Seasons,

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Seasons, Phases, Eclipses, and Tides
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Rotation
Earth rotates on its axis once every 24 hours in
a counterclockwise direction When your part of
the earth faces the sun, you experience day. What
happens to cause night?
Video clip on day and night\\LANIER_MS_FS02\VOL1\U
SERS\S1\Science sharing\6th grade earth
science\Astronomy\Streaming\Earth_s_Axis_and_Spin_
Creates_Night_and_Day.asf
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East West
Sun appears to rise in the east and set in the
west because the Earth turns on its axis from
west to east.
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Revolution
The time it takes to make one trip around the sun
is a year. That is one revolution.
Click here for an animation of a year.
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Hyperlinks to animations of rotation and
revolution.
rotation
revolution
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Leap year
It takes 365.24 days for Earth to go around the
sun one time. This means we are not at the same
place in our orbit as we began. Because of the
0.24 equals about ¼ of a day, we add a day to our
calendar every 4 years. 2008 was a leap year so
we had a February 29th. Our next February 29th
will be in 2012.
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Tilt of earth causes seasons.
Video clip on seasons
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No tilt no seasons
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Solstices
Links to animations below
Winter solstice
Summer solstice
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Equinox animation
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(No Transcript)
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Many people believe we have summer because we are
closer to the sun in the summer. Look at the
diagram and explain why they are wrong!
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Bad Astronomy Only on the day of the Vernal
(spring) Equinox, can you stand a raw egg on its
end.
Good astronomy If you can stand a raw egg on
end, it has nothing to do with the Equinox.
How it works This has to be one of the silliest
misconceptions around, and it never seems to
die. Every year, without fail, some TV station
broadcasts a news segment showing local
schoolchildren standing eggs on end on the first
day of spring. Usually, the newscaster will make
some vague mention about how this works, but it
is rarely specific, and never holds up to too
much scrutiny.
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(No Transcript)
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Now let's look at the moon.
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The moon does not make its own light. We see it
because it reflects light from the sun.
The terminator is the moving boundary between day
and night. Notice that it moves right to left.
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Daytime on the moon
Night on the moon
Terminator
Rotation/revolution
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Phases of the moon are caused by the angle
between the earth, moon, and sun.
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Waxing means getting bigger every night. Waning
means getting smaller every night.
Crescent means less than half the surface of the
moon facing you is lit by the sun. Gibbous means
more than half of the surface of the moon facing
you is lit by the sun.
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Review this diagram and name the phases on the
following slides!
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Waning crescent
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Waxing gibbous
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Waxing crescent
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Last quarter
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Waning crescent
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Waning gibbous
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First quarter
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Lunar Phase animation
Notice that the terminator is moving right to
left.
Video clip on phases
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Tides
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This is a review of tides since we studied them
already!
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Watch the change in water level in the Bay of
Fundy in Canada.
This happens two times a day because there are
two high tides and two low tides each day.
Video clip on tides
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Notice that every six hours there is a high or
low tide. If high tide occurs today at 600 am
in Savannah, GA, what time will be low tide?
When will the next high tide occur?
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Because the sun also affects the tides, there are
times with the sun and move work against each
other and times when their forces are added
together.
Video clip on sun and tides
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Eclipses - are named by which object's light is
being blocked from your view!
Two kinds Lunar eclipses Solar eclipses
Video clip on eclipses
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Lunar eclipse
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Eclipse animation
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Time lapse photography of a lunar eclipse
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Animation of solar eclipse
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Diamond ring effect just before or after a total
solar eclipse.
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This animation shows the relative sizes of the
partial and total eclipse areas. The small,
black dot is the umbra. You can see why not many
people ever see a total eclipse.
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This is a space shuttle photograph of an area of
the Earth having a total solar eclipse.
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• Types of Solar Eclipses
• Total Solar Eclipses occur when the umbra of the
  Moon's shadow touches a region on the surface of
  the Earth.
• Partial Solar Eclipses occur when the penumbra of
  the Moon's shadow passes over a region on the
  Earth's surface.
• Annular Solar Eclipses occur when a region on the
  Earth's surface is in line with the umbra, but
  the distances are such that the tip of the umbra
  does not reach the Earth's surface.

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Types of eclipses
Link to NASA eclipse page Be sure to scroll down
for a list of upcoming eclipses.
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Questions?