What is 1-1+1-1+1-1+...? How infinite sums challenge our notion of arithmetic.

How to write a sum that's infinitely long.

Here's an easy game that leads you straight to an unsolved question in maths.

How to write down unimaginably large numbers using just a few symbols.

A little trig helps to find the relative distance to the Sun and Moon.

Bob Wald tells us why probabilities are important in cosmology.