While away the days to Christmas with these Plus favourites. Now, what's behind today's door...

How many universes are there? What has made us into who we are? Is there absolute truth? These are difficult questions, but mathematics has something to say about each of them. It can probe the physical reality that surrounds us, shed light on human interaction and psychology, and it answers, as well as raises, many of the philosophical questions our minds have allowed us to dream up. On this page we bring together articles and podcasts that examine what mathematics can say about the nature of the reality we live in.

Game theory is a great way of sneaking up on maths. You can start off playing an actual game, then start thinking about strategies, and before you know it you're doing proper maths, either conceptually or using equations and formulae. In this teacher package you'll find all our articles on game theory.

One of the first bits of school maths that gives us a real glimpse of infinity are infinite series: those never-ending sums that may nevertheless add up to a finite number. For this teacher package we've brought together all our articles on these beautiful objects.

What is time? What is space? Are there parallel universes? Join Plus and FQXi on a journey exploring these and many more questions on the frontiers of physics. What do you think is science fiction and what do you think we close to proving are science facts? Find out more about scientific developments in these areas, ask your own questions and debate the answers!

In some sense, all of maths should come under the label "logic", but mathematical logic has shown that mathematics isn't entirely logical. Makes sense? If not, then this teacher package may help.

It's not long until Christmas! To help you pass the time (or ease your nerves if you're stressed), we bring you the Plus advent calendar with a mathsy goody from the Plus archive lurking behind each door. Find out what's behind today's door...