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Course: Big History Project > Unit 2
Lesson 4: Other MaterialsWATCH: How Did Our View of the Universe Change?
Geocentric to heliocentric, and beyond. An overview of the major changes in the way people have viewed the Universe.
. Created by Big History Project.
. Created by Big History Project.
Want to join the conversation?
- Did Galileo and other astronomers who first used telescopes to look at the sun go blind?(13 votes)
- I'm not sure about others, but Galileo looked at it and spent a week in a room without any light coming in and letting his eyes recover from it. There was probably damage, but he didn't end up going blind because of it.(16 votes)
- What about the ancient Egyptians? Were they be able to calculate the distance of stars with the help of pyramids?(5 votes)
- nah. they were trying to get their pharaohs into the after-life(9 votes)
- how could ptolemy propose his theory that everything revolves around the earth but how could he figured out the presence of jupter and saturn by naked eyes?(1 vote)
- Both Jupiter and Saturn can been seen with the naked eye at certain times. Like all scientific knowledge his theory was built off of thousands of years of study and observation.(12 votes)
- How and when was stellar parallax first discovered?(5 votes)
- Why do you think that Ptolemy was making Astronomy but not Philosophy? When thinking of Ptolemy's idea about taking the earth as the center of the universe and it is a place of imperfection, actually it is still quite right.
Generally we tend to think of us and our earth as the center of the universe, which is quite selfish and arrogant way of interpreting the relationship between us and the universe. Because of this distorted perception, we keep ruining our world from environment to ethics, both materially and morally. In this point of view, I find Ptolemy as a great critical thinker rather than a successful astronomer.(4 votes)- woah dude thats a very long passage no one wants to read it.(0 votes)
- Can anyone tell me a theory about the orbits that came up before ptolemy, or was he the first one to come up with a theory?(3 votes)
- you know dark energy? maybe, we can somehow use it to send rockets all the way to the "multiverse"(3 votes)
- While dark energy would make a pretty cool propellant, it would not be able to take us to another universe.(2 votes)
- And the pyramids have nothing to do with our info on our sun. The pyramids were temples for the dead(3 votes)
- like you said , the universe is expanding , but at one point in time in the past it was very small . my question is that ... the universe, like everything, must have an end... what lies beyond it? is it as dark and dead as the universe is now or is it something easier to navigate and explore(2 votes)
- We do not know yet. Though there are many theories.(2 votes)
- papi like pp(2 votes)
- yes papi like pp very much(2 votes)
Video transcript
What's the biggest question
that you could possibly ask? Surely, what it might be is,
"How did everything begin?" That's a question
that all origin stories ask and they have a huge
diversity of answers. Some say there wasn't
a beginning because everything
has always existed. Some say perhaps
a multicolored serpent was traveling through the land
and as it did so, it created the mountains
and the rivers and the streams and maybe even the stars
and maybe even you and me. Some say there was
a sort of committee of gods that created the world or perhaps the one true God
created the world. There's a huge diversity
of these stories, but each of them makes claims. And that's because
every origin story is, in a sense, an explanation. It's trying to tell you
how things happened. And as a result of that,
origin stories aren't fixed. They change. They change over time because
new information comes in, new evidence, and the explanations have
to change. Now, what we're
going to look at in this unit is how the modern,
scientific answer to that great
question emerged. And we'll see that new evidence
over several hundred years changed the story. We'll begin by going back
500 years to Europe and this is because
modern science first flourished
in Europe. Europe at the time,
500 years ago, was predominantly
a Christian region. And the Christian church,
like most religions, had its own answers
to that question, "How did everything begin?" And the Christian church's
answer was that God created the Universe
several thousand years ago, but they tied that answer
to a great model of the Universe that had been constructed
about 1,900 years ago by an astronomer called Ptolemy, who lived in Alexandria
in Egypt. Now, this is what
Ptolemy's model of the Universe
looked like. He believed that the Earth
was at the center of the Universe. And the Earth was a realm
of imperfection. And around it was the realm
of perfection. And that realm consisted
of several concentric transparent spheres
and those spheres carried the Sun, the Moon, the stars,
all the heavenly bodies moving in different ways
depending on which sphere they were in. And then beyond them was the
perfect realm of Heaven. Now, Ptolemy's model
of the Universe worked pretty well. People accepted it
not just because the Church said they should,
but also because there was a lot
of evidence for it. And this was because
astronomers in his time-- or astronomers
in the 16th century, I should say,
and in Ptolemy's time-- were studying the Earth
using the naked eye. Now, think about this. If you were studying
the Universe using just the naked eye, just looking directly
at the skies, you might be
very tempted to think that the Universe revolves
around the Earth, mightn't you? Between 1550 and 1700,
new evidence began to kick in, some of it supplied
by new technologies. And what that did
was it began to undermine Ptolemy's idea
of the Universe. Some astronomers, for example,
pointed out that every year, the planets, as they orbit
the Earth, seem to move backwards
for a period. And Ptolemy's model
really struggled to explain that. The astronomer Copernicus
in the 16th century pointed out that if you imagine
that it's actually the Sun that's at the center
of the Universe instead of the Earth,
you could solve that problem quite easily. So that's one little glitch. Then another astronomer, Kepler,
found that the orbits of the planets
are actually not perfect circles
as Ptolemy had imagined. They are ellipses,
ovals like this. That was a problem. Third, an Italian astronomer
called Galileo began to use what was
the hot new technology of the time, the telescope. And he was one
of the first astronomers to actually look
at the heavens through the telescope. And what he saw showed the
heavens were much less perfect than Ptolemy had thought. For example,
if you look at the Sun, it's got sunspots. These are real, sort of blotches on the faces of the Sun. No one liked that. And if you look at Jupiter,
you find it's not a single planet,
it's got little moons, lots of moons orbiting it. So for all of these reasons,
people began to worry about Ptolemy's model. And notice how new technologies,
new evidence and logic have begun to undermine
a traditional explanation of how the Universe works. Late in the 17th century,
the great English scientist Isaac Newton began to argue
that it wasn't concentric spheres
that held together all the bodies
of the Universe. It was actually
a mysterious force that pervaded the entire Universe
that was called gravity and it pulled everything
together. By 1700, most astronomers
had dropped Ptolemy's model
of the Universe. They now came to believe
there were no edges to the Universe,
there were no spheres or perhaps, the entire Universe
was infinite in size and infinitely old
and just held together by this force of gravity. Now, notice how evidence
has begun to change the old story. This is, in fact,
the first model of the Universe that was scientific
in the sense that it was based primarily
on evidence. And notice one more thing. Notice how scientists in different parts of the world
communicate with each other, share their information,
share their evidence to construct a new story. This is the process
that we're going to call in this course
Collective Learning. And here's a very powerful
example of how it works. Let's call this model
of the Universe we've just been describing
"Newton's Universe." It described the Universe
as infinitely large and infinitely old. And that model worked pretty
well for about 200 years. Most astronomers accepted it
until in the 19th century problems began to emerge as new forms of evidence
appeared and new technologies. Now, I'm going to describe
this new evidence and how it undermined
Ptolemy's Universe very briefly. Your job is to dig much deeper
into the evidence. So let's go. What 19th century astronomers
were really interested in was trying to map the Universe. This meant two things. First, can you find
the distance to stars? Can you tell
how far away they are? And secondly, can you figure out
how they're moving? Now, let's begin
with the problem of distance. Can you imagine
how could you figure out how far away the stars are? It's not easy at all. But in fact, the Greeks,
who were really good at thinking about the Universe
logically and rationally had already figured out
how you do it. And the method
is that of parallax. Let me try and explain. Now, take your finger,
put it right in front of your nose,
and now, hold the finger steady and waggle your head
and notice that the finger moves against the background. Okay? Now, move the finger away,
do the same thing and what you'll notice
is the finger seems to move far less against the background. Now, the Greeks had figured out
that something like this might be true
of the Universe. If there's a star
that's near us, it's a bit
like your finger. You may see it moving
against the background. By figuring out
how much it moves, you ought to be able
to calculate how far away it is using trigonometry,
which is the math all surveyors use. But there was a problem. The Greeks simply
didn't have the technology to make precise
enough measurements and the movements of stars,
even the very nearest, are absolutely tiny. So it was not until
the 19th century when new, better telescopes
emerged that we were able to make the first
parallax measurements and the first measurements
of the distance to nearby stars. Astronomers also developed
a whole series of other ways of measuring
the distance to stars. I'll give you
just one more example. It involves a special type
of star called a Cepheid. Cepheids vary. The pole star is a Cepheid. An American astronomer
called Henrietta Leavitt began to study Cepheids. And what she found out
is that from the way they vary you can tell exactly
how bright they really are. Now, if you know how bright
they really are, you can figure out
how far away they are because you can figure out
how much light has been lost in between. So that's one
of a whole series of ways of measuring the distance
to stars. Now, astronomers also began
to figure out ways of measuring whether stars
are moving away from us or towards us. At first sight,
that may sound impossible. The techniques are very clever. They're based on the principle
of the Doppler effect. Now, you know if an ambulance
goes past you, the pitch seems to drop. It goes (imitates siren)
as it moves past you. We've all seen this.
Okay? What's happening is that
the frequency is dropping as it starts moving
away from you. Now, astronomers figured out
that the same thing happens with the light
from distant stars or galaxies. Its frequency drops. That means it's shifted
towards the red end of the spectrum. So astronomers say
it's "redshifted." Now, if you find
a distant galaxy is redshifted, that means it's moving away
from us. In the 1920s, an American
astronomer, Edwin Hubble, used the Mount Wilson Telescope in L.A. to make
an astonishing discovery. What he did was he used
all the information we've just been describing
and what he found was first, that most galaxies
seem to be moving away from the Earth. That was a surprise. But they found something
even more astonishing. The further away they were,
the faster they seemed to be moving away
from Earth. Okay, think about
this for a moment. What could that possibly mean? Well, it seemed to mean first that Newton's model of the
Universe simply doesn't work. The Universe is not fixed
in time and space. Instead, it's expanding. Now, for most astronomers,
that was a quite remarkable and unexpected conclusion
because if it's expanding now, think about the past. It must have been smaller
in the past. And at some time in the past,
it must have been infinitely small. That's what
the Belgian astronomer Lemaitre called
the "primordial atom" from which everything came. Now, this was a revolution. It was a revolution
in astronomical thinking. And what it meant
was that the Universe, like you and me, has a history
of change over time. But it took 40 or 50 years
to figure out all the implications
of what Hubble had found and to actually tease out
that history.