- All right, our tradition of science,
our modern scientific
process traces its roots back
to one specific episode in history
and then we're gonna trace this forward.
But the roots go to Ancient Greece.
Roots
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of modern science,
Ancient Greece.
So this period, what are we talking about?
300-400 BC, somewhere around in there.
We'll talk to about
Ancient Greek scientists
up through about 280
under the Roman period
all the way back through, oh heavens,
about 400 BC is what we're talking about.
So maybe 400 BC to roughly 200-300 AD,
we can see important
developments going on.
So Ancient Greece is an
amazing, extraordinary episode
in history.
Now, there's a lot of
cool, awesome cultures
around the world but Ancient
Greece has given us so much
that we today have.
What did Ancient Greece give us?
Well, our traditions of
say democracy and freedom
trace their roots back to Ancient Greeks.
Democracy,
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freedom,
these ideas of Western philosophy,
all that goes straight
back to Ancient Greece.
Philosophy.
People like Plato, Aristotle,
these people have been amazing,
tremendously influential.
All sorts of amazing
things like playwriting,
the idea that okay this guy's
gonna write down a script
and these people will act it
out and there'll be an audience
and all that sort of thing.
Plays that are deliberately
written by specific people.
Comedies, tragedies, adventures,
all these sorts of things,
that tradition goes
back to Ancient Greece.
All sorts of things about
the writing of history,
the first atlas.
It's just amazing how much of our culture
begins in Ancient Greece.
And of course the scientific
side of it, absolutely.
The scientific accomplishments
of Ancient Greece
are amazing and we'll
talk about their astronomy
'cause that's really cool.
So Ancient Greek science.
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So what did the Greeks do?
What did they do that was different to why
we're studying them as opposed
to Ancient Chinese science,
which is also cool, or Ancient
Indian science or all this?
What were their key ideas
that have been passed down
through the 100 years and developed
and all this sort of thing to
get to modern science today.
Well one of the really big
giant amazing key ideas
is first of all you got these
Ancient Greek philosophers
looking for natural explanations
for things around them.
So natural explanations
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for the world.
You get this belief that
the universe is rational,
it has laws and if we think
about it we can figure them out.
Universe has laws.
We can figure them out
by observing the world,
thinking about 'em and these
the key ideas of science.
This is essential here.
Most other cultures aren't even
in this neighborhood at all.
There's thunder out there
and you ask somebody,
"Why is there thunder?"
Well you know, it's old Thor, man.
He's up there throwing his
great hammer Mjolnir around
and that's what makes the thunder.
So everything that happens,
every storm, every drought,
every problem is ascribed to, well,
it's gotta be problems with
the gods and the demons
and all these crazy
little spiritual forces
and everything has a spirit and a soul.
And, oh well, you offend the
elk then they won't allow us
to get them again.
These sorts of things like this.
And that's one way of
understanding the universe
and that's not science.
And science says, "No, there are laws."
There are reasonable things.
Every storm is not caused
by some temper tantrum
by some Nordic god,
that maybe it's due to
a high pressure zone
interacting with a low pressure zone.
And then you get all the
details, I don't know meteorology
but there are explanations for this.
We can do this by figuring things out
in a logical sort of way.
So that's one of
absolutely enormous things
that science is all about.
Second of all, they did math.
They did amazing,
colossal, cool, cool math.
Now I mean other civilizations did math.
You can't be an Egyptian
and build a pyramid
if you don't know a little bit of math.
How many blocks will it take?
How many slaves does it
take to build you a pyramid?
Or whoever it was.
But what the Greeks
did is they viewed math
as a branch of logic.
Math, a branch of logic.
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It's not just how do you
calculate the average value
of the height of the
pyramid or the obelisk
or that sort of thing.
No, it's like they thought that everything
which was mathematically
true could be figured out,
could be worked out by reason and logic
and could create a mathematical argument
just logically explaining why.
So you've got people
like Euclid, E-U-C-L-I-D.
He writes this amazing
book called "The Elements".
It's mostly a book of geometry
about lines and circles
and triangles and he goes through
and he logically demonstrates
why every triangle
has to do all this sort of thing
and the circle and all this.
It's amazing.
It's a wondrous book of geometry.
For 2,000 years, if you
wanted to study geometry
it meant you had read Euclid.
Fantastic stuff.
And then they applied their math
to these natural explanations.
On top of this, I guess
another big ingredient
we have to have for science
is the Greeks believed,
to some degree, lots of
'em believed that okay,
what we see with our eyes
we have to take seriously.
Now, there's some Greeks
that kind of argue that
what we see with--
You know, our senses
deceive us, and all that.
People like Plato and
others were not really big
on observing with their senses
but other very influential
Greeks like Aristotle
argue that no, what we
see with our eyes tells us
something useful and
meaningful about the universe
and by observing the
universe carefully in detail,
that we can learn things.
So observation
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is important.
I would say with Ancient
Greeks we don't see a whole lot
of experiments, which is another important
aspect to science.
That'll come later.
But here, we've got observation
of the universe is important
that you can learn things
by looking around you.
Key idea in science.
Mathematics, we need to use it
in order to understand things.
You know, all this not
only numbers but geometry
and then your natural
explanations for the world,
they're laws that we can figure out.
These are the foundational
ideas behind modern science
and we see these ideas put together,
used for the first time by systematically
by a group of people in Ancient Greece.
Okay, so there's Ancient
Greek science in general.
There's Ancient Greek science
written large in general,
how about astronomy?
Ancient Greek astronomy.
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Yeah, I haven't got time
to do every last detail of everything
but there's an amazing
amount of things they did.
But I wanna focus today on what they did
with the motion of the planets
because--
Motion of the planets.
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And the motion of the planets
was strange, was bizarre,
was complex, was very, very
difficult to figure out.
The motion of the moon?
No problem.
The moon's in a big circle
around the Earth every month.
The sun, well it appears
to move in a big circle
around the Earth through
the stars every year,
but the planets are complicated.
They move at different speeds.
The sun moves exactly
pretty much constant thing
through the stars.
Moon pretty much sort of thing like that.
The planets move faster and slower.
They sometimes stop and
they change direction
and they go backwards and
then they go forward again.
The motion of the planets is complicated.
Complex.
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They move backwards.
When planets move backwards
through the heavens,
we call this retrograde motion.
Retrograde.
Other times they're moving forwards.
We call this prograde, or direct motion.
So what do I mean by the
planets moving backwards?
Other things rise in the
east, set in the west,
does that mean the
planets rise in the west
and set in the east?
No, when I'm talking about
the motion of the planets
I mean the motion of the
planets relative to the stars.
So if I go out tonight, I
see a planet up in the sky.
Suppose I see Mars up there.
Here's what I'm gonna do.
So we observe the planet Mars
and suppose it's near the
constellation Leo the Lion.
Okay, so there's a rough sketch
of Leo and I look up there
and suppose I see there's Mars.
Okay, and then if I go out a week later,
Mars will not be in the same place.
Mars will be over here.
And then I go a week later
and Mars will be over here.
And if I observe over
the course of many nights
and many weeks, I will
find it moves slowly
through the stars and then
sometimes it moves backwards
and makes a loop the loop sort of pattern
through the heavens.
So here is is moving forward.
So here's maybe June, and there's July,
and then over here in August
it's moving retrograde.
There you go, it's moving in
this kind of loop the loop,
then it moves back through August
and then September it turns around again
and moves back forward again.
While it's moving backward
in retrograde motion,
it gets fantastically, amazingly bright.
So here's retrograde
and bright.
All right, so we've got
the motion of the planets
is complicated.
It's weird, it's interesting,
it's very difficult
to figure out, and the
Greeks worked at it.
They worked on all sorts of things
but this turned out to be very important.
They tried to figure out
why the planets moved
in the way they did
and they tried to come up with
a specific mathematical model
to let them exactly figure out precisely
where the planets would be
and predict where they were
gonna be in the future.
That's a key idea of science.
A scientific theory must
make specific predictions
about what's gonna happen.
So, who did that?
Well, lots of Greeks did that.
There were many, many,
many Greeks who contributed
to their ideas of the
motion of the planets.
The one who finally put it all together
in one big giant amazing package,
his name was Claudius Ptolemy.
He lived a couple hundred years AD
so he's Greek but under the Roman period
and the Romans were still
cool about the Greeks
doing their stuff as long as they obeyed
what the Romans said.
So he came up with a geocentric model
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in order to allow him to
understand why the planets
moved forward and backwards in the skies.
And what he did was his
idea was he put the Earth
at the center and he said
okay, all objects move
in perfect circles around the Earth
and so they move in a big
circle around the Earth
called a deferent.
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And then while they're
moving in this big circle
around the Earth, they're also
moving in these small circles
on top of the big circles
and the small circle
is called an epicycle.
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And so what happens is
because moving in the epicycle
as it moves around on the deferent,
it's making a loop the loop
pattern through the heavens.
It goes like this in a kind
of loop the loop pattern
through the heavens and he said okay,
here's the retrograde motion.
Retrograde.
All right, here's the prograde.
And so when we're in retrograde,
it's closer to the Earth
so that's why it's
brighter and he figured out
exactly the sizes of all
the circles necessary
to exactly account for the
motion of all the planets.
And he wrote a wonderful book about it,
which the Arabs later
called "The Almagest",
or the greatest.
And for 2,000 years, well
at least 1,500 years,
to study astronomy meant
you had studied the work of
Claudius Ptolemy, "The
Alamgest" and using that
you could predict exactly
where all the planets
would be in the sky relative to the stars
at any night there on out.
The first really great example
of a scientific theory.
Of course, there's the
minor detail that it's wrong
but other than that it's a
wonderful amazing theory.
