Download Observing the Solar System

Observing the Solar
System
Chap 16, Sec 1
Chap 16 Sec 1 Essential
Questions
1.
2.
3.
What are the geocentric and
heliocentric systems?
How did Copernicus, Galileo, and
Kepler contribute to our knowledge
of the solar system?
What objects make up the solar
system?
video
Stars
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Ancient Greeks noticed the stars are grouped
together in patterns we call constellations.
The stars in a constellation stay the same
night after night, and year after year.
There are 88 constellations
The Greeks also noticed several “stars” that
seemed to wander slowly among the stars
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The Greeks named these lights planets (which is
a Greek word for wanderers)
The Romans later named the planets they could
see: Mercury, Venus, Mars, Jupiter, and Saturn
Look on page 554 at the time lapse photo.
This was made while viewing the circumpolar
Geocentric System

Ancient Greeks believed Earth (Greek:
geo) is at the center of the revolving
planets and stars
This is known as the Geocentric system
 Ptolemy further developed the geocentric
model to show planets moving on small
circles that move on bigger circles
 His model was incorrect, but did explain the
motions observed in the sky fairly accurately
 This model was widely accepted for nearly
1500 years after Ptolemy introduced it
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The
Geocentric
Model
Heliocentric System

Another ancient Greek explanation for the
motion of the planets said the sun is at the
center and Earth and the other planets
revolve around it
This is known as the heliocentric system
(helios is Greek for sun)
 This explanation wasn’t widely accepted
because so many believed the Earth had to
be at the center
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The
Heliocentric
Model
Nicolaus Copernicus
Nicolaus Copernicus
In 1543 (almost 1500 years after
Ptolemy’s geocentric work) Copernicus
was able to work out the arrangement of
the known planets and how they move
around the sun.
 Most people couldn’t accept this new idea
– they would need proof first
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By the way, Copernicus was Polish
Galileo Galilei
Galileo Galilei

Galileo made two important discoveries using
the newly invented telescope that supported
the heliocentric model
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In 1610 he discovered four moons revolving
around Jupiter
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He discovered Venus goes through a series of
phases similar to our Moon.
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This proves not everything in space revolves around
Earth
Venus would not have a full set of phases if it encircled
Earth
Just so you know, Galileo was Italian
Tycho Brahe
Tycho Brahe
In the late 1500s Tycho Brahe and his
assistants observed and recorded the
positions of the planets (this would be
important later in changing the model
developed by Copernicus)
 They did this without telescopes because
they hadn’t been invented yet
 Brahe was Danish
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Johannes Kepler
Johannes Kepler
Kepler was an assistant to Tycho Brahe
who died in 1601.
 Kepler carefully analyzed all the
observations collected under Brahe and
eventually found that the orbit of each
planet is an ellipse (a flattened oval)
 This disproved the belief that all planets
move in perfect circles
 He was German
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Modern Discoveries
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Today we know the solar system consists of the sun,
the planets and their moons, and several kinds of
smaller objects that revolve around the sun (such as
comets and asteroids)
 A moon is a natural satellite that revolves around
a planet
We have telescopes on Earth and orbiting in space
We have sent astronauts to the moon and launched
many space probes to explore our solar system
Our understanding of the solar system continues to
grow every day.
I wonder what will be discovered during your
lifetime!
Essential Questions Answered
1.
What are the geocentric and heliocentric
systems?
The geocentric system said Earth is at the center of the
revolving planets and stars (including the sun and moon).
The heliocentric system says the sun is at the center of our
solar system and is surrounded by planets and their
moons.
2.
How did Copernicus, Galileo, and Kepler
contribute to our knowledge of the solar
system?
Copernicus – further developed the heliocentric system by
calculating the arrangement of the planets and how they
move around the sun
Galielo – used the newly invented telescope to make
discoveries that supported the heliocentric model
Kepler – discovered the orbit of each planet is an ellipse
3. What objects make up the solar system?
The sun, the planets and their moons, and several kinds of
smaller objects that revolve around the sun.