Sunday, November 29, 2015

214: In Search Of The Ultimate Math Game

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With the holiday season upon us, many of you out there are probably giving or getting new tech gadgets as gifts.    Once you unwrap your fancy new iPad, iPhone, or Android tablet, you’re probably asking yourself, “Now what do I do with this?”    While you will probably be downloading lots of fun games and apps, you will somehow need to justify all the hours you spend in front of the screen to your family.    One of the best ways to do this is to install a few math-related games, and provide some educational value for your children.   But there is a bewildering array of supposedly educational games available for these systems.   How do you know which ones to get?     Today I will share some suggestions based on my experiences.

The first thing I should point out is that there are hundreds of games out there that are basically glamorized flashcards, presenting math problems directly and giving some kind of in-game reward for correct solutions.    For example, they will put up a math problem, like “What is 5 x 5?”, and if the answer is correct, the player gets a few points.   These points can then be traded in for virtual stickers, virtual ammunition against alien robots, or similar rewards.   While there is nothing wrong with this type of game, and they have the advantage of being able to easily draw on large libraries of problems for different skill levels, I don’t find them very exciting.    My daughter will play them if I tell her she needs to practice her math, but doesn’t usually come to me asking to play them.   What I really want are original games that both teach math and can stand on their own as fun games.   Fortunately, I have found two games that fit these requirements.

The first game I want to highlight is called “DragonBox Elements”.    This game is designed to teach the basics of geometric proofs, a seemingly advanced topic, but they present it in a very accessible and intuitive way.    Each basic shape, triangles and quadrilaterals, can summon a basic type of monster related to that shape.    So if you can identify a quadrilateral among the shapes on the screen, you trace it out and summon a quadrilateral-monster.   Line segments and angles are also marked with colors, such that any two objects with the same color have equal length, and you can upgrade the monsters to “special” ones using these.   So, for example, if you notice a triangle-monster has two equal sides, you can click on them to upgrade to the slightly more powerful isoceles-monster.   The monsters also have powers, which essentially invert this process:  so if you have been given an isosceles-monster and its two equal sides are not yet colored, you can click on the monster and the two sides to mark them as equal.   They also introduce other powers related to ideas like opposite angles, radii of circles, and parallel lines.   So the basic Euclidean concepts of definitions, axioms, and theorems have been transformed into monsters and powers.    I’m not totally sure how this will translate to actual proof skills when my daughter reaches that level of math class, but laying the foundations at such a young age can’t hurt.   And more importantly, she loves this game, even asking to replay all the levels at “hard” difficulty after beating it once.

The second truly engaging iPad math game I have discovered is called “Calculords”.   This is a card game, where each turn you have a bunch of cards in hand that you can use to summon creatures for battle.   There are two types of cards, number cards and creature cards.   It’s not a simple energy system like in most popular collectible card games though:   in order to summon a creature for battle, you need to add, subtract, and multiply number cards to reach the creature’s number.   The creatures are then placed on a lane-based battlefield, where they fight the evil monsters summoned by an alien enemy.    For example, suppose you have a Hungry Blob card, a monster with a summoning cost of 15, and your number cards are 3, 3, 4, and 1.   You can form a 15 using 3 x 4 + 3, so you can play those cards to summon your blob.   But an additional wrinkle, adding to the mathematical challenge, is that you also gain extra bonuses if you precisely use up all your number or creature cards.   So a better move would be to play 3 x 4 x 1 + 3, which still reaches your 15, but uses up your numbers.    Since you have 9 creature cards and 9 number cards on each turn, the number of potential choices and calculations is quite large, and the strategy to summon the best set of monsters while trying to use up cards to get the bonus can get very involved.    But the game offers many enemies at a variety of difficulty levels;  my daughter has been playing at the easier levels since she was in 2nd grade.   This is another game that she and I have found quite addictive, and an amazing way to get her to eagerly practice her basic arithmetic.   And at the top difficulty levels, even I find it challenging, when I sneak in a chance to play on my own.

So, in short, these are the two truly original smartphone/tablet math games I currently recommend for elementary-age students:   DragonBox Elements and Calculords.   Naturally, these are heavily influenced by my 4th-grade daughter’s tastes, and their effectiveness probably varies a lot at older and younger ages.   DragonBox elements provides the amusing and engaging transformation of Euclidean definitions, axioms, and theorems into monsters and powers.   And Calculords provides a strategic challenge involving arithmetic calculations that is accessible to young children at lower levels, and fun even for adult math geeks at the hardest settings.   If you have kids at the upper elementary level who could use some extra math practice, be sure to take a look at these excellent games.   Also be sure to post reviews on iTunes or similar sites if you like them, as this will increase the chance of further games appearing from these talented authors..   And as always, I’ll be interested to hear from you on this topic:  with such an overwhelming number of smartphone and tablet games out there, I’m sure there are a few great ones that I haven’t discovered yet.   

And this has been your math mutation for today.


Sunday, October 25, 2015

213: Proof of the Fourth Dimension

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Rudolf Steiner was a prolific Austrian author and philosopher of the late 19th and early 20th centuries.    He felt a strong connection to mysticism and spiritualism, ever since he supposedly communicated with the ghost of a recently deceased aunt at the age of 9.   Steiner is well-known for having led a group that split off from the popular circle of European mystics known as the Theosophical Society, which seemed heavily inclined to regard the religions of East Asia as somehow providing the keys to understanding spirituality.   Steiner called his new group the Anthroposophical Society, and this competing group believed that Western science and culture were just as strongly connected to the spiritual-- it was just a matter of intepreting them properly.    One particular Western idea that Steiner was fond of was the concept of a fourth physical dimension, another mathematically-defined direction that we cannot percieve but is just as real as length, width, and height.     Steiner believed that our consciousness extended into this fourth dimension, and that phenomena like ghosts and ESP resulted from activity in this hidden dimension.      And most interestingly, he believed he had a simple philosophical proof that this fourth dimension really does exist, and our human minds really do extend into this additional dimension.

Here's how Steiner's proof goes.   We all know that a creature of a particular dimension, if it looks out at its world, really only sees a view that is one dimension smaller.   For example, a one-dimensional creature living in Lineland, a universe that exists entirely on a single straight line, can only perceive a single point on either side of himself:   a zero-dimensional view.    Similarly, a two-dimensional Flatlander, living on a plane, really only sees a line;  it is only us three-dimensional creatures, looking down on the plane from above, who can truly comprehend its full two-dimensional world.    And in real life, when we look out with our eyes, we are only seeing a plane.   Yet somehow we do believe we fully understand and perceive the three dimensions of our world.   Steiner draws what he believes is a natural conclusion from this:   "The fact that we can delineate external beings in three dimensions and manipulate three-dimensional spaces means that we ourselves must be four-dimensional...  We float in a sea of the fourth dimension just like ice cubes on water."   In other words, our ability to fully perceive our three-dimensional space shows that our minds must extend beyond those three dimensions.  

It's a fun thought, but you can see something fishy there right away, if you think about the world of modern computing.    I can think of all sorts of situations in which an object in three dimensions is represented by a model in fewer dimensions.     For example, most computer memories and circuits that power modern three-dimensional computer games are essentially stored in flat two-dimensional circuit boards.   While these are technically 3-D like all physical objects, the memory storage can be thought of as truly two-dimensional in some sense, as each (x,y) coordinate on the circuit board only stores one encoded value at any given time.    More basically, you may recall the concept of a Turing Machine discussed in some earlier podcasts:  this is a theoretical model of computing, based on writing and reading values from a long, essentially one-dimensional, tape.   It has been shown that any modern computer can be modelled by a very slow, but 100% accurate, Turing machine equivalent.    So even the 3-D models in a modern computer game could, with enough work, be represented in one dimension.

I think the main flaw in Steiner's argument is his fundamental premise, that a creature of n dimensions can only perceive n-1 dimensions.   It is true that through the sense of sight, a creature can only see one dimension lower, but our senses are not limited to sight.   Think about a blind man, who perceives the world mainly by walking around and tapping items with his cane to understand their form:  he can walk forward, back, right, or left, and even climb ladders up and down.    He is truly perceiving the full three dimensions of his world, travelling within all three of those dimensions and building a mental model based on his real experiences.    This applies to the lower-dimensional examples as well:   the flatlander can move around and perceive his full plane, and even the poor Linelander can move back and forth on his line.    Thus, the idea that perceiving your full dimensionality requires capabilities from a greater dimensionality does not really seem to ring true.    You need to think of perception much more generally than simple line-of-sight.

Naturally, this does not fundamentally prove that Steiner was wrong about our minds extending into the fourth dimension; it just means that the proof of such an idea is not so simple.   So it's still entirely possible that the concept of our mystical four-dimensional minds is correct but unproven, and the rest of Steiner's Anthroposophical Society ideas might still be valid.    This philosophy of the fourth dimension was just a launching point for a variety of mystic concepts, related to traveling along this fourth dimension to the astral plane where you could encounter ghosts, life after death, etc.   Some of Steiner's lectures get amusingly specific on details of the astral plane-- apparently he believed that his meditation and similar activities had actually taken him to this place, so he could talk about how astral dimensions mirrored our own, and writing there would appear backwards.   Personally, I'm a bit of a skeptic on this topic, but these kinds of ideas do seem to have a lasting appeal, as shown by the New Age sections you can find in many modern bookstores.   If you're into that stuff, try meditating hard enough, and maybe you too can follow Steiner's path into the astral plane through the fourth dimension.   While you're there. see if you can track down Steiner's spirit, to discuss the flaws in his philosophical proofs.

And this has been your math mutation for today.


Sunday, September 27, 2015

212: De-Abstracting Your Life

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One of the core principles of mathematics is the idea of abstraction, generalizing from various experiences to describe simplified models that enable rigorous reasoning.   For example, if you look at a street map of your city, nothing there qualifies as a pure Euclidean triangle:  all roads have thickness, varying slopes, squished raccoons, etc.     But by reasoning about ideal triangles and lines, we can make powerful deductions about the distances between points that are very useful and accurate for practical purposes.   However, there is a dark side to abstraction-- when used too much in your daily life, it can cause you to over-generalize and lead to issues like stereotyping and prejudice.  

For example, 20 years ago I had a Scottish roommate named Lloyd.    Lloyd was a great guy, but I could not understand a word he said, due to his outrageous Scottish accent.   Eventually we started keeping a notepad in the room so he could write down anything important he needed to communicate.   After a few months with him, I was on the verge of insanity.    Now, whenever I'm being introduced to someone from Scotland, I inwardly cringe, bracing myself for a similar experience.  In effect, I have abstracted Lloyd as the general Scotsman in my mind, impacting my further relationships and experiences with his countrymen.   It hasn't been that much of an impact in my life, as most residents of Scotland have yet to discover the joys of Hillsboro, Oregon, but it's still a bad habit.    Is there something simple I can do to try to cure myself of this way of thinking?     One intriguing set of ideas comes from a 20th-century pop philosophy movement known as General Semantics.

General Semantics was first created by Polish count Alfred Korzybski in the 1930s, and  detailed in a book called "Science and Sanity".    This book describes a wide-ranging philosophy based on evaluating our total "semantic response" to reality, and learning to separate true reality, our observations of reality, and our language that describes the reality.    By becoming conscious of our tendency to over-abstract, we can improve our own level of sanity, hence the book title "Science and Sanity".    While serious philosophers and linguists generally don't consider Korzybski's ideas very deep, he attracted a devoted cult following, who believe that the General Semantics tools can significantly improve people's lives by reducing the errors that result from over-abstraction.   This movement also led to the proposal for "E Prime", the variant English language without the verb "to be", which I described back in podcast 196.    Amusingly, Korzybski was also a bit of a math geek:  when his Institute for General Semantics in Chicago was assigned the address 1232 East 56th Street, he had the address changed to 1234, in order to create a nice numerical progression.

Among the key tools that General Semantics provides for fixing over-abstractions are the "extensional devices", new ways to think about the world that help you to correct your natural tendencies.   Many of these involve attaching numbers to words.   The most basic is "indexing", mentally assigning numbers to help emphasize the differences between similar objects.    For example, I might think of my friend Lloyd as Scotsman-1.   Then, if introduced to another person from Scotland, I can think of him as Scotsman-2, emphasizing that he is a completely different person from Scotsman-1 despite their common origin.   If I go out with my new friend for a yummy Haggis dinner, I would think of the waiter as Scotsman-3, again recognizing his essential uniqueness and separating him from the other two.   Through this assignment of numbers, I can avoid grouping them all into the single abstraction of Scotsmen, and help force myself to treat them as individuals.

Another important extensional device is called "Dating", similar to indexing but based on time.    With this device, you attach dates to objects, indicating when you observed or experienced them.   The Lloyd I remember should really be thought of as Lloyd-1993, since that's when I knew him, and I'm really only familiar with his characteristics at that time.   If he emails me that he's coming to town, I should now think of him as Lloyd-2015, who may be a different person in many ways.   Perhaps he has been working on his accent a bit, or maybe due to my 20+ years of engineering experience, my ears have gotten better at discerning words in unusual accents.    I should not over-abstract and assume that his most notable characteristics at one time, and my perception of them, will be the same today as in the past.    Like everything in the universe, he and I are constantly changing, and I can use this extensional device to remind myself of that.

There are a number of additional extensional devices in General Semantics, such as the use of Et Cetera, quotes, and hyphens to further qualify your abstracted language.    These seem a bit more awkward to me, though some may prefer them.     Overall, I think the general concepts behind Korzybski's extensional devices probably can serve as a useful tool, especially if I go to Scotland sometime, though perhaps they are not quite as profound as General Semantics fanatics like to think.    Korzybski's movement still seems to be going strong, with active institutes in New York, Australia, and Europe that have a presence on the web and in social media, and a quarterly newsletter still in print since 1943.     Naturally, I've grossly oversimplified many of the core ideas for this short podcast, but if this has served to whet your appetite, you can find many other details at the links in the show notes. 

 And this has been your math mutation for today.


Sunday, August 30, 2015

211: Saving A Few Million Years

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Those of you who follow the Math Mutation facebook feed may have noticed that a book I co-authored was just released: "Formal Verification: An Essential Toolkit for Modern VLSI Design". Now, I need to caution you that this is not a Math Mutation book-- it's a technical book, aimed at electrical and computer engineers invovled in chip design. However, I do think Math Mutation listeners might have some interest in the core concepts on which the book is based. So, today I'll try to give you a brief summary of what Formal Verification is, and why it's worth writing a book about.

You're probably aware that modern computer chips are pretty complicated, by many measures the most complex devices ever created by man. For new ones coming out this year, the number of transistors is measured in the billions. So it makes sense to ask the question: how do we know these things will work? It would be prohibitively expensive to just build them first and then test them, so we need to discover and fix as many of the bugs as possible during the design stage. The process of finding these bugs is known as design validation. For many years, the most popular technology used in design validation has been simulation: testing how a software model of the design will behave for various sets of inputs.

Unfortunately, even a simple chip design has so many possible behaviors that there is no way to simulate them all. For example, suppose you are designing a simple integer adder: it will take 2 numbers as inputs, each expressed with 32 bits, or binary digits, which can each be 1 or 0. It will then output their sum. How many possible input sets are there for this design? Since each input has 32 bits, it has 2^32 possible values, thus resulting in 2^64 possible values for the pair. If we assume we have a fast simulator that can check 2^20 values per second, that means that we will need 2^44 seconds to check all possible values-- over half a million years. Most managers are not very happy when given a time estimate on this order to finish a project. And needless to say, most chips sold today are many orders of magnitude more complex than a simple adder.

So, what can we do to make sure our chip designs really will work? A variety of technologies have been developed over the past few decades to try to find a good set of example values to simulate. And they do seem to be doing a decent job: most electronic devices you buy today seem to more-or-less do what you want them to. But it still seems like there should be a better way to validate them: no matter how good you make it, simulation and related methods can never cover more than a tiny portion of your design's possible behaviors.

That's where formal verification comes in. The idea of formal verification is to take a totally different approach: instead of trying specific values for your design, why not just mathematically prove that it will always be correct? That way you don't have to worry about trying every possible test case. If there is a single set of values that would generate an incorrect result, your proof will fail, and you will know your design has a bug. If you do succeed in mathematically proving your design correct, then you know that there is no bug, and do not need to waste time simulating lots of testcases. In effect, formally verifying a design is equivalent to simulating all possible values. Many would argue that philosophically, this is really the "right" way to validate chip designs. You may have heard the famous Guindon quote, "Writing is nature’s way of letting you know how sloppy your thinking is." Formal Verification pioneer Leslie Lamport expanded on this with "Math is nature's way of letting you know how sloppy your writing is.", and later added "Formal math is nature's way of letting you know how sloppy your math is."

You've probably guessed by now that there has to be a catch. Formal verification is easier defined than done: when billions of transistors are involved, how do we even get our heads around the problem of creating mathematical proofs? It's far beyond what anyone could manually do, so to make this method a possibility, humans need to be aided by intelligent software that helps to automate proofs. To further complicate matters, it's also been shown that any formal verification system needs to internally solve what are known as NP-complete problems. If you remember our discussion way back in episode 13, an NP-complete problem is "provably hard" in some sense, meaning that no piece of computer software can ever solve it efficiently in 100% of cases. However, researchers have worked for many years to try to develop practical software that could utilize clever tricks to enable real proofs on a wide variety of actual industrial product designs.

The good news is that, in the past decade, formal technology has advanced to the point where it really is practical for an average design engineer to use in many cases. While formal verification software can't handle full multi-billion-transistor chip designs, it can often enable an engineer to create solid proofs on major sub-blocks that go into a chip design, massively reducing overall risk of bugs. Using formal verification software remains a bit of an art though. Due to the NP-completeness issue, the software may get stuck or progress very slowly: the user must often give subtle hints and suggest shortcuts to enable the proofs to complete. In addition, formal verification is a problem that is impossible to fully automate: no matter how good your software gets at proving stuff, a human still has to somehow be able to tell it what stuff to prove-- what is the overall intent of the design in the first place? Ultimately, someone has to carefully transfer the design intent from their human brain into a machine-readable form, and understand the possible limitations and pitfalls in this process. Sadly, computer software that directly plugs into your brain is probably still many years away, and even then I have the feeling that many of us think too sloppily to enable this level of verification directly.

Thus, the need for a Formal Verification book. While there have been many books on Formal Verification published over the past few decades, most have focused on internal algorithms that would be needed to develop the software involved. Our book is one of the first real practical manuals designed to help deesign and validation engineers use formal verification software on real-life design targets.
Anyway, that quick summary should give you an idea of what our new book is about. If you're in a field where you do chip design or something related, please visit our book's website at, order a copy, and tell all your friends about it!   If you're not in this field, the book probably won't make much sense to you, but hopefully you've still enjoyed this episode of the podcast.

And this has been your Math Mutation for today.


Sunday, July 26, 2015

210: Two Plus Two Equals Five

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Before we start, I'd like to thank listener D. Zemke, who posted another nice review on iTunes.  Thanks D!

Now, on to today's topic.   Recently I heard someone quote a clever metaphor in a casual conversation,  "Life is when nature takes 2 and 2 to make 5."   It's a nice statement of how living creatures are more than the sum of their parts.  If you took all the chemical compounds in my body and dumped them on the ground in the right proportions, all you would get is a mess.   Yet somehow I am here, and at least sentient enough to record math podcasts.    I went online to try to find the source of this quotation, and was surprised to see the number of references to this seemingly silly nonsense equation, 2+2=5.

Most of us are probably familiar with the equation from George Orwell's classic novel 1984.   As you probably recall, in the book, people are told that if the government says that 2+2=5, it is the duty of all citizens to believe it-- not just say it, but actually come to believe that it is true.   Surprisingly, Orwell did not come up with this out of thin air:  a real-life totalitarian government, the Soviet Union, actually did use 2+2=5 as part of its propaganda, in a poster with the title ""2+2=5: Arithmetic of a counter-plan plus the enthusiasm of the workers."    It wasn't quite as blatantly absurd as in 1984, but the Soviet propaganda poster used it as a metaphor:   supposedly a 5-year plan could be completed in 4 years, because the entuhsiasm of the workers provided an invisible additive factor.   Sadly, most of this "enthusiasm" was mainly due to fear of being sent to the Gulag prison camps, which resulted in many managers doctoring the statistics to match the results that the government wanted-- on paper only.   It's also reported that Nazi Herman Goering actually used this metaphor in real life, once saying "“If the F├╝hrer wants it, two and two makes five!”

The phrase 2+2=5 actually existed in the arts dating from the early 19th century.   According to Wikipedia, the phrase was first coined in a letter from Lord Byron, where he wrote ""I know that two and two make four—& should be glad to prove it too if I could—though I must say if by any sort of process I could convert 2 & 2 into five it would give me much greater pleasure."   He may have been making an indirect reference to Rene Descartes' Meditations, where the famous philosopher discussed whether equations such as 2+3=5 exist outside the human mind, and whether they can be doubted:  "And further, as I sometimes think that others are in error respecting matters of which they believe themselves to possess a perfect knowledge, how do I know that I am not also deceived each time I add together two and three, or number the sides of a square, or form some judgment still more simple, if more simple indeed can be imagined?"

Later Victor Hugo used this concept in a critique of tthe mob rule that had led to Napolean, foreshadowing Orwell's later political metaphor:  ""Now, get seven million five hundred thousand votes to declare that two and two make five, that the straight line is the longest road, that the whole is less than its part; get it declared by eight millions, by ten millions, by a hundred millions of votes, you will not have advanced a step."   Russian authors Ivan Turgenev, Leo Tolstoy, and Fyodor Dostoyevsky also made use of this metaphor.   Turgenev used it to symbolize divine intervention:  "Whatever a man prays for, he prays for a miracle. Every prayer reduces itself to this: Great God, grant that twice two be not four."    In the 20th century, there are many instances of authors following Orwell's lead and again using this metaphor for the struggle against totalitarianism, including Albert Camus and Ayn Rand.

An intriguing question is whether there are cases when it is actually valid to say that 2+2=5.   A well-known mathematicians' joke is that "2+2=5, for particularly large values of 2."   This may refer to issues with rounding:  if you start, for example, with the obviously correct equation "2.4 + 2.4 = 4.8", and ask someone to round all the numbers to the nearest integer, you do indeed derive "2+2=5" from this true equation.   It also might be a case of playing with the definitions of symbols:  perhaps you can define the symbol that we normally write as "2" to actually be an algebraic variable representing the value 2.5.   A trickier example is a "proof" that 2+2=5 that is circulating the web, where many lines of complex algebra are used.   These many lines are artificially complex in order to misdirect you from one invalid step, where a term t is replaced with the square root of t squared.   Remember that you can only do such a replacement if t is positive, a fact glossed over in the so-called proof.   I won't bore you by trying to cite all the lines of equations in an audio podcast, but you can find them linked online in the show notes if you're curious.

An amusing spoof article online points out some real-life situations where 2 and 2 might really make 5.   Ancient Incas used knotted ropes to track business transactions, and if you tie together two ropes that each have two knots, the resulting rope will have 5 knots, including the one used to tie them together.   Another example is if you put 2 male and 2 female rabbits in a cage-- pretty soon you will see numbers way larger than 5.   I'm pretty sure that most people who experience these situations in real life can make the distinction between the messiness of reality and the related arithmetic though.

But that last example brings us back around to the quote that started this whole thing.   Ironically, my web searching did not succeed in uncovering the source of the clever comparison between life and making two plus two equal five.   Most likely I didn't remember the phrasing exactly right, or else someone was just coining this on the fly and it didn't really come from a famous quote.   If you have heard it before and know its origin, please send me an email!

And this has been your math mutation for today,


Sunday, June 21, 2015

209: Wheels That Aren't Round

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Most of us are generally familiar with the concept that wheels are usually round.   But do they have to be this way?    What are the properties that make a round wheel useful?   Yes, you might think that eight years of math podcasting has finally driven me insane, to question something so obvious.     But math geeks are famous for requiring proofs of the obvious-- and this is a case where common instincts might lead us astray.   Now of course, for a wide variety of reasons, circular shapes do tend to make the best wheels.     In certain cases, though, there is a more general class of figures that can be substituted for the circular shape, with some important real-life applications.   These are known as curves of constant width.

To simplify the discussion and avoid the complications of axles, let's discuss simple rollers. Suppose you want to smoothly roll a large plank across the top of a bunch of logs.   If the logs have a circular cross section, it's pretty obvious that the plank can roll  smoothly along, without wobbling up and down.    But what is the property that enables this?   The reason for the plank's smooth rolling is that the circle is a curve of constant width.    This means that if you put parallel lines above and below a circle and touching it, the distance will be a constant, the diameter of a circle.    However, a surprising fact discovered by Euler in the 18th century is that there are many other curves of constant width that could be used instead and still allow smooth rolling.

The most famous non-circular curve in this class is known as the Reuleaux Triangle, a kind of equilateral triangle with rounded edges.   To create one, start with an ordinary equilateral triangle.  Then, for each vertex, replace the opposite side with the arc of a circle whose center is that vertex, and whose radius matches the side of the triangle.   If you think about it for a minute, you should see that this curve will be of constant diameter:   if a plank is rolling over the top, at any given moment either the plank or the ground will be touching a vertex, and the opposite surface will be touching a curved edge.    Since the circle used to form that curved edge is defined as the set of points equidistant from its center, the opposite vertex in this case, the distance between the plank and the ground will be a constant value equal to the circle's radius.    Thus, logs with a Reuleaux cross section will be rolled over just as smoothly as circular ones.   

As you can probably see from how we constructed it, the Reuleaux Triangle is just one representative of a large class of curves of constant width.   Take any regular polygon with an odd number of sides, and replace side opposite each vertex with an arc of a circle centered at that vertex.   There are also many other curves in this class, with more complicated construction methods; you can read up on these in the show notes if you're curious.

The surprising discovery of this large class of shapes has led to some useful real-life applications.   Reuleaux, the 19th-century engineer for whom the triangle is named (despite Euler's earlier knowledge of it), became famous for investigating a variety of uses based on converting circular into other types of motion.   Later this led to applications in mechanisms as diverse as film projectors and automotive engines.   Since a rotating Reuleaux triangle traces a shape that is nearly square, it has also been used to construct a special drill bit that enables woodworkers to drill square holes.     By basing the drill on other curves of constant width, a similar method can be used to drill pentagon, hexagon, or octagon-shaped holes as well.     This shape has also been used in the design of pencils, with the claim that the constant diameter but non-circular shape provide a comfortable grip while reducing the chance of spontaneously rolling off a table.      And in several countries, non-circular curves of constant width have been used as the shape of coins, with their constant diameter providing advantages in the design of vending machines.   You can see nice pictures of these and other applications at the links in the show notes.

But one of the most useful aspects of the Reuleaux Triangle and related shapes is as a non-circular counterexample, forcing us to question basic assumptions about simple geometric properties.   According to some sources, engineers working on the doomed space shuttle Challenger tried to verify the cylindrical shape of some components by measuring their width at various sampling points, not being aware of the existence of non-circular curves of constant diameter.    Too bad they didn't have math podcasts back then, though techncially the engineers could have read Martin Gardner's classic essay on the topic.    Anyway, if the shapes were not circular, this would mean that various types of stress would affect the parts unevenly.   This may have contributed to the shuttle's eventual destruction.

So, be sure to think about the existence of these non-circular curves of constant width, next time you are assembling a mechanical device, minting your nation's currency, or designing a space shuttle.

And this has been your math mutation for today.


Sunday, May 24, 2015

208: Your Kids Are Smarter Than You

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Before we start, I'd like to thank listeners Don-e Merson and Seasoncolor, who have posted some more nice reviews on iTunes.   Thanks guys!

Now, on to today's topic.   Did you know that, measured by constant standards, the average Intelligence Quotient, or IQ, of the world's population has been steadily increasing as long as it has been measured?  In fact, by today's standards, your great-grandparents most likely would be formally diagnosed as mentally retarded.  It's a little confusing, since the IQ tests are continually re-normalized, so the "average IQ" at  any given time is pegged to 100.   But if we look at the raw test scores and compare them across decades, we see that in every modern industrialized country, the IQ has slowly been creeping upwards.   This effect is known as the Flyyn Effect, named after the New Zealand psychiatrist who first noticed it in the 1980s.  This seems pretty surprising-- could our entire population really be steadily increasing its intelligence?  

When I first heard about this effect, I was a bit skeptical.     If you've read Stephen Jay Gould's classic "The Mismeasure of Man", you have learned about all sorts of broken and ridiculous ways in which people have attempted to measure intelligence at various times.   My favorite example was an IQ test from the early 20th century where your intelligence was, in part, dependent on your ability to recall the locations of certain Ivy League colleges.    Even though such egregious examples no longer are likely to appear, you could easily hypothesize that the Flynn Effect was merely measuring the fact that over the past century, kids have been progressively exposed to a lot more miscellaneous trivia first through radio, then TV, growing mass media, and finally on the Internet.   

Even simple things such as the expanding access to books and magazines throughout the 20th century might have contributed; I remember all the hours I spent biking between local used bookstores as a teenager, looking for cool math and science books, and I doubt my father had such an opportunity at his age.   My daughter won't even have to think about such absurdities, having instant access to virtually all major literature published by the human race over the Internet.   But it turns out that the belief that this IQ growth is just measuring access to accumulated factoids is not quite right-- the growth has been very minor in tests dependent on this type of factual knowledge, and is really measuring an increased ability to do abstract reasoning using simple concepts.

In our modern lives, we take the concept of abstraction for granted:  the ability to talk about and compare ideas, rather than just discuss concrete items and actions that are immediately relevant.   And of course all of modern mathematics, including topics we often discuss in this podcast, is dependent on the ability to do this kind of abstraction.   But this is not something to take for granted:  it has been slowly growing in our society from generation to generation.    For example, one of the online articles linked in the show notes talks about a study done on an isolated tribe in Liberia.   They took a bunch of random objects from the village and asked the villagers to sort them into categories.    Instead of sorting into groups of clothing, tools, and food, as we might do, they put items together that were used together, such as a potato with a knife, since the knife is used to cut the potato.     So apparently modern IQ tests are largely measuring our ability to think in abstract categories, and this is the ability that is increasing.   Flynn has argued that we should really label this kind of thinking as "more modern" rather than "more intelligent"-- can we really say objectively that one kind of thinking is better?   However, we probably can say that this modern thinking is a critical component in the explosion of science and technology that we observe in the modern world.

There are numerous theories to try to explain the Flynn Effect.   Most center on social or societal factors.   Perhaps the explosion of media exposure is important not because of miscellaneous factoids, but because of the generally more cognitively complex environment, forcing us to think in abstractions to make sense of the massive bombardment of ideas coming at us from literature, television, and the Internet.   The growth of intellectually demanding work, where more and more of us have jobs that involve at least some thinking rather than pure manual labor, may also contribute.     Another possible factor is the reduced family size in the Western world:  with fewer kids around, each gets more parental attention, and this may foster development of abstract thought.    And of course, in recent years, I'm sure there has been an IQ explosion among the very important subset of the population who listen to Math Mutation.

Aside from social factors, there are more basic physical ones:    basic improvements to health and welfare, such as massively reduced malnutrition and disease, could also be important here.     You may remember that back in podcast 110, "One Intestinal Worm Per Child", we discussed how simple health can have a much bigger effect on educational success than fancy computers.   There is also the theory that we are simply measuring the effects of Darwinian natural selection, where parents with this more modern thinking style are more likely to reproduce, due to coping better in our technological 20th-21st century society.     But most biologists believe that the Flynn effect has set upon us too quickly to be evolution-based.

To further complicate the discussion, some recent studies in Northern Europe seem to show that the Flynn Effect is disappearing or getting reversed.   It's unclear whether this is a real effect, or an artifact of recent population shifts:  over the past two decades, there has been massive immigration from the Third World into these countries, and it could be that we are just measuring the fact that a lot of new immigrants are just in earlier stages of the Flynn Effect treadmill.   But as in every generation, there is no shortage of commentators who can find good reasons why today's young whippersnappers are supposedly getting dumber, such as a focus on repetitive video games and social-network inanity.   We need to contrast this with  their parents' more intellecutal pursuits, such as Looney Tunes and Jerry Springer.

So, what does this all mean?    We certainly do see some effects in society that may very well be partially due to the Flynn Effect, such as the explosion of new technology in recent years.    I think we should do whatever we can to continue making our kids smarter, and enabling more modern and abstract thinking-- though of course, that would be true with or without the Flynn Effect anyway.    Encourage your kids to engage in cognitively complex tasks such as reading lots of books, learning to play a musical instrument, and discussing cool math podcasts.   But when they tell you in a few years that you're going senile, don't take it personally, you really are dumber than they are, due to the Flynn Effect.

And this has been your math mutation for today.