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.
![](https://i0.wp.com/chalkdustmagazine.com/wp-content/uploads/2024/04/calum.jpg?resize=150%2C150&ssl=1)
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.
More from Chalkdust
Cryptic wordsearch, Issue 19
Can you solve it?A day in the life: teachers
We talk to three teachers, working in different countriesOn the cover: skyrmions
Sven Bjarke Gudnason and Calum Ross introduce you to the wonderful world of skyrmionsClosing the Gap
A review of Vicky Neale's new book about the quest to understand prime numbers.The new Chalkdust T-shirt
Have you been wondering what the pattern on it means?Thoughts on the crossnumber
Did you use meta-logic to solve the crossnumber?