Tuesday, February 28, 2006

I Gotta Mind Like A Sieve

Lucky numbers, in the math world, are a set of numbers created through a specific weeding process. First, start with an infinite list of numbers starting with 1, and remove all of the even numbers. The lowest number remaining greater than 1 is 3. Therefore, remove every third number. the next lowest number that remains is 7, so remove every seventh number. Continue on like that.

The resulting numbers should go: 1, 3, 7, 9, 13, 15, 21, 25 and so on.

The process of creating a pattern to eliminate numbers in math is called sieving. The most well-known sieve is for prime numbers. Because prime numbers are only divisible by 1 and themselves, the sieve is a process of going through each number and removing all future multiples.

Looking up information about sieves lead me to a page about colanders.

Apparently, there is an urban legend about cops who would place a colander on the head of a suspect and wire it to a photo copier. The photo copier had a piece of paper on it that said “Lying.” Every time the police would ask a question, they would press the copy button. When the suspect finally confessed, the cops would switch the paper in the machine.

According to the story, this always got thrown out of court.

There is also a story, that I read in a Robertson Davies book, about a culture that tested the virginity of their young women by having them carry water in a sieve. Only virgins, apparently, could do it. The trick was to grease your sieve, and the oil would keep the water from going through the holes.


Pirke Avot is a Jewish ethics guide from the fourth century, and the last chapter is a collection of aphorisms. Number 18 is:

“There are four types among those who sit in the presence of the sages: the sponge, the funnel, the strainer, and the sieve. 

‘The sponge,’ who soaks up everything. ‘The funnel,’ who takes in at this end and lets out at the other. ‘The strainer,’ who lets out the wine and retains the dregs. ‘The sieve,’ who removes the coarse meal and collects the fine flour.”

Which doesn’t bode well for this site.

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