Nothingness is an awe-inspiring, largely undigested concept that many regard with anxiety, nausea and panic — that's according to the *Encyclopaedia of Philosophy*. But as John D. Barrow explains in this lecture, once you invent a handy symbol for this nothingness and learn how to calculate with it, it can turn into something friendly and incredibly useful. Barrow traces the history of the concept of zero, looks at its role in areas of mathematics and science, from group theory to black holes, and even finds a link to the London Underground map.

The talk was part of a lecture series organised by Gresham College and the British Society for the History of Mathematics.
John D. Barrow is Professor of Mathematical Sciences at the University of Cambridge, best-selling author, and Director of the Millennium Mathematics Project, of which *Plus* is a part.