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  • When you think of Archimedes' "Eureka!" moment,

  • you probably think of this.

  • As it turns out, it may have been more like this.

  • In the third century BC, Hieron, king of the Sicilian city of Syracuse,

  • chose Archimedes to supervise

  • an engineering project of unprecedented scale.

  • Hieron commissioned a sailing vessel

  • 50 times bigger than a standard ancient warship,

  • named the Syracusia after his city.

  • Hieron wanted to construct the largest ship ever,

  • which was destined to be given as a present

  • for Egypt's ruler, Ptolemy.

  • But could a boat the size of a palace possibly float?

  • In Archimedes's day, no one had attempted anything like this.

  • It was like asking, "Can a mountain fly?"

  • King Hieron had a lot riding on that question.

  • Hundreds of workmen were to labor for years on constructing the Syracusia

  • out of beams of pine and fir from Mount Etna,

  • ropes from hemp grown in Spain,

  • and pitch from France.

  • The top deck, on which eight watchtowers were to stand,

  • was to be supported not by columns,

  • but by vast wooden images of Atlas holding the world on his shoulders.

  • On the ship's bow,

  • a massive catapult would be able to fire 180 pound stone missiles.

  • For the enjoyment of its passengers,

  • the ship was to feature a flower-lined promenade,

  • a sheltered swimming pool,

  • and bathhouse with heated water,

  • a library filled with books and statues,

  • a temple to the goddess Aphrodite,

  • and a gymnasium.

  • And just to make things more difficult for Archimedes,

  • Hieron intended to pack the vessel full of cargo:

  • 400 tons of grain,

  • 10,000 jars of pickled fish,

  • 74 tons of drinking water,

  • and 600 tons of wool.

  • It would have carried well over a thousand people on board,

  • including 600 soldiers.

  • And it housed 20 horses in separate stalls.

  • To build something of this scale,

  • only for that to sink on its maiden voyage?

  • Well, let's just say that failure

  • wouldn't have been a pleasant option for Archimedes.

  • So he took on the problem: will it sink?

  • Perhaps he was sitting in the bathhouse one day,

  • wondering how a heavy bathtub can float,

  • when inspiration came to him.

  • An object partially immersed in a fluid is buoyed up by a force

  • equal to the weight of the fluid displaced by the object.

  • In other words, if a 2,000 ton Syracusia displaced exactly 2,000 tons of water,

  • it would just barely float.

  • If it displaced 4,000 tons of water, it would float with no problem.

  • Of course, if it only displaced 1,000 tons of water,

  • well, Hieron wouldn't be too happy.

  • This is the law of buoyancy,

  • and engineers still call it Archimedes' Principle.

  • It explains why a steel supertanker can float as easily as a wooden rowboat

  • or a bathtub.

  • If the weight of water displaced by the vessel below the keel

  • is equivalent to the vessel's weight,

  • whatever is above the keel will remain afloat above the waterline.

  • This sounds a lot like another story involving Archimedes and a bathtub,

  • and it's possible that's because they're actually the same story,

  • twisted by the vagaries of history.

  • The classical story of Archimedes' Eureka! and subsequent streak through the streets

  • centers around a crown, or corona in Latin.

  • At the core of the Syracusia story is a keel, or korone in Greek.

  • Could one have been mixed up for the other?

  • We may never know.

  • On the day the Syracusia arrived in Egypt on its first and only voyage,

  • we can only imagine how residents of Alexandria thronged the harbor

  • to marvel at the arrival of this majestic, floating castle.

  • This extraordinary vessel was the Titanic of the ancient world,

  • except without the sinking, thanks to our pal, Archimedes.

When you think of Archimedes' "Eureka!" moment,

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B2 US TED-Ed archimedes displaced vessel float eureka

【TED-Ed】The real story behind Archimedes’ Eureka! - Armand D'Angour

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    稲葉白兎 posted on 2015/03/19
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