Observing the Solar System

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Observing the Solar System

• Chap 16, Sec 1

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Chap 16 Sec 1 Essential Questions

1. What are the geocentric and heliocentric systems?
2. How did Copernicus, Galileo, and Kepler
   contribute to our knowledge of the solar system?
3. What objects make up the solar system?

video
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Stars

• 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
• 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
  constellations that circle around the north star.

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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
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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 wasnt widely accepted because
  so many believed the Earth had to be at the center

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The Heliocentric Model
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Nicolaus Copernicus
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Nicolaus Copernicus

• In 1543 (almost 1500 years after Ptolemys
  geocentric work) Copernicus was able to work out
  the arrangement of the known planets and how they
  move around the sun.
• Most people couldnt accept this new idea they
  would need proof first
• By the way, Copernicus was Polish

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Galileo Galilei
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Galileo Galilei

• Galileo made two important discoveries using the
  newly invented telescope that supported the
  heliocentric model
• In 1610 he discovered four moons revolving around
  Jupiter
• This proves not everything in space revolves
  around Earth
• He discovered Venus goes through a series of
  phases similar to our Moon.
• Venus would not have a full set of phases if it
  encircled Earth
• Just so you know, Galileo was Italian

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Tycho Brahe
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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
  hadnt been invented yet
• Brahe was Danish

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Johannes Kepler
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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

• 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!

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Essential Questions Answered

• 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.
• 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

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• 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.