# MathsJam Gathering 2015

This is a list of the talks presented at the 2014 conference, along with slides where we have them. If you'd like to send us your slides, or more detail about your talk, please email manchester@mathsjam.com.

## Saturday

### Session 1

#### An Interesting Sequence - Ross Atkins

Ross told us about an interesting sequence - and an unexpected relationship to Φ.

- Sequence A019444 on OEIS

#### Matt Parker doesn't know when to stop - Matt Parker

Matt explained his new obsession with Optimal stopping problems - assuming you'd rather get something good than not miss something perfect.

- Optimal Stopping, on Wikipedia

#### The Double Pendulum - Richard Gould

Richard applied Lagrangian mechanics to a double pendulum, with animations (and a little accidental DJ-ing).

#### Joining the dots - Noel-Ann Bradshaw

Noel-Ann talked about the game of Match Dots, and how it can be used to teach graph theory. She also showed us a few other mathematical phone app games.

- Slides (PDF)
- Slides (PPTX)
- Match dots, on Google Play
- Match dots, on the Apple Store

#### Optimal Finger Counting - Michael Gibson

Michael proposed a fairly easy way to count to 399 (and do some simple arithmetic) on your fingers.

#### Make your own Soma cube in 122 easy steps - Alison Kiddle

Alison talked us through an origami Soma Cube, and made use of our casual labour creating Sonobe units to make one.

- Slides (PDF)
- Slides (PPT)
- Soma cube, on Wikipedia

#### dVq, or five 500-year-old recreations - Tiago Hirth

Tiago showed us five interesting puzzles, and maybe three solutions.

#### Shuffling Perfectly - Dave Gale

To finish the first session, Dave talked about how soon repeating a 'perfect' (non-random) shuffle will get back to the original order.

### Session 2 - 15:30 - 16:30

#### Everything Old is New Again - Adam Atkinson

Adam showed an oldie but a goodie - proving that a right angle is equal to a right angle plus a small non-zero angle. Hang on a minute...

#### How to see inside a cake without cutting it - Martin Whitworth

Martin explains the process of x-ray microtomorgaphy, and uses it to look inside some delicious cakes.

#### A Sequence: 1,2,4, ... - Noel France

Noel's sequence starts 1, 2, 4, 6, 16,... but how does it continue? We were left guessing.

- Noel's sequence, on OEIS

#### Fun with Microsoft Excel. No, really. - Phil Ramsden

Phil has used MS Excel spreadsheets to display photos (inspired by Matt Parker), and to generate some even more exciting graphics, including fractals.

#### Table cloths on wobbly tables - Tarim

Tarim shared with us the wobbly table theorem, and his issues with the practicality of the question.

#### A new circle dissection - Stephen Worsley

Stephen showed us some variations on the classic pizza-slicing problem - can you cut a circle into congruent pieces so that not all of them touch the centre?

#### Estimating log 3 using a piano - Francis Hunt

Francis talked about how logs can be calculated from musical intervals.

#### Discriminants and Resultants - Joel Haddley

Joel talked discriminants and resultants, matrices and determinants and showed us some Geogebra.

#### Games used at the Maths Arcade - Peter Rowlett

Peter presents the Maths Arcade, and how well it's doing at universities around the country - plus introduces some of the games played there.

- Slides (PDF)
- Maths Arcade, on the IMA Website

#### Maths with your eyes closed - geometrical callisthenics + Gestalt ambiguity - John Bibby

### Session 3 - 17:00 - 18:00

#### Squaring the Torus - Geoffrey Morley

Can the surface of a torus be split into different sized squares? Geoffrey showed us how.

#### Negative Prices in Supermarkets - Adam Atkinson

According to Adam, certain products in Waitrose are discounted and reduced in such a way that you can actually end up paying negative amounts of money for them.

#### Harmonograph Revisited - John Bradshaw

John showed us his modern reimagining of a harmonograph - using an electronic graphics tablet and stylus.

- Harmonograph, on Wikipedia
- Photo of John's harmonograph, by @standupmaths on Twitter

#### Entropy is Your Friend - Andrew Macdonald

Andrew explained the concept of entropy - just how much information does a message really contain?

#### Selected at random - Martyn Parker

Martyn showed us some different methods of selecting a chord at random from a circle, and how they can have very different distributions.

#### Infinitely many infinities - Julia Collins

Julia challenged us to the task of drawing uncountably infinitely many infinity symbols on a piece of paper. Is it possible?

#### MegaMenger - Katie Steckles

Katie described the MegaMenger project, and listed the many locations around the world in which menger sponges have been built in order to constitute a distributed Level 4 Menger Sponge around the world.

- Slides (PDF) - mostly photos of Menger Sponges
- MegaMenger project website

#### Martin Gardner - a Celebration of Mind - Matt Parker

In honour of Martin Gardner's centenary, Matt said a few words about Martin Gardner and his work, and the activities that take place in his honour - including the MathsJam itself.

## Sunday

### Session 1 - 09:00 - 09:30

#### Let's talk about x - Christian Perfect

How do you write the letter x? Christian P did a quick survey, then got us all thinking about multiplicative inverses, and why negative numbers are written the way they are but the same doesn't apply to division.

- Let's Talk About X, at The Aperiodical

#### A proof of Pythagoras' theorem - Paul Taylor

Paul demonstrated a simple proof of Pythagoras' theorem which surprised us with its elegance and neatness.

#### Spurious Chat - Martyn Parker

Martyn showed us some spurious correllations between unrelated variables - which, as mathematicians, we understand don't imply causations.

#### Superpermutations - Robin Houston

Robin told us about Superpermutations, which contain every possible permutation as a substring.

#### More MegaMenger - Ben Sparks

Ben continued the MegaMenger-related chat by describing his experiences building the Bath sponge (no puns), and told us some of the Menger Sponge's interesting properties.

### Session 2 - 10:10 - 11:00

#### Squaring a chessboard - John Foley

John discussed the problem of covering a chessboard with squares of integer size.

#### How to break Excel - Tom Button

Tom showed us a way in which Microsoft Excel doesn't, and explained why that happens.

#### A Stab at Promoting Motivation - Ken McKelvie

Ken got us all motivated to learn about maths, including showing us a nice picture hanging puzzle.

#### Yuen Ng - Maths of the London Underground

Yuen shared with us some of the graph theory behind the modern tube map, as well as ways to estimate the number of people using the tube in a given year.

#### Waves in a car park - Ben Ashforth

Ben described the time he stuck a sensor on a broom handle out of his car window to measure the waves coming from a transmitter across a car park, and how this information can be reconstructed into an image of the coverage in the area.

- Slides (PDF)
- Slides (PPTX)
- Ben's video of waves (AVI, 6MB)

#### Phil Ramsden - Goodstein Sequences

Phil described some sequences which get impossibly big and then implausibly go to zero.

- Slides (PDF)
- Slides (PPTX)
- Goodstein Sequences, on Wikipedia

#### 16 tiles and a hidden item - Colin Wright

Colin demonstrated an impossible mathematical magic trick, in which his assistant flips one of sixteen tiles while he is absent, and Colin is able to determine which one.

### Session 3 - 11:30 - 12:30

#### An unusual proof that 1 equals 2 - Colin Beveridge

Colin presented a proof that 1=2.

#### The Hypergame Paradox - Miles Gould

The Hypergame is a game in which players make a move by choosing a game to play, and making a move in that game. But is it a finite game, and if so can you choose hypergame as your game? Miles explained the paradox.

#### Nut Spinner - Alistair Bird

Alistair presented the Nut Spinner, an object found on the SS Great Britain, but whose use is a mystery - maybe for a game of chance?

#### Sofia Kovalevskaya: Nihilist Girl - Nicholas Jackson

Nicholas told us about the mathematician Sofie Kovalevskaya.

- Slides (PDF)
- Sofia Kovalevskaya, on Wikipedia
- Sofia Kovalevskaya Google Doodle

#### My difficulty with applied mathematics - Tony Mann

Tony explained some of his difficulties when applying maths to the real world - does the amount of liquid a cup can hold depend on your altitude?

#### Overhanging Bricks - David Bedford

David demonstrated a nice fact about divergent series by building an improbable and dangerous stack of bricks, hopefully not above someone's laptop...

- Slides (PDF)
- Slides (PPTX)
- Video of David, by @peterrowlett on Twitter