Archive for The Mathcast

Follow Up: Loops and the Harmonic Series.

In an earlier post Spaghetti Loops, we asked several problems that we promised had something to do with the number e.

The first question really has to do more with the famous harmonic series; in this post we showed that the sum

1 + 1/2 + 1/3 + 1/4 + …. + 1/n

adds up to about the natural log of n, plus a small constant, Euler’s γ ≈ .577215664901… In other words, to sum up to, say N, at least e(N- γ) terms are used.

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Paperdolls!

The topology of paper doll folding patterns explains geometrical symmetries, as Chaim explains in this short video:

(And much more deeply in The Symmetries of Things.)

The video was produced by Research Frontiers, at the University of Arkansas

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EO. Spaghetti Loops

Just why does e appear in so many guises?

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EN. Plinko

We settle some business and address the game of Plinko.

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EM. Awash in Billiard Balls

We discuss math on TV, the smallest ungoogleable number and a devilish game with billiard balls.

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EL. Math Dance with Dr Schaffer and Mr Stern

Karl Schaffer of Math Dance shows us some geometry tricks!

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EK. The Law of Small Numbers

We answer last weeks puzzle, discuss the law of small numbers and ask again what is the smallest positive counting number that Google can’t find?

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EJ. Math Factor at the Farmer’s Market

We visit the Fayetteville Farmer’s Market, soliciting math questions, and pose a problem about funny walks.

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EI. How to Pass a Cube Through Itself!

We conclude our interview with Dana Richards, editor of Martin Gardner’s Colossal Book of Short Puzzles and Problems pondering how to cut a hole through a cube large enough that another, same-sized cube can pass through!

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Follow Up: The Harmonic Series

That the worm falls off the end of the rope depends on the fact that the incredible
harmonic series

1 + 1/2 + 1/3 + 1/4 + . . .
diverges to infinity, growing as large as you please!

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