## Maths in a minute

Want facts and want them fast? Our *Maths in a minute* series explores key mathematical concepts in just a few words. From symmetry to Euclid's axioms, and from binary numbers to the prosecutor's fallacy, learn some maths without too much effort.

*dark matter*. But if it's invisible how do they know it's there?

Here's a quick introduction to the beauty queen amongst mathematical formulas.