In 2015 The Aperiodical went from strength to strength again, with 179 posts published by 18 authors. I’ve collected our ten most popular posts from 2015, in case you missed them.

#### 10. Take the 30 second arithmetic challenge

*by Christian*

Me first! Just squeezing into the top 10 is my post about a rather hard arithmetic game I made, provoked by my grandma-in-law’s ceaseless goading. I think the game was popular with teachers.

#### 9. New pentagonal tiling discovered

*by Katie*

Proof News always does well, and the first such entry in our list is Katie’s post about the newly-discovered irregular pentagon which tiles the plane.

#### 8. π, Phase Space, and Bouncing Billiard Balls

*by Colin Wright*

Colin wrote this comprehensive post about a classic mathematical dinner party trick; calculating π by bouncing billiard balls off each other.

It doesn’t work in practice, of course, but that doesn’t stop Colin finding an enlightening perspective on the problem.

#### 7. Mathematical myths, legends and inaccuracies: some examples

*by Peter*

Peter asked Twitter for examples of commonly-held myths about maths and mathematicians, and Twitter obliged with some surprising stories.

#### 6. The Topological Tverberg Conjecture is False

*by Katie*

Proof News again! This time, the world of topological combinatorics was rocked by the revalation that the topological Tverberg conjecture wasn’t quite true.

#### 5. Terence Tao has solved the Erdős discrepancy problem!

*by Christian*

More Proof News, and yet another big achievement by Terry Tao, at the culmination of the Polymath5 project.

This post also features a strong contender for The Aperiodical’s GIF of the Year:

#### 4. Riemann Hypothesis not proved, part 2

*by Christian*

The biggest Not Proof News story of 2015 – Opeyemi Enoch’s claimed proof of the Riemann hypothesis. Best to start with part 1, but this caused enough of a ruckus that our follow-up on the reaction to the first reactions still made it to position 4 on this list.

#### 3. Counting From Infinity – A film about Yitang Zhang

*by Katie*

Yitang Zhang’s story was begging to be made into a film. Back in January, George Csicsery brought out this documentary.

Only the trailer is available online, but that was interesting enough to propel this post to the third spot on our list.

#### 2. Apiological: mathematical speculations about bees (Part 1: Honeycomb geometry)

*by Alistair Bird*

ALISTAIR FINISHED HIS BEES POST!

We’ve been haranguing Alistair for literally years to finish off a post he’d promised to write us about the maths of bees. Well, 2015 was the year it finally happened. And what a post it is! Split into 3 sections because of the huge amounts of bee maths Alistair uncovered.

#### 1. Riemann Hypothesis not proved

*by Katie and Christian*

By a long, long, way this was our most popular post of 2015. Long story short: dude claims he’s solved the Riemann Hypothesis and won a million dollars; BBC reporter believes him; everyone believes the BBC; turns out there’s no reason to believe the dude.

There was always the slightest chance that it would turn out he *did* have a good proof, but nothing of the sort has yet emerged.

And who am I kidding, this has to be The Aperiodical’s best GIF of 2015: