TED-Ed
Adam Savage: How simple ideas lead to scientific discoveries
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Adam Savage walks through two spectacular examples of profound scientific discoveries that came from simple, creative methods anyone could have followed -- Eratosthenes' calculation of the Earth's circumference around 200 BC and Hippolyte Fizeau's measurement of the speed of light in 1849. Find more TED-Ed videos on our new YouTube channel: youtube.com/TEDEd.
Adam Savage - Maker, critical thinker
Adam Savage is an internationally renowned television producer, host and public speaker. Full bio
Adam Savage is an internationally renowned television producer, host and public speaker. Full bio
Double-click the English transcript below to play the video.
(Musique)
Ce qui est drôle avec notre cerveau
00:14
One of the funny things
about owning a brain
about owning a brain
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c'est le manque de contrôle sur ce qu'il amasse et retient,
00:16
is that you have
no control over the things
no control over the things
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00:18
that it gathers and holds onto,
the facts and the stories.
the facts and the stories.
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les faits et les histoires. Et plus on vieillit, pire c'est.
00:21
And as you get older, it only gets worse.
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Certaines choses restent là des années parfois
00:23
Things stick around for years sometimes
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avant que l'on comprenne pourquoi elles nous intéressent,
00:25
before you understand
why you're interested in them,
why you're interested in them,
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pourquoi elles sont importantes pour vous.
00:28
before you understand their import to you.
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Alors voila trois de mes histoires.
00:30
Here's three of mine.
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Quand Richard Feynman était un jeune garçon dans le Queens,
00:31
When Richard Feynman
was a young boy in Queens,
was a young boy in Queens,
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il est allé se promener avec son père, sa carriole et une balle.
00:34
he went for a walk with his dad
and his wagon and a ball.
and his wagon and a ball.
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Il a remarqué que lorsqu'il tirait la carriole
00:38
He noticed that when he pulled the wagon,
the ball went to the back of the wagon.
the ball went to the back of the wagon.
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la balle allait à l'arrière de la carriole.
Alors il a demandé à son père :"Pourquoi est-ce que la balle va à l'arrière de la carriole?"
00:42
He asked his dad, "Why does
the ball go to the back of the wagon?"
the ball go to the back of the wagon?"
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Et son père a répondu: "C'est l'inertie"
00:45
And his dad said, "That's inertia."
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Il a dit: "C'est quoi l'inertie?" Et son père a dit:
00:47
He said, "What's inertia?"
And his dad said, "Ah.
And his dad said, "Ah.
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"Ah. L'inertie, c'est le nom que les scientifiques donnent
00:50
Inertia is the name that scientists give
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00:52
to the phenomenon of the ball
going to the back of the wagon."
going to the back of the wagon."
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au phénomène de la balle qui va à l'arrière de la carriole.
Mais en réalité, personne ne sait vraiment."
00:55
(Laughter)
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00:57
"But in truth, nobody really knows."
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Feynam a ensuite obtenu des diplômes
01:00
Feynman went on to earn degrees
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au MIT, à Princeton, il a résolu la catastrophe de Challenger,
01:02
at MIT, Princeton, he solved
the Challenger disaster,
the Challenger disaster,
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il a ensuite remporté le prix Nobel de Physique
01:05
he ended up winning
the Nobel Prize in Physics
the Nobel Prize in Physics
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pour les diagrammes de Feynman qui décrivent le mouvement des particules subatomiques.
01:08
for his Feynman diagrams, describing
the movement of subatomic particles.
the movement of subatomic particles.
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Il affirme que cette conversation avec son père
01:12
And he credits that conversation
with his father as giving him a sense
with his father as giving him a sense
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lui a permis de comprendre
que les questions les plus simples peuvent vous transporter aux confins du savoir humain,
01:16
that the simplest questions could carry
you out to the edge of human knowledge,
you out to the edge of human knowledge,
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et c'est là qu'il voulait s'amuser.
01:21
and that that's where he wanted to play.
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Et il s'est bien amusé.
01:23
And play he did.
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Eratosthène, le troisième bibliothécaire de la grande Bibliothèque d'Alexandrie,
01:25
Eratosthenes was the third librarian
at the great Library of Alexandria,
at the great Library of Alexandria,
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a apporté de nombreuses contributions à la science.
01:29
and he made many contributions to science.
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Mais on se souvient surtout de lui pour celle
01:32
But the one he is most remembered for
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qui a commencé par une lettre venant de la ville de Swenet, au sud d'Alexandrie,
01:34
began in a letter that he received
as the librarian,
as the librarian,
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reçue quand il était bibliothécaire,.
01:37
from the town of Swenet,
which was south of Alexandria.
which was south of Alexandria.
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La lettre racontait une anecdote qui a marqué Eratosthène,
01:41
The letter included this fact
that stuck in Eratosthenes' mind,
that stuck in Eratosthenes' mind,
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l'auteur disait quà midi
01:44
and the fact was that the writer said,
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au solstice, quand il regardait au fond de son puit,
01:46
at noon on the solstice,
when he looked down this deep well,
when he looked down this deep well,
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il pouvait y voir son reflet, et il pouvait aussi voir que sa tête
01:49
he could see his reflection at the bottom,
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01:51
and he could also see
that his head was blocking the sun.
that his head was blocking the sun.
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bloquait le soleil.
Là, je dois vous dire - l'idée que Christophe Colomb a découvert que la terre était ronde
01:54
I should tell you -- the idea
that Christopher Columbus
that Christopher Columbus
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c'est n'importe quoi. C'est absolument faux.
01:57
discovered that the world
is spherical is total bull.
is spherical is total bull.
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En fait, toute personne instruite savait que la terre était sphérique
01:59
It's not true at all.
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02:00
In fact, everyone who was educated
understood that the world was spherical
understood that the world was spherical
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depuis l'époque Aristote, et Aristote l'avait démontré
02:04
since Aristotle's time.
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par une observation très simple.
02:05
Aristotle had proved it
with a simple observation.
with a simple observation.
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Il avait constaté que l'ombre de la Terre sur la Lune
02:07
He noticed that every time you saw
the Earth's shadow on the Moon,
the Earth's shadow on the Moon,
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était circulaire
et la seule forme qui produit invariablement une ombre circulaire
02:11
it was circular,
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02:12
and the only shape that constantly
creates a circular shadow
creates a circular shadow
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c'est la sphère. CQFD, la Terre est ronde.
02:15
is a sphere, Q.E.D. the Earth is round.
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Mais personne n'en connaissait la taille
02:18
But nobody knew how big it was
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avant qu'Eratosthènes ne recoive cette lettre.
02:19
until Eratosthenes got
this letter with this fact.
this letter with this fact.
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Il a ainsi compris que le soleil était directement au-dessus de la ville de Swenet,
02:23
So he understood that the sun
was directly above the city of Swenet,
was directly above the city of Swenet,
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car en regardant dans un puit, on avait une ligne droite
02:26
because looking down a well,
it was a straight line
it was a straight line
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depuis le fond jusqu'au soleil, en passant par la tête du type.
02:29
all the way down the well,
right past the guy's head up to the sun.
right past the guy's head up to the sun.
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Eratosthène savait autre chose.
02:33
Eratosthenes knew another fact.
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Il savait qu'un bâton planté dans le sol à Alexandrie,
02:34
He knew that a stick stuck
in the ground in Alexandria
in the ground in Alexandria
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à la même heure et le même jour, à midi
02:37
at the same time
and the same day, at noon,
and the same day, at noon,
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au zénith du soleil, le jour du solstice,
02:40
the sun's zenith, on the solstice,
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sous le soleil produisait une ombre portée décentrée de 7,2 degrés.
02:42
the sun cast a shadow that showed
that it was 7.2 degrees off-axis.
that it was 7.2 degrees off-axis.
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Donc, si vous connaissez la circonférence d'un cercle,
02:49
If you know the circumference of a circle,
and you have two points on it,
and you have two points on it,
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et vous avez deux points dessus,
tout ce qu'il vous faut, c'est la distance entre ces deux points,
02:53
all you need to know is the distance
between those two points,
between those two points,
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et vous pourrez en déduire la circonférence.
02:56
and you can extrapolate the circumference.
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360 degrés divisés par 7,2 est égal à 50.
02:58
360 degrees divided by 7.2 equals 50.
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Je sais, c'est un peu rond comme chiffre, et ça me fait aussi douter de cette histoire,
03:02
I know it's a little bit
of a round number,
of a round number,
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mais c'est une bonne histoire, alors nous allons continuer.
03:04
and it makes me suspicious
of this story too,
of this story too,
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03:06
but it's a good story,
so we'll continue with it.
so we'll continue with it.
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Il devait trouver la distance entre Swenet et Alexandrie,
03:08
He needed to know the distance
between Swenet and Alexandria,
between Swenet and Alexandria,
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et ça tombait bien car Eratosthène était bon en géographie.
03:11
which is good because Eratosthenes
was good at geography.
was good at geography.
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En fait, c'est lui qui a inventé le mot géographie.
03:15
In fact, he invented the word geography.
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La route entre Swenet et Alexandrie
03:17
(Laughter)
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03:19
The road between Swenet and Alexandria
was a road of commerce,
was a road of commerce,
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était une route commerciale,
et le négoce devait connaître le temps nécessaire à ce trajet.
03:22
and commerce needed to know
how long it took to get there.
how long it took to get there.
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Il devait connaitre la distance exacte, alors il savait très précisément
03:25
It needed to know the exact distance,
so he knew very precisely
so he knew very precisely
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que la distance entre les deux villes était de 800 km.
03:28
that the distance between
the two cities was 500 miles.
the two cities was 500 miles.
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Multipliez par 50 et vous obtenez 40 000,
03:31
Multiply that times 50, you get 25,000,
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03:34
which is within one percent
of the actual diameter of the Earth.
of the actual diameter of the Earth.
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soit, à moins d'un pourcent près, la circonférence de la Terre.
Il a calculé ça il ya 2 200 ans.
03:38
He did this 2,200 years ago.
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Maintenant, nous sommes à une époque où
03:42
Now, we live in an age where
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03:44
multi-billion-dollar pieces of machinery
are looking for the Higgs boson.
are looking for the Higgs boson.
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des machines de plusieurs milliards de dollars cherchent le boson de Higgs.
Nous découvrons des particules qui pourraient se déplacer plus vite que la vitesse de la lumière,
03:48
We're discovering particles
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03:50
that may travel faster
than the speed of light,
than the speed of light,
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et toutes ces découvertes sont possibles
03:52
and all of these discoveries
are made possible
are made possible
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grâce à la technologie développée ces dernières décennies.
03:55
by technology that's been developed
in the last few decades.
in the last few decades.
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Mais au cours de l'histoire de l'humanité,
03:58
But for most of human history,
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nous avons dû faire ces découvertes grâce à nos yeux, nos oreilles et nos esprits.
04:01
we had to discover these things using
our eyes and our ears and our minds.
our eyes and our ears and our minds.
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Armand Fizeau était un physicien expérimental à Paris.
04:06
Armand Fizeau was
an experimental physicist in Paris.
an experimental physicist in Paris.
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Sa spécialité consistait à affiner et confirmer les résultats des autres,
04:10
His specialty was actually refining
and confirming other people's results,
and confirming other people's results,
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et ça peut sembler un peu ringard,
04:15
and this might sound
like a bit of an also-ran,
like a bit of an also-ran,
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mais c'est en fait l'âme de la science,
04:17
but in fact, this is the soul of science,
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car un fait qui ne peut être indépendamment corroboré n'existe pas.
04:19
because there is no such thing as a fact
that cannot be independently corroborated.
that cannot be independently corroborated.
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Il connaissait bien les expériences de Galilée
04:23
And he was familiar
with Galileo's experiments
with Galileo's experiments
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pour tenter de déterminer si la lumière avait une vitesse.
04:26
in trying to determine
whether or not light had a speed.
whether or not light had a speed.
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Galilée avait réalisé cette superbe expérience
04:29
Galileo had worked out this
really wonderful experiment
really wonderful experiment
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où son assistant et lui avaient une lampe,
04:32
where he and his assistant had a lamp,
each one of them was holding a lamp.
each one of them was holding a lamp.
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chacun d'eux tenait une lampe. Galilé allumait sa lampe, et son assitant allumait la sienne.
04:36
Galileo would open his lamp,
and his assistant would open his.
and his assistant would open his.
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Et ils ont bien travaillé leur timing.
04:39
They got the timing down really good.
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Ils le maîtrisaient bien. Ensuite, ils se postaient sur deux collines,
04:41
They just knew their timing.
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04:42
And then they stood at two hilltops,
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séparées de 3km, et faisaient le même geste ; l'hypothèse
04:44
two miles distant,
and they did the same thing,
and they did the same thing,
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de Galilée était que si la vitesse de la lumière était perceptible,
04:47
on the assumption from Galileo
that if light had a discernible speed,
that if light had a discernible speed,
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le rayonnement de la lampe de son assistant arriverait avec un certain retard.
04:50
he'd notice a delay in the light
coming back from his assistant's lamp.
coming back from his assistant's lamp.
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Mais la lumière était trop rapide pour Galilée.
04:53
But light was too fast for Galileo.
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Il se trompait de plusieurs ordres de grandeur quand il a estimé
04:56
He was off by several orders
of magnitude when he assumed
of magnitude when he assumed
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que la lumière allait environ 10 fois plus vite que la vitesse du son.
04:58
that light was roughly ten times
as fast as the speed of sound.
as fast as the speed of sound.
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Fizeau connaissait cette expérience. Il vivait à Paris
05:02
Fizeau was aware of this experiment.
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05:04
He lived in Paris, and he set up
two experimental stations,
two experimental stations,
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et il y avait établi deux stations expérimentales,
à environ 9 km l'une de l'autre.
05:09
roughly 5.5 miles distant, in Paris.
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Il a résolu le problème de Galilée,
05:12
And he solved this problem of Galileo's,
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et il l'a fait avec un équipement relativement banal.
05:14
and he did it with a really relatively
trivial piece of equipment.
trivial piece of equipment.
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Il l'a fait avec ceci.
05:19
He did it with one of these.
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Je vais ranger la télécommande un instant
05:21
I'm going to put away
the clicker for a second
the clicker for a second
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car je veux que vous réfléchissiez ici.
05:23
because I want to engage
your brains in this.
your brains in this.
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Voici une roue dentée. Elle a des encoches
05:25
So this is a toothed wheel.
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05:27
It's got a bunch of notches
and it's got a bunch of teeth.
and it's got a bunch of teeth.
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et elle a des dents.
C'était la solution de Fizeau pour envoyer des impulsions de lumière discontinues.
05:30
This was Fizeau's solution
to sending discrete pulses of light.
to sending discrete pulses of light.
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Il a mis un faisceau derrière une de ces encoches.
05:33
He put a beam behind one of these notches.
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Si je vise un miroir à 8 km, à travers cette encoche avec un faisceau
05:35
If I point a beam
through this notch at a mirror,
through this notch at a mirror,
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le rayon est renvoyé par le miroir
05:39
five miles away, that beam
is bouncing off the mirror
is bouncing off the mirror
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et revient vers moi à travers l'encoche.
05:41
and coming back to me through this notch.
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Mais quand il tourne la roue plus vite, quelque chose d'intéressant se produit.
05:44
But something interesting happens
as he spins the wheel faster.
as he spins the wheel faster.
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C'est comme une porte qui commence à se fermer
05:47
He notices that it seems
like a door is starting to close
like a door is starting to close
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sur le rayon lumineux qui revient vers ses yeux.
05:50
on the light beam
that's coming back to his eye.
that's coming back to his eye.
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Pourquoi ?
05:53
Why is that?
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Parce que l'impulsion de lumière ne revient pas
05:55
It's because the pulse
of light is not coming back
of light is not coming back
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par la même encoche. En fait, elle se heurte à une dent.
05:57
through the same notch.
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05:59
It's actually hitting a tooth.
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Et s'il tourne la roue suffisament vite,
06:00
And he spins the wheel fast enough
and he fully occludes the light.
and he fully occludes the light.
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il bloque totalement la lumière. Ensuite,
en fonction de la distance entre les deux stations,
06:05
And then, based on the distance
between the two stations
between the two stations
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06:08
and the speed of his wheel
and the number of notches in the wheel,
and the number of notches in the wheel,
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de la vitesse de sa roue et du nombre d'encoches,
il calcule la vitesse de la lumière à 2 % près.
06:11
he calculates the speed of light
to within two percent of its actual value.
to within two percent of its actual value.
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Et ça, il le fait en 1849.
06:16
And he does this in 1849.
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C'est ça qui me plaît dans la science.
06:21
This is what really gets me
going about science.
going about science.
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Quand j'ai du mal à comprendre un concept, je fais des recherches sur ceux qui ont découvert ce concept.
06:23
Whenever I'm having trouble
understanding a concept,
understanding a concept,
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06:26
I go back and I research
the people that discovered that concept.
the people that discovered that concept.
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Je regarde les évènements qui les ont amenés à le comprendre.
06:29
I look at the story of how
they came to understand it.
they came to understand it.
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Et quand on se penche sur ce à quoi ces chercheurs pensaient
06:31
What happens when you look
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06:33
at what the discoverers
were thinking about
were thinking about
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au moment de leur découverte, on comprend
06:35
when they made their discoveries,
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06:37
is you understand that
they are not so different from us.
they are not so different from us.
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qu'ils ne sont pas si différent de nous.
Nous sommes tous des sacs de viande et d'eau. Nous partons tous avec les mêmes outils.
06:42
We are all bags of meat and water.
We all start with the same tools.
We all start with the same tools.
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J'aime l'idée que les différentes branches de la sciences soient appelées des domaines de recherche.
06:46
I love the idea that different branches
of science are called fields of study.
of science are called fields of study.
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La plupart des gens voient la science comme une boite noire fermée,
06:50
Most people think of science
as a closed, black box,
as a closed, black box,
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alors qu'il s'agit en fait d'un domaine ouvert.
06:53
when in fact it is an open field.
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Et nous sommes tous des explorateurs.
06:56
And we are all explorers.
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Ceux qui ont fait ces découvertes ont simplement réfléchi un peu plus
06:58
The people that made these discoveries
just thought a little bit harder
just thought a little bit harder
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à ce qu'ils voyaient, et ils étaient un peu plus curieux.
07:01
about what they were looking at,
and they were a little bit more curious.
and they were a little bit more curious.
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Leur curiosité a changé notre vision du monde,
07:05
And their curiosity changed the way
people thought about the world,
people thought about the world,
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et a ainsi changé le monde.
07:08
and thus it changed the world.
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Ils ont changé le monde, et vous le pouvez aussi.
07:10
They changed the world, and so can you.
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Merci
07:14
Thank you.
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ABOUT THE SPEAKER
Adam Savage - Maker, critical thinkerAdam Savage is an internationally renowned television producer, host and public speaker.
Why you should listen
Adam Savage's mother is a psychologist; his father was a celebrated artist, painter and filmmaker. From the youngest age they encouraged his flights of fancy. Savage has been a paperboy, a projectionist, juggler, unicycle rider, sculptor, graphic designer, scenic painter, robot builder, welder, carpenter, machinist, prop maker, toy designer, actor, writer, executive producer and director. He spent six years in theater and 10 years in commercial and film special effects working for clients such as Nike, Corning, Hershey's, and Coca-Cola, and films like Star Wars, The Matrix films, A.I., Space Cowboys, Terminator 3 and Galaxy Quest.
Savage has built everything from theater sets to miniature particle accelerators. From spaceships to animatronic arms. He's made Rube Goldberg machines, hand props and spacesuits. His online videos have generated over 230 million page views. He's written for Popular Mechanics, the Wall Street Journal and Wired Magazine, among others. His program "Mythbusters" produced 270 episodes that aired in over 100 countries for 14 years. Adam shares his builds, his love for movie props and costumes, and passion for the transformative power of making on his award winning website Tested.com. He lives in San Francisco with his wife Julia, his twin boys Thing1 and Thing2, and two amazing dogs.
(Photo: Michael Shindler)
Adam Savage | Speaker | TED.com