The German mathematician Adam Ries (1492-1559) was the author of the most successful textbook of commercial arithmetic of his day. The book, published in 1552, earned such a high reputation that the German phrase nach Adam Ries is used to this day to indicate a correct calculation.

You may have seen Foucault's pendulum. There's one in the Science Museum in London (part of the National Museum of Science and Industry), and there are many more in various locations around the UK (for instance, in Glasgow) and the world (including one at the United Nations Headquarters and a famous example at Le Panthéon in Paris).

In the 1950's, Ernst Straus asked a seemingly simple problem. Imagine a dark room with lots of turns and side-passages, where all the walls are covered in mirrors - just like the Hall of Mirrors in an old-fashioned fun-fair. Is it true that if someone lights a match somewhere in the room, then wherever you stand in the rest of the room (even down a side-passage) you can see a reflection of the match?

Bisecting a given angle using only a pair of compasses and a straight edge is easy. But trisecting it - dividing it into three equal angles - is in most cases impossible. Why?

On June 25th 1998 the Solar and Heliospheric Observatory known as SOHO, a small spacecraft that monitors the sun, went missing. An error in the instructions given to it from ground control left it spinning out of control. However, there is a glimmer of hope.

Since we first wrote about the Goldbach Conjecture we've had many requests for more information about  it and about how our Goldbach calculator works. We answer some of your questions here but the Goldbach conjecture touches on a strange area of maths that may leave you even more curious than before...

We know there is infinitely many primes, but are there infinitely many twin primes?

Sir Walter Raleigh is perhaps best known for laying down his cloak in the mud for Queen Elizabeth I. But, he also started a mathematical quest which to this day remains unsolved.

Can every even number greater than 2 can be written as the sum of two primes? It's one of the trickiest questions in maths.