img10 - Chalkdust

Rubeus Hair-grit: it’s helpful to assume that hairs grow in a grid pattern with 1mm gaps between hairs. That’s a gap of around 13 hair-widths, so only 1 out of 196 `hair spaces’ are filled.

Calum Ross

Calum is a lecturer in physics at Edge Hill University where he studies topological solitons and enjoys talking about maths and physics to anyone who will listen. He can often be found on the side of a mountain or out on a bike, talking to himself about solitons.

Oπnions: In defence of toy models
Calum gets on his soap box about toy models
Easy to state, hard to prove: The Collatz conjecture
90 years later, we're still unable to prove this surprisingly simple statement
Cryptic wordsearch, Issue 19
Can you solve it?
On the cover: skyrmions
Sven Bjarke Gudnason and Calum Ross introduce you to the wonderful world of skyrmions
Mathscon: reshaping the world’s perception of mathematics
Introducing Mathscon, a mathematics conference with a difference!
Prize crossnumber, Issue 02
Win £100 in our famous original crossnumber