# Plus Advent Calendar Door #19: How many dimensions are there?

Space is three-dimensional ... or is it? When we spoke to theoretical physicist David Berman in October this year we found out that in fact, we are all used to living in a curved, multidimensional universe. And a mathematical argument might just explain how those higher dimensions are hidden from view.

Kaluza, Klein and their story of a fifth dimension — David Berman explains the concept of dimension and how a mathematical idea suggests that we might well live in five of them.

The ten dimensions of string theory — String theory has one very unique consequence that no other theory of physics before has had: it predicts the number of dimensions of space-time. David Berman explains where these other dimensions might be hiding and how we might observe them.

How many dimensions are there? – the podcast — You can listen to an interview with David Berman as he tells us how Kaluza, Klein and their fifth dimension might help us understand the ten dimensions of string theory.