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When you think of Archimedes' "Eureka!" moment,
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you probably think of this.
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As it turns out, it may have been more like this.
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In the third century BC, Hieron, king of the Sicilian city of Syracuse,
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chose Archimedes to supervise
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an engineering project of unprecedented scale.
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Hieron commissioned a sailing vessel
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50 times bigger than a standard ancient warship,
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named the Syracusia after his city.
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Hieron wanted to construct the largest ship ever,
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which was destined to be given as a present
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for Egypt's ruler, Ptolemy.
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But could a boat the size of a palace possibly float?
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In Archimedes's day, no one had attempted anything like this.
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It was like asking, "Can a mountain fly?"
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King Hieron had a lot riding on that question.
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Hundreds of workmen were to labor for years on constructing the Syracusia
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out of beams of pine and fir from Mount Etna,
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ropes from hemp grown in Spain,
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and pitch from France.
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The top deck, on which eight watchtowers were to stand,
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was to be supported not by columns,
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but by vast wooden images of Atlas holding the world on his shoulders.
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On the ship's bow,
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a massive catapult would be able to fire 180 pound stone missiles.
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For the enjoyment of its passengers,
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the ship was to feature a flower-lined promenade,
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a sheltered swimming pool,
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and bathhouse with heated water,
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a library filled with books and statues,
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a temple to the goddess Aphrodite,
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and a gymnasium.
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And just to make things more difficult for Archimedes,
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Hieron intended to pack the vessel full of cargo:
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400 tons of grain,
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10,000 jars of pickled fish,
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74 tons of drinking water,
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and 600 tons of wool.
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It would have carried well over a thousand people on board,
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including 600 soldiers.
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And it housed 20 horses in separate stalls.
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To build something of this scale,
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only for that to sink on its maiden voyage?
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Well, let's just say that failure
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wouldn't have been a pleasant option for Archimedes.
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So he took on the problem: will it sink?
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Perhaps he was sitting in the bathhouse one day,
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wondering how a heavy bathtub can float,
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when inspiration came to him.
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An object partially immersed in a fluid is buoyed up by a force
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equal to the weight of the fluid displaced by the object.
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In other words, if a 2,000 ton Syracusia displaced exactly 2,000 tons of water,
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it would just barely float.
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If it displaced 4,000 tons of water, it would float with no problem.
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Of course, if it only displaced 1,000 tons of water,
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well, Hieron wouldn't be too happy.
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This is the law of buoyancy,
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and engineers still call it Archimedes' Principle.
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It explains why a steel supertanker can float as easily as a wooden rowboat
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or a bathtub.
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If the weight of water displaced by the vessel below the keel
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is equivalent to the vessel's weight,
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whatever is above the keel will remain afloat above the waterline.
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This sounds a lot like another story involving Archimedes and a bathtub,
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and it's possible that's because they're actually the same story,
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twisted by the vagaries of history.
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The classical story of Archimedes' Eureka! and subsequent streak through the streets
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centers around a crown, or corona in Latin.
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At the core of the Syracusia story is a keel, or korone in Greek.
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Could one have been mixed up for the other?
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We may never know.
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On the day the Syracusia arrived in Egypt on its first and only voyage,
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we can only imagine how residents of Alexandria thronged the harbor
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to marvel at the arrival of this majestic, floating castle.
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This extraordinary vessel was the Titanic of the ancient world,
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except without the sinking, thanks to our pal, Archimedes.