Articles

Introducing the Klein bottleA Klein bottle can't hold any liquid because it doesn't have an inside. How do you construct this strange thing and why would you want to?

Maths in a minute: Writing infinite sumsHow to write a sum that's infinitely long.

When things get weird with infinite sumsWhat is 1-1+1-1+1-1+...? How infinite sums challenge our notion of arithmetic.

Mathematical mysteries: Hailstone sequencesHere's an easy game that leads you straight to an unsolved question in maths.

Writing the unwritable: up-arrow notationHow to write down unimaginably large numbers using just a few symbols.

The Sun, the Moon and trigonometryA little trig helps to find the relative distance to the Sun and Moon.

In the beginning…Bob Wald tells us why probabilities are important in cosmology.

Ebola: Evidence from numbersWhy maths is an important tool in the fight against Ebola.

So you think you can add up?Why do we add fractions the way we do? A very close look at addition reveals the answer — and it also works for negative numbers.

Outer space: Where to stand to look at statuesJohn D. Barrow tells us how to get the best view!

Solving quadratics in picturesHow to derive the famous quadratic formula from pictures, just like the Babylonians did.

Maths in a minute: Euclid's fourth axiomEuclid's fourth axiom says that all right angles are equal. But isn't that obvious?