Tag Archives: history

Galileo & Pheidippides

I’m thinking about using this image to promote The Western Civ User’s Guide to Time & Space.

It’s Galileo, who invented the pendulum clock, and the Greek hero Pheidippides, who ran 26 miles from Marathon to Athens with news of victory over the Persians.

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How he did it

Just to recap from the last couple of posts: First, Eratosthenes guessed the Earth was round like a ball. Second, he knew that at noon on the Summer solstice, the Sun shone directly overhead in the town of Syene, which was 5,000 stadia south of Eratosthenes.

Third, Eratosthenes guessed the Sun was really big—huge, even. He noticed that shadows cast by the Sun are all parallel, so all the Sun’s rays must be parallel, too. Parallel means 2 or more lines that never touch—they stay the same distance from each other. Think train tracks.

SO, Eratosthenes—in Alexandria, 5,000 stadia north of Syene—put a stick (like the gnomon of a sundial) in the ground and made sure it was plumb. That stick was pointing down to the center of the Earth. If Earth is round, the well in Syene and Eratosthenes’ stick won’t be parallel, right? They’ll be at an angle to each other. Eratosthenes didn’t know exactly how many degrees that angle was, but in Alexandria at noon on June 21st, his stick cast a shadow.

There weren’t any shadows in Syene, because the Sun was directly overhead. He measured the stick, he measured the shadow, and used those measurements to draw an angle. The angle turned out to be a little over 7 degrees, or 1/50 of a circle.

Eratosthenes knew the distance from Alexandria to Syene was 5,000 stadia. He multiplied 5,000 by 50 to get the circumference of the Earth—250,000 stadia. In modern measurements that works out to be 28,738.418 miles or 46,250 kilometers.

The actual polar circumference of Earth is about 24,860 miles or just a bit over 40 thousand kilometers. The stadion Eratosthenes used may have been a little different from the standard unit. But even today, right now, if you search the internet for the circumference of the Earth, you won’t get just one answer.

Eratosthenes was a genius who used what he knew and observed, along with what he guessed at, to calculate something that no one knew—and he did it pretty accurately.

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Eratosthenes


Head-Librarian Eratosthenes explains to a student how to laminate a dust jacket.

In an earlier post, I hinted about how over 2,000 years ago somebody calculated the circumference (how big around) of the Earth. This guy did it using only a well, a protractor and a stick (okay, maybe instead of a stick he used a column, but you could use a stick and get the same result).

I’m talking about Eratosthenes, the head librarian at the Great Library of Alexandria. Alexandria is an ancient city in Egypt, located where the Nile River flows into the Mediterranean Sea. Many scholars lived in Alexandria—like Ctesibius, who perfected the water-clock.

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Summer solstice

Okay, here comes some sciency stuff.

Summer solstice happens twice a year—once in the Northern Hemisphere (June 21) and once in the Southern Hemisphere (December 22). Those are the two days when the Sun spends the most time in the sky.

If you have a globe handy, you’ll see that there’s a line that goes all the way around the middle of the Earth. That’s the equator. It separates the Earth into a northern half and a southern half. Each half is called a hemisphere—’hemi’ means ‘half’ and ‘sphere’ is another word for ‘globe’.

The Sun appears to travel across the sky, but ackshually the Earth is traveling around the Sun and spinning on her axis at the same time. An axis is the line that goes through the center of the Earth from the North Pole to the South Pole. Did you notice that your globe’s axis is tilted? It’s tilted at a little over 27 degrees, because Earth is tilted at a little over 27° in relation to its orbit around the Sun. Because of this tilt, half the year (the time it takes to orbit the Sun) the Northern Hemisphere receives more of the Sun’s rays. The other half of the year, the Southern Hemisphere receives more of the Sun’s rays. The equator gets the Sun’s rays all year round, so it’s always hot there.

It takes one year for Earth to orbit the Sun. When the Northern Hemisphere is tilted toward the Sun it’s Summer there. When the Southern Hemisphere is tilted toward the Sun it’s Summer there.

Getting back to that equator—let’s look at the globe again. There are 2 other lines that also run around the Earth. In the Northern Hemisphere, there’s the Tropic of Cancer. In the Southern Hemisphere, there’s the Tropic of Capricorn. On June 21, the Northern Hemisphere tilts toward the Sun and the Tropic of Cancer gets the Sun’s rays directly. You could draw a line from the Earth’s center through the Tropic of Cancer to the Sun. On December 22, the Southern Hemisphere tilts toward the Sun and the Tropic of Capricorn gets the Sun’s rays directly. You could draw a line from the Earth’s center through the Tropic of Capricorn to the Sun.

On June 21, the Northern Hemisphere has the most daylight of any day of the year. Six months later, on December 22, the Southern Hemisphere has the most daylight of any day of the year.

Remember, when the Northern Hemisphere has the most hours of daylight (Summer solstice) the Southern Hemisphere has the fewest hours of daylight (Winter solstice). The opposite is true at solstice six months later.

Three months after solstice is the day when the day is split equally in two, with 12 hours of daylight and 12 hours of nighttime. This is the equinox. The autumnal (Fall) equinox is September 22 in the Northern Hemisphere. March 21 is the vernal (Spring) equinox.

Why am I telling you this? Well, over two thousand years ago a Greek librarian figured out exactly how big around the Earth is using only a well and a stick—and he did it at noon during the Summer solstice.

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What’s a Grecian earn?

About 14 drachmas an hour! Har har har!

Okay, can I get a do-over? I’m not entirely happy with the drawing I did for that last post about Greek measurements. Didn’t look Greek enough, or just didn’t have pizazz or something. So I drew a new version of it, this time taking the drawings on those wonderful old Grecian urns as my inspiration. Tell me what you think.

Here’s an old Greek urn—these drawings are gorgeous. I love the light terra-cotta-colored figures on a rich black background.

Here’s the new sketch.

Greek measurements

The Greeks measured length roughly the way the Egyptians did: a daktylos is a finger-joint, or inch; a pous is a foot, or 12 inches; a pēchys is a cubit, half a yard, or 18 inches. Longer distances were a bēma, a pace, 5 feet; an orgyia, a fathom, 6 feet; a stadion, 600 feet (an eighth of a mile); a milion, a mile.

Marathon

One of the important battles in the wars between the Greeks and Persians took place on the Plains of Marathon. Herodotus tells about how in 490 bc, when the Greeks were seriously outnumbered, a messenger named Pheidippides (Fay DIP e deez) ran from Athens to Sparta to get their help. Then he ran to Marathon to join the fight, THEN ran back to Athens to tell everybody that the Greeks won.

Around the world we still celebrate Pheidippides’ heroic run in races called marathons. If you run a marathon, it’s 26 miles and 385 yards—the distance from the Plains of Marathon to Athens. The very fastest runners have done it in a little over 2 hours!

Herodotus of Halicarnassus

Herodotus reading his Histories to the crowd

“These are the researches of Herodotus of Halicarnassus, which he publishes, in the hope of thereby preserving from decay the remembrance of what men have done, and of preventing the great and wonderful actions of the Greeks and the Barbarians from losing their due meed of glory; and withal to put on record what were their grounds of feuds.”

While the Greeks did think of time as a cycle, there was still a desire to reach back in time to remember stories from the past. We saw how Homer kept alive the story of the siege of Troy through his epic poem, the Iliad.

Herodotus (Hay ROD oh toos) was a Greek who lived in the fourth century bc and is thought to be the first historian. He wrote The Histories mostly about the wars between the Greeks and Persians and how they got started. Herodotus was a great storyteller, but what made him a historian is that he investigated, he did research—he got his information from several sources; he visited the places where the history took place; he went to the library; he interviewed people—then he arranged the information he’d gathered to explain how and why something happened.

I have a paperback copy of The Histories. It’s not an easy read, but I like to ‘dip into’ my copy and read whatever I open to. The battle of Thermopylae is in there—that story has since been made into a graphic novel and movie, The 300—and the battles of Marathon and Salamis. Herodotus included lots of oddball side-stories and observations, which are also fun. The Persian emperors Cyrus, Darius and Xerxes are in there (Xerxes is thought to be the party-boy king Ahasuerus from the biblical Book of Esther).

History is often about the big military battles and wars. I want this history, the one you’re reading right now, to be about ideas. But I’m telling you, if the Greeks hadn’t broken the will of the mighty Persian Empire and eventually beat ‘em, there would have been no flowering of art, literature, philosophy and democracy that happened after the wars—and was the Greeks’ gift to us.

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Image

Siege of Troy—tight sketch

The Iliad

The Iliad is an epic poem written by the blind poet Homer in the 4th century bc, about events that happen during the siege of Troy—known back then as Ilium—in the 12th century bc.

In those days poems like the Iliad were recited in front of an audience. They were written with a specific rhythm and often-repeated phrases in order to help the poet memorize the whole thing. The Iliad is mostly about war, the destruction it causes, and a code of honor that was part of Greek culture.

Because I’m a swell guy, I condensed the whole Iliad in to one sentence. You can take a really deep breath and recite it without stopping:

Nine years into the Trojan War the Greeks attack a town on Troy’s side and make off with a couple of Trojan girls Chryseis and Briseis Agamemnon takes Chryseis and Achilles who is the Greeks’ best warrior takes Briseis to be their girlfriends Chryseis’s dad offers to pay to get her back but Agamemnon says no dice Dad prays to Apollo Apollo inflicts a plague on the Greeks and a lot of them die Agamemnon figures out making Chryseis his girlfriend is the cause of this plague so he gives her back but he still wants a girlfriend so he makes Achilles give him Briseis this ticks Achilles off so he says he’s not going to fight for the Greeks anymore and even asks his mom Thetis who is a sea-goddess remember she married the mortal Peleus and wouldn’t invite Eris to their wedding to ask Zeus to help the Trojans who are the Greeks’ enemies so Zeus is on Troy’s side now and Achilles won’t fight so the Greeks get their hats handed to them there’s lots of fighting with some featured fights between Paris the shepherd with the good judgement who stole the beautiful Helen and Menelaus who is Helen’s husband and Hector and Ajax the Greeks don’t do so good the Trojans beat the Greeks back as far as their ships Diomedes and Odysseus get some inside info about the Trojans’ battle plans but the Trojans set one of the Greek ships on fire so things are looking pretty bad for the Greeks because without the ships how do they get back home Achilles still won’t help his pals but Nestor says let Patroclus wear Achilles’ armor so the Greeks will think yay Achilles is back in the game Patroclus is good but Apollo sees what’s going on and knocks Patroclus’ armor off of him and Hector kills him the Greeks and Trojans fight over the body and armor Hector gets the armor the Greeks get Patroclus’ body Achilles feels like a heel and tells Agamemnon okay I’ll fight those Trojans now Achilles’ mom Thetis the sea-goddess gets the god Hephaestus to make Achilles some new armor and Achilles goes out to fight the Trojan army who for some reason are sleeping outside the city walls and when they see Achilles coming they say feet do your stuff and try to beat it back inside Troy but they’re not fast enough and Achilles kills every Trojan he sees he even fights the god of the river Xanthus who complains about all the dead bodies Achilles sees Hector and chases him around the city three times until Hector stops running and fights Achilles but Achilles kills Hector and ties Hector’s body to the back of his chariot and drags it back to the Greek camp Patroclus gets a big funeral Achilles drags Hector’s body in circles around Patroclus’ coffin every day for the next nine days Hector’s dad the king of Troy tells Achilles come on man that’s not right Achilles says yeah you’re right I’m sorry and returns Hector’s corpse to the Trojans Hector gets a big funeral and everybody stops fighting for a while.

The reason I’m telling you this is because I’m interested in how people thought about time. Homer’s poem is about things that happened 800 years before he was born. Maybe the Iliad was a comment on wars happening in Homer’s own time. It was definitely a way of remembering events long gone.

The Iliad is an epic story, but too fanciful to be considered a history. We’ll have to look to another Greek to see who invented the idea of history.

Thanks to Spark Notes

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