The real story behind Archimedes’ Eureka! - Armand D'Angour

View full lesson: http://ed.ted.com/lessons/the-real-story-behind-archimedes-eureka-armand-d-angour

When you think of Archimedes’ Eureka moment, you probably imagine a man in a bathtub, right? As it turns out, there's much more to the story. Armand D'Angour tells the story of Archimedes' biggest assignment -- an enormous floating palace commissioned by a king -- that helped him find Eureka.

Lesson by Armand D'Angour, animation by Zedem Media.

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.