Miscellaneous announcements

1
Miscellaneous announcements

• Pick up graded homework
• Congratulations to our first winner of the Monty
  Python Galaxy Song Challenge!

2
The Moon and Eclipses

• 8 September 2006

3
Today

• Motions and phases of the moon
• Eclipses
• Measuring the moons size and distance

4
Motion of the Moon

• On any given day, the moons motion is
  essentially the same as that of a star (rises in
  the east, sets in the west).
• The moons position is always near the ecliptic
  (the suns apparent path among the stars).
• The moons motion doesnt keep up with the stars
  or the sun It completes only 348º of a circle
  in 24 hours.
• Falling 12º behind the sun each day, the moon
  completes a full circle (with respect to the sun)
  once every 30 days (actually 29). One month!

5
Phases of the Moon
Crescent
Half
Gibbous
Full
Gibbous
Crescent
New
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(No Transcript)
7
(No Transcript)
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(No Transcript)
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Solar Eclipse(Moon passes in front of sun)
Moon
Earth
Sun
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Lunar Eclipse(Moon passes through earths shadow)
Earth
Moon
Sun
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Lunar eclipse photos
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Size of the moon
Earths Shadow
Moons diameter is about 1/3 that of earths
shadow, or about 1/4 that of the earth
(Aristarchus).
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Distance to the moon(Big circle problem)

1. Imagine a big circle, passing through the moon,
   centered on you.
2. 720 moons would fit around the circle.
3. Each moon is 1/4 earths diameter, so 180 earths
   would fit around circle.
4. Radius (distance) is circumference divided by
   about 6, or 30 earth diameters (about 240,000
   miles).

1/2 degree
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Earth and moon to scale
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Distance to the sun?
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Distance to the sun?
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Distance to the sun?
Angle?
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Distance to the sun?
Angle?
The angle is indistinguishable from 90º.