Archive for infinity

CW. The Surreal Numbers

What follows after 0, 1, 2, … , once you’ve managed to list every counting number?

Around 1875, Georg Cantor created — or discovered if you like — the transfinite ordinals : the list continues 0, 1, 2, …, then ω , ω + 1, ω + 2, etc, for quite a long long way. John H. Conway tells us about his Surreal Numbers , which add in such gems as

1 / √ ω

Check out Knuth’s Surreal Numbers, Conway & Guy’s Book of Numbers , or for more advanced users, Conway’s On Numbers and Games.

 
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CK. The Third Tree

Niclas Hedell, a listener, poses a problem from his days in the Swedish military: given two trees in the forest, and a rope twice as long as the distance between the trees, how do you find a third tree so that all three make a right triangle.

And we explain how the Stork can catch the Frog.

 
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Follow-up: The Stork and The Frog

Amusingly, this problem has exactly the same solution as the proof that there are as many rational numbers as there are counting numbers. And the proof generalizes: one stork can catch three frogs, or ten or fifty.

Here are some bonus problems:

  1. The stork can catch the frog even if it can start at any rational number and hop any fixed rational distance each step.
  2. However, if the frog can start at any real number or hop any real distance, the stork has no strategy that guarantees a catch. This is, in effect, the same as proving that the real numbers are not countable.

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CH. Rayo’s Number!

A contestant for our Million-Dollar-Give-Away sent in Rayo’s Number, hitherto the largest number ever used for any real purpose: to wit, winning the

LARGE NUMBER CHAMPIONSHIP

rayo_poster.jpg

Check out the article by Scot Aaronson that inspired them to duke it out! And this thread on the math forum is quite interesting as well.

 
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BL. Eternally diminishing returns

With enough time and patience and bananas, can we go as far as we please?

 
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BK. Bananas and Rockets

A classic puzzle reveals why rockets require so much fuel, even for wee payloads.

 
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AH. QED

There are vastly many more real numbers than fractions!

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AG. The Eagle

How to do infinitely many things in a few minutes!

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AF. Counting All Rationals

Are there more fractions than counting numbers?

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AD. Bigger and Smaller Infinities

Are there only half as many even numbers as counting numbers?

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