Day 820: The Mind Behind The Map

originally published March 30, 2014

Were we to kick aside the boulders of our base knowledge – the works of Newton, Galileo, Edison, Tesla, Shakespeare and the mighty triumvirate of Bell, Biv and Devoe – we would eventually reach the fortified foundation of our species’ early great minds. These are the men (unfortunately, the great female minds were generally thwacked into silence back then) whose cerebral gushings topped the intellectual charts back before the era of empirical science. Hell, we’re even going back before humankind had figured out how to build a decent pair of pants.

Ancient Greece was the time of Plato, of Aristotle, of Socrates – not to mention a number of titan thinkers who haven’t had numerous pizza joints named in their honor. Today I’m talking about the grand-pappy of geography, one of the first great mathematicians, a poet, an astronomer and a music theorist. He voiced an unpopular criticism of Homer’s Odyssey and developed a series of complex calculations that – well, had Chris Columbus read through them a few centuries later they could have really saved him some headaches.

This guy held the most prominent intellectual job posting of his era, and singlehandedly influenced the entire course of science, of map-making, and of how we keep track of history. His name was Eratosthenes. Don’t fret if you haven’t heard of him – I hadn’t until his name flittered across my computer screen this morning.

Eratosthenes was born in Cyrene, a town in modern-day Libya that had been founded by the Greeks back in 630 BC. Thanks to the economic policies of the local head honcho, Ptolemy I Soter (one of Alexander the Great’s generals), Cyrene was a happening burg in which intellectualism and prosperity flourished. Eratosthenes had a standout mind, which led him up to Athens to complete his studies. He was taught Stoicism by the movement’s founder, Zeno of Citium. He became known for his meticulous poetry and a scholarly treatise on the mathematical foundations of Plato’s philosophies, none of which I will repeat here because I’d rather skip ahead to the juicy stuff.

The first great invention credited to Eratosthenes – and this seems like a common-sense thing that should have always been kicking around – is the notion of scientific chronology. He created a lengthy tome called Chronographies in which he listed off the important dates in history, beginning with the Trojan War. Other nuggets of trivia, like a detailed list of 38 kings of the Egyptian Thebes and a comprehensive chronology of the winners of the Olympic Games were also included.

That’s the thing – nobody had thought to record linear history in this way. It simply wasn’t done. But Eratosthenes was just getting started.

This is an armillary sphere. With a ball representing Earth in the middle, the swooshing rings around it indicate the procession of stars around the planet. There was no flat-earth concerns in Eratosthenes’ mind – he knew the planet was round and he was very intrigued by that concept. The armillary sphere which he invented would serve as the principle tool for astronomers to determine celestial positioning until the telescope made its debut almost two millennia down the road.

When he turned 30, Eratosthenes was hired by the pharaoh Ptolemy III Euergetes to work as a librarian at the Library of Alexandria. This was huge – the great library was the single most important repository of human information in the world at that point. Eratosthenes sought to expand the library’s inventory too – it became mandatory that every book in the land be turned into the library’s possession so that a duplicate could be made, always by hand and always so meticulously well that the copy was almost indiscernible from the original.

Within five years, Eratosthenes was promoted to head librarian. Given the limited stash of recorded information back then, this was akin to Eratosthenes being made King of the Internet.

Perhaps his greatest accomplishment was calculating the circumference of the earth, which was no easy feat given the tiny amount of it that was known at that time. He used a gnomon, which is that pointy triangle-thing that sticks up from a sundial, to measure the angle of the sun’s elevation at noon on the summer solstice in Alexandria. He then measured the same thing in the city of Syene, which he calculated to be 5000 stades from Alexandria (a stade is either the equivalent of 157.5 meters or 185 meters, depending on which standard he used). Figuring this distance between the two cities was the hardest part, as Eratosthenes had to rely on how long it took to travel between the two cities by camel. Not exactly scientific.

Eratosthenes probably used the ‘Attic stade’ measurement (185 meters), which, after crunching his calculations with the sun angles between the two cities would have given him a global circumference of about 46,620 km, or about 16% off the truth. Not bad. Had he used the Egyptian stade (157.5 meters), his calculations would have led him to 39,690 km, which is about 1.6% off. Either way, had Christopher Columbus read up on Eratosthenes’ work he’d have known that he wasn’t going to land in India when he set off from Europe.

Using his knowledge of the earth, Eratosthenes began to sketch it. Using the vast library of travel books at his disposal in the Great Library, he pieced together an actual map of the known world, which featured the names of over 400 cities. This was history’s first map, and while it has been lost to the ages, a team of experts was able to reconstruct it into the map above. This was ground zero for the eventual discipline of geography; Eratosthenes used parallels and meridians to link the world together, the forerunners of latitudes and longitudes.

This made it possible for people to estimate their distance from other locations around the planet. Eratosthenes followed it up with a political map which demonstrated the reach of various empires and realms. He also pinpointed five distinct climate zones: two polar zones, two temperate zones and the tropical region where he lived. The guy was so far ahead of his time, he practically defined it.

Among his other achievements, Eratosthenes also calculated the sun’s diameter – albeit at a modest 27 times the size of earth. He’s the guy who figured out there were 365 days in the year, with an extra leap day required every four years. He calculated the distance to the sun and to the moon, though again he was using stadia as a measuring tool and he was a wee bit off. That colorful squadron of numbers up there is known as Eratosthenes’ Sieve, a simple way to pick out prime numbers without having to do a day’s worth of math.

Eratosthenes was critical of Homer’s works, which earned him a bit of scorn in those days when The Odyssey was considered the gospel truth. But Eratosthenes was all about science, and Homer was a little too literary for his tastes. He published works on philosophy, grammar, poetry and even literary and theatrical criticism. Of course, the moral to any historical story is that humankind sucks ass, and so when the Great Library of Alexandria was burned to the ground, most of his work was lost.

The guy lived to be 82 years old, which is like 160 in our years. He went blind as old age crept in on him, and after the depression of no longer being able to observe the world took its toll, he starved himself to death. That’s a hell of a final chapter to a hell of a mind.

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