We all know mathematicians are the coolest people on the planet. But it turns out that of all the people not on the planet, all of them are in fact either mathematicians, or have mathematical backgrounds or training. Astronauts – and Russian cosmonauts – are all super mathsy people, and if they weren’t already awesome enough, this really seals the deal for me.

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### Carnival of Mathematics 145

Welcome to the **145th Carnival of Mathematics**, hosted here at The Aperiodical.

If you’re not familiar with the Carnival of Mathematics, it’s a monthly blog post, hosted on some kind volunteer’s maths blog, rounding up their favourite mathematical blog posts (and submissions they’ve received through our form) from the past month, ish. If you think you’d like to host one on your blog, simply drop an email to katie@aperiodical.com and we can find an upcoming month you can do. On to the Carnival!

### Cutting an oval pizza – video

As if there wasn’t enough maths/pizza news lately, the story has hit the red-tops recently that UK supermarkets are scamming consumers by offering them oval-shaped pizzas – marketed in the high-end/’Extra Special’ ranges, with more expensive (sounding) ingredients like *mozzarella di bufala*, *roquito peppers* and *merguez sausage*, and a distinctive pair of artisanally different radii. These pizzas apparently cost more per gram, because their elliptical shape means they’re actually smaller than a circle with the same diameter. Cue plenty of ‘costing you dough’ and ‘cheesed off’ puns.

While we’re not massively bothered by the pricing, the articles do raise, and then completely fail to address, an interesting point: an oval pizza is harder to cut into equally sized pieces! Luckily, maths is here to save the day. I found a nice method and made a video explaining how it works:

Take a look and improve your future pizza cutting technique!

### Review: Hidden Figures

Mega-late to the party, I’ve now arrived back from a week lecturing in Indonesia and have found time to go and see the incredibly well-received and widely talked-about NASA women maths film, Hidden Figures. I’ve heard an incredible number of wildly positive responses to the film, from as long ago as January, and have been looking forward to it greatly.

The film is a painstaking and at times brutally realistic depiction of the struggles faced by African-Americans, and by women, during the era of the early space missions.

### Happy Birthday to me

“Life moves very fast. It rushes from Heaven to Hell in a matter of seconds.”

― Paulo Coelho

This week, I was suddenly reminded of a fact I’d been meaning to keep track of, and I was disappointed to discover that even though I always endeavour to remember birthdays and holidays (mainly due to a system of elaborate reminders, notes and excessive list-making), I’d missed a hugely significant anniversary. Shortly after the clock struck midnight on New Year’s eve, I had passed one billion seconds old.

### Mobile Numbers: Products of Twin Primes

*In this series of posts, Katie investigates simple mathematical concepts using the Google Sheets spreadsheet app on her phone. If you have a simple maths trick, pattern or concept you’d like to see illustrated in this series, please get in touch.*

Having spoken at the MathsJam annual conference in November 2016 about my previous phone spreadsheet on multiples of nine, I was contacted by a member of the audience with another interesting number fact they’d used a phone spreadsheet to investigate: my use of `=MID()`

to pick out individual digits had inspired them, and I thought I’d share it here in another of these columns (LOL spreadsheet jokes).

### Mobile Numbers: Multiples of nine

*In this series of posts, Katie investigates simple mathematical concepts using the Google Sheets spreadsheet app on her phone. If you have a simple maths trick, pattern or concept you’d like to see illustrated in this series, please get in touch.*

We’re all (hopefully) aware that a pleasing property of numbers that are divisible by nine is that the sum of their digits is also divisible by nine.

It’s actually more well known that this works with multiples of three, and an even more pleasing fact is that the reason three and nine work is because nine is one less than the number base (10), and anything that’s a factor of this will also work – so, in base 13, this should work for multiples of 12, 6, 4, 3 and 2. Proving this is a bit of fun.

Once when I was thinking about this fact, an interesting secondary question occurred.