37 of 100: Fibonacci

In the current "Flashback: Your Weekly History Quiz" in the New York Times, I had most of the events—Descartes; invention of the first automobile, and of Pilates; creation of X-Men; launch of the Hubble Space Telescope—situated correctly in time. But I missed placing the Italian mathematician Fibonacci (aka Leonardo of Pisa), by a long shot. I had no idea he lived ca. 1200! (1170–ca. 1240/50, to be rather inexact.) I've always thought of him as... somewhat modern? Well, at least Renaissance.

Maybe that's because he's a living presence in our household. My husband, David, is a mathematician, and a musician, and a geocacher. And Fibonacci inhabits all these personas. David's geocaching handle is FifiBonacci. He uses Fibonacci rhythms in his composing. Math: well, that's obvious. If we ever get another pet—an iguana, perhaps—we might just name it Fibonacci. Why not?

I did not know, until just now, that Fibonacci introduced the Hindu-Arabic number system, with ten digits including a zero and positional notation, to Western Europe in his Liber Abaci of 1202. This replaced Roman numerals, Egyptian multiplication, and an abacus, and no doubt assisted the growth of banking and accounting in Europe (and the spread of filthy capitalism, but don't get me started).

He also, in that same book, posited a problem involving the growth of a population of rabbits—which led to the Fibonacci sequence, in which each number is the sum of the previous two: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55... In his own calculations, Fibonacci only got to step 14: the value 233. But it, of course, goes on and on, infinitely.

And that in turn leads to the Golden Ratio, which... well, it's math. But it has real-world manifestation—in pine cones, sunflowers, spiral aloes, nautilus shells, and on and on. 

The Fibonacci Quarterly was established in 1963 to investigate this beautiful phenomenon more closely.

And then there are Fibonacci primes—because who doesn't love to get all wonky with prime numbers? As of September 2023, the largest known certain Fibonacci prime was F201107, with 42,029 digits. Those wacky mathematicians. How many pages would that number even fill?

Meanwhile, and perhaps more usefully, Fibonacci has a pizzeria in Columbus, Ohio, and another in Buenos Aires. Both of which I will definitely need to visit, next time I'm in the neighborhood.