Models of the Universe

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Models of the Universe

• Highlights of yesterdays workshop
• Observations, virtually
• Todays workshop compare two models

E.J. Zita
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Yesterdays workshop

• Q1 Do you believe the Sun orbits the Earth, or
  Earth orbits the Sun?
• Q2 Why do you believe this?
• Q3 How can you know?
• Q4 Does it matter?

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Why we believe Earth orbits Sun

• We were told its so
• by someone we trust
• by a reliable or persuasive authority
• by a textbook
• Its common knowledge, common sense, or a
  paradigm
• Possible evidence?
• seasons
• phases of Venus and Mercury
• retrograde motion of Mars
• gravity Sun is bigger
• photos or videos from outside the solar system

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Evidence what do we experience?

• Gravity why do things fall toward the center of
  the Earth? Because the Earth is the center of
  the universe? If the Sun is the center, why
  dont things fall toward the Sun?
• Seasons what do these tell us about the motion
  of Earth or Sun?
• Motion what should it feel like if Earth were
  whizzing around the Sun?

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Evidence what do we see in the sky?

• Motion of Sun
• Motion of Stars
• Motion of planets
• Other evidence gravity? seasons?
• Implications for Earth?

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Virtual observations

• We will use planetarium demonstrations to
  investigate a few of these phenomena.
• First, PREDICT WHICH of these you expect to see,
  if Earth orbits the Sun
• stellar parallax (relative motion of the fixed
  stars yes or no?)
• phases of Venus and Mercury (yes or no?)
• retrograde motion of Mars (against the fixed
  stars) yes or no?

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Stellar Parallax - Q

• If Earth orbits the Sun, then we should see the
  fixed stars moving. Why? Model
• - Hold out a finger as a fixed star
• Let your right eye be Earth in January
• Let your left eye be Earth in June

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Stellar Parallax - Investigation

• EXPERIMENT
• Blink one eye shut,
• then the other.
• REASON
• If Earth moves (eyes),
• then the stars should
• appear to move (finger)

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Stellar Parallax - OBSERVE

• Well use the planetarium to observe a
  constellation
• year after year, with some stars closer and other
  stars further away from Earth.
• If Earth orbits the Sun, what do you predict you
  will see in the stars?
• Watch the planetarium demo do you see the stars
  change positions?
• What does this imply about the relative motion of
  Earth and Sun?

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Stellar Parallax last nights N sky
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Stellar Parallax Sept March
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Phases of the Moon

• Why do we see these? http//www.mysteriousworld.co
  m/Journal/2003/Summer/SerpentMound/

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Phases of planets Q1

• IF we see phases of the Moon because the Moon
  goes around Earth,
• THEN, IF we saw phases of Venus and Mercury,
• - would that mean Venus and Mercury go around
  Earth?
• - would that mean Venus and Mercury and Earth go
  around Sun?

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Phases of planets Q2

• IF we see phases of the Moon because the Moon
  goes around Earth,
• THEN, IF we DONT see phases of Venus and
  Mercury,
• - would that mean Venus and Mercury dont go
  around Earth?
• - would that mean Venus and Mercury and Earth go
  around Sun?

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Phases of planets - OBSERVE

• Watch the planetarium demonstration.
• Can you see phases (e.g. a crescent shape) of
  Mercury or Venus?
• What could this tell you about the relative
  motion of Earth and Sun?

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Phases of planets - VENUS
http//academic.evergreen.edu/curricular/beliefand
truth/lessons/movies/venus
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Retrograde motion of Mars

• Watch the planetarium demo.
• What is Mars doing? Why?
• What could this tell you about the relative
  motion of Earth and Sun?

http//academic.evergreen.edu/curricular/beliefand
truth/lessons/movies/mars
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We report, you decide

• Youve seen the evidence.
• Now do the workshop.
• Which model fits the evidence best?

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MODELS OF THE UNIVERSE workshop