By Hamish Johnston

What’s your favourite number, and does the fact that you are interested in physics inform your choice?

I have been thinking about this today after hearing an interview on BBC radio with the mathematics writer Alex Bellos, author of the book Alex’s Adventures in Numberland, or Here’s looking at Euclid if you are in North America.

Bellos (right) has launched an online survey asking people for their choices and the reasons behind their picks. He also requests for a small amount of biographical information.

What did I say? Three, because of the old adage “Two’s company, three’s a crowd”. Although a small number, three is fascinating because it can cause very large problems in social settings.

Three is also interesting from a physics point of view. Solving problems involving three bodies is much more difficult than those involving two. And then there’s the Efimov effect, whereby a group of three particles will bind together, even though pairs of the constituent particles will not.

How about you, perhaps it’s one over the fine-structure constant (137) or Avogadro’s number?

You can read more about the project and listen to an interview with Bellos here.