the world."
Read more: What is the most beautiful equation?