Some of the comics last week don’t leave me much to talk about. Well, there should be another half-dozen comics under review later in the week. You’ll stick around, won’t you please?
Anthony Blades’s Bewley for the 16th is a rerun, and an old friend. It’s appeared the 14th of August, 2016, and in April 2015 and in May 2013. Maybe it’s time I dropped the strip from my reading. The scheme by which the kids got the right answer out of their father is a variation on the Clever Hans trick. Clever Hans was a famous example of animal perception: the horse appeared to be able to do arithmetic, tapping his hoof to signal a number. Brilliant experimental design found what was going on. Not that the horse was clever enough to tell (to make up an example) 18 divided by 3. But that the horse was clever enough to recognize the slight change in his trainer’s expression when he had counted off six. Animals (besides humans) do have some sense of numbers, but not that great a sense.
Jeff Stahler’s Moderately Confused for the 16th is the old joke told about accountants and lawyers when they encounter mathematics, recast to star the future disgraced former president. The way we normally define ‘two’ and ‘plus’ and ‘two’ and ‘equals’ and ‘four’ there’s not room for quibbling about their relationship. Not without just lying, anyway. Thus this satisfies the rules of joke formation.
Olivia Jaimes’s Nancy for the 16th is, I think, the point that Jaimes’s Nancy has appeared in my essays more than Guy Gilchrist’s ever did. Well, different artists have different interests. This one depicts Nancy getting the motivation she needed to excel in arithmetic. I’m not convinced of the pedagogical soundness of the Nancy comic strip. But it’s not as though people won’t practice things for rewards.
The title doesn’t mean anything. My laptop’s random-draw of pictures pulled up one from the county fair last year is all. I’m just working too close to deadline to have a good one. Pet rabbit has surgery scheduled and we are hoping that turns out well for everyone involved.
Jeffrey Caulfield and Alexandre Rouillard’s Mustard and Boloney for the 12th has the blackboard of mathematical symbols. Familiar old shorthand of conflating mathematics ability with genius, or at least intelligence. The blackboard isn’t particularly full of expressions, possibly because Caulfield and Rouillard’s art might not be able to render too much detail clearly. It’s also got a sort-of appearance of Einstein’s most famous equation. Although with perhaps an extra joke to it. Suppose we’re to take ‘E’ and ‘M’ and ‘C’ to mean what they do in Einstein’s use. Then has to equal zero. And there are many things you can safely do with zero. Dividing by it, though, isn’t one. I shan’t guess whether Caulfield and Rouillard were being that sly, though.
Marty Links’s Emmy Lou rerun for the 13th tries to be a paradox. How can one like mathematics without liking figures? But arithmetic is just one part of mathematics. Surely the most-used part, if we go by real-world utility. But not everything. Arithmetic is often useful, yes. But you can do good work in (say) logic or knot theory or geometry with only a slight ability to add or subtract or multiply. There’s not enough emphasis put on that in early education. I suppose it reflects the reasonable feeling that people do need to be competent at arithmetic, which is useful. But it gives one a distorted view of what mathematics can be.
Mark Parisi’s Off The Markfor the 13th is the anthropomorphic numerals joke for the week. And it presents being multiplied by zero as a terrifying fate for other numbers. This seems to reflect the idea that being multiplied by zero is equivalent to being made into nothing. That it’s being killed. Zero enjoys this dual meaning, culturally, representing both a number and the concept of a thing that doesn’t exist and the concept of non-existence. If being turned from one number to another is a numeral murder, then a 2 sneaking in with a + sign would be at least as horrifying. But that joke wouldn’t work, and I know that too.
Olivia Jaimes’s Nancy for the 14th is another recreational-mathematics puzzle. I know nothing of Jaimes’s background but apparently it involves a keen interest in that kind of play that either makes someone love or hate mathematics. (Myself, I’m only slightly interested in these kinds of puzzles, most of the time.) This one — add one line to ‘fix’ the equation 5 + 5 + 5 + 5 = 555 — I hadn’t encountered before. Took some fuming to work it out. The obvious answer, of course, is to add a slash across the = sign so that it means “does not equal”.
But that answer’s dull. What mathematicians like are statements that are true and interesting. There are many things that 5 + 5 + 5 + 5 does not equal. Why single out 555 from that set? So negating the equals sign meets the specifications of the problem, slightly better than Nancy does herself. It doesn’t have the surprise of the answer Nancy’s teacher wants.
If you don’t get how to do it, highlight over the paragraph below for a hint.
There are actually three ways to add the stroke to make this equation true. The three ways are equivalent, though. Notice that the symbols on the board comprise strokes and curves and consider that the meaning of the symbol can be changed by altering the composition of those strokes and curves.
Ted Shearer’s Quincy for the 21st of May, 1979, and rerun the 14th is a joke about making mathematics problems relevant. And, yeah, I’ll give Mrs Glover credit for making problems that reflect stuff students know they’re going to have to deal with. Also that they may have already dealt with and so have some feeling for what plausible answers will be. It’s tough to find many problems like that which don’t repeat themselves too much. (“If your pants need a new patch every two months how many would you have in three years?”).
If we suppose the number whose square we want is then we can find . The calculation on the right-hand side of this is easy; double your number and subtract one. Then to the lookup table; find the angle whose cosine is that number. That angle is two times θ. So divide that angle in two. Cosine of that is, well, and most people would agree that’s a square root of without any further work.
Why can’t I do the same thing with a triple-angle formula? … Well, here’s my choices among the normal trig functions:
Yes, I see you in the corner, hopping up and down and asking about the cosecant. It’s not any better. Trust me.
So you see the problem here. The number whose cube root I want has to be the . Or the cube of the sine of theta, or the cube of the tangent of theta. Whatever. The trouble is I don’t see a way to calculate cosine (sine, tangent) of 3θ, or 3 times the cosine (etc) of θ. Nor to get some other simple expression out of that. I can get mixtures of the cosine of 3θ plus the cosine of θ, sure. But that doesn’t help me figure out what θ is.
Can it be worked out? Oh, sure, yes. There’s absolutely approximation schemes that would let me find a value of θ which makes true, say,
But: is there a way takes less work than some ordinary method of calculating a cube root? Even if you allow some work to be done by someone else ahead of time, such as by computing a table of trig functions? … If there is, I don’t see it. So there’s another point in favor of logarithms. Finding a cube root using a logarithm table is no harder than finding a square root, or any other root.
If you’re using trig tables, you can find a square root, or a fourth root, or an eighth root. Cube roots, if I’m not missing something, are beyond us. So are, I imagine, fifth roots and sixth roots and seventh roots and so on. I could protest that I have never in my life cared what the seventh root of a thing is, but it would sound like a declaration of sour grapes. Too bad.
If I have missed something, it’s probably obvious. Please go ahead and tell me what it is.
The first half of last week’s comics are mostly ones from Comics Kingdom and Creators.com. That’s unusual. GoComics usually far outranks the other sites. Partly for sheer numbers; they have an incredible number of strips, many of them web-only, that Comics Kingdom and Creators.com don’t match. I think the strips on GoComics are more likely to drift into mathematical topics too. But to demonstrate that would take so much effort. Possibly any effort at all. Hm.
Bill Holbrook’s On the Fastrack for the 8th of July is premised on topographic maps. These are some of the tools we’ve made to understand three-dimensional objects with a two-dimensional representation. When topographic maps come to the mathematics department we tend to call them “contour maps” or “contour plots”. These are collections of shapes. They might be straight lines. They might be curved. They often form a closed loop. Each of these curves is called a “contour curve” or a “contour line” (even if it’s not straight). Or it’s called an “equipotential curve”, if someone’s being all fancy, or pointing out the link between potential functions and these curves.
Their purpose is in thinking of three-dimensional surfaces. We can represent a three-dimensional surface by putting up some reasonable coordinate system. For the sake of simplicity let’s suppose the “reasonable coordinate system” is the Cartesian one. So every point in space has coordinates named ‘x’, ‘y’, and ‘z’. Pick a value for ‘x’ and ‘y’. There’s at most one ‘z’ that’ll be on the surface. But there might be many sets of values of ‘x’ and ‘y’ together which have that height ‘z’. So what are all the values of ‘x’ and ‘y’ which match the same height ‘z’? Draw the curve, or curves, which match that particular value of ‘z’.
Topographical maps are a beloved example of this, to mathematicians, because we imagine everyone understands them. A particular spot on the ground at some given latitude and longitude is some particular height above sea level. OK. Imagine the slice of a hill representing all the spots that are exactly 10 feet above sea level, or whatever. That’s a curve. Possibly several curves, but we just say “a curve” for simplicity.
A topographical map will often include more than one curve. Often at regular intervals, say with one set of curves representing 10 feet elevation, another 20 feet, another 30 feet, and so on. Sometimes these curves will be very near one another, where a hill is particularly steep. Sometimes these curves will be far apart, where the ground is nearly level. With experience one can learn to read the lines and their spacing. One can see where extreme values are, and how far away they might be.
Topographical maps date back to 1789. These sorts of maps go back farther. In 1701 Edmond Halley, of comet fame, published maps showing magnetic compass variation. He had hopes that the difference between magnetic north and true north would offer a hint at how to find longitude. (The principle is good. But the lines of constant variation are too close to lines of latitude for the method to be practical. And variation changes over time, too.) And that shows how the topographical map idea can be useful to visualize things that aren’t heights. Weather maps include “isobars”, contour lines showing where the atmospheric pressure is a set vale. More advanced ones will include “isotherms”, each line showing a particular temperature. The isobar and isotherm lines can describe the weather and how it can be expected to change soon.
This idea, rendering three-dimensional information on a two-dimensional surface, is a powerful one. We can use it to try to visualize four-dimensional objects, by looking at the contour surfaces they would make in three dimensions. We can also do this for five and even more dimensions, by using the same stuff but putting a note that “D = 16” or the like in the corner of our image. And, yes, if Cartesian coordinates aren’t sensible for the problem you can use coordinates that are.
If you need a generic name for these contour lines that doesn’t suggest lines or topography or weather or such, try ‘isogonal curves’. Nobody will know what you mean, but you’ll be right.
Ted Key’s Hazel for the 9th is a joke about the difficulties in splitting the bill. It is archetypical of the sort of arithmetic people know they need to do in the real world. Despite that at least people in presented humor don’t get any better at it. I suppose real-world people don’t either, given some restaurants now list 15 and 20 percent tips on the bill. Well, at least everybody has a calculator on their phone so they can divide evenly. And I concede that, yeah, there isn’t really specifically a joke here. It’s just Hazel being competent, like the last time she showed up here.
Mark Anderson’s Andertoons for the 11th is the Mark Anderson’s Andertoons for the week. And it’s a bit of geometry wordplay, too. Also about how you can carry a joke over well enough even without understanding it, or the audience understanding it, if it’s delivered right.
Rick DeTorie’s One Big Happy for the 11th is another strip about arithmetic done in the real world. I’m also amused by Joe’s attempts to distract from how no kid that age has ever not known precisely how much money they have, and how much of it is fairly won.
Bill Griffith’s Zippy the Pinhead for the 11th is another example of using understanding algebra as a show of intelligence. And it follows that up with undrestanding quantum physics as a show of even greater intelligence. One can ask what’s meant by “understanding” quantum physics. Someday someone might even answer. But it seems likely that the ability to do calculations based on a model has to be part of fully understanding it.
I apologize for not having a more robust introduction here. My week’s been chopped up by concern with the health of the older of our rabbits. Today’s proved to be less alarming than we had feared, but it’s still a lot to deal with. I appreciate your kind thoughts. Thank you.
Meanwhile the comics from last week have led me to discover something really weird going on with the Mutt and Jeff reruns.
Charles Schulz’s Peanuts Classics for the 6th has the not-quite-fully-formed Lucy trying to count the vast. She’d spend a while trying to count the stars and it never went well. It does inspire the question of how to count things when doing a simple tally is too complicated. There are many mathematical approaches. Most of them are some kind of sampling. Take a small enough part that you can tally it, and estimate the whole based on what your sample is. This can require ingenuity. For example, when estimating our goldfish population, it was impossible to get a good sample at one time. When tallying the number of visible stars in the sky, we have the problem that the Galaxy has a shape, and there are more stars in some directions than in others. This is why we need statisticians.
Zach Weinersmith’s Saturday Morning Breakfast Cereal for the 6th looks initially like it’s meant for a philosophy blog’s Reading the Comics post. It’s often fruitful in the study of ethics to ponder doing something that is initially horrible, but would likely have good consequences. Or something initially good, but that has bad effects. These questions challenge our ideas about what it is to do good or bad things, and whether transient or permanent effects are more important, and whether it is better to be responsible for something (or to allow something) by action or inaction.
It comes to mathematics in the caption, though, and with an assist from the economics department. Utilitarianism seems to offer an answer to many ethical problems. It posits that we need to select a primary good of society, and then act so as to maximize that good. This does have an appeal, I suspect even to people who don’t thrill of the idea of finding the formula that describes society. After all, if we know the primary good of society, why should we settle for anything but the greatest value of that good? It might be difficult in practice, say, to discount the joy a musician would bring over her lifetime with her performances fairly against the misery created by making her practice the flute after school when she’d rather be playing. But we can imagine working with a rough approximation, at least. Then the skilled thinkers point out even worse problems and we see why utilitarianism didn’t settle all the big ethical questions, even in principle.
The mathematics, though. As Weinersmith’s caption puts it, we can phrase moral dilemmas as problems of maximizing evil. Typically we pose them as ones of maximizing good. Or at least of minimizing evil. But if we have the mechanism in place to find where evil is maximized, don’t we have the tools to find where good is? If we can find the set of social parameters x, y, and z which make E(x, y, z) as big as possible, can’t we find where -E(x, y, z) is as big, too? And isn’t that then where E(x, y, z) has to be smallest?
And, sure. As long as the maximum exists, or the minimum exists. Maybe we can tell whether or not there is one. But this is why when you look at the mathematics of finding maximums you realize you’re also doing minimums, or vice-versa. Pretty soon you either start referring to what you find as extremums. Or you stop worrying about the difference between a maximum and a minimum, at least unless you need to check just what you have found. Or unless someone who isn’t mathematically expert looks at you wondering if you know the difference between positive and negative numbers.
Bud Fisher’s Mutt and Jeff for the 7th has run here before. Except that was before they redid the lettering; it was a roast beef in earlier iterations. I was thinking to drop Mutt and Jeff from my Reading the Comics routine before all these mysteries in the lettering turned up. Anyway. The strip’s joke starts with a work-rate problems. Given how long some people take to do a thing, how long does it take a different number of people to do a thing? These are problems that demand paying attention to units, to the dimensions of a thing. That seems to be out of fashion these days, which is probably why these questions get to be baffling. But if eating a ham takes 25 person-minutes to do, and you have ten persons eating, you can see almost right away how long to expect it to take. If the ham’s the same size, anyway.
Olivia Jaimes’s Nancy for the 7th is built on a spot of recreational mathematics. Also on the frustration one can have when a problem looks like it’s harmless innocent fun and turns out to take just forever and you’re never sure you have the answers just right. The commenters on GoComics.com have settled on 18. I’m content with that answer.
Sunday’s comics post got me thinking about ways to calculate square roots besides using the square root function on a calculator. I wondered if I could find my own little approach. Maybe something that isn’t iterative. Iterative methods are great in that they tend to forgive numerical errors. All numerical calculations carry errors with them. But they can involve a lot of calculation and, in principle, never finish. You just give up when you think the answer is good enough. A non-iterative method carries the promise that things will, someday, end.
And I found one! It’s a neat little way to find the square root of a number between 0 and 1. Call the number ‘S’, as in square. I’ll give you the square root from it. Here’s how.
First, take S. Multiply S by two. Then subtract 1 from this.
Next. Find the angle — I shall call it 2A — whose cosine is this number 2S – 1.
You have 2A? Great. Divide that in two, so that you get the angle A.
Now take the cosine of A. This will be the (positive) square root of S. (You can find the negative square root by taking minus this.)
Let me show it in action. Let’s say you want the square root of 0.25. So let S = 0.25. And then 2S – 1 is two times 0.25 (which is 0.50) minus 1. That’s -0.50. What angle has cosine of -0.50? Well, that’s an angle of 2 π / 3 radians. Mathematicians think in radians. People think in degrees. And you can do that too. This is 120 degrees. Divide this by two. That’s an angle of π / 3 radians, or 60 degrees. The cosine of π / 3 is 0.5. And, indeed, 0.5 is the square root of 0.25.
I hear you protesting already: what if we want the square root of something larger than 1? Like, how is this any good in finding the square root of 81? Well, if we add a little step before and after this work, we’re in good shape. Here’s what.
So we start with some number larger than 1. Say, 81. Fine. Divide it by 100. If it’s still larger than 100, divide it again, and again, until you get a number smaller than 1. Keep track of how many times you did this. In this case, 81 just has to be divided by 100 the one time. That gives us 0.81, a number which is smaller than 1.
Twice 0.81 minus 1 is equal to 0.62. The angle which has 0.81 as cosine is roughly 0.90205. Half this angle is about 0.45103. And the cosine of 0.45103 is 0.9. This is looking good, but obviously 0.9 is no square root of 81.
Ah, but? We divided 81 by 100 to get it smaller than 1. So we balance that by multiplying 0.9 by 10 to get it back larger than 1. If we had divided by 100 twice to start with, we’d multiply by 10 twice to finish. If we had divided by 100 six times to start with, we’d multiply by 10 six times to finish. Yes, 10 is the square root of 100. You see what’s going on here.
(And if you want the square root of a tiny number, something smaller than 0.01, it’s not a bad idea to multiply it by 100, maybe several times over. Then calculate the square root, and divide the result by 10 a matching number of times. It’s hard to calculate with very big or with very small numbers. If you must calculate, do it on very medium numbers. This is one of those little things you learn in numerical mathematics.)
So maybe now you’re convinced this works. You may not be convinced of why this works. What I’m using here is a trigonometric identity, one of the angle-doubling formulas. Its heart is this identity. It’s familiar to students whose Intro to Trigonometry class is making them finally, irrecoverably hate mathematics:
Here, I let ‘S’ be the squared number, . So then anything I do to find gets me the square root. The algebra here is straightforward. Since ‘S’ is that cosine-squared thing, all I have to do is double it, subtract one, and then find what angle 2θ has that number as cosine. Then the cosine of θ has to be the square root.
Oh, yeah, all right. There’s an extra little objection. In what world is it easier to take an arc-cosine (to figure out what 2θ is) and then later to take a cosine? … And the answer is, well, any world where you’ve already got a table printed out of cosines of angles and don’t have a calculator on hand. This would be a common condition through to about 1975. And not all that ridiculous through to about 1990.
This is an example of a prosthaphaeretic rule. These are calculation tools. They’re used to convert multiplication or division problems into addition and subtraction. The idea is exactly like that of logarithms and exponents. Using trig functions predates logarithms. People knew about sines and cosines long before they knew about logarithms and exponentials. But the impulse is the same. And you might, if you squint, see in my little method here an echo of what you’d do more easily with a logarithm table. If you had a log table, you’d calculate instead. But if you don’t have a log table, and only have a table of cosines, you can calculate at least.
Is this easier than normal methods of finding square roots? … If you have a table of cosines, yes. Definitely. You have to scale the number into range (divide by 100 some) do an easy multiplication (S times 2), an easy subtraction (minus 1), a table lookup (arccosine), an easy division (divide by 2), another table lookup (cosine), and scale the number up again (multiply by 10 some). That’s all. Seven steps, and two of them are reading. Two of the rest are multiplying or dividing by 10’s. Using logarithm tables has it beat, yes, at five steps (two that are scaling, two that are reading, one that’s dividing by 2). But if you can’t find your table of logarithms, and do have a table of cosines, you’re set.
This may not be practical, since who has a table of cosines anymore? Who hasn’t also got a calculator that does square roots faster? But it delighted me to work this scheme out. Give me a while and maybe I’ll think about cube roots.
Three of these essays in a row now that Jef Mallett’s Frazz has done something worth responding to. You know, the guy lives in the same metro area. He could just stop in and visit sometime. There’s a pinball league in town and everything. He could view it as good healthy competition.
Bill Hinds’s Cleats for the 1st is another instance of the monkeys-on-typewriters metaphor. The metaphor goes back at least as far as 1913, when Émile Borel wrote a paper on statistical mechanics and the reversibility problem. Along the way it was worth thinking of the chance of impossibly unlikely events, given enough time to happen. Monkeys at typewriters formed a great image for a generator of text that knows no content or plan. Given enough time, this random process should be able to produce all the finite strings of text, whatever their content. And the metaphor’s caught people’s fancy I guess there’s something charming and Dadaist about monkeys doing office work. Borel started out with a million monkeys typing ten hours a day. Modern audiences sometimes make this an infinite number of monkeys typing without pause. This is a reminder of how bad we’re allowing pre-revolutionary capitalism get.
Sometimes it’s cut down to a mere thousand monkeys, as in this example. Often it’s Shakespeare, but sometimes it’s other authors who get duplicated. Dickens seems like a popular secondary choice. In joke forms, the number of monkeys and time it would take to duplicate something is held as a measure of the quality of the original work. This comes from people who don’t understand. Suppose the monkeys and typewriters are producing truly random strings of characters. Then the only thing that affects how long it takes them to duplicate some text is the length of the original text. How good the text is doesn’t enter into it.
Jef Mallett’s Frazz for the 1st is about the comfort of knowing about things one does not know. And that’s fine enough. Frazz cites Fermat’s Last Theorem as a thing everyone knows of but doesn’t understand. And that choice confuses me. I’m not sure what there would be to Fermat’s Last Theorem that someone who had heard of it would not understand. The basic statement of it — if you have three positive whole numbers a, b, and c, then there’s no whole number n larger than 2 so that equals — has it.
But “understanding” is a flexible concept. He might mean that people don’t know why the Theorem is true. Fair enough. Andrew Wiles and Richard Taylor’s proof is a long thing that goes deep into a field of mathematics that even most mathematicians don’t study. Why it should be true can be an interesting question, and one that’s hard to ever satisfyingly answer. What is the difference between a proof that something is true and an explanation for why it’s true? And before you say there’s not one, please consider that many mathematicians do experience a difference between seeing something proved and understanding why something is true.
And Frazz might also mean that nobody knows what use Fermat’s Last Theorem is. This is a fair complaint too. I’m not aware offhand of any interesting results which follow from its truth, nor of anything neat that would come about had it been false. It’s just one of those things that happens to be true, and that we’ve found to be pretty, perhaps because it is easy to ask whether it’s true and hard to answer. I don’t know.
Morrie Turner’s Wee Pals for the 2nd has a kid looking for a square root. We all have peculiar hobbies. His friends speak of it as though it’s a lost physical object. This is a hilarious misunderstanding until it strikes you that we speak about stuff like square roots “existing”. Indeed, the language of mathematics would be trashed if we couldn’t speak about numerical constructs “existing” somewhere to be “found”. But try to put “four” in a box and see what you get. That we mostly have little trouble understanding what we mean by showing some mathematical construct exists, and what we hope to do by looking for it, suggests we roughly know what we mean by the phrases. All right then; what is that, in terms a kid could understand?
There are many ways to numerically compute a square root, if you have to do it by hand and it isn’t a perfect square. My preference is for iterative methods, in which you start with a rough guess and try to improve things. One good enough method for we call the Babylonian method, reflecting how old we think it is. Start with your number S whose square root you want. And start with a number x0, a first guess for what the square root is. This can be anything. The great thing about iterative methods is even if you start with a garbage answer, you get to a good answer soon enough. Still, if you have a suspicion of what the square root should be, start there.
Your first iteration, the first guess for a better answer, is to calculate the number . Typically, x1 will be closer to the square root of S than will x0 be. And in any case, we can get closer still. Use x1 to calculate a new number. This is . And then x3 and x4 and x5 and so on. In theory, you never finish; you’re stuck finding an infinitely long sequence of better approximations to the square root. In practice, you finish; you find that you’re close enough to the square root. Well, the square root of a whole number is either a whole number (if it was a perfect square to start) or is an irrational number. You were going to stop on an approximation sooner or later.
The method requires doing division. Long division, too, after the first couple steps. I don’t know a way around that which doesn’t divert into something less pleasant, such as logarithms and exponentials. Or maybe into trigonometric functions. This can be tedious to do by hand. Great thing, though, is if you make a mistake? That’s kind of all right. The next iteration will (usually) correct for it. That’s the glory of iterative methods. They tend to be forgiving of numerical error, whatever its source. Another iteration reduces, or even eliminates, the mistake of the previous iteration.
For more of these Reading the Comics posts please follow this link. If you’re only interested in Reading the Cleats strips, please use this link instead. But Cleats is a new tag this essay, so for now, there aren’t others. If you’re hoping to see all my Reading the Comics posts about Frazz, try this link. If you’d like more of my essays which mention Wee Pals, you can use this link. And if you’d like more Reading the Comics posts that mention Harley, use this link. That’s another new tag, but I believe Dan Thompson is still making new examples of the strip. So it may appear again.
The last half of last week was not entirely the work of Chuckle Brothers and Saturday Morning Breakfast Cereal. It seemed like it, though. Let’s review.
Patrick Roberts’s Todd the Dinosaur for the 28th is a common sort of fear-of-mathematics joke. In this case the fear of doing arithmetic even when it is about something one would really like to know. I think the question got away from Todd, though. If they just wanted to know whether they had enough money, well, they need twelve dollars and have seven. Subtracting seven from twelve is only needed if they want to know how much more they need. Which they should want to know, but wasn’t part of the setup.
Brian Boychuk and Ron Boychuk’s The Chuckle Brothers for the 28th uses mathematics as the sine qua non of rocket science. As in, well, the stuff that’s hard and takes some real genius to understand. It’s not clear to me that the equations are actually rocket science. There seem to be a shortage of things in exponentials to look quite right to me. But I can’t zoom in on the art, so, who knows just what might be in there.
Zach Weinersmith’s Saturday Morning Breakfast Cereal for the 28th is a set theory joke. Or a logic joke, anyway. It refers to some of the mathematics/logic work of Bertrand Russell. Among his work was treating seriously the problems of how to describe things defined in reference to themselves. These have long been a source of paradoxes, sometimes for fun, sometimes for fairy-tale logic, and sometimes to challenge our idea of what we mean by definitions of things. Russell made a strong attempt at describing what we mean when we describe a thing by reference to itself. The iconic example here was the “set of all sets not members of themselves”.
Russell started out by trying to find some way to prove Georg Cantor’s theorems about different-sized infinities wrong. He worked out a theory of types, and what kinds of rules you can set about types of things. Most mathematicians these days prefer to solve the paradox with a particular organization of set theory. But Russell’s type theory still has value, particularly as part of the logic behind lambda calculus. This is an approach to organizing relationships between things that can do wonderful things, including in computer programming. It lets one write code that works extremely efficiently and can never be explained to another person, modified, or debugged ever. I may lack the proper training for the uses I’ve made of it.
Brian Boychuk and Ron Boychuk’s The Chuckle Brothers for the 29th is a lottery joke. It does happen that more than one person wins a drawing; sometimes three or even four people do, for the larger prizes. The chance that there’s a million winners? Frightfully unlikely unless something significant went wrong with the lottery mechanism.
So what are the chances of a million lottery winners? If I’m not mistaken the only way to do this is to work out a binomial distribution. The binomial distribution is good for cases where you have many attempts at doing a thing, where each thing can either succeed or fail, and the likelihood of success or failure is independent of all the other attempts. In this case each lottery ticket is an attempt; it winning is success and it losing is failure. Each ticket has the same chance of winning or losing, and that chance doesn’t depend on how many wins or losses there are. What is that chance? … Well, if each ticket has one chance in a million of winning, and there are a million tickets out there, the chance of every one of them winning is about one-millionth raised to the millionth power. Which is so close to zero it might as well be nothing. … And yet, for all that it’s impossible, there’s not any particular reason it couldn’t happen. It just won’t.
Jef Mallet’s Frazz for the 29th is a less dire take on what-you-learned-this-year. In this case it’s trivia, but it’s a neat sort of trivia. Once you understand how it works you can understand how to make all sorts of silly little divisibility rules. The threes rule — and the nines rule — work by the same principle. Suppose you have a three-digit number. Let me call ‘a’ the digit in the hundreds column, ‘b’ the digit in the tens column, and ‘c’ the digit in the ones column. Then the number is equal to . And, well, that’s equal to . Which is . 99 times any whole number is a multiple of 9, and also of 3. 9 times any whole number is a multiple of 9, and also of 3. So whether the original number is divisible by 9, or by 3, depends on whether is. And that’s why adding the digits up tells you whether a number is a whole multiple of three.
This has only proven anything for three-digit numbers. But with that proof in mind, you probably can imagine what the proof looks like for two- or four-digit numbers, and would believe there’s one for five- and for 500-digit numbers. Or, for that matter, the proof for an arbitrarily long number. So I’ll skip actually doing that. You can fiddle with it if you want a bit of fun yourself.
Also maybe it’s me, or the kind of person who gets into mathematics. But I find silly little rules like this endearing. It’s a process easy to understand that anyone can do and it tells you something not obvious from when you start. It feels like getting let in on a magic trick. That seems like the sort of thing that endears people to mathematics.
Mike Thompson’s Grand Avenue for the 29th is trying to pick its fight with me again. I can appreciate someone wanting to avoid kids losing their mathematical skills over summer. It’s just striking how Thompson has consistently portrayed their grandmother as doing this in a horrible, joy-crushing manner.
Zach Weinersmith’s Saturday Morning Breakfast Cereal for the 29th gets into a philosophy-of-mathematics problem. Also a pure philosophy problem. It’s a problem of what things you can know independently of experience. There are things it seems as though are true, and that seem independent of the person who is aware of them, and what culture that person comes from. All right. Then how can these things be relevant to the specifics of the universe that we happen to be in just now? If ‘2’ is an abstraction that means something independent of our universe, how can there be two books on the table? There’s something we don’t quite understand yet, and it’s taking our philosophers and mathematicians a long while to work out what that is.
I’ve broken the habit of watching my WordPress readership statistics day-to-day. This is good. It’s too easy to read random fluctuations as significant changes. And to go from that to supposing that everyone’s decided they hate me now. I do still check monthly. And I try to think what I can learn from that data. Not too hard, and not enough to change what I do. But to where I might think I learned something.
I had another 12-post month. As seems to keep happening I started out with an ambitious program of the weekly Reading the Comics posts, finishing up a couple of open-ended essay threads, and then a few drop-ins as I ran across something interesting. And then my days got all busy and stuff demanded my attention and all I had time for was the comics posts after all. It turned out mostly all right, though. Here’s just how all right:
So for the sixth month running I beat a thousand page views. Came in at 1,077. It’s my thinnest margin since back in February when there were a mere 1,062 page views. Still, I had a more than this large comfortable round number of page views. The number of unique visitors dropped also, to 681. That’s my lowest number of visitors since February again. But that just seems to reflect there being less traffic overall in June; the number of views per visitor was 1.58, basically the same as May’s 1.52 and April’s 1.53. No archive-divers here, seems.
There were 94 things liked in June; that’s up from April’s and May’s 73, and down from March’s 142. There were 30 comments posted in June, up from May’s 17 and April’s 13, but down from March’s 53. All respectable enough; none exactly suggesting I know how to write stuff people love to share or comment on. Which is on me, of course; no reader’s got the job of responding to stuff they don’t care to.
The popular posts were nearly what I would have guessed: the Buggles and some comics stuff. But there were surprises even in the top five:
So I’m surprised that last month’s readership review post would be among the most popular. I guess it shows the value of having any picture at all, however marginally interesting, in a post. Still seems dangerously self-absorbed. The non-Euclidean geometry one also surprises me, since it was only up for two days and still got as many readers as anything else posted in June. The lesson here, I suppose, is that people love seeing me not know stuff that’s obvious to people familiar with a topic. This is promising for future essays, though, since there are so many obvious things I don’t know.
Then there’s the list of countries that sent me readers to include, since that’s apparently a thing people like:
Hong Kong SAR China
United Arab Emirates
There were 55 countries sending me any readers, down from 58 for three months in a row. There were 19 single-reader countries, down from 22 in May, up from 14 in April. Brunei and South Korea were single-reader countries two months in a row. Serbia’s had a single reader for me four months in a row now.
The Insights panel tells me July started with this blog having had 63,897 total page views, from an admitted 31,020 unique visitors. It logs for the year 2018 a total of 78 posts that attracted, to that point, 196 comments. And that there had been 535 total likes given to something over the year so far. This comes to an average of 2.5 comments per post, and 6.8 likes per posting. By the end of May I had gotten only 2.4 comments and 6.7 likes per post, so, at least I’ve got something figured out.
By the end of June I had posted 69,051 words as WordPress logs things; that’s 13,374 words over June, a bit more than I posted over May despite June being the shorter month. I’m up to an average of 885.3 words per post; at the end of May I was at a mere 843.6 words per post. The trend is obvious; by the end of the year I’ll just never stop writing things. You’ll just see a continuous feed of me putting more heaps of words onto this pile. You’ll be shocked how many times and how many different ways I can type ‘that’ wrong and correct it. Or how often an ‘of course’ creeps into my writing and I have to edit that out.
As ever, I encourage you to read this post and more like it. You can add this page to your WordPress reader by using the button at the upper-right corner of this page. This link is the RSS feed, which gets all my posts as they’re posted, and which you can add to your RSS reader without my ever knowing about. I’m @Nebusj on Twitter. If you see me on Tumblr you’ve found a hoax, since I’m not on Tumblr and every time I look at it I feel helpless and confused.
For a while I thought this essay would include only the mathematically-themed strips which Comic Strip Master Command sent out through to June 26th, which is picking up the nickname Stitch Day (for 6-26, the movie character’s experiment number). And then I decided some from last Sunday weren’t on-point enough (somehow), and there were enough that came later in the week that I couldn’t do a June 26th Only edition. Which is my longwinded way of saying this one doesn’t have a nonsense name. It just has a name that’s only partially on point.
Mike Baldwin’s Cornered for the 26th is the Rubik’s Cube/strange geometry joke for the week. It seems to me I ought to be able to make some link between the number of various ways to arrange a Rubik’s Cube — which pieces can and which ones cannot be neighbors to a red piece, say, no matter how one scrambles the cube — and the networking between people that you can get from an office where people have to see each other. But I’m not sure that I can make that metaphor work. I’m blaming the temperature, both mine (I have a cold) and the weather’s (it’s a heat wave).
Mark Leiknes’s Cow and Boy for the 26th makes literal the trouble some people have with the phrase “110 percent”. Read uncharitably, yes, “110 of a hundred” doesn’t make sense, if 100 percent is all that could conceivably be of the thing. But if we can imagine, say, the number of cars passing a point on the highway being 90 percent of the typical number, surely we can imagine the number of cars also being 110 percent. To give an example of why I can’t side with pedants in objecting to the phrase.
Jef Mallett’s Frazz for the 26th is just itching for a fight. From me and from the Creative Writing department. Yes, mathematics rewards discipline. All activities do. At the risk of making a prescription: if you want to do something well, spend time practicing the boring parts. For arithmetic, that’s times tables and regrouping calculations and factoring and long division. For writing, that’s word choice and sentence structure and figuring how to bring life to describing dull stuff. Do the fun stuff too, yes, but because it is fun. Getting good at the boring stuff makes you an expert. When you discover that the boring stuff is also kinda fun, you will do the fun stuff masterfully.
But to speak of mathematics as pursuing a single right answer — well, perhaps. In an elementary-school problem there is typically just the one right answer, and the hope is that students learn how to get there efficiently. But if the subject is something well-worn, then there are many ways to do any problem. All are legitimate and the worst one can say of a method is maybe it’s not that efficient, or maybe it’s good here but doesn’t generally work. If the subject is on the edge of what mathematics we know, there may be only one way to get there. But there are many things to find, including original ways to understand what we have already found. To not see that mathematics is creative is to not see mathematics. Or, really, any field of human activity.
Samson’s Dark Side of the Horse for the 27th edges up to being the anthropomorphic numerals joke for the week. I need a good name for this sort of joke about mathematical constructs made tangible, even if they aren’t necessarily characters.
So. A “graph” is a thing that’s turned up in my A To Z serieses. In this context a graph is a collection of points, called “vertices”, and a collection of “edges” that connect vertices. Often the vertices represent something of interest and the edges ways to turn one thing into another. Sometimes the edges are the thing of interest and the vertices are just there to be manipulated in some way by edges. It’s a way to make visual the studying of how stuff is connected, and how things can pass from one to another.
A “stochastic process” is about random variables. Random variables are some property about a system. And you know some things about that variable’s value. You know maybe the range of possible values it could have. You know whether some values are more likely than others. But you do not know what the value is at any particular moment. Consider, say, the temperature outside where you live at a particular time of day. You may have no idea what that is. But you can say, for example, whether today it is more likely to be 90 degrees Fahrenheit or 60 degrees Fahrenheit or 20 degrees Fahrenheit. For a stochastic process we have some kind of index. We can say, for example, which values of temperature are more likely today, the 1st of July, and which ones will be more likely the 1st of August, and which ones will be less likely the 1st of December. Calling it a “process”, to my intuition, makes it sound like we expect something to happen that causes the likelihood of some temperatures to change. And many processes are time-indexed. They study problems where something interesting changes in time, predictable in aggregate but not in detail.
So a graph like this, representing a stochastic process, is a shorthand. Each vertex is a state that something might be in. Each edge is a way to get from one state to another when — something — happens. Doesn’t matter what thing.
A “drunk walk”, or as it’s known to tenderer writers a “random walk”, is a term of art. Not a deep one. It’s meant to evoke the idea of a severely drunk person who yes, can move, but has no control over which way. Thus he wanders around, reaching any point only by luck. Many things look like random walks, in which there is no overall direction, just an unpredictable shuffling around. A drunk walk on this graph would be, well, start at any of the vertices. Then follow edges, chosen randomly. If you start at the uppermost point of the triangle on top, for example, there’s two places to go on the second step: the lower-left or the center-right vertex on the upper triangle. Suppose you go to the center-right vertex. On the next step, you might go right back where you started. You might go to the lower-left vertex on the triangle. You might drop down that bridge to the top of that quadrilateral. And so on, for another step.
Do that some presumably big number of times. Where are you? … Anywhere, of course. But are there vertices you’re more likely to be on? Ones you’re less likely to be on? How does the shape of the graph affect that likelihood? How does how long you spend walking affect that? These tell us things about the process, and are why someone would draw this graph and talk about a random walk on it.
I got a book about the philosophy of mathematics, Stephan Körner’s The Philosophy of Mathematics: An Introductory Essay. It’s a subject I’m interested in, despite my lack of training. Made it to the second page before I got to something that I had to stop and ponder. I thought to share that point and my reflections with you, because if I had to think I may as well get an essay out of it. He lists some pure-mathematical facts and some applied-mathematical counterparts, among them:
(2) any (Euclidean) triangle which is equiangular is also equilateral
(5) if the angles of a triangular piece of paper are equal then its sides are also equal
So where I stopped was: what is the (Euclidean) doing in that first proposition there? Or, its counterpart, about being pieces of paper?
I’m not versed in non-Euclidean geometry. My training brought me to applied-physics applications right away. I never needed a full course in non-Euclidean geometries and have never picked up much on my own. It’s an oversight I’m embarrassed by and I sometimes think to take a proper class. So this bit about equiangular-triangles not necessarily being equilateral was new to me.
Euclidean geometry everyone knows; it’s the way space works on table tops and in normal rooms. Non-Euclidean geometries are harder to understand. It was surprisingly late that mathematicians understood they were legitimate. There are two classes of non-Euclidean geometries. One is “spherical geometries”, the way geometry works … on the surface of a sphere or a squished-out ball. This is familiar enough to people who navigate or measure large journeys on the surface of the Earth. Well. The other non-Euclidean geometry is “hyperbolic geometry”. This is how shapes work on the surface of a saddle shape. It’s familiar enough to … some mathematicians who work in non-Euclidean geometries and people who ride horses. Maybe also the horses.
But! Could someone as amateur as I am in this field think of an equiangular but not equilateral triangle? Hyperbolic geometries seemed sure to produce one. But it’s hard to think about shapes on saddles so I figured to use that only if I absolutely had to. How about on a spherical geometry? And there I got to one of the classic non-Euclidean triangles. Imagine the surface of the Earth. Imagine a point at the North Pole. (Or the South Pole, if you’d rather.) Imagine a point on the equator at longitude 0 degrees. And imagine another point on the equator at longitude 90 degrees, east or west as you like. Draw the lines connecting those three points. That’s a triangle with three right angles on its interior, which is exactly the sort of thing you can’t have in Euclidean geometry.
(Which gives me another question that proves how ignorant I am of the history of mathematics. This is an easy-to-understand example. You don’t even need to be an Age of Exploration navigator to understand it. You only need a globe. Or a ball. So why did it take so long for mathematicians to accept the existence of non-Euclidean geometries? My guess is that maybe they understood this surface stuff as a weird feature of solid geometries, rather than an internally consistent geometry. But I defer to anyone who actually knows something about the history of non-Euclidean geometries to say.)
And that’s fine, but it’s also an equilateral triangle. I can imagine smaller equiangular triangles. Ones with interior angles nearer to 60 degrees each. They have to be smaller, but that’s all right. They all seem to be equilateral, though. The closer to 60 degree angles the smaller the triangle is and the more everything looks like it’s on a flat surface. Like a piece of paper.
So. Hyperbolic geometry, and the surface of a saddle, after all? Oh dear I hope not. Maybe I could look at something else.
So while I, and many people, talk about spherical geometry, it doesn’t have to be literally the geometry of the surface of a sphere. It can be other nice, smooth shapes. Ellipsoids, for example, spheres that have got stretched out in one direction or other. For example, what if we took that globe and stretched it out some? Leave the equatorial diameter at (say) twelve inches. But expand it so that the distance from North Pole to South Pole is closer to 480 miles. This may seem extreme. But one of the secrets of mathematicians is to consider cartoonishly extreme exaggerations. They’re often useful in getting your intuition to show that something must be so.
Ah, now. Consider that North Pole-Equator-Equator triangle I had before. The North-Pole-to-equator-point distance is right about 240 miles. The equator-point-to-other-equator-point distance is more like nine and a half inches. Definitely not equilateral. But it’s equiangular; all the interior angles are 90 degrees still.
My doubts refuted! And I didn’t have to consider the saddle shape. Very good. “Euclidean” is doing some useful work in that proposition. And the specification that the triangles are pieces of paper does the same work.
And yes, I know that all the real mathematicians out there are giggling at me. This has to be pretty near the first thing one learns in non-Euclidean geometry. It’s so easy to run across, and it so defies ordinary-world intuition. I ought to take a class.
Please let it not be a big milkshake duck. I can’t take it if it is.
Larry Wright’s Motley for the 21st uses mathematics as emblem of impossibly complicated stuff to know. I’m interested to see that biochemistry was also called in to represent something that needs incredible brainpower to know things that can be expressed in one panel. Another free little question: what might “2,368 to the sixth power times pi” be an answer to? The obvious answer to me is “what’s the area of a circle of radius 2,368 to the third power”. That seems like a bad quiz-show question to me, though. It tests a legitimate bit of trivia, but the radius is such an ugly number. There are some other obvious questions that might fit, like “what is the circumference of a circle of radius [ or diameter ] of (ugly number here)?” Or “what is the volume of a circle of radius (similarly ugly number here)?” But the radius (or diameter) of those surfaces would have to be really nasty numbers, ones with radicals of 2,368 — itself no charming number — in it.
And “2,368 to the sixth power times pi” is the answer to infinitely many questions. The challenge is finding one that’s plausible as a quiz-show question. That is it should test something that’s reasonable for a lay person to know, and to calculate while on stage, without pen or paper or much time to reflect. Tough set of constraints, especially to get that 2,368 in there. The sixth power isn’t so easy either.
Well, the biochemistry people don’t have an easy time thinking of a problem to match Debbie’s answer either. “Hydro- ” and “mono- ” are plausible enough prefixes, but as far as I know there’s no “nucleatic acid” to have some modified variant. Wright might have been thinking of nucleic acid, but as far as I know there’s no mononucleic acid, much less hydromononucleic acid. But, yes, that’s hardly a strike against the premise of the comic. It’s just nitpicking.
Charlie Pondrebarac’s CowTown for the 22nd is on at least its third appearance since I started reading the comics for the mathematics stuff regularly. I covered it in June 2016 and also in August 2015. This suggests a weird rerun cycle for the comic. Popping out of Jim Smith’s mouth is the null symbol, which represents a set that hasn’t got any elements. That set is known as the null set. Every set, including the null set, contains a null set. This fact makes set theory a good bit easier than it otherwise would be. That’s peculiar, considering that it is literally nothing. But everything one might want to say about “nothing” is peculiar. That doesn’t make it dispensable.
Julie Larson’s Dinette Set for the 22nd sees the Penny family’s adults bemoaning the calculator their kid needs for middle school. I admit feeling terror at being expected to buy a hundred-dollar calculator for school. But I also had one (less expensive) when I was in high school. It saves a lot of boring routine work. And it allows for playful discoveries about arithmetic. Some of them are cute trivialities, such as finding the Golden Ratio and similar quirks. And a calculator does do essentially the work that a slide rule might, albeit more quickly and with more digits of precision. It can’t help telling you what to calculate or why, but it can take the burden out of getting the calculation done. Still, a hundred bucks. Wow.
Tony Carrillo’s F Minus for the 23rd puts out the breaking of a rule of arithmetic as a whimsical, inexplicable event. A moment of two plus two equalling five, whatever it might do for the structure of the universe, would be awfully interesting for the philosophy of mathematics. Given what we ordinarily think we mean by ‘two’ and ‘plus’ and ‘equals’ and ‘five’ that just can’t happen. And what would it mean for two plus to to equal five for a few moments? Mathematicians often think about the weird fact that mathematical structures — crafted from definitions and logic — describe the real world stunningly well. Would this two plus two equalling five be something that was observed in the real world, and checked against definitions that suddenly allowed this? Would this be finding a chain of reasoning that supported saying two plus two equalled five, only to find a few minutes later that a proof everyone was satisfied with was now clearly wrong?
That’s a particularly chilling prospect, if you’re in the right mood. We like to think mathematical proofs are absolute and irrefutable, things which are known to be true regardless of who knows them, or what state they’re in, or anything. And perhaps they are. They seem to come as near as mortals can to seeing Platonic forms. (My understanding is that mathematical constructs are not Platonic forms, at least in Plato’s view of things. But they are closer to being forms than, say, apples put on a table for the counting would be.) But what we actually know is whether we, fallible beings comprised of meat that thinks, are satisfied that we’ve seen a proof. We can be fooled. We can think something is satisfactory because we haven’t noticed an implication that’s obviously wrong or contradictory. Or because we’re tired and are feeling compliant. Or because we ate something that’s distracting us before we fully understand an argument. We may have a good idea of what a satisfactory logical proof would be. But stare at the idea hard enough and we realize we might never actually know one.
Although the hyperbolic cosine is interesting and I could go on about it.
Eric the Circle for the 18th of June is a bit of geometric wordplay for the week. A secant is — well, many things. One of the important things is it’s a line that cuts across a circle. It intersects the circle in two points. This is as opposed to a tangent, which touch it in one. Or missing it altogether, which I think hasn’t got any special name. “Secant” also appears as one of the six common trig functions out there.
In value the secant of an angle is just the reciprocal of the cosine of that angle. Where the cosine is never smaller than -1 nor larger than 1, the secant is always either greater than 1 or smaller than -1. It’s a useful function to have by name. We can write “the secant of angle θ” as . The otherwise sensible-looking is unavailable, because we use that to mean “the angle whose cosine is θ”. We need to express that idea, the “arc-cosine” or “inverse cosine”, quite a bit too. And would look like we wanted the cosine of one divided by θ. Ultimately, we have a lot of ideas we’d like to write down, and only so many convenient quick shorthand ways to write them. And by using secant as its own function we can let the arc-cosine have a convenient shorthand symbol. These symbols are a point where you see the messy, human, evolutionary nature of mathematical symbols at work.
We can understand the cosine of an angle θ by imagining a right triangle with hypotenuse of length 1. Set that so the hypotenuse makes angle θ with respect to the x-axis. Then the opposite leg of that right triangle will be the cosine of θ away from the origin. The secant, now, that works differently. Again here imagine a right triangle, but this time one of the legs has length 1. And that leg is at an angle θ with respect to the x-axis. Then the far leg of that right triangle is going to cross the x-axis. And it’ll do that at a point that’s the secant of θ away from the origin.
Larry Wright’s Motley Classics for the 19th speaks of algebra as the way to explain any sufficiently complicated thing. Algebra’s probably not the right tool to analyze a soap opera, or any drama really. The interactions of characters are probably more a matter for graph theory. That’s the field that studies groups of things and the links between them. Occasionally you’ll see analyses of, say, which characters on some complicated science fiction show spend time with each other and which ones don’t. I’m not aware of any that were done on soap operas proper. I suspect most mathematics-oriented nerds view the soaps as beneath their study. But most soap operas do produce a lot of show to watch, and to summarize; I can’t blame them for taking a smaller, easier-to-summarize data set to study. (Also I’m not sure any of these graphs reveal anything more enlightening than, “Huh, really thought The Doctor met Winston Churchill more often than that”.)
Dave Whamond’s Reality Check for the 19th is our Venn Diagram strip for the week. I say the real punch line is the squirrel’s, though. Properly, yes, the Venn Diagram with the two having nothing in common should still have them overlap in space. There should be a signifier inside that there’s nothing in common, such as the null symbol or an x’d out intersection. But not overlapping at all is so commonly used that it might as well be standard.
Teresa Bullitt’s Frog Applause for the 21st uses a thought balloon full of mathematical symbols as icon for far too much deep thinking to understand. I would like to give my opinion about the meaningfulness of the expressions. But they’re too small for me to make out, and GoComics doesn’t allow for zooming in on their comics anymore. I looks like it’s drawn from some real problem, based on the orderliness of it all. But I have no good reason to believe that.
My week got busier than I imagined, but it was in ways worthwhile. I apologize for running late, and for not having an essay I meant to put up here this week. But I should be back to something more normal next week. I keep saying that. Also, for what seems like a rarity, all the strips for this essay are comic strips. No panels. That won’t last, I know.
Johnny Hart’s Back to B.C. for the 14th features arithmetic as a demonstration of The Smartest Man in the World’s credentials. I understand using a bit of arithmetic as a quick check that someone has any intelligence at all. It seems to me that checking “two plus two” is more common than “one plus one”, and either is more common than, say, “one plus two” or “three plus five” or anything. I’m curious why that is, though. Might one plus one just seem too simple? Or is it the bias against odd numbers and feeling that two plus two is somehow more balanced? If only there were some smart person I could ask.
Jef Mallett’s Frazz for the 14th has a blackboard full of arithmetic as the icon of “doing a lot of school work”. Can’t say it’s age-inappropriate or anything. It’s just an efficient way to show a lot of work that’s kind of tiring to do has been done. … Also somehow one of the commenters didn’t understand the use of ‘flag’ as meaning to lose energy or enthusiasm. Huh.
Jef Mallett’s Frazz for the 15th is a percentages joke, built on confusion between how to go from percentages to fractions and back again. Must say that I had thought 50 percent was tied well enough to one-half in ordinary language (or in phrases like splitting something fifty-fifty) that someone wouldn’t be confused by that. But everyone does miss some obvious things.
Mark Pett’s Lucky Cow for the 16th is a probability strip. It is based on what seems obvious, that the fact of any person’s existing is an incredibly unlikely event. We can imagine restarting the universe, and letting it all develop again. And we’re forced to conclude there are so many other ways that galaxies might form and stars might come into being and planets might form and life might develop and evolution might proceed and people might meet and children might be born, and only one way that gets us here. So the chance of any of us existing is impossibly tiny. This is all consistent with the “frequentist” idea of what probability means. In that, we say the probability of a thing happening is all the ways that it could happen divided by all the ways that something could happen. (There are a bunch of technical points to go along with this.)
But there are a lot of buried assumptions in there. Many of them seem reasonable. For example: could the universe unfold any differently? It seems obvious that, for example, the radius of the Earth’s orbit around the sun is arbitrary and might be anything in a band that could support life. And, surely, if the year had more or fewer days to it all human history would be different. But then this seems obvious: drop a bunch of short needles across a set of parallel straight lines. The number of needles that cross any of those lines should be arbitrary and unpredictable. Except that it is predictable; there’s a well-known formula that says how many of those needles have to cross those lines. The prediction can be lousy for a handful of needles. For millions of needles, though, it’ll be dead on. The universe won’t make sense any other way.
I can’t go so far as to say that it’s impossible for a universe to exist without me existing and just as I am. That seems egotistical. Even the needle-drop talk has room for variations on the universe. In ten million needle drops, one needle crossing more or less would not be an implausible difference. Ten or a thousand needles falling differently wouldn’t stand out. But, then, after enough needle drops? … If infinitely many needles dropped, I could say exactly what percentage of them crossed lines. (I am speaking so very casually about very difficult technical points. Please pretend I have clear answers for them.) There are deep philosophical questions about the idea of “other universes” that we have to ask if we want to take the subject seriously. But there are deep mathematical questions too.
Bob Shannon’s Tough Town for the 16th is more or less the anthropomorphized Roman Numerals joke for the week. I don’t know that there’s a strong consensus about why X was used to represent “ten”. Likely it’s impossible to prove any explanation is right. But X has settled into meaning ten, and to serve a host of other uses in typography and in symbols. Some of them are likely connected. Some are probably just coincidence.
I have another Reading the Comics post with a title that’s got nothing to do with the post. It has got something to do with how I spent my weekend. Not sure if I’ll ever get around to explaining that since there’s not much mathematical content to that weekend. I’m not sure whether the nonsense titles are any better than trying to find a theme in what Comic Strip Master Command has sent the past week. It takes time to pick something when anything would do, after all.
Scott Hilburn’s The Argyle Sweater for the 10th is the anthropomorphic numerals strip for the week. Also arithmetic symbols. The ÷ sign is known as “the division symbol”, although now and then people try to promote it as the “obelus”. They’re not wrong to call it that, although they are being the kind of person who tries to call the # sign the “octothorp”. Sometimes social media pass around the false discovery that the ÷ sign is a representation of a fraction, , with the numbers replaced by dots. It’s a good mnemonic for linking fractions and division. But it’s wrong to say that’s what the symbol means. ÷ started being used for division in Western Europe in the mid-17th century, in competition with many symbols, including / (still in common use), : (used in talking about ratios or odds), – (not used in this context anymore, and just confusing if you do try to use it so). And ÷ was used in northern Europe to mean “subtraction” for several centuries after this.
Tom Toles’s Randolph Itch, 2am for the 11th is a repeat; the too-short-lived strip has run through several cycles since I started doing these summaries. But it is also one of the great pie chart jokes ever and I have no intention of not telling people to enjoy it.
Pie charts, and the also-mentioned bar charts, come to us originally from the economist William Playfair, who in the late 1700s and early 1800s devised nearly all the good ways to visualize data. But we know them thanks to Florence Nightingale. Among her other works, she recognized in these charts good ways to represent her studies about Crimean War medicine and about sanitation in India. Nightingale was in 1859 named the first woman in the Royal Statistical Society, and was named an honorary member of the American Statistical Association in 1874.
Olivia Jaimes’s Nancy for the 12th uses arithmetic as iconic for classwork nobody wants to do. Algebra, too; I understand the reluctance to start. Simultaneous solutions; the challenge is to find sets of values ‘x’ and ‘y’ that make both equations true together. That second equation is a good break, though. makes it easy to write what ‘y’ has to be in terms of ‘x’. Then you can replace the ‘y’ in the first equation with its expression in terms of ‘x’. In a slightly tedious moment, it’s going to turn out there’s multiple sets of answers. Four sets, if I haven’t missed something. But they’ll be clearly related to each other. Even attractively arranged.
is an equation that’s true if the numbers ‘x’ and ‘y’ are coordinates of the points on a circle. This is if the coordinates are using the Cartesian coordinate system for the plane, which is such a common thing to do that mathematicians can forget they’re doing that. The circle has radius . So you can look at the first equation and draw a circle and write down a note that its radius is and you’ve got it. looks like an equation that’s true if the numbers ‘x’ and ‘y’ are coordinates of the points on a hyperbola. Again in the Cartesian coordinate system. But I have to feel a little uncomfortable saying this. If the equation were (say) then it’d certainly be a hyperbola, which mostly looks like a mirror-symmetric pair of arcs. But equalling zero? That’s called a “degenerate hyperbola”, which makes it sound like the hyperbola is doing something wrong. Unfortunate word, but one we’re stuck with.
The description just reflects that the hyperbola is boring in some way. In this case, it’s boring because the ‘x’ and ‘y’ that make the equation true are just the points on a pair of straight lines that go through the origin, the point with coordinates (0, 0). And they’re going to be mirror-images of each other around the x- and the y-axis. So it seems like a waste to use the form of a hyperbola when we could do just as well using the forms of straight lines to describe the same points. This hyperbola will look like an X, although it might be a pretty squat ‘x’ or a pretty narrow one or something. Depends on the exact equation.
So. The solutions for ‘x’ and ‘y’ are going to be on the points that are on both a circle centered around the origin and on an X centered around the origin. This is a way to see why I would expect four solutions. Also they they would look about the same. There’d be an answer with positive ‘x’ and positive ‘y’, and then three more answers. One answer has ‘x’ with the same size but a minus sign. One answer has ‘y’ with the same size but a minus sign. One has both ‘x’ and ‘y’ with the same values but minus signs.
Sorry I wasn’t there to partner with.
Dave Coverly’s Speed Bump for the 12th is a Rubik’s Cube joke. Here it merges the idea with the struggles of scheduling anything anymore. I’m not sure that the group-theory operations of lining up a Rubik’s cube can be reinterpreted as the optimization problems of scheduling stuff. But there are all sorts of astounding and surprising links between mathematical problems. So I wouldn’t rule it out.
John Allen’s Nest Heads for the 13th is a lotteries joke. I’m less dogmatic than are many mathematicians about the logic of participating in a lottery. At least in the ones as run by states and regional authorities the chance of a major payout are, yes, millions to one against. There can be jackpots large enough that the expectation value of playing becomes positive. In this case the reward for that unlikely outcome is so vast that it covers the hundreds of millions of times you play and lose. But even then, you have the question of whether doing something that just won’t pay out is worth it. My taste is to say that I shall do much more foolish things with my disposable income than buying a couple tickets each year. And while I would like to win the half-billion-dollar jackpot that would resolve all my financial woes and allow me to crush those who had me imprisoned in the Château d’If, I’d also be coming out ahead if I won, like, one of the petty $10,000 prizes.
To close out last week’s comics I got a bunch of strips that were repeats, or that touch on topics I’ve discussed quite a bit around these parts already. I’m pretty sure all the words I have here are new in their specific organization. The words themselves are pretty old.
Maria Scrivan’s Half Full for the 4th is the Rubik’s Cube joke for the week. I ought to write up a proper description of the algebra of Rubik’s Cubes. The real stuff is several books’ worth of material, yes. But a couple hundred words about what’s interesting should be doable. … Or I could just ask folks if they’ve read good descriptions of the group theory that cubes show off. I’m always open to learning other people have said stuff better than me. This is part of why I’ve never published an essay about Cantor’s Diagonal Proof; many people have written such essays and I couldn’t add anything useful to that heap of words.
Ryan North’s Dinosaur Comics for the 5th is about the heap paradox. Or the sorites paradox, depending on what book you’ve been reading from. The problem is straightforward enough. As God, in the strip says, a big pile of sand is clearly a heap. One or two grains of sand is clearly not. If you remove grains from the heap, eventually, you lose the heap-ness. T-Rex suggests solving the question of when that happens by statistical survey, finding what people on average find to be the range where things shift over.
As with many attempts to apply statistical, or experimental, methods to philosophical questions it misses the point. There are properties that things seem to have only as aggregations. Where do they come from? How can there be something true about a collection of things that isn’t true about any part of the thing? This is not just about messy real-world properties either; we can say stuff about groups of mathematical objects that aren’t true about individual objects within the set. For example, suppose we want to draw a real number at random, uniformly, from the continuous interval 0 to 10. There’s a 50% chance we’ll draw a number greater than 5. The chance of drawing any specific number greater than 5, though, is zero. But we can always draw one. Something weird is happening here, as often happens with questions we’ve been trying to answer for thousands of years.
Norm Feuti’s Retail for the 6th is a new strip, although the joke’s appeared before. There’s some arithmetic calculations that are easy to do, or that become easy because you do them a lot. Or because you see them done a lot and learn what the patterns are. A handful of basic tricks — like that 80 percent off is 20 percent of something, or that 20 percent of a thing is one-fifth the original thing — can be stunning. Stage magicians find the same effect.
Bob Shannon’s Tough Town for the 7th is the anthropomorphized abacus joke of the week. Been a while since we had one of those. I suppose an adding machine would be at least as good a representative of the abstract concept of doing arithmetic, but it’s likely harder to draw too. This is just tiring to draw.
Zach Weinersmith’s Saturday Morning Breakfast Cereal for the 8th presents the old complaint about mathematics’s utility, here in an ancient setting. I’m intereste that the caveman presents counting in terms of matching up other things to his fingers. We use this matching of one set of things to another even today. It gets us to ordinal and cardinal numbers, and the to what we feel pretty sure about with infinitely large sets. An idea can be ancient and basic and still be vital.
Steve Sicula’s Home and Away for the 9th is about the hatred people profess for mathematics. Some of that is more hatred of how it’s taught, which is too often as a complicated and apparently pointless activity. Some of that is hatred of how it’s used, since it turns up in a lot of jobs. And for some reason we’ve designed society so that we do jobs we don’t like. I don’t know why we think that’s a good idea. We should work on that.
Once again the name of this Reading the Comics edition has nothing to do with any of the strips. I’m just aware that Weezer’s cover of Africa is quite popular right now and who am I to deny people things they want? (I like the cover, but it’s not different enough for me to feel satisfied by it. I tend to like covers that highlight something minor in the original, or that go in a strange direction. Shifting a peppy song into a minor key doesn’t count anymore. But bear in mind, I’m barely competent at listening to music. Please now enjoy my eight hours of early electronica in which various beeps and whistles are passed off as music.)
Samson’s Dark Side of the Horse for the 3rd is the Roman numerals joke for the week. And a welcome return for Dark Side of the Horse. It feels like it’s been gone a while. I wouldn’t try counting by Roman numerals to lull myself to sleep; it seems like too much fussy detail work. But I suppose if you’ve gotten good at it, it’s easy.
Jef Mallett’s Frazz for the 3rd builds on removing statistics from their context. It’s a common problem. It’s possible to measure so very many things. Without a clear idea of what we should expect as normal the measurement doesn’t tell us much. And it can be hard to know what the right context for something even is. Let me deconstruct Caulfield’s example. We’re supposed to reflect on and consider that 40% of all weekdays are Monday and Friday too. But it’s not only weekdays that people work. Even someone working a Sunday might take a sick day. Monday and Friday are a bit over 28% of the whole week. But more people do work Monday-to-Friday than do Saturdays and Sundays, so the Sunday sick day is surely rarer than the Monday. So even if we grant Caulfield’s premise, what does it tell us?
Jason Chatfield’s Ginger Meggs for the 3rd is a bit of why-learn-mathematics propaganda. Megg’s father has a good answer. But it does shift the question back one step. Also I see in the top row that Meggs has one of those comic-strip special editions where the name of the book is printed on the back cover instead. (I’m also skeptical of the photo and text layout on the newspaper Megg’s father is reading. But I don’t know the graphic design style of Australian, as opposed to United States, newspapers.)
Zach Weinersmith’s Saturday Morning Breakfast Cereal for the 3rd may belong on some philosopher’s Reading the Comics blog instead. No matter. There’s some mathematical-enough talk going on here. There’s often many ways to approach the same problem. For example, approaching a system as a handful of items. Or as a huge number of them. Or as infinitely many things. Or as a continuum of things. There are advantages each way. A handful of things, for example, we can often model as interactions between pairs of things. We can model a continuum as a fluid. A vast number of things can let one’s computer numerically approximate a fluid. Or infinitely many particles if that’s more convenient.
To describe all these different models as sharing an “ontology-space” is good mathematical jargon too. In this context the “-space” would mean the collection of all these things that are built by the same plan but with different values of whichever parameter matters.
Bud Blake’s Tiger for the 6th of August, 1965 features Einstein’s famous equation. I suppose it’s showing how well-informed Julian is, that he knows and can present such a big result. There is beauty in mathematics (and physics). Mathematicians (and physicists) find the subject beautiful to start with, and try to find attractive results. I’m curious what the lay reader makes of mathematical symbols, though, just as pieces of art. I remember as a child finding this beauty in a table of integrals in the front of one of my mother’s old college textbooks. All those parallel rows of integral symbols drew me in though nothing I’d seen in mathematics had prepared me to even read it. I still find that beautiful, but I can’t swear that I would even if I hadn’t formed that impression early in life. Are lay and professional readers’ views of mathematical-expression beauty similar? How are they different?
And now I’ve got caught up with last week’s comics. I can get to readying for this coming Sunday looking at … so far … nine comic strips that made the preliminary cut. Whimper.
This time the name does mean something.
Thaves’s Frank and Ernest for the 31st complains about not being treated as a “prime number”. There’s a lot of linguistic connotation gone into this strip. The first is the sense that to be a number is to be stripped of one’s humanity, to become one of a featureless horde. Each number is unique, of course; Iva Sallay’s Find the Factors page each day starts with some of the features of each whole number in turn. But one might look at, oh, 84,644 and not something very different from 84,464.
And yet there’s the idea that there are prime numbers, celebrities within the anonymous counting numbers. The name even says it; a prime something is especially choice. And we speak of prime numbers as somehow being the backbone of numbers. This reflects that we find unique factorizations to be a useful thing to do. But being a prime number doesn’t make a number necessarily better. There are reasons most (European) currencies, before decimalization, divided their currency unit into 20 parts of 12 parts each. And nobody divided them into 19 parts of 13 parts each. As often happens, whether something is good depends on what you’re hoping it’s good for.
Nate Fakes’s Break of Day for the 1st of June is more or less the anthropomorphized numerals installment for the week. It’s also a bit of wordplay, so, good on them. There’s not so many movies about mathematics. Darren Aronofsky’s Pi, Ron Howard’s A Beautiful Mind, and Theodore Melfi’s Hidden Figures are the ones that come to mind, at least in American cinema. And there was the TV detective series Numbers. It seems odd that there wasn’t, like, some little studio prestige thing where Paul Muni played Évariste Galois back in the day. But a lot of the mathematical process isn’t cinematic. People scribbling notes, typing on a computer, or arguing about something you don’t understand are all hard to make worth watching. And the parts that anyone could understand — obsession, self-doubt, arguments over priority, debates about implications — are universal to any discovery or invention. Note that the movies listed are mostly about people who happen to be doing mathematics. You could change the specialties to, say, chemical engineering without altering the major plot beats. Well, Pi would need more alteration. But you could make it about any process that seems to offer reliable forecasting in a new field.
Greg Evans’s Luann Againn for the 1st takes place in mathematics class. The subject doesn’t matter for the joke. It could be anything that doesn’t take much word-balloon space but that someone couldn’t bluff their way through.
Ted Shearer’s Quincy for the 7th of April, 1979 has Quincy thinking what he’ll do with his head for figures. He sees accounting as plausible. Good for him. Society always needs accountants. And they probably do more of society’s mathematics than the mathematicians do.
Bill Abbott’s Spectickles for the 1st features the blackboard-full-of-mathematics to represent the complicated. It shows off the motif that an advanced mathematical formula will be a long and complicated one. This has good grounds behind it. If you want to model something interesting that hasn’t been done before, chances are it’s because you need to consider many factors. And trying to represent them will be clumsily done. It takes reflection and consideration and, often, new mathematical tools to make a formula pithy. Famously, James Clerk Maxwell introduced his equations about electricity and magnetism as a set of twenty equations. By 1873 Maxwell, making some use of quaternions, was able to reduce this to eight equations. Oliver Heaviside, in the late 19th century, used the still-new symbols of vector mechanics. This let him make an attractive quartet. We still see that as the best way to describe electromagnetic fields. As with writing, much of mathematics is rewriting.
Last week’s offerings from Comic Strip Master Command got away from me. Here’s some more of the strips that had some stuff worth talking about. I should have another installment this week. I’m back to nonsense edition names; sorry.
Lincoln Pierce’s Big Nate for the 29th of May is about the gambler’s fallacy. Everyone who learns probability learns about it. The fallacy builds on indisputable logic: your chance of losing at something eighteen times in a row is less than the chance of your losing at that thing seventeen times in a row. So it makes sense that if you’ve lost seventeen times in a row then you must be due.
And that’s one of those lies our intuition tells us about probability. What’s important to Nate here is not the chance he’s in an 18-at-bat losing streak. What’s important is the chance that he’s in an 18-at-bat losing streak, given that he’s already failed 17 times in a row. These are different questions. The chance of an 18th at-bat in a row being a failure (for him) is much larger than the chance of an 18-at-bat losing streak starting from scratch.
That said I can’t go along with Francis’s claim that the chance of Nate getting a hit isn’t enhanced by his long dry spell. We can, and often do, model stuff like at-bats as though they’re independent. That is, that the chance of getting a hit doesn’t depend on what came before. Doing it this way gives results that look like real sports matches do. But it’s very hard to quantify things like losing streaks or their opposite, hot hands. It’s hard to dismiss the evidence of people who compete, though. Everyone who does has known the phenomenon of being “in the zone”, where things seem easier. I was in it for two games out of five just last night at pinball league. (I was dramatically out of it for the other three. I nearly doubled my best-ever game of Spider-Man and still came in second place. And by so little a margin my opponent thought the bonus might make the difference. Such heartbreak.)
But there is a huge psychological component to how one plays at a game. Nate thinks differently about what he’s doing going up to bat after seventeen failures in a row than he would after, say, three home runs in a row. It’s hard to believe that this has no effect on how he plays, even if it’s hard to track down a consistent signal through the noise. Maybe it does wash out. Maybe sometimes striking out the first three at-bats in a game makes the batter give up on the fourth. Meanwhile other times it makes the batter focus better on the fourth, and there’s no pinning down which effect will happen. But I can’t go along with saying there’s no effect.
John Zakour and Scott Roberts’s Working Daze for the 29th is an infinite-monkeys joke. Well, given some reasonable assumptions we can suppose that sufficiently many monkeys on typewriters will compose whatever’s needed, given long enough. Figuring someone’s work will take fewer monkeys and less time is a decent probability-based insult.
Ted Key’s Hazel for the 30th has the maid doing a bit of tutoring work. That’s about all I can make of this either. Doesn’t seem like a lot of fun, but there is only so much to do with arithmetic computation like this. It’s convenient to know a times table by memory.
Scott Hilburn’s The Argyle Sweater for the 30th has a chalkboard full of mathematical symbols as iconic for deep thinking. And it’s even Einstein’s chalkboard. And it’s even stuff that could plausibly be on Einstein’s chalkboard at some point. Besides E = mc2 the other formulas are familiar ones from relativity. They’re about the ways our ideas of how much momentum or mass a thing has has to change if we see the thing in motion. (I’m a little less sure about that expression, but I think I can work something out.) And as a bonus it includes the circle-drawing compass as Galileo might have used. Well, he surely used a compass; I’m just not sure that the model shown wouldn’t be anachronistic. As though that matters; fortune cookies, after all, are a 20th century American invention and we’re letting that pass.
Zach Weinersmiths’s Saturday Morning Breakfast Cereal for the 30th builds on a fun premise. Underneath the main line it gets into some whimsical ratios built on important numbers you’d never use for this sort of thing, such as π, and the imaginary unit . The Golden Ratio makes an appearance too, sneaking a definition for φ in in terms of espresso and milk. Here’s a free question: is there a difference between the “infiniccino” and “just espresso” except for the way it’s presented? … Well, presentation can be an important part of a good coffee.
π is well-known. Not sure I have anything interesting to add to its legend. φ is an irrational number a bit larger than 1.6. I’m not sure if I’ve ever called it the Boba Fett of numbers, but I should have. It’s a cute enough number, far more popular than its importance would suggest. is far more important. Suppose that there is some number, which we give that name, with the property that equals -1. Then we get complex-valued numbers, which let us solve problems we’d like to know but couldn’t do before. It’s a great advance.
The name tells you how dubiously people approached this number, when it was first noticed. I wonder if people would be less uneasy with “imaginary numbers” if it weren’t for being told how there’s no such thing as the square root of minus one for years before algebra comes along and says, well, yes there is. It’s hard to think of a way that, say, “negative four” is more real than , after all, and people are mostly all right with -4. And I understand why people are more skeptical of -4 than they are of, say, 6. Still, I wonder how weird would look if people weren’t primed to think it was weird.
Could I say what a “most improved” pinball player looks like? Well, I can give a rough idea. A player’s improving if their rankings increase over the the season. The most-improved person would show the biggest improvement. This definition might go awry; maybe there’s some important factor I overlooked. But it was a place to start looking.
So here’s the first problem. It’s the plot of my own data, my league scores over the season. Yes, league night 2 is dismal. I’d had to miss the night and so got the lowest score possible.
Is this getting better? Or worse? The obvious thing to do is to look for a curve that goes through these points. Then look at what that curve is doing. The thing is, it’s always possible to draw a curve through a bunch of data points. As long as there’s not something crazy like there’s four data points for the same league night. As long as there’s one data point for each measurement you can always connect those points to some curve. Worse, you can always fit more than one curve through those points. We need to think harder.
Here’s the thing about pinball league night results. Or any other data that comes from the real world. It’s got noise in it. There’s some amount of it that’s just random. We don’t need to look for a curve that matches every data point. Or any data point particularly. What if the actual data is “some easy-to-understand curve, plus some random noise”?
It’s a good thought. It’s a dangerous thought. You need to have an idea of what the “real” curve should be. There’s infinitely many possibilities. You can bias your answer by choosing what curve you think the data ought to represent. Or by not thinking before you make a choice. As ever, the hard part is not in doing a calculation. It’s choosing what calculation to do.
That said there’s a couple safe bets. One of them is straight lines. Why? … Well, they’re easy to work with. But we have deeper reasons. Lots of stuff, when it changes, looks like it’s changing in a straight line. Take any curve that hasn’t got a corner or a jump or a break in it. There’s a straight line that looks close enough to it. Maybe not for long, but at least for some stretch. In the absence of a better idea of what ought to be right, a line is at least a starting point. You might learn something even if a line doesn’t fit well, and get ideas for why to look at particular other shapes.
So there’s good, steady mathematics business to be found in doing “linear regression”. That is, find the line that best fits a set of data points. What do we mean by “best fits”?
The mathematical community has an answer. I agree with it, surely to the comfort of the mathematical community. Here’s the premise. You have a bunch of data points, with a dependent variable ‘x’ and an independent variable ‘y’. So the data points are a bunch of points, for a couple values of j. You want the line that “best” matches that. Fine. In my pinball league case here, j is the whole numbers from 1 to 8. is … just j again. All right, as happens, this is more mechanism than we need for this problem. But there’s problems where it would be useful anyway. And for , well, here:
For the linear regression, propose a line described by the equation . No idea what ‘m’ and ‘b’ are just yet. But. Calculate for each of the values what the projection would be, that is, what . How far are those from the actual data?
Are there choices for ‘m’ and ‘b’ that make the difference smaller? It’s easy to convince yourself there are. Suppose we started out with ‘m’ equal to 0 and ‘b’ equal to 472. That’s an okay fit. Suppose we started out with ‘m’ equal to 100,000,000 and ‘b’ equal to -2,038. That’s a crazy bad fit. So there must be some ‘m’ and ‘b’ that make for better fits.
Is there a best fit? If you don’t think much about mathematics the answer is obvious: of course there’s a best fit. If there’s some poor, some decent, some good fits there must be a best. If you’re a bit better-learned and have thought more about mathematics you might grow suspicious. That term ‘best’ is dangerous. Maybe there’s several fits that are all different but equally good. Maybe there’s an endless series of ever-better fits but no one best. (If you’re not clear how this could work, ponder: what’s the largest negative real number?)
Good suspicions. If you learn a bit more mathematics you learn the calculus of variations. This is the study of how small changes in one quantity change something that depends on it; and it’s all about finding the maxima or minima of stuff. And that tells us that there is, indeed, a best choice for ‘m’ and ‘b’.
(Here I’m going to hedge. I’ve learned a bit more mathematics than that. I don’t think there’s some freaky set of data that will turn up multiple best-fit curves. But my gut won’t let me just declare that. There’s all kinds of crazy, intuition-busting stuff out there. But if there exists some data set that breaks linear regression you aren’t going to run into it by accident.)
So. How to find the best ‘m’ and ‘b’ for this? You’ve got choices. You can open up DuckDuckGo and search for ‘matlab linear regression’ and follow the instructions. Or ‘excel linear regression’, if you have an easier time entering data into spreadsheets. If you’re on the Mac, maybe ‘apple numbers linear regression’. Follow the directions on the second or third link returned. Oh, you can do the calculation yourself. It’s not hard. It’s just tedious. It’s a lot of multiplication and addition and you know what? We’ve already built tools that know how to do this. Use them. Not if your homework assignment is to do this by hand, but, for stuff you care about yes. (In Octave, an open-source clone of Matlab, you can do it by an admirably slick formula that might even be memorizable.)
If you suspect that some shape other than a line is best, okay. Then you’ll want to look up and understand the formulas for these linear regression coefficients. That’ll guide you to finding a best-fit for these other shapes. Or you can do a quick, dirty hack. Like, if you think it should be an exponential curve, then try fitting a line to x and the logarithm of y. And then don’t listen to those doubts about whether this would be the best-fit exponential curve. It’s a calculation, it’s done, isn’t that enough?
Back to lines, back to my data. I’ll spare you the calculations and show you the results.
Done. For me, this season, I ended up with a slope ‘m’ of about 2.48 and a ‘b’ of about 451.3. That is, the slightly diagonal black line here. The red circles are what my scores would have been if my performance exactly matched the line.
That seems like a claim that I’m improving over the season. Maybe not a compelling case. That missed night certainly dragged me down. But everybody had some outlier bad night, surely. Why not find the line that best fits everyone’s season, and declare the most-improved person to be the one with the largest positive slope?