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.
(Musica)
Una delle cose più divertenti dell'avere un cervello
00:14
One of the funny things
about owning a brain
about owning a brain
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è non avere nessun controllo su ciò che raccoglie e trattiene,
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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che siano fatti o storie.
Con il passare del tempo le cose non fanno che peggiorare.
Con il passare del tempo le cose non fanno che peggiorare.
00:21
And as you get older, it only gets worse.
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A volte le cose rimangono lì per anni,
00:23
Things stick around for years sometimes
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prima di riuscire a capire perché sono interessanti
00:25
before you understand
why you're interested in them,
why you're interested in them,
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o importanti per noi.
00:28
before you understand their import to you.
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Tre esempi che mi riguardano.
00:30
Here's three of mine.
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Da piccolo Richard Feyman, che viveva a Queens,
00:31
When Richard Feynman
was a young boy in Queens,
was a young boy in Queens,
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uscì per una passeggiata con il padre, con un carretto e una palla.
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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Notò che quando tirava il carretto,
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 palla arretrava in fondo al carretto.
Perciò chiese al padre "Perché la palla si sposta indietro?".
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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E il padre rispose "È l'inerzia".
00:45
And his dad said, "That's inertia."
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Feynman chiese "Che cos'è l'inerzia?".
E suo padre rispose: "Ah!
E suo padre rispose: "Ah!
00:47
He said, "What's inertia?"
And his dad said, "Ah.
And his dad said, "Ah.
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Inerzia è la parola che gli scienziati usano per
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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descrivere il fenomeno della palla che si sposta verso il retro del carretto.
Ma la verità è che nessuno lo sa".
00:55
(Laughter)
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00:57
"But in truth, nobody really knows."
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In seguito Feyman si diplomò all'MIT e a Princeton,
01:00
Feynman went on to earn degrees
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risolse il caso del disastro del Challenger,
01:02
at MIT, Princeton, he solved
the Challenger disaster,
the Challenger disaster,
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e infine vinse il Nobel per la fisica per i diagrammi di Feynman,
01:05
he ended up winning
the Nobel Prize in Physics
the Nobel Prize in Physics
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che descrivono il movimento delle particelle subatomiche.
01:08
for his Feynman diagrams, describing
the movement of subatomic particles.
the movement of subatomic particles.
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Feynman attribuisce a quella conversazione con il padre
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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il merito di avergli fatto capire
che sono le domande più semplici a condurre ai limiti estremi della conoscenza,
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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e quello era quello che voleva esplorare.
01:21
and that that's where he wanted to play.
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Ed è ciò che fece.
01:23
And play he did.
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Eratostene era il terzo bibliotecario della Biblioteca di Alessandria,
01:25
Eratosthenes was the third librarian
at the great Library of Alexandria,
at the great Library of Alexandria,
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e diede molti contributi importanti al progresso della scienza.
01:29
and he made many contributions to science.
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Quello per il quale è maggiormente ricordato
01:32
But the one he is most remembered for
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iniziò con una lettera che ricevette dal bibliotecario
01:34
began in a letter that he received
as the librarian,
as the librarian,
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della città di Syene, a sud di Alessandria.
01:37
from the town of Swenet,
which was south of Alexandria.
which was south of Alexandria.
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La lettera descriveva un fatto che rimase impresso nella mente di Eratostene.
01:41
The letter included this fact
that stuck in Eratosthenes' mind,
that stuck in Eratosthenes' mind,
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Lo scrivente sosteneva che a mezzogiorno
01:44
and the fact was that the writer said,
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del solstizio, sporgendosi al di sopra di un profondo pozzo,
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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poteva vedere la propria immagine riflessa sul fondo e vedeva anche che la sua testa
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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bloccava la luce del sole.
Adesso ve lo devo dire: l'idea che sia stato Cristoforo Colombo a scoprire che la Terra è rotonda
01:54
I should tell you -- the idea
that Christopher Columbus
that Christopher Columbus
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è una stupidaggine. Non è assolutamente vera.
01:57
discovered that the world
is spherical is total bull.
is spherical is total bull.
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La verità è che qualsiasi persona con un minimo di cultura sapeva che la Terra era rotonda
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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sin dai tempi di Aristotele e Aristotele lo aveva dimostrato
02:04
since Aristotle's time.
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con una semplice osservazione.
02:05
Aristotle had proved it
with a simple observation.
with a simple observation.
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Aveva notato che l'ombra che la Terra proietta sulla Luna
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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è circolare.
L'unica forma la cui ombra è sempre circolare
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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è la sfera, e infatti la Terra è rotonda.
02:15
is a sphere, Q.E.D. the Earth is round.
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Ma nessuno ne conosceva le dimensioni
02:18
But nobody knew how big it was
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finché Eratostene non ricevette quella lettera.
02:19
until Eratosthenes got
this letter with this fact.
this letter with this fact.
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Capì che il sole si trovava esattamente sopra la città di Syene
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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perché i raggi solari arrivavano dritti
02:26
because looking down a well,
it was a straight line
it was a straight line
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sul fondo del pozzo, passando sopra la testa fino al sole.
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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Eratostene era a conoscenza di un altro fatto.
02:33
Eratosthenes knew another fact.
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Sapeva che ad Alessandria un palo conficcato nel terreno
02:34
He knew that a stick stuck
in the ground in Alexandria
in the ground in Alexandria
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a mezzogiorno di un certo giorno,
02:37
at the same time
and the same day, at noon,
and the same day, at noon,
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ossia il solstizio, quando il sole raggiunge lo zenit,
02:40
the sun's zenith, on the solstice,
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proiettava un'ombra che si discostava dall'asse di 7,2 gradi.
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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Ora, se si conosce la circonferenza di un cerchio,
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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e sono dati due punti sulla circonferenza,
basta conoscere la distanza fra quei due punti
02:53
all you need to know is the distance
between those two points,
between those two points,
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per calcolare la circonferenza.
02:56
and you can extrapolate the circumference.
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Trecentosessanta gradi diviso 7,2 fa 50.
02:58
360 degrees divided by 7.2 equals 50.
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Mi rendo conto che 50 un numero fin troppo tondo e fa dubitare anche me della veridicità della storia,
03:02
I know it's a little bit
of a round number,
of a round number,
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ma trattandosi di una storia divertente continuerò a raccontarvela.
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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Eratostene aveva bisogno di conoscere la distanza fra Syene e Alessandria,
03:08
He needed to know the distance
between Swenet and Alexandria,
between Swenet and Alexandria,
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il che era un bene, perché Eratostene era bravo in geografia.
03:11
which is good because Eratosthenes
was good at geography.
was good at geography.
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Tanto bravo che la parola geografia l'aveva inventata lui.
03:15
In fact, he invented the word geography.
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La strada che collegava Syene ad Alessandria
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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era una strada commerciale
e i mercanti dovevano sapere quanto ci voleva a percorrerla.
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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Eratostene doveva conoscere la distanza esatta
03:25
It needed to know the exact distance,
so he knew very precisely
so he knew very precisely
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fra le due città e sapeva che era di 800 chilometri.
03:28
that the distance between
the two cities was 500 miles.
the two cities was 500 miles.
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Moltiplicate 800 per 50 e otterrete 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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che corrisponde al diametro della Terra con un errore dell'un per cento.
Questa scoperta risale a 2200 anni fa.
03:38
He did this 2,200 years ago.
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Viviamo in un'epoca in cui
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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si usano macchinari da miliardi di dollari per scoprire il bosone di Higgs.
Stiamo scoprendo particelle che potrebbero superare la velocità della luce.
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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Tutte queste scoperte sono rese possibili
03:52
and all of these discoveries
are made possible
are made possible
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dalla tecnologia sviluppata negli ultimi decenni.
03:55
by technology that's been developed
in the last few decades.
in the last few decades.
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Ma per gran parte della storia dell'umanità
03:58
But for most of human history,
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abbiamo dovuto scoprire le cose usando occhi, orecchie e cervello.
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 era un fisico sperimentale parigino.
04:06
Armand Fizeau was
an experimental physicist in Paris.
an experimental physicist in Paris.
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Era specializzato nel rifinire e confermare le scoperte altrui,
04:10
His specialty was actually refining
and confirming other people's results,
and confirming other people's results,
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il che potrebbe farlo sembrare l'ultimo arrivato,
04:15
and this might sound
like a bit of an also-ran,
like a bit of an also-ran,
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ma in realtà la scienza consiste proprio in questo,
04:17
but in fact, this is the soul of science,
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perché non esiste fatto che non possa essere corroborato indipendentemente.
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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Conosceva gli esperimenti di Galileo
04:23
And he was familiar
with Galileo's experiments
with Galileo's experiments
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che cercavano di determinare se la luce avesse velocità.
04:26
in trying to determine
whether or not light had a speed.
whether or not light had a speed.
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Galileo aveva escogitato questo magnifico esperimento
04:29
Galileo had worked out this
really wonderful experiment
really wonderful experiment
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nel quale lui e il suo assistente tenevano ciascuno una lampada.
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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Galileo accendeva la sua lampada e lo stesso faceva il suo assistente,
04:36
Galileo would open his lamp,
and his assistant would open his.
and his assistant would open his.
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riuscendo a sincronizzarsi perfettamente.
04:39
They got the timing down really good.
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Quando trovarono la sincronia perfetta si misero ciascuno sulla cima di due colline distanti
04:41
They just knew their timing.
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04:42
And then they stood at two hilltops,
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tre chilometri l'una dall'altra e fecero la stessa cosa.
04:44
two miles distant,
and they did the same thing,
and they did the same thing,
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Galileo pensava che se la luce fosse stata dotata di velocità finita
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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avrebbe notato un ritardo nella luce che arrivava dalla lampada del suo assistente.
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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Ma la luce era troppo veloce per Galileo.
04:53
But light was too fast for Galileo.
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Si sbagliò di diversi ordini di grandezza quando suppose
04:56
He was off by several orders
of magnitude when he assumed
of magnitude when he assumed
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che la velocità della luce fosse circa 10 volte quella del suono.
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 conosceva questo esperimento.
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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A Parigi, dove viveva, costruì due stazioni sperimentali
distanti l'una dall'altra circa nove chilometri.
05:09
roughly 5.5 miles distant, in Paris.
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Così riuscì a risolvere il problema di Galileo
05:12
And he solved this problem of Galileo's,
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utilizzando un dispositivo relativamente semplice,
05:14
and he did it with a really relatively
trivial piece of equipment.
trivial piece of equipment.
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simile a questo.
05:19
He did it with one of these.
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Per il momento non userò il puntatore
05:21
I'm going to put away
the clicker for a second
the clicker for a second
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perché voglio che ci ragioniate sopra.
05:23
because I want to engage
your brains in this.
your brains in this.
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Questa è una ruota dentata. È dotata di una serie di tacche
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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e di una serie di denti.
Fizeau risolse così il problema dei segnali luminosi separati.
05:30
This was Fizeau's solution
to sending discrete pulses of light.
to sending discrete pulses of light.
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Mise il raggio di luce dietro a una delle tacche.
05:33
He put a beam behind one of these notches.
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Se punto un raggio di luce verso uno specchio a otto chilometri di distanza,
05:35
If I point a beam
through this notch at a mirror,
through this notch at a mirror,
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attraverso una delle tacche, il raggio viene riflesso dallo specchio
05:39
five miles away, that beam
is bouncing off the mirror
is bouncing off the mirror
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e ritorna verso di me sempre passando attraverso una tacca.
05:41
and coming back to me through this notch.
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Ma aumentando la velocità della ruota si verifica qualcosa di molto interessante.
05:44
But something interesting happens
as he spins the wheel faster.
as he spins the wheel faster.
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Quando il raggio di luce torna indietro, a Fizeau sembra di vedere
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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qualcosa di simile a una porta che sta per chiudersi.
05:50
on the light beam
that's coming back to his eye.
that's coming back to his eye.
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Di cosa si tratta?
05:53
Why is that?
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La spiegazione è che il raggio luminoso non torna indietro
05:55
It's because the pulse
of light is not coming back
of light is not coming back
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attraverso la stessa tacca, ma colpisce un dente.
05:57
through the same notch.
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05:59
It's actually hitting a tooth.
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Facendo girare la ruota abbastanza velocemente
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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la luce viene bloccata completamente.
Sulla base della distanza fra le due stazioni,
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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la velocità e il numero di tacche della ruota,
è possibile calcolare la velocità della luce con un errore del due per cento.
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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Fizeau lo fa nel 1849.
06:16
And he does this in 1849.
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È questo che mi piace della scienza.
06:21
This is what really gets me
going about science.
going about science.
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Ogni volta che non riesco a capire un concetto, faccio delle ricerche sulla persona che lo ha scoperto
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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e analizzo la storia del modo usato per chiarirlo.
06:29
I look at the story of how
they came to understand it.
they came to understand it.
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Quando si studia il processo mentale
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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che ha permesso di fare una certa scoperta, si capisce
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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che gli scienziati non sono poi così diversi da noi.
Siamo tutti involucri di carne e acqua.
Partiamo tutti con gli stessi strumenti.
Partiamo tutti con gli stessi strumenti.
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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Adoro l'idea che le diverse branche della scienza siano chiamate campi di studio.
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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Gran parte delle persone vedono la scienza come un territorio oscuro e delimitato
06:50
Most people think of science
as a closed, black box,
as a closed, black box,
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quando in realtà è un campo aperto.
06:53
when in fact it is an open field.
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Siamo tutti esploratori.
06:56
And we are all explorers.
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Chi scopre qualcosa si avventura solo un po' più in profondità con il pensiero,
06:58
The people that made these discoveries
just thought a little bit harder
just thought a little bit harder
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ed è un po' più curioso.
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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La curiosità di queste persone ha cambiato il modo in cui la gente percepisce il mondo,
07:05
And their curiosity changed the way
people thought about the world,
people thought about the world,
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cambiando il mondo stesso.
07:08
and thus it changed the world.
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Loro hanno cambiato il mondo, e la stessa cosa potete fare voi.
07:10
They changed the world, and so can you.
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Grazie.
07:14
Thank you.
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(Applause)
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(Applausi)
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