- Hey, smart people, Joe here.
If your science education was anything like mine,
you probably learned about the scientific method.
The way that it's taught to us,
you make an observation,
you come up with a guess about what's going on,
and you test that idea with an experiment
to figure out if you're right or wrong.
Rinse, repeat, Newton's your uncle
and hopefully you end up with a better picture of reality
(bell dinging) than you had yesterday.
But that hasn't always been a thing.
Humans invented science.
The scientific method?
We invented that, too.
And I wanna tell you a story about how that happened.
(upbeat music)
Just follow me in here.
(gravel crunching)
(plastic crinkling)
Okay, guys, I think I'm too old for this.
This is the inside of a bouncy castle
and we turned it into a camera obscura.
(playful music)
A camera obscura is basically just a dark room
with a tiny hole at one end
that lets an image of the outside
be projected onto this back wall.
Now, it takes a lot of light for this to work,
but luckily the sun has us covered there.
And it takes a really sensitive camera
to make the shot even possible,
but to the naked eye in here, I gotta tell you,
this is an incredible experience.
It's amazing that this works.
What you're seeing happening behind me here is not a trick.
Whatever Thomas is doing,
(trumpet music)
This is the direct technological ancestor
of the cameras that we use today.
It's one of the oldest methods of projecting images.
And the reason that we're in here
is because around 1,000 years ago
a mathematician named Al-Hassan Ibn al-Haytham
made a promise to the ruler of Egypt
that he'd build a dam across the Nile River
to stop its catastrophic floods.
Problem was, even al-Haytham had never seen the Nile River.
(al-Haytham humming)
And when he got to Egypt it was
way bigger than he expected. - Whoa.
- And suddenly, he was in a little bit of trouble
because the ruler of Egypt was famous
for killing or banishing anything he didn't like.
Legend has it, he even banished a vegetable once.
(sad music)
So to cover his mistake,
Ibn al-Haytham decided to fake insanity
and go into house arrest rather than lose his head.
And he's sitting in his dark room
and the only thing he had to entertain him was light
beaming in through a tiny hole.
His room likely acted as a camera obscura
just like this one.
In a camera obscura the image projected
from the outside world is flipped upside down,
which must have looked pretty strange
to somebody 1,000 years ago.
In fact, it looks pretty strange today too.
But as Ibn al-Haytham studied this light
beaming into his little dark chamber,
what he found was going to change science forever.
Ibn al-Haytham emerged from his imprisonment
with all sorts of new ideas about light.
He showed how it travels in a straight line,
how it bounces off of different surfaces in different ways,
how it makes an image in the eye
100s of years before thinkers in Europe
refigured those things out.
Eventually, he wrote a book that laid the whole foundation
for what we know about the physics of light today.
But all of this wasn't even the biggest impact
of Ibn al-Haytham's work.
In the process of revolutionizing optics,
he pioneered what's perhaps the first version
of the scientific method as we know it today.
Born in that dark room over 1,000 years ago,
today the backbone of modern science,
but what is the scientific method really?
Back when he was studying
that light hitting the wall of his room,
there was no such thing as the scientific method,
but there were other ways of making sense of the world.
For example, for as long as humans have been humans,
they've observed patterns in nature.
Cycles, like seasons and years.
What plants made them feel better when they were sick.
Which seeds would grow into the biggest grains.
That let them make calendars,
medicines and invent agriculture.
Not bad.
What these ancient humans were doing
was a key piece of science.
They were using observations from the past
to make predictions about the future.
And ancient people built up tons of knowledge
about the natural world this way.
But what those ancient people didn't ask
is why things are the way they are.
Ask an ancient Maya, Babylonian, Egyptian,
why the sun comes up or the wind blows,
they'd probably point to a myth or a God.
Not to astronomy or physics.
Then the Greeks showed up. (rock music)
Ancient Greek philosophy dudes were some of the first people
that we know of who started looking for natural explanations
to things in a really organized way.
The Greeks were masters at this thing called reasoning.
Basically using logic to explain things.
For instance, the Greek philosopher Pythagoras
noticed that if you pluck a string,
the sound that it makes depends on how long or short it is.
And he figured out that the notes in the musical scale
aren't random, they're mathematically related to each other.
So, if scales are defined by math
and music is made by scales,
he reasoned that math was the basis of all music.
These philosophers believed the truth was out there
and reason and logic
were the way to uncover it. (eerie music)
Those are important ingredients
for how science is done today.
But there's one key thing
that those philosophers didn't do very much of.
Experiments.
Eventually, some Greeks began dabbling with experiments.
Like one summer day.
Eratosthenes observed shadows in different Egyptian cities
so that he could calculate the size of the earth.
A physician named Galen was setting fire to his own skin
so he could test
different burn remedies. (Galen screaming)
That's commitment.
Experiments let these scholars actually test their ideas
about how the world works.
Ideas couldn't just stick around
because they were good enough anymore, they had to be right.
Now, some historians argue
that these experiments were actually the seeds
of the modern scientific method.
But by the second century
the Orthodox church was getting big in Greece
and the church wasn't that into science.
So, the experimentation party fizzled out
before it really got going.
Then around the seventh century,
science was about to have another big moment,
this time in the Islamic Empire.
It was the largest empire on earth at the time,
stretching all the way from Spain to India.
Islamic scholars read the works of the Greeks and others
and built off of their knowledge,
making lots of new discoveries and inventions.
Ever heard of algebra?
That's theirs.
But the scientific method, as we know it,
didn't get its start until Ibn al-Haytham
got stuck in that dark room.
So remember, one thing he noticed about the camera obscura
is that images from out here in the outside world
are flipped upside down.
So why does that happen?
Ibn al-Haytham reasoned
that light had to travel in a straight line
from every point on the object outside.
So the light rays coming from the top and the bottom
cross as they enter the dark room
so that when they hit the wall, they're flipped.
But that was just a logical guess
and guessing isn't science.
It's what he did next
that would end up changing the course of history.
He put his guess, his hypothesis to the test.
He placed lanterns in different positions outside the room
and looked where the light from each one struck the wall.
If you cover one, it disappears over here.
Sure enough, the spot on the wall
always made a perfectly straight line
through the hole to the lamp.
So, light travels in a straight line.
Check.
Ibn al-Haytham performed a lot of other experiments
in that dark room with a hole in it.
The size of the hole,
how the moon and solar eclipses looked,
how lenses and mirrors bent and bounced light.
He wrote up these ideas about light
in what's known as the "Book of Optics".
He explained all of the experiments that he did
in meticulous detail so that others could adopt his method,
reproduce his work.
He showed that science wasn't just reason or logic
or even observation wasn't enough on its own.
It took experiments to find the truth.
And after him, there was no going back.
Now, Ibn al-Haytham didn't change
the way science was done instantaneously.
The modern scientific method came together over centuries.
And things really got going
after a Latin translation of his book
began making the rounds in Europe.
One of the people to read that
was an Englishman named Roger Bacon in the 13th century.
Bacon really loved that stuff
about optics and light just fine,
but what he really latched onto
were Ibn al-Haytham's ideas about how to do science.
Bacon helped popularize this idea
that science was about experimentation
and checking each other's work
in order to establish one single scientific truth,
which sounds pretty familiar, doesn't it?
Plenty of scientists from the time
of the scientific revolution have direct or indirect links
to Ibn al-Haytham.
We know that Kepler and Galileo read his book
and they made a few important discoveries thanks to science.
We associate names like Newton and Snell
with the origin of the physics of light,
but we know Ibn al-Haytham's work
was being passed around their circle of friends.
So, I have to wonder if even the great Newton
got some of his ideas from somewhere else.
Today, a lot of that old science wouldn't pass peer review,
but all of these characters were doing something
that at least looks a lot like science as we know it.
Each of them uncovered fundamental observations
about why the universe works the way that it does
and it's probably no coincidence that many of them
had Ibn al-Haytham's book on their shelves.
It would be wrong to say that one person invented science
because, well, that isn't how science works,
but Ibn al-Haytham gave those who came after him
a whole new way to explore the world
and get closer to truth by making predictions,
doing experiments, and most importantly,
challenging existing ideas
and being willing to replace those ideas with new ones.
Today, these are the key parts of what we universally call
the scientific method.
Although, different types of scientists
have different ways of uncovering new knowledge,
they all trace their roots to this story.
This shift in how we seek to explain the world.
Science is often looked at and often taught
like it's a collection of facts,
but that's not really what it is.
Science as a practice, as a verb,
asks us to be enemies of facts.
One thing Ibn al-Haytham seemed to just get
was that what we don't know is as important as what we know
Because knowing what we don't know
can tell us where we should be looking.
I mean, in a way,
all scientists are sitting in the dark
looking at the little bit of light
let in from the outside world.
And Ibn al-Haytham gave us a way to examine that light
and get a little bit closer to the truth.
Stay curious.
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Stay curious.
(stumbles) His name every time.
All right.
One thing Ibn al-Haytham seemed to just get
was that we don't, ugh.