Sphericon, National Curve Bank, and Cardioid String Art

Welcome to this week’s Math Munch!

Behold the Sphericon!

What is that? Well, it rolls like a sphere, but is made of two cones attached with a twist– hence, the spheri-con! The one in the video is made out of pie (not sure why…), but you can make sphericons out of all kinds of materials.

Wooden sphericonIt was developed by a few people at different times– like many brilliant new objects. But it entered the world of math when mathematician Ian Stewart wrote about it in his column in Scientific American. The wooden sphericon was made by Steve Mathias, an engineer from Sacramento, California, who read Ian’s article and thought sphericons would be fun to make. To learn more about how Steve made those beautiful wooden sphericons, check out his site!

Even if you’re not a woodworker, like Steve, you can still make your own sphericon. You can start with two cones and make one this way, by attaching the cones at their bases, slicing the whole thing in half, rotating one of the halves 90 degrees, and attaching again:How to make a sphericon

Or you can print out this image, cut it out, fold it up, and glue (click on the image for a larger printable size):

Sphericon pattern

If you do make your own sphericon (which I recommend, because they’re really cool), watch the path it makes as it rolls. See how it wiggles? What shape do you think the path is?

ncbmastertitleI found out about the sphericon while browsing through an awesome website– the National Curve Bank. It’s just what it sounds like– an online bank full of curves! You can even make a deposit– though, unlike a real bank, you can take out as many curves as you like. The goal of the National Curve Bank is to provide great pictures and animations of curves that you’d never find in a normal math book. Think of how hard it would be to understand how a sphericon works if you couldn’t watch a video of it rolling?

epicycloidaThere are lots of great animations of curves and other shapes in the National Curve Bank– like the sphericon! Another of my favorites is the “cycloid family.” A cycloid is the curve traced by a point on a circle as the circle rolls– like if you attached a pen to the wheel of your bike and rode it next to a wall, so that the pen drew on the wall. It’s a pretty cool curve– but there are lots of other related curves that are even cooler. The epicycloid (image on the right) is the curve made by the pen on your bike wheel if you rode the bike around a circle. Nice!

You should explore the National Curve Bank yourself, and find your own favorite curve! Let us know in the comments if you find one you like.

String cardioid

String art cardioid

Finally, to round out this week’s post on circle-y curves (pun intended), check out another of my favorite curves– the cardioid. A cardioid looks like a heart (hence the name). There are lots of ways to make a cardioid (some of which we posted about for Valentine’s Day a few years ago). But my favorite way is to make it out of string!

String art is really fun. If you’ve never done any string art, check out the images made by Julia Dweck’s class that we posted last year. Or, try making your own string art cardioid! This site shows you how to draw circles, ovals, cardioids, and spirals using just straight lines– you could follow the same instructions, replacing the straight lines you’d draw with pieces of string attached to tacks! If you’re not sure how the string part would work, check out this site for basic string art instructions.

Bon appetit!

Pi Digit, Pi Patterns, and Pi Day Anthem

pivolant1

Painting by Renée Othot for Simon Plouffe’s birthday.

Welcome to this week’s Math Munch!

It’s here—the Pi Day of the Century happens on Saturday: 3-14-15!

How will you celebrate? You might check to see if there are any festivities happening in your area. There might be an event at a library, museum, school, or university near you.

(Here are some pi day events in NYC, Baltimore, San Francisco, Philadelphia, Houston, and Charlotte.)

 

John Conway at the pi recitation contest in Princeton.

John Conway at the pi recitation contest in Princeton.

There’s a huge celebration here in Princeton—in part because Pi Day is also Albert Einstein’s birthday, and Albert lived in Princeton for the last 22 years of his life. One event involves kids reciting digits of pi and and is hosted by John Conway and his son, a two-time winner of the contest. I’m looking forward to attending! But as has been noted, memorizing digits of pi isn’t the most mathematical of activities. As Evelyn Lamb relays,

I do feel compelled to point out that besides base 10 being an arbitrary way of representing pi, one of the reasons I’m not fond of digit reciting contests is that, to steal an analogy I read somewhere, memorizing digits of pi is to math as memorizing the order of letters in Robert Frost’s poems is to literature. It’s not an intellectually meaningful activity.

I haven’t memorized very many digits of pi, but I have memorized a digit of pi that no one else has. Ever. In the history of the world. Probably no one has ever even thought about this digit of pi.

And you can have your own secret digit, too—all thanks to Simon Plouffe‘s amazing formula.

plouffe

Simon’s formula shows that pi can be calculated chunk by chunk in base 16 (or hexadecimal). A single digit of pi can be plucked out of the number without calculating the ones that come before it.

Wikipedia observes:

The discovery of this formula came as a surprise. For centuries it had been assumed that there was no way to compute the nth digit of π without calculating all of the preceding n − 1 digits.

Check out some of Simon's math art!

Check out some of Simon’s math art!

Simon is a mathematician who was born in Quebec. In addition to his work on the digits of irrational numbers, he also helped Neil Sloane with his Encyclopedia of Integer Sequences, which soon online and became the OEIS (previously). Simon is currently a Trustee of the OEIS Foundation.

There is a wonderful article by Simon and his colleagues David Bailey, Jonathan Borwein, and Peter Borwein called The Quest for Pi. They describe the history of the computation of digits of pi, as well as a description of the discovery of their digit-plucking formula.

According to the Guinness Book of World Records, the most digits that someone has memorized and recited is 67,890. Unofficial records go up to 100,000 digit. So just to be safe, I’ve used an algorithm by Fabrice Bellard based on Simon’s formula to calculate the 314159th digit of pi. (Details here and here.) No one in the world has this digit of pi memorized except for me.

Ready to hear my secret digit of pi? Lean in and I’ll whisper it to you.

The 314159th digit of pi is…7. But let’s keep that just between you and me!

And just to be sure, I used this website to verify the 314159th digit. You can use the site to try to find any digit sequence in the first 200 million digits of pi.

Aziz and Peter's patterns.

Aziz & Peter’s patterns.

Next up: we met Aziz Inan in last week’s post. This week, in honor of Pi Day, check out some of the numerical coincidences Aziz has discovered in the early digits in pi. Aziz and his colleague Peter Osterberg wrote an article about their findings. By themselves, these observations are nifty little patterns. Maybe you’ll find some more of your own. (This kind of thing reminds me of the Strong Law of Small Numbers.) As Aziz and Peter note at the end of the article, perhaps the study of such little patterns will one day help to show that pi is a normal number.

And last up this week, to get your jam on as Saturday approaches, here’s the brand new Pi Day Anthem by the recently featured John Sims and the inimitable Vi Hart.

Bon appetit!

Sequence Day, Penguins, and a little folding

Welcome to this week’s Math Munch! And… happy Sequence Day!

Sequence day

If you didn’t know that today was Sequence Day, don’t feel bad– I didn’t know until I ran across this article written by Aziz Inan, an electrical engineering professor at the University of Portland. Why is today Sequence Day? Well, because all of the digits in the sequence 0, 1, 2, 3, 4, 5 appear in today’s date– 3-4-2015!

This particular Sequence Day isn’t super special. There will be another one with the exact same sequence on April 3 (4-3-2015). But, according to Aziz, April 3 will be the last Sequence Day of this year– and the last until 2031! Aziz made this chart of all the Sequence Days that will happen this century. There are 48 all together– and if you look carefully at the chart, you may notice some interesting patterns.

Sequences days this century

See how the Sequence Days mostly occur at the beginnings of decades, in the first half of the month, and never later in the year than June? Why do you think that might be? Also, the last Sequence Day of the 21st century is in 2065. That means we’ll have to wait almost 40 years for the next Sequence Day after that– until 2103! But, in the scheme of things, this actually isn’t so bad– there were no Sequence Days at all in the last century. (Why might that be?)

We all know about days like Pi Day (coming up soon on 3-14-15 — and it’s a special one because we’ve got those two additional digits this year!), but, as Aziz likes to show, lots of days can be mathematical holidays– if you just look carefully enough. Maybe you’ll find a mathematical holiday of your own! If you do, let us know. We love any excuse to have a party!

Next up, you think penguins are cute, right? Well, take a look at this:

You may have heard the narrator say, “Something more organized is going on.” Well, several mathematicians wondered what that more organized thing was… and it turns out to be very mathematical!

How many penguins do you see?

Francois Blanchette, a mathematician at the University of California, Merced, had the idea to use math to study how penguins keep warm while watching penguin movies like this one. He studies the math of something called fluid dynamics, which, basically, is how things like water and air flow. Francois and several other mathematicians at the University of Erlangen-Nuremberg in Germany noticed that when one penguin in a huddle moves just a little bit, it triggers a chain reaction in which all of the other penguins move in an organized way to keep warm. Their tiny movements cause the huddle to organize into the best shape for all penguins to keep warm during the cold of winter.

Huddle up, little guy!

Scientists and mathematicians are only now realizing all of the amazing ways that math comes into play in the lives of animals, especially in large groups. It seems that penguins are only the beginning! To learn more about the organization of large groups of animals, I suggest you check out this awesome PBS documentary about animal swarms.

Finally, we haven’t heard from Vi Hart in a while. If you’ve been feeling the need for some math art fun in your life, check out this video I dug up from the archives. Origami meets Pythagorean Theorem– what could be better?

Stay warm, and bon appetit!

 

SquareRoots, Concave States, and Sea Ice

Welcome to this week’s Math Munch!

The most epic Pi Day of the century will happen in just a few weeks: 3/14/15! I hope you’re getting ready. To help you get into the spirit, check out these quilts.

American Pi.

American Pi.

African American Pi.

African American Pi.

There’s an old joke that “pi is round, not square”—a punchline to the formula for the area of a circle. But in these quilts, we can see that pi really can be square! Each quilt shows the digits of pi in base 3. The quilts are a part of a project called SquareRoots by artist and mathematician John Sims.

John Sims.

John Sims.

There’s lots more to explore and enjoy on John’s website, including a musical interpretation of pi and some fractal trees that he has designed. John studied mathematics as an undergrad at Antioch College and has pursued graduate work at Wesleyan University. He even created a visual math course for artists when he taught at the Ringling College of Art and Design in Florida.

I enjoyed reading several articles (1, 2, 3, 4) about John and his quilts, as well as this interview with John. Here’s one of my favorite quotes from it, in response to “How do you begin a project?”

It can happen in two ways. I usually start with an object, which motivates an idea. That idea connects to other objects and so on, and, at some point, there is a convergence where idea meets form. Or sometimes I am fascinated by an object. Then I will seek to abstract the object into different spatial dimensions.

simstrees

Cellular Forest and Square Root of a Tree, by John Sims.

You can find more of John’s work on his YouTube channel. Check out this video, which features some of John’s music and an art exhibit he curated called Rhythm of Structure.

Next up: Some of our US states are nice and boxy—like Colorado. (Or is it?) Other states have very complicated, very dent-y shapes—way more complicated than the shapes we’re used to seeing in math class.

Which state is the most dent-y? How would you decide?

3fe3acace86442e7a0ddf5c7369f14dc.480x480x351

West Virginia is pretty dent-y. By driving “across” it, you can pass through many other states along the way.

The mathematical term for dent-y is “concave”. One way you might try to measure the concavity of a state is to see how far outside of the state you can get by moving in a straight line from one point in it to another. For example, you can drive straight from one place in West Virginia to another, and along the way pass through four other states. That’s pretty crazy.

But is it craziest? Is another state even more concave? That’s what this study set out to investigate. Click through to find out their results. And remember that this is just one way to measure how concave a state is. A different way of measuring might give a different answer.

Awesome animal kingdom gerrymandering video!

Awesome animal kingdom gerrymandering video!

This puzzle about the concavity of states is silly and fun, but there’s more here, too. Thinking about the denty-ness of geographic regions is very important to our democracy. After all, someone has to decide where to draw the lines. When regions and districts are carved out in a way that’s unfair to the voters and their interests, that’s called gerrymandering.

Karen Saxe

Karen Saxe.

To find out more about the process of creating congressional districts, you can listen to a talk by Karen Saxe, a math professor at Macalester College. Karen was a part of a committee that worked to draw new congressional districts in Minnesota after the 2010 US Census. (Karen speaks about compactness measures starting here.)

Recently I ran across an announcement for a conference—a conference that was all about the math of sea ice! I never grow tired of learning new and exciting ways that math connects with the world. Check out this video featuring Kenneth Golden, a leading mathematician in the study of sea ice who works at the University of Utah. I love the line from the video: “People don’t usually think about mathematics as a daring occupation.” Ken and his team show that math can take you anywhere that you can imagine.

Bon appetit!

Reflection sheet – SquareRoots, Concave States, and Sea Ice

Braids, Hacktastic, and Rock Climbing

Welcome to this week’s Math Munch!

lym_angel

Math hair braiding art by So Yoon Lym, shown at the 2014 Joint Mathematics Meetings.

First up, a little about one of my favorite things to do (and part of what got me into math in the first place!): hair braiding. If you’ve ever done a complicated braid in someone’s hair before, you might have had an inkling that something mathematical was going on. Well, you’re right! Mathematicians Gloria Ford Gilmer and Ron Eglash have spent much of their careers studying and teaching about the math that goes into hair braiding.

SYL_Diosnedys_new1

See the tessellation?

In their research, Gloria and Ron investigate how math can improve hair braiding, how hair braiding can improve math, and how the overlap between the two can teach us about how different cultures use and understand math. As Gloria shows in her article on math and braids, tessellations are very important to braided designs.

braids

And so are fractals! Ron studies how fractals are used in African and African American designs, including in the layouts of towns, tile patterns, and cornrow braids. (Watch his TED Talk to learn more!) On his beautiful website dedicated to the math of cornrows, Ron shows how braiders use tools essential to making fractals to design their braids.

programmed braid

Just like when making a fractal, braid designers repeat the same shape while shifting, rotating, reflecting, and shrinking it. You can design your own mathematical cornrow braid using Ron’s braid programming app! If you’ve ever used Scratch, this app will look very familiar. I made the spiral braid on the right using the app. Next challenge: try to make your braid on a real head of hair…

trig bracelets Laura Taalman

Next up, a little about something I wish I could do: make awesome 3D-printed art! Here’s a blog that might help me (and you) get started. Mathematician Laura Taalman (who calls herself @mathgrrl on Twitter) writes a blog called Hacktastic all about making math designs, using a 3D-printer and many other tools. She has designs for all kinds of awesome things, from Menger sponges to trigonometric bracelets. One of the best things about Laura’s site is that she tells you the story behind how she came up with her designs, along with all the instructions and code you’ll ever need to make her designs yourself.

Rock climbing Skip

Skip Garibaldi, climbing

Finally, a little about something I’m trying to learn to do better: rock climbing! Mathematician Skip Garibaldi loves both math and rock climbing– so he decided to combine his interests for the better of each. In this video, Skip discusses some of the mathematical ideas important to rock climbing– including some essential to a type of climbing that I find most intimidating, lead climbing. Check it out!

Bon appetit!

Dearing, Edmark, and The Octothorpean Order

Welcome to this week’s Math Munch!

Dearing Wang

Dearing Wang

First up is a wonderful mathematical artist I found on instagram, under the name dearing_draws. Click to see the wonderful work of Dearing Wang. The instagram stream includes lots of timelapse videos showing the creation of the images, which is lovely, but even better is that Dearing has a youtube channel and a website devoted to teaching people how to make their own!! You should click over and follow a tutorial. Make something beautiful and send us a picture.

3 Fish in a Pond

3 Fish in a Pond

Tutorial Video

The Diamond Wedge Pattern

The Diamond Wedge Pattern

Tutorial Video

Impossible Octagon

Impossible Octagon

Tutorial Video

Another great thing about Dearing’s website is that he has a page where you can print out blank sheets to color, if that’s your thing. Not quite as mathematical, maybe, but it is nice. I like to color sometimes, and if you color systematically, maybe symmetrically, then it’s fairly mathematical after all. UPDATE: Dearing has agreed to let us host some some of his coloring sheets on Math Munch.  Click here for easily downloadable sheets to color.

John Edmark

John Edmark

Up next is another mathematical artist, John Edmark, a designer and adjunct professor at Stanford University. I was introduced to John’s incredible work through the following video. Just watch and let your jaw hit the floor in amazement.

This is a video of a zoetrope. The pieces spin and the camera shutter is timed to only show certain points in their rotation. What we see is sort of like a little loop of film showing us several frames of the animation. It’s impressive that John put all those frames together into sculptures that are beautiful, even when they’re not spinning.

PatTurn

PatTurn

But that isn’t all, there’s lots more to see on John’s website. I found his spiral videos pretty mesmerizing and fantastic. I also really like his artist statement, which begins “If change is the only constant in nature, it is written in the language of geometry.” I also just really like hearing artists talk about their work, because it’s a sort of behind the scenes look into their creative process and thinking.

(3D printable files are also available here for the incredibly fortunate among us with access to a 3D printer.)

An octothorpe

An Octothorpe

Finally, if you like solving riddles and puzzles, check out The Octothorpean Order. This is sort of an online puzzle hunt, with clues and tips on the website. You can read about it, but the best thing to do is dive in and start solving puzzles. You probably have to create a user name, but it’s good fun. I recommend it.

By the way,  “octothorpe” is the technical word for the “hashtag” or “pound” or “number sign.” It means eight fields, and I think it represents a farmers house in the middle and eight fields arround it. Cool right?

Here’s to having a mathematical week.  Bon appetit!

Squircles, Coloring Books, and Snowfakes

Welcome to this week’s Math Munch!

Squares and circles are pretty different. Squares are boxy and have their feet firmly on the ground. Circles are round and like to roll all over the place.

Superellipses.

Superellipses.

Since they’re so different, people have long tried to bridge the gap between squares and circles. There’s an ancient problem called “squaring the circle” that went unsolved for thousands of years. In the 1800s, the gap between squares and circles was explored by Gabriel Lamé. Gabriel invented a family of curves that both squares and circles belong to. In the 20th century, Danish designer Piet Hein gave Lamé’s family of curves the name superellipses and used them to lay out parts of cities. One particular superellipse that’s right in the middle is called a squircle. Squircles have been used to design everything from dinner plates to touchpad buttons.

The space of superellipsoids.

The space of superellipsoids.

Piet had the following to say about the gap between squares and circles:

Things made with straight lines fit well together and save space. And we can move easily — physically or mentally — around things made with round lines. But we are in a straitjacket, having to accept one or the other, when often some intermediate form would be better. … The super-ellipse solved the problem. It is neither round nor rectangular, but in between. Yet it is fixed, it is definite — it has a unity.

"Squaring the Circle" by Troika.

“Squaring the Circle” by Troika.

These circles aren't what they seem to be.

These circles aren’t what they seem to be.

There’s another kind of squircular object that I ran across recently. It’s a sculpture called “Squaring the Circle”, and it was created by a trio of artists known as Troika. Check out the images on this page, and then watch a video of the incredible transformation. You can find more examples of room-sized perspective-changing objects in this article.

Next up: it’s been a snowy week here on the east coast, so I thought I’d share some ideas for a great indoor activity—coloring!

Marshall and Violet.

Marshall and Violet.

Marshall Hampton is a math professor at University of Minnesota, Duluth. Marshall studies n-body problems—a kind of physics problem that goes all the way back to Isaac Newton and that led to the discovery of chaos. He also uses math to study the genes that cause mammals to hibernate. Marshall made a coloring book full of all kinds of lovely mathematical images for his daughter Violet. He’s also shared it with the world, in both pdf and book form. Check it out!

Screen Shot 2015-01-27 at 1.35.54 PM Screen Shot 2015-01-27 at 1.36.11 PM Screen Shot 2015-01-27 at 1.36.31 PM

Inspired by Mashrall’s coloring book, Alex Raichev made one of his own, called Contours. It features contour plots that you can color. Contour plots are what you get when you make outlines of areas that share the same value for a given function. Versions of contour plots often appear on weather maps, where the functions are temperature, atmospheric pressure, or precipitation levels.

Contour plots are useful. Alex shows that they can be beautiful, too!

Screen Shot 2015-01-27 at 1.19.18 PM Screen Shot 2015-01-27 at 1.19.48 PM Screen Shot 2015-01-27 at 1.20.13 PM

And there are even more mathematical patterns to explore in the coloring sheets at Patterns for Colouring.

Screen Shot 2015-01-27 at 10.55.35 AM
Screen Shot 2015-01-27 at 10.51.45 AM
Screen Shot 2015-01-27 at 11.07.17 AM

Last up, that’s not a typo in this week’s post title. I really do want to share some snowfakes with you—some artificial snowflake models created with math by Janko Gravner and David Griffeath. You can find out more by reading this paper they authored, or just skim it for the lovely images, some of which I’ve shared below.

Screen Shot 2015-01-27 at 2.05.49 PM Screen Shot 2015-01-27 at 2.05.28 PM Screen Shot 2015-01-27 at 2.06.04 PM

I ran across these snowfakes at the Mathematical Imagery page of the American Mathematical Society. There are lots more great math images to explore there.

Bon appetit!

Reflection sheet – Squircles, Coloring Books, and Snowfakes