This is the second of a four-part look the neat things that happened when people started tinkering with the Chinese Four Great Inventions.
Let's start by thinking about an element of household mystery--the kitchen magnet. Like every inquisitive toddler, your humble writer as a younger human spent hours sticking magnets to the fridge and pulling them off again.
Lodestone
The Chinese were also interested in the magic of magnets--specifically lodestone, one of only two naturally magnetized rocks on earth. While lodestone was described in about the fifth century, it took another five hundred years before we get a description of the first compass. It looked a lot different from what we'd include in our Zombie Apocalypse Preparedness Kits. Step 1: Make a fish out of lodestone. Step 2: Float fish in a bowl of water. The fish's head will point north. Step 3: ???? Step 4: Profit.
The Chinese compass evolved. The fish turned into a ladle, and it was placed in the middle of a square plate representing the cosmos. Very useful if you wanted to practice geomancy. Not terribly useful for taking on a camping trip.
Today, with compasses being so common-place that they're included as consolation prizes at Skee-Ball rinks, we might take pause to see the compass ranked as a great invention. But do not pause! No! Resist the pausing! Be assured the humble compass changed the world by opening up the map to exploration.
The true power of the compass couldn't be realized however until two other inventions came on the scene. The first was the sextant, a tool used to accurately measure the distance between two points in the sky. The second was the marine chronometer, nothing more than a really really solid, accurate clock.
Latitude
This is what the ancients thought the world looked like. And why they needed better navigation.
Think of how easy it is to get lost, even these days with iPads equipped with Google Maps. Antiquity did not have iPods or Google, and because of this they suffered from an almost chronic case of disorientation. Maps were bad and often centuries out of date. Roads were treacherous when they existed, rife with tolls both official and unofficial and ruffian-enforced. And--unless you risked the moods of the sea or were rich enough to afford a horse--you had to make all your wrong turns on foot. The heroic historian Fernand Braudel estimated that in the 16th Century it took news roughly thirty days at top speed to get from the center of Europe to the edge.
Here's where the compass comes in. With a compass, you can orient yourself north. This is useful enough. But knowing where magnetic north becomes almost magical if you can get an accurate measurement of the sky.
No sextant jokes today.
To do this we have to wait until the sixteenth century for the invention of the sextant. The sextant is a majestic work of technology elegantly combining no less than three genius inventions. It consists of a telescope (necessary inventions: glass grinding; optics), a mirror, and a frame. If you know how to use a sextant, you can use it to find the distance between any two points in the sky.
Big whoop, boy scout, I can hear you snickering. But wait. If you know which way's north, and you can measure the position of the starts accurately, then you can fix you latitude with astonishing accuracy. This is convenient when your caravan gets stuck in the winding streets of Istanbul and you want to know how long it will take to make it to the Black Sea, but it can be downright life-saving if you are a booty-laden ship drifting across the Atlantic Ocean, wondering whether you took a wrong turn at Ireland.
Once people were able to get a handle of how far up or down the earth they were, the distance of the seas essentially shrunk. Ocean travel was less dangerous. The world was a little freer for commerce and freedom.
Longitude
But not, you know, completely free. Because while seamen could figure how much they'd moved up or down the earth, they were still could only guess how far East or West they were. The problem of longitude was a great concern for sailors.
The problem was that to figure out your longitude by looking at the stars, you needed to know exactly what time it was. Well, the haters are already saying to themselves, why don't they just use a watch?
Didn't you hear me say exactly? I mean exactly. The earth moves about fifteen degrees every hour, so an inaccuracy of a minute or two on the clock can mean a difference of hundreds of miles on land--that's the difference between landing your sloop in Manhattan or landing it in Maine. Added to this was the fact that the high seas were not very kind to clocks. On a long ocean voyage, clocks would heaved up and down by the crashing waves, they would stop, they would run fast or slow, their parts would expanded by the heat, and corroded by the humidity.
The solution was there for everyone to see. You just needed a really awesome clock. But while the solution was obvious, actually building an awesome clock without a pendulum was dreadfully difficult, and the intellectual giants of the 18th Century (I'm looking at you, Newton) didn't even think it was possible.
In the 18th Century, the British Government, knowing both the necessity of discovering longitude and that impossible things could indeed be achieved if you threw money at it, introduced the Longitude Prize to spur those dastardly inventors to invent a clock that could be used on the high seas. John Harrison, a British clockmaker, devoted his life to making this clock of all clocks in a story stuffed with so much event that it merited a book so wonderful to merit a TV series based on the book.
Once Harrison made the awesomest clock ever (officially called a marine chronometer, but whatevs) navigation became less guesswork, and more science. We came a long way from a lodestone fish floating in a pool of water. But remember--that's where it started, with Chinese geomancers playing with rocks.
Thanks for sticking around for this fact! I promise the next one won't be so involved! Please check back tomorrow, when we'll be looking at the third great Chinese invention--the printing press.
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