Seasons, Tides, and Phases of the Moon

1
Seasons, Tides, and Phases of the Moon

• J. C. Sprott
• Department of Physics
• University of Wisconsin
• Madison, WI 53706
• Presented to the
• Green County Science Teachers Workshop
• on February 25, 2000

2
Science Literacy

• Over 200 studies document scientific illiteracy.
• Scientific illiteracy hurts Nation and
  individuals.
• Teachers are uncomfortable teaching science.
• Science has fallen out of favor.
• We have a public-relations problem.

3
What causes the seasons?
Earth
Sun
4
How many times does the earth rotate about its
axis in a year?
365.242 1 366.242
Sun
Earth
5
As seen from the North Pole, which direction does
the earth rotate?
Counter-clockwise
Sun
Earth
6
How do we know the earth is rotating?

• Foucault Pendulum (1851)
• Coriolis Effect
• Wind Patterns
• Projectile Deflection

7
How do we know the earth orbits the sun?

• Annual Parallax of the Stars (1837) - nearby
  stars appear to move
• Aberration of Starlight (1727) - change in
  apparent direction of stars, cf raindrops

8
What causes the phases of the moon?
Sun
Earth
Moon
9
When you observe a crescent moon in the evening,
do the tips point left or right?
Facing South
sun
West
10
Can a full moon rise at midnight?
Sun
No!
New Moon
Half Moon
Earth
Full Moon
11
How can you tell the moon is close and the sun is
far?
Moon
Sun
Half Moon
Sun
Earth
12
On the scale of the earth as a 10 globe, how far
is the moon, sun, etc.?
Moon
25 feet
Sun
1.9 miles
Pluto
73 miles
Alpha Centauri
500,000 miles
Space Shuttle
0.25 inch
13
What causes an eclipse?
Sun
Solar Eclipse
Earth
Lunar Eclipse
14
Why do we always see the same face of the moon?
Earth
Moon
15
What causes the tides?
Sun
Moon
Earth
Moon
16
Where is the center-of-mass of the earthmoon?
Moon
R 0.75R
e
Earth
17
Where is the center-of-mass of the sunearth?
Earth
R 0.0006R
s
Sun
18
What does the orbit of the moon around the sun
look like?
Moon
Sun