## HoTT Coq

Univalent Foundations Redefines Mathematics - "When a legendary mathematician found a mistake in his own work, he embarked on a computer-aided quest to eliminate human error. To succeed, he has to rewrite the century-old rules underlying all of mathematics." (previously)
posted by kliuless on Jun 9, 2015 - 13 comments

## Keeping It Fair

You're sitting down with your friends to play a boardgame, and you find yourself in a conundrum: how do you choose a first player? Sure, you could roll a standard die and take highest number, but what if there's a tie? That could take forever! Besides, wouldn't you rather be mathematically sure that everyone has a fair shot at each spot in the turn order? Of course you would!
posted by tocts on Jun 9, 2015 - 58 comments

## 3Blue1Brown: Reminding the world that math makes sense

Understanding e to the pi i - "An intuitive explanation as to why e to the pi i equals -1 without a hint of calculus. This is not your usual Taylor series nonsense." (via via; reddit; previously)
posted by kliuless on Jun 6, 2015 - 28 comments

## The toilet seat: up or down?

"I amused myself for over a year thinking about the impacts of different toilet seat administration policies and how to measure them – doing calculations in my head, considering ratios of Standing events to Sitting events, and I slowly began to understand some of the specific differences in the basic policies that know to be administered most often. Finally, I decided to perform a probabilistic analysis". Essential Toilet Seat Analytics.
posted by paleyellowwithorange on Jun 4, 2015 - 73 comments

## But is it fools' gold?

The Golden Ratio or the Golden Mean is touted as universal principle of mathematics, aesthetics, and architecture. Its natural occurrences are often associated with beauty and health. But naysayers think the Golden Ratio is myth or even a scam. Golden ratio previously and previouslier.
posted by immlass on May 26, 2015 - 28 comments

Alcazar is a neat little path-finding logic game. There are also printable puzzles, strategy tips and metapuzzles to be had.
posted by Wolfdog on May 2, 2015 - 15 comments

## When Is Cheryl’s Birthday?

How would you fare in a room full of adolescent math competitors in Singapore?
posted by roomthreeseventeen on Apr 14, 2015 - 76 comments

## At FedEx, we considered that problem for about three seconds

The FedEx Problem: In which the author uses Euclidean geometry to determine, based on the US Population, the idea location for FedEx's giant hub in Memphis (spoiler: It's about 315 miles off). Then, the guy who wrote the original scheduling software for FedEx shows up at Hacker News with the real story, and some war stories about the founding of FedEx:
posted by joshwa on Mar 28, 2015 - 38 comments

## I got cosines / on a cloudy day

The goofy, lofi math music of Al G. Bra and friends: Pi GirlSay That Funky Number, Math Guy — Mathonna's Mathematical Girl. Plus: a trailer for math thriller Live and Let Pi, featuring the title track by Paul DesCartney.
posted by cortex on Mar 14, 2015 - 5 comments

## Celebrate Vi day.

Vi Hart rants about what day today is. (previous celebrations)
posted by Obscure Reference on Mar 14, 2015 - 47 comments

## "You blew it, and you blew it big!"

The Time Everyone “Corrected” the World’s Smartest Woman
posted by brundlefly on Feb 20, 2015 - 295 comments

## They evolved. They rebelled. There are many copies. And they have a plan

The Philadelphia 76ers are currently the worst team in basketball, but in terms of expected value, they are crushing.
posted by Potomac Avenue on Feb 16, 2015 - 108 comments

## "Where is the door?"

Profile: Breaking down the problem of bound gaps [New Yorker]: After graduating with a Ph.D. in algebraic geometry from Purdue in 1991, Yiting Zhang kept the books for a friend's Subway franchise and found other odd jobs before taking up a part-time calculus teaching position at the University of New Hampshire in 1999.
“For years, I didn’t really keep up my dream in mathematics,” he said.

“You must have been unhappy.”

He shrugged. “My life is not always easy,” he said.
He published one paper in 2001. Then, in 2013, he submitted "Bounded Gaps Between Primes" to Annals of Mathematics, one of the most prestigious journals in the field, which contained a proof for a finite bound within which there exist an infinite number of pairs of primes. It was a stunning mathematical breakthrough.
posted by ilicet on Jan 27, 2015 - 67 comments

## Arithmeticfilter

Nothing but an endless supply of mental arithmetic problems. Five levels of difficulty, from "10 - 6" to "√370881."
posted by Iridic on Jan 26, 2015 - 20 comments

## Stephen Hawking is not part of the solution, he is part of the problem.

The equations on the blackboard may be the problem. Mathematics, the language of science, may have misled the scientists. “The idea,” says physicist Lee Smolin, “that the truth about nature can be wrestled from pure thought through mathematics is overdone… The idea that mathematics is prophetic and that mathematical structure and beauty are a clue to how nature ultimately works is just wrong.”
posted by leotrotsky on Jan 19, 2015 - 88 comments

## Thanks, Common Core.

Thanks, Common Core. Physics blogger Chad Orzel writes about the way kids do math now. (Spoiler: he likes it.)
posted by escabeche on Jan 15, 2015 - 65 comments

## No Pentagons

Imperfect Congruence - It is a curious fact that no edge-to-edge regular polygon tiling of the plane can include a pentagon ... This website explains the basic mathematics of a particular class of tilings of the plane, those involving regular polygons such as triangles or hexagons. As will be shown, certain combinations of regular polygons cannot be extended to a full tiling of the plane without involving additional shapes, such as rhombs. The site contains some commentary on Renaissance research on this subject carried out by two renowned figures, the mathematician-astronomer Johannes Kepler and the artist Albrecht Dürer.
posted by Wolfdog on Jan 14, 2015 - 16 comments

How to tell correlation from causation - "The basic intuition behind the method demonstrated by Prof. Joris Mooij of the University of Amsterdam and his co-authors is surprisingly simple: if one event influences another, then the random noise in the causing event will be reflected in the affected event."
posted by kliuless on Jan 12, 2015 - 25 comments

## Fake 3D Until You Make 3D

Louis Gorenfeld lovingly explores the mathematics and techniques behind early, pseudo-3D games.
posted by gilrain on Jan 9, 2015 - 16 comments

## Sacred Typography

Lettering Around :mandalas for all you font-fetishes out there. From Linda Alila.
posted by es_de_bah on Jan 8, 2015 - 3 comments

## "Science is when you think a lot."

Two enjoyable chapters [PDF, 33 pages] from the book Math from Three to Seven: The Story of a Mathematical Circle for Preschoolers. "This book does not purport to show you how to create precocious high achievers. It is just one person's story about things he tried with a half-dozen young children."
posted by Wolfdog on Dec 29, 2014 - 11 comments

## Still Combining Numbers On A Grid To Get Bigger Numbers, But Different

Get 10 is a new browser game from veewo, creators of 1024.
posted by Rinku on Dec 9, 2014 - 31 comments

## It's too early on a Monday morning for this hot math nonsense, come on

Numberphile demonstrates that the digit three is in almost all integers.

The integers are a unique factorization domain, so we can’t tune pianos. That is the saddest thing I know about the integers.
posted by jenkinsEar on Dec 1, 2014 - 94 comments

## Rainy Day

Pencil and Paper Games is devoted to games you can play with nothing more than a pencil and a piece of paper (some of which can be played on the site, for those who do not have access to a pencil and paper, or remember what those are.)
posted by Wolfdog on Nov 26, 2014 - 11 comments

## Visualisations: oh, I get it now!

Explained Visually (EV) is an experiment in making hard ideas intuitive [source: hackernews] There are plenty more mathematical visualisations around, too...
posted by katrielalex on Nov 15, 2014 - 9 comments

## Alexander Grothendieck

Alexander Grothendieck, who brought much of contemporary mathematics into being with the force of his uncompromising vision, is dead at 86, some twenty-five years after leaving academic mathematics and retreating into a spiritual seclusion in the countryside. "As if summoned from the void," a two-part account of Grothendieck's life, from the Notices of the American Math Society: part I, part II.
posted by escabeche on Nov 13, 2014 - 33 comments

## √2N

At the Far Ends of a New Universal Law
The law appeared in full form two decades later, when the mathematicians Craig Tracy and Harold Widom proved that the critical point in the kind of model May used was the peak of a statistical distribution. Then, in 1999, Jinho Baik, Percy Deift and Kurt Johansson discovered that the same statistical distribution also describes variations in sequences of shuffled integers — a completely unrelated mathematical abstraction. Soon the distribution appeared in models of the wriggling perimeter of a bacterial colony and other kinds of random growth. Before long, it was showing up all over physics and mathematics. “The big question was why,” said Satya Majumdar, a statistical physicist at the University of Paris-Sud. “Why does it pop up everywhere?”
posted by the man of twists and turns on Oct 28, 2014 - 17 comments

## 100 Years of Martin Gardner!

In Honor of the Centennial of Martin Gardner's birth (October 21, 1914), we've lined up Thirty-One Tricks and Treats for you: Magazine articles, new and classic puzzles, unique video interviews, and lots more.The Nature of Things / Martin Gardner [46min video] ✤ The College Mathematics Journal, January 2012 dedicated to Gardner with all articles readable online.
posted by Wolfdog on Oct 23, 2014 - 32 comments

## The Math Behind the Rolling Shutter Effect.

Here's a pair of blog posts explaining the math behind the "Rolling Shutter Effect": Playing Detective with Rolling Shutter Photos and Rolling Shutters.
posted by empath on Oct 13, 2014 - 13 comments

## запомнить практики запоминать практика запоминать практику

Time after time, professors in mathematics and the sciences have told me that building well-ingrained chunks of expertise through practice and repetition was absolutely vital to their succes Understanding doesn’t build fluency; instead, fluency builds understanding. In fact, I believe that true understanding of a complex subject comes only from fluency.
posted by sammyo on Oct 3, 2014 - 19 comments

## Take that, Keanu Reeves.

Privilege and oppression explained through math - specifically, matrices and Venn diagrams.
posted by divabat on Oct 1, 2014 - 89 comments

## Calculus without limits

Hyperreal numbers: infinities and infinitesimals - "In 1976, Jerome Keisler, a student of the famous logician Tarski, published this elementary textbook that teaches calculus using hyperreal numbers. Now it's free, with a Creative Commons copyright!" (pdf—25mb :)
posted by kliuless on Sep 17, 2014 - 34 comments

## Selected Lectures on Science and Engineering in the Boston Area

If you live in the Boston area and would like to attend science, technology, math, or engineering lectures, you'll find Fred Hapgood's exhaustive and continually-updated list of Selected Lectures on Science and Engineering in the Boston Area very useful. (Here's his list of sources.) Perhaps you know of a list like this for lectures in your locality or field of preference?
posted by not_on_display on Sep 15, 2014 - 6 comments

## You miss that train all because of that nickel.

posted by GrammarMoses on Sep 6, 2014 - 73 comments

## Middle East Peace Potential through Dynamics in Spherical Geometry

Middle East Peace Potential through Dynamics in Spherical Geometry: Engendering connectivity from incommensurable 5-fold and 6-fold conceptual frameworks. This is an exploration of the hypothesis that unique belief systems depend for their coherence on distinctive patterns typically embodied in geometrical symbols in two dimensions. On the basis of that assumption, the case tentatively explored here is that of the "incommensurability" of the 5-fold Star of Islam and the 6-fold Star of David of Judaism...Mathematically these patterns cannot be readily combined. This issue is described in mathematics in terms of tiling...A set of hexagons and pentagons can however be uniquely fitted together as a particular three-dimensional polyhedron, namely the truncated icosahedron.
posted by leahwrenn on Aug 21, 2014 - 32 comments

## It's just a jump to the ... well, in any legal direction really

The Peg Solitaire Army is a problem spun off from a classic recreation, and yet another example of the golden ratio turning up where you least expect it. If you want to look at the game more deeply, George Bell's solitaire pages are the ne plus ultra: There's more about the solitaire army (and variants), ...
posted by Wolfdog on Aug 15, 2014 - 6 comments

## do while !glory

Welcome to Al Zimmermann's Programming Contests. You've entered an arena where demented computer programmers compete for glory and for some cool prizes. The current challenge is just about to come to an end, but you can peruse the previous contests and prepare for the new one starting next month.
posted by Wolfdog on Aug 14, 2014 - 11 comments

## 2014 Fields Medals

The 2014 Fields Medals have been awarded to Artur Avila, Manjul Bhargava, Martin Hairer, and Maryam Mirzakhani. Mirzakhani, a professor at Stanford, is the first woman to win math's highest prize, and Avila is the first South American. Erica Klarreich at Quanta Magazine has profiles of all four winners.
posted by escabeche on Aug 12, 2014 - 35 comments

## Math and equations are fun.

The power of math: 17 Equations That Changed the World - a one table summary of the book by Ian Stewart FRS. Business Insider gives its interpretation of the importance of each equation. Brain pickings (2012) on this book and equations, and another extract from the book.
posted by Wordshore on Aug 10, 2014 - 36 comments

## The Foehr Reef

The Foehr Reef is part of the worldwide Crochet Coral Reef Project. It was made by over 700 women and combines more than 4000 individual pieces of marine wonder. A short video shows its beauty [alternating English and German audio]. PDFs with pictures. "The Crochet Coral Reef is a woolly celebration of the intersection of higher geometry and feminine handicraft, and a testimony to the disappearing wonders of the marine world." It originated out of a desire to increase awareness of environmental threats to the world's reefs and is a conjunction of art, environmentalism, and geometry.
posted by travelwithcats on Aug 10, 2014 - 7 comments

## 21st Century Wiener

Norbert Wiener: The Eccentric Genius Whose Time May Have Finally Come (Again) - "The most direct reason for Wiener's fall to relative obscurity was the breakthrough of a young mathematician and engineer named Claude Shannon."
posted by kliuless on Jul 11, 2014 - 12 comments

## musical mathematical journeys

Trio for Three Angles (1968) is one of many beautiful acclaimed visually-oriented short films with music by mathematical filmmakers Bruce and Katharine Cornwell, some animated by hand and some using early digital technology. It inspired three sequels: Similar Triangles (1975), Congruent Triangles (1976), and Journey to the Center of a Triangle (1978) (previously).
posted by beryllium on Jul 6, 2014 - 5 comments

## I Can Tell By The Pixels

Visualizing Algorithms shows you how computer algorithms can be represented visually, leading to better understanding of how the algorithms work:

"Have you ever implemented an algorithm based on formal description? It can be hard! Being able to see what your code is doing can boost productivity. Visualization does not supplant the need for tests, but tests are useful primarily for detecting failure and not explaining it. Visualization can also discover unexpected behavior in your implementation, even when the output looks correct."
posted by quiet earth on Jun 26, 2014 - 29 comments

## Eigendemocracy: crowd-sourced deliberative democracy

Scott Aaronson on building a 'PageRank' for (eigen)morality and (eigen)trust - "Now, would those with axes to grind try to subvert such a system the instant it went online? Certainly. For example, I assume that millions of people would rate Conservapedia as a more trustworthy source than Wikipedia—and would rate other people who had done so as, themselves, trustworthy sources, while rating as untrustworthy anyone who called Conservapedia untrustworthy. So there would arise a parallel world of trust and consensus and 'expertise', mutually-reinforcing yet nearly disjoint from the world of the real. But here's the thing: anyone would be able to see, with the click of a mouse, the extent to which this parallel world had diverged from the real one."
posted by kliuless on Jun 23, 2014 - 45 comments

## The University of Illinois' Altgeld Math Models

The Altgeld Math Models. Below you will find around 170 of the models that were photographed in March 2005 when the third floor model cases had to be emptied and moved. The models were carefully moved into the undergraduate lounge and arranged in a miniature "model museum" for two weeks, where each was carefully photographed and is now available for your enjoyment below.
posted by obscurator on Jun 3, 2014 - 11 comments

## Who or what broke my kids?

Who or what broke my kids? "The basic premise of the activity is that students must sort cards including probability statements, terms such as unlikely and probable, pictorial representations, and fraction, decimal, and percent probabilities and place them on a number line based on their theoretical probability. I thought it would be an interactive way to gauge student understanding. Instead it turned into a ten minute nightmare where I was asked no less than 52 times if their answers were “right”. I took it well until I was asked for the 53rd time and then I lost it. We stopped class right there and proceeded to have a ten minute discussion on who broke them."
posted by escabeche on Jun 1, 2014 - 107 comments

## Number Sense

Five reasons not to share that Common Core worksheet on Facebook
posted by eviemath on May 25, 2014 - 202 comments

## One plus one is equal to two - calculus in text is left as an excercise

I was surprised to learn that few people knew that almost all maths was written rhetorically before the 16th century, often in metered poetry. Even our wonderful symbol for equality – you know, those two parallel lines – was not used in print before 1575.
posted by sammyo on May 24, 2014 - 39 comments

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