To celebrate the centenary of the general theory of relativity we asked physicist David Tong to explain the theory and the equation that expresses it. Watch the video or read the article!

Read about the rocky road to one of Einstein's greatest achievements: the general theory of relativity, which celebrates its centenary this year.

General relativity, Einstein's rise to international stardom, and his legacy.

How longitude presented one of the greatest problems in history.

Why the North Star tells you your latitude.

Can you measure information? It's a tricky question — but people have tried and come up with very interesting ideas.

To celebrate the release of more English translations of Einstein's papers, we revisit one of his previously unknown models of the Universe.

The self-taught Indian genius would have turned 127 this month.

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

How to derive the famous quadratic formula from pictures, just like the Babylonians did.

Euclid's fourth axiom says that all right angles are equal. But isn't that obvious?

Five basic facts from the father of geometry.