Are there parallel universes? Universes in which, rather than reading this article, you are still asleep; in which you are happier, unhappier, richer, poorer, or even dead? The answer is "possibly". It's a controversial claim but one that has won more and more followers over the last few decades.
Could there be more than three?
A possible way of resolving the greatest problem of physics.
Explore the biggest problem in modern physics.
We reflect on the late John Conway, the thoughts he shared with us over two interviews, and the experience of meeting him as a person and a mathematician.