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06 July 2007

PIZZAQ: the shape of all suspended free-dangling chains

Clicking will very likely yield positive things.

Ah fooey if I don't post this image already, it will just sink to the bottom of my hard disk and never be seen again. And I like it.

Richard Feynman asked why Physical Reality -- your everyday neighborhood, your iPhone, your gravity, your molecules and atoms, your quarks and hadrons and leptons, your feet, your breakfast toast, your binoculars, your car, your bicycle, the stars, planets, galaxies -- is all precisely describable by mathematics and all seems to obey elementary mathematics, even simple arithmetic.

And he answered: We have utterly no idea why. But it just does.

Here we got an ordinary metal chain, and a huge heavy chain-like thing that looks like the reproductive organ of a Transformer. I have no idea what the huge thing is. But whatever it is, it was designed to have the properties of an ordinary, familiar chain -- to dangle like a suspended chain. It's a chain. They're both chains.

All chains (and heavy ropes, and cables) which are suspended from both ends and allowed to dangle freely -- to let ordinary gravity shape them -- share the same mathematical shape.

I think I've talked about The Shape of All Chains before. But of all mathematical curves, for some strange reason, I just love The Shape of All Chains, and its related family of curves and surfaces, which have all sorts of surprising and useful real-world properties, as well as a very rip-snorting, fascinating history.

You love Angelina Jolie, you love Leonardo diCaprio.

I love the Shape Of Freely Suspended Chains.

And just as Feynman predicted, The Shape Of All Chains can be described by a particular equation. Numbers and mathematical rules seem to tell all chains how to dangle.

Why is that? How does the chain know it's supposed to behave like a math equation tells it to behave?

Anyway, 2 slices with tomato sauce and cheese: I want

* the technical WORD for the Shape

* the EQUATION for the Shape

and double anchovies for any interesting other stuff you can tell me about freely suspended chains and cables and ropes, and the mathematical rules they all slavishly obey. You might want to start with The Human Earth Person who first figured out the Equation.

I filched The Transformer's Schwantz from the site of a math professor at Haverford College, an extraordinarily fine private liberal-arts college outside Philadelphia. The other chain you can see in the window of the jewelry store down at the shopping mall. Gold, silver, iron, steel, platinum -- they may have different price tags, but they all take the same shape. Nobody knows why the Universe works that way.

3 comments:

James J. Olson said...

My high school calculus teacher, we'll call him "Mr. X", suggested after my first exam that I go sign into a study hall, since I might learn more.

He was singularly unable to explain to bright, but mathematically challenged students like me how and why calculus was interesting and beautiful.

Take for example this beautiful curve. It is called a catenary curve, it is the shape of all dangling changes and cables. It is a special curve, and is NOT a parabola.

It's shape has to do with gravity pulling on the cable. The closer to the bottom you get, the slope of the curve decreases because there is less weight pulling on it.

Galileo apparently thought it was a parabola, but this was disproved by a man named Jungius in 1669. As early as 1661, Leibniz, Huygens and Bernoulli all had come up with the formula for a catenary. Liebniz coined the term.

y=a * cosh (x/a) = a/2 * (e^x/a + e^-x/a), where a=T/P, where T=tension (a constant) and P=weight per length unit.

Thank you, Calculus I, 4th ed. by Lester Crane. (Houghton Mifflin, 1979)

Vleeptron Dude said...

okay okay i got a heavy day -- it's SWMBO's BIRTHDAY!!! -- but i don't want to piss you off the way I pissed off Mike by delaying your Pizza Award.

YOU WIN THE CATENARY PIZZA!

(from "catena," Latin for chain.)

Yeah, gravity pulls it down and makes its shape.

But in St. Louis, you can take the elevator up the insides of a big-ass UPSIDE DOWN CATENARY! The Gateway Arch, by the architect I.M. Pei!

Dreamy. The catenary, its lovely, sublime name, its equation of hyperbolic cosines and e = 2.718281828... , its history of brilliant geniuses studying it (Newton's among them) ... just dreamy.

On this week of Scooter Libby's Free Pass, of Bush again asking the American people to Give War A Chance ... is it any wonder that a Math Geek Thing like this moves me like a shower under a cool tropical waterfall?

James J. Olson said...

Happy Birthday to your lovely and talented spouse.

And, you owe me so much pizza at this point that I think I'm going to insist that you come to Boston and spend the day wandering around the city with me before you buy me pizza at a restaurant to be named later.