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Monday, February 11, 2013

Prime numbers

Prime_numbers


Partner and I share a mystical feeling about numbers. We like playing games with them, and matching them up, and making them make sense. I think both of us are convinced that there’s no such thing as a “random” number; when we watch the Rhode Island Lottery drawing in the evening, we both call out numbers in advance, as if somehow we can break the code.

 

 

And maybe someday we will.

 

 

Partner is especially taken with the Fibonacci series: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, et cetera. If you don’t see the pattern, here it is: start with zero and one, then add each pair of numbers in succession. 0 + 1 = 1. 1 + 1 = 2. 1 + 2 = 3. 2 + 3 = 5. And so forth.

 

 

You’d think that this is just a meaningless pattern, except that it’s everywhere in nature. It shows up in snail shells and the centers of sunflowers. It shows up in natural cycles. See how simple and elegant it is?:

 

 

Fibonacci

 

 

I myself prefer prime numbers. There is something brave and tribal and mysterious about them. Mathematicians have bashed their brains against them for centuries, trying to figure out their pattern and their frequency. Every so often, someone computes the (new) “largest” prime number; it doesn’t look like there’s really a largest one, though.

 

 

And then there are the twinned primes, that follow the pattern x / x+2: 11 and 13, 29 and 31, 137 and 139. Mathematicians have proved, more or less, that there is no limit to these. They become scarcer as the numbers get bigger, but there will never be a “largest” set of twinned primes.

 

 

How about “emirp” primes? They’re prime forward and backward. 13 backward is 31. 17 backward is 71.

 

 

There are Fermat primes, and Mersenne primes, and relative primes. I love them all.

 

 

When I go to the health club, I try always to find a locker with a prime number; it’s a sad day when I have to settle for an even number (other than 2), or some sodden multiple like 51 or 57.

 

 

One of my favorite writers, Ursula LeGuin, created a whole civilization, on a planet of the star Tau Ceti, which includes mathematics as part of its religious life, and where they “chant the primes.”

 

 

Tell me how to get there, and I’ll go.


 

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