Phys 104

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At the scale of the Milky Way Galaxy, distances
are described in terms of Light-years, which is
the distance light travels in one year.
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What do you think?

• Do the stars stay in the same position in the sky
  all day/night long?
• Do we see the same stars all year round every
  night?

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What do you think?

• What causes the stars to move?
• Do the stars actually move in the way they appear
  to be moving from Earth?
• Is the daily motion of the Sun different from the
  stars?

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Consider the dome of the sky over our heads.
mixing bowl
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Consider the dome of the sky over our heads.
inverted mixing bowl .
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Imagining a spinning Celestial Sphere surrounding
Earth aids in thinking about the position and
motion of the sky.
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Imagining a spinning Celestial Sphere surrounding
Earth aids in thinking about the position and
motion of the sky.
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Imagining a spinning Celestial Sphere surrounding
Earth aids in thinking about the position and
motion of the sky.
What would this look like from the ground?
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Pre Tutorial Question

• You observe a star rising due east. When this
  star reaches its highest position above the
  horizon, where will it be?

A) high in the northern sky B) high in the
eastern sky C) high in the southern sky D) high
in the western sky E) directly overhead
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Tutorial Position p.1

• Work with a partner.
• Read the instructions and questions carefully.
• Talk to each other and discuss your answers with
  each another, but BOTH write in your own book.
• Come to a consensus answer you both agree on.
• If you get stuck or are not sure of your answer,
  ask another group.
• If you get really stuck or dont understand what
  the Lecture Tutorial is asking, ask me for help.

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Is the horizon shown a real physical horizon, or
an imaginary plane that extends from the observer
and Earth out to the stars? Can the observer
shown see an object located below the
horizon? Is there a star that is in an
unobservable position? When a star travels from
being below the observers horizon to being above
the observers horizon, is that star rising or
setting?
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Post Tutorial Question

• Stars that never appear to set are called
  circumpolar. As you move from Earths equator
  toward the North Pole, the number of stars that
  are circumpolar

A) increases. B) decreases. C) stays the same.
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Post Tutorial Question

• Imagine you are standing at the North Pole. Of
  the stars that you can see, roughly how many of
  these stars are circumpolar?

A) none B) less than half C) more than half D)
all
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Post Tutorial Question

• You are observing the sky from your southern
  hemisphere location in Australia. You see a star
  rising directly to the east. When this star
  reaches its highest position above the horizon,
  where will it be?

A) high in the northern sky B) high in the
eastern sky C) high in the southern sky D) high
in the western sky E) directly overhead
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• In what direction would you face (look) to see
  Star A when it is highest in the sky?

A) toward the north B) toward the south C) toward
the east D) toward the west E) directly overhead
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• Which of the stars will set on the western
  horizon?

A) both Star A and Star B B) only Star A C)
neither Star A nor Star B D) only Star B
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GO CONFIDENTLY IN THE DIRECTION OF YOUR DREAMS!!
LIVE THE LIFE YOUVE IMAGINED