# Domino Computer, Knitting, and Election MArTH

Welcome to this week’s Math Munch!

First up this week is one of the coolest things I’ve seen in a long time: the world’s largest computer made out of dominoes.  A computer made out of dominoes?! you say.  How??

The Domputer, as it’s been called, was the great idea of mathematician, teacher, and entertainer Matt Parker (see a previous post about Matt here), and he and many volunteers built it at the Manchester Science Festival at the end of October.

Matt and some of his teammates testing domino circuits.

So, what is a domino computer, and how does it work?  As Matt is quoted saying in a podcast that featured the project, “A domino computer is exactly that: a computer made out of chains of dominoes.  Flicking over one domino sends a signal racing along the chain, just like current flows down a wire.  And then interacting lines of dominoes can manipulate the signal exactly the way circuit components do.”

At its very, very basic level, a computer is a machine that does calculations in binary.  You input some sequence of 0s and 1s by flipping signals on and off, and your input starts a chain of electrical communications that results in an output of 0s and 1s.  Most computers do this with electrical circuits.  But it can also be done with dominoes – sending an “on” signal means flipping a domino over, and sending an “off” signal means not flipping a domino, or having a chain of falling dominoes that becomes blocked and stops falling.

Making the domputer.

There are lots of different kinds of commands that you can send by flipping switches on and off and making those signals interact.  For example, suppose you want something to happen only if two switches are on – if the first switch is on AND the second switch is on.  For this you would need to make something called an “AND gate” – an interaction in chains of current that will continue the chain if both switches are on and will stop the chain if either (or both) is off.  How would you do that with dominoes?  In this video, Matt demonstrates how to make an AND gate out of dominoes: Domino AND gate.  Check out this video for OR (the chain continues if one or the other or both are on) and XOR (“exclusive or,” the chain continues if one or the other, but not both, are on) gates:

Matt’s Domputer does something very simple: it adds numbers in binary.  But, as you might imagine, it was extremely complicated to build!  According to the Manchester Science Festival Twitter feed, the Domputer used about 10,000 dominoes and would take about 13,600 years to do what a normal processor could do in a second.  Wow!

Here it is in action.  It messed up on this calculation (9+3), but succeeded in later attempts – and is fascinating to watch nonetheless!

Awesome!

Next up, we’ve written about mathematical knitting before (remember Wooly Thoughts and the prime factorization sweater?), but here’s a great site I recently found made by mathematician, knitter, and dancer Sarah-Marie Belcastro.

This site is full of articles and about and patterns for all kinds of cool mathematical objects – like Klein bottles (which make great hats, by the way)!  In her post about knitted Klein bottles (and all of the other objects she makes), Sarah-Marie not only describes how to knit the objects but a lot of mathematics about them.  I don’t know about you, but I always find mathematical ideas easier to understand when I can make models of them, or at least read about models being made.  Sarah-Marie does a great job of blending mathematical descriptions with how-to-make-it recipes.

Some other patterns that I love are Sarah-Marie’s 8-colored two-hole torus pants and this knitted trefoil knot.

Finally, are you wondering what to do with all those campaign posters you have left over from the election?  Here’s George Hart’s take on what to do with them:

Bon appetit!

# 4 Million Digits, Fifteen Furlongs, and 5 Eames Vids

Welcome to this week’s Math Munch!

We’ve written about Pi before, but when I found this new way of visualizing the number, Pi, I knew I’d have to share it with you. In 2011, Shigeru Kondo and Alex Yee concluded an incredible project – to design and execute a program to calculate digits in the decimal expansion of Pi. What makes their attempt so remarkable is that the program ran for over a year (371 days), during which time it calculated precisely the first 10 trillion digits of Pi! (1 with 13 zeroes!)

A New York design firm, called Two-N, built a wonderful website using the first 4 million digits to help us see the patterns in the digits (or lack thereof). Each digit was assigned a color, and included in the image as a single pixel. What we see is a long (really long) string of colored digits. You can drag across the screen to zoom in on rows. There’s even a search bar so that you can find where your birthday appears, or any other 6-digit string for that matter.

If you’re having a hard time wrapping your head around 4,000,000 digits, check out Fifteen Furlongs. It’s a website designed by Kevin Wang, a college student at the University of Chicago, and it’s designed to help us understand different sizes and units of measurements. Try it.

Fifteen Furlongs? – “That’s about two minutes on the highway.” Didn’t help me  much, but 1 Furlong? – “That’s just under one Empire State Building tall.” Which is really interesting. So, if we laid down several empire state buildings in a row to make a highway, then I could drive over 15 of them in about 2 minutes. Cool! How can I understand 4 million?

• 4 million pounds is the weight of 1,000 cars.  hmmmm.
• 4 million cups is about one Olympic-sized pool.  whoa.
• 4 million seconds is just over forty-six day’s time.  so cool.

Maybe you can play around and figure out just how big 10 trillion is. After each answer there’s a place for you to say whether or not the information was useful, which I assume they use that to improve the responses. Have fun.

Kevin agreed to answer a few questions for us, which you can read in our Q&A section.  If you have ideas for how to improve the site, Kevin wants to hear them. Just leave it in the comments, and he’ll see what he can do.

Finally, some mathematical videos by the well-known 20th century design team of Charles and Ray Eames. In 1961 they worked on an exhibition for IBM called “Mathematica: A World of Numbers and Beyond,” which included a huge timeline with descriptions of famous mathematicians and mathematical discoveries from antiquity to modern times. It also included a “mathematics peepshow,” a collection of fantastic short math films, some of which can be seen on YouTube:

Actually my favorites aren’t even available online! There are 5 more videos available in a new fantastic, free iPad app called Minds of Modern Mathematics. If you donwload the app, check out “Symmetry” and “Exponents.” They’re simply stunning.

The best-known Eames vid is probably Powers of Ten, (embedded below) their 1977 film meant to illustrate the incredible scale of the universe, big and small, and how exponents can help us keep track of the different “levels.” It surely inspired the Huang Twins when they designed The Scale of the Universe.

You know, we typically feature at least one video a week, and they’re starting to pile up! Good news, though: we’ve been keeping track on a YouTube playlist of every video ever Featured on Math Munch. You can also use the Videos link at the top of any page.

Have a great week. Bon appetit!

# Faces, Blackboards, and Dancing PhDs

Welcome to this week’s Math Munch!

What does a mathematician look like? What does a mathematician do? Here are a couple of things I ran across recently that give a window into what it’s like to be a professional research mathematician—someone who works on figuring out new math as their job.

Gary Davis, who blogs over at Republic of Mathematics, recently posted a short piece that challenges stereotypes about mathematicians. It’s called What does a mathematician look like?

Who here is a mathematician? Click through to find out!

Gary’s point is that you can’t tell who is or isn’t a mathematician just by looking at them. Mathematicians come from every background and heritage. Gary followed up on this idea in another post where he highlighted some notable mathematicians who are black women. Here’s a website called Black Women in Mathematics that shares some biographies and history. And here’s a link to the Infinite Possibilities Conference, a yearly gathering “designed to promote, educate, encourage and support minority women interested in mathematics and statistics.” Suzanne Weekes, one of the five mathematicians pictured above, was a speaker at this conference in 2010.

Richard Tapia, another of the mathematicians above, is featured in the following video. His life story both inspires and delights.

And what does this diversity of mathematicians do all day? Well, one thing they do is talk to each other about math! And though there are many new technologies that help people to do and share and collaborate on mathematics (like blogs!), it’s hard to beat a handy chalkboard as a scribble pad for sharing ideas.

At Blackboard of the Day, Mathieu Rémy and Sylvain Lumbroso share the results of these impromptu math jam sessions. Every day they post a photograph of a blackboard covered in doodles and calculations and sketches of ideas. The website is in French, but the mathematical pictures are a universal language.

Diana Davis, putting the finishing touches on a blackboard masterpiece

Sharing mathematical ideas can take many forms, and sometimes choosing the right medium can make all the difference. Mathematicians use pictures, words, symbols, sculptures, movies, songs—even dances! Let me point you to the “Dance your Ph.D.” Contest. It’s exactly what it sounds like—people sharing the ideas of their dissertations (their first big piece of original work) through dance. Entries come in from physicists, chemists, biologists, and more.  Below you’ll find an entry by Diana Davis, a mathematician who completed her dissertation at Brown University this past spring. Diana often studies regular polgyons and especially ways of “dissecting” them—breaking them up into pieces in interesting ways.

Thanks to The Aperiodical—a great math blog—for sharing Diana’s wonderful video!

Some pages from Diana’s notebooks

All kinds of mathematicians study math and share it in so many ways. It’s like a never-ending math buffet!

Bon appetit!