## Posts Tagged ‘Robin Sloan’

### Tidbits and notes posted on FB and Twitter. Part 193

Posted on: May 5, 2018

Tidbits and notes posted on FB and Twitter. Part 193

Note: I take notes of books I read and comment on events and edit sentences that fit my style. I pa attention to researched documentaries and serious links I receive. The page is long and growing like crazy, and the sections I post contains a month-old events that are worth refreshing your memory.

The ancient Greeks came up with a system called the Sieve of Eratosthenes for easily determining which numbers are prime. It works by simply eliminating the multiples of each prime number. Any numbers left over will be prime. (The ancient Greeks couldn’t do this in gifs, though.)

## Robin Sloan wrote the bestselling mystery Mr. Penumbra’s 24-Hour Bookstore, in which every number was a prime (except 24 of course).

Usage of Prime Numbers:

1) Getting into Gear

Before primes were used to encrypt information, their only true practical use was at the auto-body shop. The gears in a car—and every other machine—work most reliably when the teeth are arranged by prime numbers. When gears have 13 or 17 or 23 teeth, it ensures that every gear combination is used, which helps to evenly distribute dirt, oil, and overall wear and tear.

2) Talking with Aliens

In his sci-fi novel Contact, Carl Sagan suggested that humans could communicate with aliens through prime numbers. This wasn’t a new idea. In the summer of 1960, the National Radio Astronomy Observatory searched for intelligent extraterrestrial messages by searching for prime numbers. Years later, the astronomer Frank Drake proposed that humans could communicate with aliens by transmitting “semiprimes”—that is, multiples of two prime numbers—into space.

3) Making Nature’s Music

The French modernist composer Olivier Messiaen wrote music containing transcribed birdsong and prime numbers, which helped create unusual and unpredictable rhythms, note duration, and time signatures. Messiaen, a Roman Catholic, said that musical prime numbers represented the indivisibility of God. His Liturgie de Cristal is a grand example. Listen to Messien put prime numbers into practice here.

A “prime-numbered life cycle had the most successful survival strategy” in nature, since cycles of boom and drop of resources are consistent and predictable

An emirp is a prime number that, when its decimal digits are reversed, results in a different prime. Think 13, 17, 31, 37, 71, 73, 79 …. According to Wikipedia, the largest known emirp is 10^10006+941992101×10^4999+1.

Mersenne prime numbers, named after a 17th-century French monk, are a special breed: They’re prime numbers that are one less than a power of two

Jonathan Pace is one of the volunteers participating in the Great Internet Mersenne Prime Search GIMPS. The prime he discovered (notated as 2^77,232,917-1) contains 23,249,425 digits—nearly a million digits longer than the previous record holder.

Since 1996, GIMPS volunteers have discovered 16 new numbers. “There are tens of thousands of computers involved in the search. On average, they are finding less than one a year.” (He was awarded \$3,000 for 14 years of work)

Mathematician G H Hardy wrote that he avoided “practical” mathematics: it was dull and too often exploited for military gain. His discoveries in Prime Numbers were useful: They’ve aided the fields of genetics research, quantum physics, and thermodynamics. Today, his research on the distribution of prime numbers is the bedrock for our current understanding of how prime numbers operate.

Le Chuiche (al shemmace?)

Halla2 saar fi mou3aradat: Al Moustakbal lan yet 7alaf ma3 Hezbollah bil intikhabaat. Haaza lan ya3ni 3adam al ta7alof ma3 al mouta7alifeen ma3 al Moukawamat. Kelna moukawamat.

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