Lecture2 part2 video

Summary

This lecture delves into the contributions of ancient Greek astronomers to modern science. It highlights their systematic approach to building and testing models based on observations, emphasizing the importance of logic and mathematics in their methodology. The Greeks' belief in a geocentric universe is discussed, along with their accurate calculations of the Earth's size and the relative sizes and distances of celestial bodies. The lecture also touches on the concept of parallax and its influence on the geocentric model, leading to the development of the complex Ptolemaic system. It sets the stage for future discussions on the transition to the heliocentric model and the scientific revolution in Europe.

Takeaways

• 🔭 Ancient Greek astronomers laid the groundwork for modern science by creating models based on observations and systematically testing them.
• 🌌 They used logic and mathematics, especially the latter, to understand the universe, believing in the perfection of shapes like the sphere for celestial bodies.
• 🌐 Pythagoras and Aristotle contributed to the understanding that the Earth is spherical, with Aristotle providing observational evidence like the shadow during a lunar eclipse.
• 📏 The Greeks were the first to estimate the size of the Earth, the Moon, and the Sun, and the distances between them, with remarkable accuracy for their time.
• 🌟 They believed in a geocentric model where the Earth was at the center of the universe, influenced by their inability to observe stellar parallax with the naked eye.
• 🌠 The Greeks, particularly Claudius Ptolemy, developed complex models involving epicycles to explain the retrograde motion of planets, which were later used for over a millennium.
• 📚 Despite the fall of the Greek Empire, their astronomical knowledge was preserved and advanced by Islamic and Asian scholars during Europe's Dark Ages.
• 🔄 The Ptolemaic model was eventually challenged by the simplicity of the heliocentric model, leading to a scientific revolution in Europe during the Renaissance and Enlightenment.
• 🌍 The transition from a geocentric to a heliocentric model was a significant shift in understanding the cosmos, marking a major advancement in the history of science.
• 🔬 The script highlights the importance of scientific methodology and the iterative process of model-building and testing, which is fundamental to scientific progress.

Q & A

What was the primary method ancient Greek astronomers used to study the universe?

Ancient Greek astronomers built models based on their observations and tested those models systematically against what they could see in the sky.

Why is the focus on ancient Greek astronomers in the study of astronomy?

Ancient Greek astronomy laid the foundations of modern science, emphasizing logic and mathematics, particularly the use of systematic observation and testing.

What were the limitations of ancient Greek astronomers in their observations?

Ancient Greek astronomers were limited to naked-eye observations and did not have telescopes, which restricted their understanding of certain astronomical phenomena.

Who was Pythagoras and what was his contribution to the understanding of Earth's shape?

Pythagoras was a Greek philosopher who led a mathematical cult and propagated the idea that the Earth was round, believing the sphere to be a perfect shape.

How did Aristotle support the idea that the Earth is spherical?

Aristotle used naked-eye observations such as the round shadow of the Earth during a partial lunar eclipse, the varying visibility of stars at different locations, and the way ships disappear over the horizon to support the spherical Earth theory.

What was the significance of Aristarchus's contributions to astronomy?

Aristarchus, around 300 BC, figured out the relative sizes of the Earth, Moon, and Sun, and their distances from each other, which was a significant step in understanding the scale of the solar system.

How did Eratosthenes measure the Earth's size and what was his result?

Eratosthenes measured the Earth's size by observing the shadow cast by a stake at different places on Earth and calculating the distance between those places. He obtained a value close to the actual size, about 27,500 miles.

Why did the Greeks believe in a geocentric solar system?

The Greeks believed in a geocentric solar system because they did not observe parallax, which they expected if the Earth was moving around the Sun. They were unaware of the vast scale of the universe and the distances to the stars.

What was the significance of the parallax argument in the geocentric model of the Greeks?

The parallax argument was significant because the lack of observable parallax in the positions of stars relative to each other led the Greeks to conclude that the Earth must be stationary at the center of the universe.

How did Ptolemy's model of the solar system explain the retrograde motion of planets?

Ptolemy's model explained the retrograde motion of planets by suggesting that planets moved in epicycles—small loops superimposed on larger orbits around the Earth—which accounted for their apparent backward motion in the sky.

What was the ultimate fate of Ptolemy's model in the history of astronomy?

Ptolemy's model was used for over 1,500 years until it was replaced by the heliocentric model during the scientific revolution, which better explained the observed motions of celestial bodies without the complexity of epicycles.

Outlines

00:00

🌌 Ancient Greek Astronomy and the Foundations of Science

This paragraph introduces the focus on ancient Greek astronomers and their significant contributions to the field of astronomy. It explains that their methods of observation, logical reasoning, and mathematical modeling laid the groundwork for modern scientific practices. The Greeks are noted for their systematic approach to testing models against observable phenomena, despite being limited to naked-eye observations. The paragraph also highlights the Greeks' love for mathematics and logic, which played a crucial role in their scientific methodology. The contributions of Pythagoras and Aristotle are mentioned, with Pythagoras advocating for a spherical Earth due to its perfection, and Aristotle providing observational evidence to support this idea.

05:00

🌍 Understanding Earth's Sphericity and Size

The second paragraph delves into how the Greeks determined the Earth's sphericity and calculated its size. It discusses the use of lunar eclipses, the visibility of stars at different locations, and the disappearance of ships over the horizon as evidence for a round Earth. The paragraph then describes the work of Aristarchus and Eratosthenes, who calculated the relative sizes of celestial bodies and the Earth's diameter, respectively. Their methods involved angular measurements and observations of shadows, leading to remarkably accurate estimates of the Earth's size and the distances to the Moon and Sun.

10:02

🌐 Geocentrism and the Parallax Argument

This section explores the Greek belief in a geocentric solar system, where the Earth was considered the center of the universe. It explains the concept of parallax and how the Greeks used it to argue against a heliocentric model. They observed no parallax in the stars, leading them to conclude that the Earth must be stationary. The paragraph also touches on the debate between Aristarchus, who suggested the Sun as the center, and other Greeks who countered with the lack of observable parallax. The Greeks' misunderstanding of the vastness of the universe and the limitations of naked-eye observations are highlighted as reasons for their geocentric model.

15:06

🪐 The Complex Model of the Geocentric Universe

The fourth paragraph discusses the complexities of the geocentric model developed by the Greeks to explain the observed motions of the planets. It details the challenges in creating a model that aligns with the observed retrograde motion of planets. The Greeks, believing in a geocentric system, devised a model involving epicycles—small loops that planets made while attached to larger spheres rotating around the Earth. This model, although incorrect, was able to predict planetary positions accurately and was used for over 1,500 years until it was replaced by simpler models that better matched observations.

20:07

📚 The Legacy of Greek Astronomy and the Dawn of the Scientific Revolution

The final paragraph reflects on the enduring impact of Greek astronomical models and the eventual transition to more accurate understandings of the universe. It mentions the fall of the Greek model under Occam's razor, which favors simplicity in explanations. The paragraph also discusses the preservation of Greek knowledge by Islamic and Asian scholars during Europe's Dark Ages and the eventual Renaissance and Enlightenment in Europe, which saw a revival and advancement of scientific learning. The anticipation is set for the next lecture, which will cover the scientific revolution and the shift from the geocentric to the heliocentric model of the solar system.

Keywords

💡Ancient Greek astronomers

Ancient Greek astronomers were early contributors to the field of astronomy, laying the groundwork for modern scientific methods. They are highlighted in the video for their systematic approach to observing the sky, building models based on observations, and testing those models. This scientific methodology is a central theme of the video, emphasizing the importance of observation, hypothesis, and testing in the advancement of knowledge.

💡Naked eye observations

Naked eye observations refer to the practice of observing celestial bodies without the aid of optical instruments like telescopes. The video mentions that ancient Greek astronomers were limited to such observations, which influenced their beliefs about the universe. This concept is crucial as it sets the historical context for their understanding of the cosmos and the limitations they faced.

💡Logic and mathematics

Logic and mathematics were central to the scientific approach of the ancient Greeks. The video underscores the Greeks' deep appreciation for mathematics, which they considered almost religious. This love for math was integral to their methodological approach to understanding the universe, as they sought to apply logical and mathematical principles to explain astronomical phenomena.

💡Pythagoras

Pythagoras was a prominent ancient Greek philosopher and mathematician, famous for the Pythagorean theorem. In the context of the video, he is noted for his belief in a spherical Earth, influenced by his view of the sphere as a perfect shape. This example illustrates the video's theme of how early philosophical and mathematical ideas contributed to the development of scientific thought.

💡Aristotle

Aristotle, another famous ancient Greek philosopher, is mentioned for his observations supporting the spherical shape of the Earth. His observations, such as the shape of the Earth's shadow during a lunar eclipse, are used in the video to exemplify the empirical approach to understanding the physical world, which is a key aspect of the scientific method.

💡Aristarchus

Aristarchus, an ancient Greek astronomer, is highlighted for his work in determining the relative sizes of the Earth, Moon, and Sun, as well as the distances between them. His contributions are significant as they represent early attempts to quantify the cosmos, which is a fundamental aspect of the scientific pursuit of understanding the universe.

💡Eratosthenes

Eratosthenes, a Greek scholar, is noted for being the first to measure the Earth's size and diameter with remarkable accuracy. His method, which involved observations of shadows at different locations, is an example in the video of how ancient astronomers used innovative techniques to gather data and make precise measurements, a practice that is essential to the scientific method.

💡Geocentric model

The geocentric model, which posits that the Earth is at the center of the universe with all other celestial bodies orbiting around it, is a key concept in the video. This model was widely accepted among the ancient Greeks and is discussed to illustrate the historical progression of astronomical thought and the eventual shift towards the heliocentric model.

💡Parallax

Parallax is a principle that involves the apparent shift in an object's position relative to more distant objects, when viewed from different positions. In the video, the concept is used to explain why the ancient Greeks believed in a geocentric universe; they did not observe parallax in the stars, leading them to conclude that the Earth was stationary. This term is crucial for understanding the limitations of their observations and the development of later astronomical theories.

💡Epicycles

Epicycles refer to the small circular orbits that, in the geocentric model, planets were thought to make on top of their larger orbit around the Earth. This concept is discussed in the video to demonstrate the complexity of the geocentric model and how it was an attempt to explain the observed retrograde motion of planets. The term 'epicycles' is integral to understanding the historical models of celestial motion.

💡Ptolemy

Ptolemy, a Greek astronomer, is known for his geocentric model of the universe, which included the concept of epicycles. His model is mentioned in the video as a significant scientific achievement of its time, despite being incorrect by modern standards. Ptolemy's work is important for illustrating the video's theme of the evolution of scientific understanding and the eventual transition to more accurate models.

Highlights

Ancient Greek astronomers laid the foundations of modern science by building models based on observations and testing them systematically.

Greeks were limited to naked-eye observations, leading to certain beliefs that were later proven incorrect with the advent of telescopes.

Ancient Greeks were heavily invested in logic and mathematics, particularly in the field of astronomy.

Pythagoras, known for the Pythagorean theorem, led a mathematical cult and believed in a spherical Earth due to its perfection.

Aristotle supported the spherical Earth theory with observations like the round shadow during a lunar eclipse.

Different stars visible at different locations on Earth further supported the spherical Earth theory.

The disappearance of a boat's hull before its mast as it sails away suggested a curved Earth to the Greeks.

The Greeks accurately determined the Earth was round long before the common misconception of a flat Earth belief.

Aristarchus of Samos calculated the relative sizes of the Earth, Moon, and Sun, and their distances from one another.

Eratosthenes measured the Earth's size and diameter with remarkable accuracy for his time.

The Greeks believed in a geocentric model where the Earth was the center of the universe, influenced by the lack of observable parallax.

The concept of parallax, crucial for depth perception, was misunderstood by the Greeks in the context of the Earth's position in the solar system.

The lack of observable parallax led the Greeks to conclude the Earth was stationary, which was incorrect due to the vast scale of the universe.

The Greeks' geocentric model was challenged by the observed retrograde motion of planets.

Cleomedes proposed a model with epicycles to explain the retrograde motion of planets in a geocentric system.

Ptolemy's model, though complex, was used for 1500 years due to its predictive accuracy despite being based on a geocentric view.

The fall of the Greek Empire and the subsequent Dark Ages in Europe led to a loss of scientific knowledge, preserved elsewhere.

The Renaissance and Enlightenment in Europe marked a resurgence of scientific learning, including advancements in astronomy.

Transcripts

hello everyone and welcome to part two

of lecture two now in this part of this

lecture we're gonna be talking about

what the ancient Greek astronomers

worked now ancient Greek astronomers

were not the only people doing astronomy

but there is a reason why we're gonna

focus on them

ancient Greek astronomy built the

foundations of modern science what they

were using what they were doing was

building models based on their

observations and then testing those

models in a systematic way against what

they could see in the sky so basically

what they did was they looked at what

happens in the sky and they tried to

figure out why it was happening and

predict what would happen in the future

that is science as in science is now

they were limited to naked eye

observations so they did not have

telescopes and because of that there are

certain things that they believed that

makes sense given what they could see

but today we don't believe it's true all

right but they were also and this is a

big part of why we talk about the Greeks

and science Greeks of science were huge

into logic and mathematics especially

mathematics they loved math for the

Greeks mathematics was actually kind of

literally religious now what their their

methodology how they went about study in

the universe is actually as important as

the discoveries they made themselves

some of their quote-unquote discoveries

turns out today we know are wrong but a

lot of them are just facts so what were

the Greeks up to well as far back as 500

BC Pythagoras ooh that's a name you

might recognize of Pythagorean theorem

Fame Pythagoras who actually led a

a mathematical cult it was literally a

cult Greeks were really really into math

Pythagoras believed and propagated the

idea that the earth was round okay a

spherical earth and he basically

believed this because he believed the

sphere was a perfect shape a perfect

shape a sphere is a very simple

construct it only all you really needed

to describe a sphere is a radius it's

very simple and for that reason he

thought it was kind of the perfect shape

and because of that he thought that the

gods would use a perfect shape making a

world so he thought that world was round

now a couple hundred years later

Aristotle another pretty famous name

actually put forward a series of naked

eye observation so no telescopes

involved that supported the idea of the

earth is actually spherical in shape so

first of all if you watch a partial

lunar eclipse so this is when the Moon

moves into the Earth's shadow if you

actually just watch it and draw the moon

every say 15 minutes and then you stack

those drawings on top of each other like

this what you see is the shape of the

Earth shadow the shape of the Earth

shadow is round so yeah what kind of

object projects a round shadow well a

sphere would there are also other

observations that Aristotle laid out for

example he pointed out that at different

spots on the earth you can see different

stars so for example if you're here at

position Y your horizon looks like this

so anything below that horizon you can't

see because it would be like looking out

go outside tonight look out at your

street anything that's below the ground

would be below your horizon you can't

see it it hasn't risen yet but if your

position X here well your horizon looks

like this which means that you can see

this star where is that why you

can't that only works that the earth is

round

okay furthermore like if you literally

the Greeks were people who had votes if

you watch a boat sail over the horizon

the bottom of the boat the hole

disappears first and the mast the top of

the sails disappear last it only happens

if you're going over a curved surface

okay if you're going over a curved

surface so fine I want to make it clear

that if people tell you that people used

to believe the earth was flat that's

actually not really true as far back as

the Greeks people have known the earth

is round

it's sphere

now the size of the earth how big the

earth is well that was actually also

figured out by the Greeks but actually

the first thing they figured out was

actually how big the earth is relative

to the moon and the Sun okay so they

actually figured out

Aristarchus Aristarchus okay like 300 BC

figured out how big the earth was

compared to the moon and compared to the

Sun so the Greeks actually understood

that the moon is one quarter of the

Earth's size and the Sun is a hundred

times the earth size in in diameter and

they also understood that how far apart

the earth the moon and the earth and the

Sun were in fact about seventy-five

years after Aristarchus figured out the

relative sizes a Greek name a Rasta

knees actually measured the size of the

earth and once they knew the size of the

earth they then knew the size of the

moon and the Sun and how far apart they

were in literal terms and they wouldn't

have used miles but you know something

like miles okay

the way you do the relative sizes and

distances I don't want to get into too

much depth about this but they use

angular sizes in the sky right or

something is far farther away from you

it looks smaller if it's closer to you

it looks bigger this is angular size how

big it looks in the sky melted how far

away it is in any case you can use these

kinds of angular measures to figure out

how far away things are and how

physically large they are in diameter so

fine rhasta knees about 200 years BC a

makes the first actual measurement of

the earth size and diameter he obtains

the value of today about 27 25,000 miles

which is actually really close to the

actual value you use today the only

reason why he

wrong about the Earth's diameter was

that they assumed the earth was a

perfect sphere turns out that like a lot

of us

the earth bulges out a bit at the

equator so it's actually a little bit

larger at the equator than anywhere else

it bulges out a little bit so it's not

quite a perfect sphere but he was really

close to the right answer um again I

don't want to get into how exactly he

figured this out but it had to do with

sticking a stake into the ground at

various places on the earth and looking

at the shadow that was cast and how long

that shadow is and measuring the

distance between those two places on the

earth all right now one thing I want to

get into a little bit has to do with

something that Greeks believe the Greeks

believed that the solar system was in

fact Earth centered okay we call this a

geocentric idea the geocentric solar

system so the earth is the center of the

solar system and the Sun and all the

planets and the stars all go around the

earth now today we know this is not true

the Earth orbits the Sun the Sun orbits

the center of our galaxy the Galaxy

itself is just one of billions and

billions of galaxies we're not the

center of anything as it turns out but

the Greeks believed the earth was the

center of the universe the center of our

solar system they believed it for a very

good reason it was not a religious

reason they believed it for a

mathematical reason now this has to do

with something we call parallax now

parallax is something that you probably

use every day in your life whether or

not you know it a parallax is why you

have two eyeballs two eyeballs allows

depth perception what you can do with

two eyeballs is that you're seeing the

world from two different positions that

are slow

different spots from each other so with

your eyeballs it's like two inches apart

and because your eyeballs are two inches

apart you get depth perception now how

does this work well this is what the

Greeks would have said they would have

said look let's say the Sun is the

center of our solar system and the earth

goes around the Sun okay and in fact

some Greeks argued this might be the

case because they knew again as they

knew the size of the Sun they knew the

Sun was much larger than the earth and

so Aristarchus said hey maybe the sun's

the center but other Greeks said yeah

okay fine but there's a problem with

that if the Sun is the center of the

solar system and the earth goes around

the Sun well then earth in July when

earth is here okay if you were to look

out at the stars in the sky and you saw

a star that was relatively close to us

well that star would appear to be here

relative to stars that are further away

and in January so six months later when

the earth is here that same star from

our point of view would appear to be

here relative to the background stars

now keep in mind this star here itself

is not moving okay what they're saying

is that if the earth goes around the Sun

well the earth moves and so when we see

the star from two different positions as

the earth goes around the Sun it's

basically having two eyeballs you're

looking at it from two different

positions and it should appear to shift

slightly relative to things that are

further away so for example if you were

to take your face I'm gonna draw a

terrible face here okay here's your

eyeball okay if you hold your thumb in

front of your face okay hold it like one

foot away from your foot face now if you

focus on the background and you blink

back and forth

your eyes what you're gonna see is it

appears that your thumb moves relative

to the background it seems to be in one

spot bleak your eye to the other eye it

seems to be another spot

okay that's parallax this is how your

brain percept perceives depth and what

the Greeks said was like look we go

outside at night and we keep really good

track of all the stars in the sky and we

don't see this we don't see a stars

position some stars the stars that are

closer if the earth moves around the Sun

we should see them move position

relative to other stars and we don't

therefore the earth cannot be moving and

here's the thing in the sense that if

the earth goes around the Sun if that is

true you should be able to see parallax

that is true however what the Greeks did

not understand was just how big the

universe is okay this star here the next

nearest star to us the closest star to

us other than the Sun is more than four

light years away the earths of the Sun

that's eight light minutes to the next

nearest star it's four light-years a

little bit more than four light years

it's hugely far apart the universe is

much much bigger than the Greeks assumed

it could be but what that means is that

while it is true that stars close to the

earth do show parallax we can measure

this today you need a telescope you

cannot observe this with the naked eye

in fact even the closest star to us the

angle a the amount that it actually

moves in the sky is less than a one

arcsecond now an arcsecond is a very

small measure of angle it's how big a

diamond

look if it was two miles away the human

eye can't see a dime that's two miles

away there's no way you can see this

effect without a telescope they didn't

know that they didn't know how far apart

the stars were and because they could

not see this effect they assumed the

earth was the center of the of the well

for them the universe today we call the

solar system and the earth was

stationary that's why all right now when

the Greeks are trying to figure out a

model for our soul just what it looks

like again they believe the earth has to

be the center and all the things go

around the earth and you know things

like stars and the Sun you can explain

that pretty easily because the Stars

have you watch them night to night they

kind of seem to spin around the earth

they look from our point of view like

they spin around the earth and that's

fine that's actually easy to explain you

could have a big sphere that surrounds

the earth so the earth is here and you

have a big sphere that surrounds the

earth and that sphere spins and all the

stars are attached to that sphere and

they all spin around the earth the you

can imagine another sphere that had the

Sun on it sorry

better spear okay with the Sun on it

and that sphere goes around the earth so

that if you're looking up and you see

the Sun well you're not going to see the

stars because the Sun is too bright okay

at night you're gonna look in the other

direction from the Sun or rather the Sun

will be over here and at night you can

see the stars that are this guy fine one

problem with that all of that though is

the planets the planets first of all all

the planets from our point of view we

seem in the night sky they will be in

the zodiac okay the zodiacal

constellations we talked about those

last time these are the constellations

that are the Sun moves through them they

are in the plane of the ecliptic the

Earth's orbit around the Sun

and the planets will always be found

within the zodiac because the planets

orbit around the Sun in the same plane

as the earth does yes we understand why

today the planets are always to be near

the zodiac all right but the planets

when they go around the Sun it remember

that the earth also goes around the Sun

and it turns out that the earth moves

faster its orbit than Mars does but

slower its orbit than Venus does and

Mars has a larger orbit than the earth

and because of this as the earth laps

Mars or Venus laughs the earth Mars and

Venus and our sky from our point of view

seem to do weird things in the sky Hey

well they always rise east to west right

they always rise in the east and set in

the West but if you look at their motion

relative to stars in the night sky so if

you look at Mars tonight and then

tomorrow night in the next night you

compared where was two of the stars that

were near by it the previous night okay

the apparent motion is usually from west

to east in relative to the Stars but

every once in a while

planets like Mars will change that so

this is July 2005 Mars moves forward

until October but you'll notice it slows

down and then it turns around relative

to the background stars so again each

night you're just gonna see Mars rise

and set but a relative to the background

stars it is a weird little loop in the

skies weird a little zigzag in the sky

we call this retrograde motion and today

we understand why it happens it has to

do the fact that the earth is not the

center of the solar system but the

Greeks observing this remember they

believed the earth had to be the center

of the solar system

so what they did was they tried to build

a model of our solar system that would

explain why this happens and okay so

they had a geosynchronous

centric model idea basically the earth

the center and everything goes around

the earth but the simplest geocentric

model where everything goes around the

earth in in circles that does not match

will you actually observe in the sky and

again this is the birth of science if

the model does not match what you

actually see so your model makes

predictions if it doesn't predict what

you actually see well the model is wrong

so they went about figuring out a better

model okay so they had this model with

the earth the center and all of the

things in the solar system orbiting

around the earth but again this simple

model could not explain the motion of

the star or the planets rather in the

sky relative to the stars so told me

about Andrea

a Greek Egyptian astronomer and

mathematician devised a model in which

the earth was the center but the planets

rather than being attached to one sphere

they were attached to two spheres one

sphere a small one that was attached to

a bigger one and the small one did

little thing spins and the big one did

big spins if you added those motions

together what you would get is a planet

that does little epicycles little loops

in the sky so Antonis idea planets the

reason why they do these little zigzags

in our sky from our point of view is

because they're literally doing loops in

space now this model we know today it's

not correct right the earth is not the

center the reason why epicycles happen

we'll talk about next lecture or the

next part of this lecture by this model

worked in that you could use it to

predict where plants would be in the sky

in fact this model is used for the next

1,500 years across North Africa the

Middle East into

Asia and Europe although will talk a bit

about what happens in Europe in a minute

but this model it works so well that

it's used for 1,500 years we know today

it's wrong but again this is a model

that makes predictions and those

predictions turned out to be correct

although it is noteworthy that this

model over time does fall apart you have

to like reboot it have to take new data

to put into it and when we talk next

time the next part of this lecture we're

to talk about what was happening in

Europe about 1,500 years later okay now

this model again it works and while

there are discrepancies this model is

continued to be used and tell about the

1500s ultimately it collapses under the

idea that we know as Occam's razor which

basically states that all the things

being equal the simplest explanation so

the simplest explanation is usually the

best explanation ptolemies model is very

complicated right you have a sphere

attached to a spheres the planet of

these weird looky-loos literally in

space very complicated the actual story

of why planets go through epicycles

turns out to be actually pretty simple

but Ptolemies model works now over the

next fifteen hundred years the Greek

Empire collapses and in Europe Europe

goes through as long as the Dark Ages I

do want to make one thing clear when

Europe goes to the Dark Ages in Europe

basically all science and learning and

actually even literally literacy

disappears but in other areas of the

world of the Islamic world

the Middle East people continue to use

the learnt what the Greeks learned about

the heavens they continue to use

ptolemies model and they develop things

like algebra and Arabic numeral

in the Asian world things continue on

pace they continue to do astronomy and

do math and science but in Europe and

Europe things go dark we call the Dark

Ages they're pretty bad but but at the

end of the Dark Ages in Europe we get

what's called the Renaissance and the

Enlightenment and in this period of time

largely based on learnings that were

held together by Islamic countries and

Asian countries that the Europeans were

able to bring back after the Dark Ages

in Europe

[Music]

there was a revolution in science and

specifically astronomy but science in

general and physics that occurred that

were to talk about next time all right

so stay tuned