Since all the cool kids are using Twitter these days, this is the first in a sporadic series of Twitter recommendation posts which will tend to take place on Fridays. If you’re not on Twitter, feel free to use this as a source of interesting facts and links, but if you are, I’ll post tweets here from users I think it’s worth following (with associated qualifications).

# You're reading: Blackboard Bold

### Knitted Spiky Icosahedron

As an avid knitter, and mathematician, the birth of a small human in my family inspired me to create a mathematical toy for the tiny person to enjoy while learning about shapes. With my favourite platonic solid being the icosahedron, it was the obvious choice for a knitted toy, and with stellation being all the rage, sticking a point on each face was the obvious next step, especially when it’s such a convenient thing for tiny inexperienced hands to grasp.

### Carnival of Mathematics 89

Welcome to the 89th Carnival of Mathematics, this month hosted here at The Aperiodical. While The Aperiodical team is involved in administrating the Carnival (more information about the Carnival can be found here), it is hosted on a different blog each month. Last month cp’s mathem-o-blog was the host for Carnival of Mathematics 88, and next month the Carnival will be hosted by Mike Croucher at Walking Randomly.

### More and Less

I’m currently reading The Undercover Economist by Tim Harford, presenter of Radio 4 maths show More or Less. It’s very good, but one thing is stopping me from giving it an unqualified recommendation: it’s full of passages like this:

[T]he government spends three hundred dollars per person (five times less than the British government and seven times less than the American government)

Because of its lousy education system, Cameroon is perhaps twice as poor as it could be.

The poorest tenth of the population spends almost seven times less on fuel than the richest tenth, as a percentage of their much smaller income.

### Spelling Bees Puzzle Blog

Hello. I’ve been talked into writing another blog post about my latest puzzle to appear in the Puzzlebomb. Spelling Bees appeared in the May and June issues. The solver is presented with a honeycomb grid containing letters and one bee (of the insect variety; the grid may contain several or no Bs). Their task is to find the two words (or phrases) that can be traced along a path through every cell (to use jargon that will be familiar to cruciverbalists and beekeepers alike) in the honeycomb grid. The bee acts as a wild card and will stand for a different letter in both words. The cells which are the first and last letters of each word are shaded to give an extra helping hand.

### Grow Your Own Food

I recently heard about Herman, the German Friendship Cake (bear with me), a cake which is divided and spread among friends, and it got me thinking about some other foodstuffs I’ve heard of which are made in such a way that the amount you have will grow exponentially. A Herman cake is a special type of sourdough cake which is made with yeast. It’s explained fully here, but the idea is that you start with a solution of yeast, which lives in a little milk, sugar and flour. This small amount of goo can live happily at room temperature on a shelf, and if you stir it every day and give it a little more flour and sugar to eat every few days, after ten days it’s ready to make into a cake.

### What is a mathematician?

I recently got a new set of business cards printed. I wanted to keep them as simple as possible, and have them communicate only the important information – my name and contact details. But then came the question of what to put underneath my name. I don’t currently have a full time job anywhere, but I do spend pretty much all my time working freelance as a maths communicator, talking to people about maths and popularising the subject. I also do loads of maths related things in my spare time, including running a Maths Jam, and I’m still in the process of writing a paper based on the work I did in my PhD thesis, which I finished last summer. How do you sum that up? I recall recently our own Peter Rowlett struggled similarly when filling in the corresponding field on his census form.