Transcript Rotation & revolution

The Reason for the Seasons
Rotation
Earth spins on axis (imaginary
line through center of Earth from
North to South Pole)
 Rotation is counter clockwise as
seen from North Pole
 Earth spins on its axis like a top
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Polaris
Rotation - Axis
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Earth tilt = 23.5°
Axis currently pointed
at Polaris (the North
Star)
Rotation
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Earth rotates once
every 24 hrs
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The rotation causes
day & night
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Earth’s rotation
causes celestial
objects to appear to
move from east to
west in Northern
Hemisphere
Night and Day Map
Just Checking…
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What does it mean when we say the
Earth rotates?
How would you define or explain the
concept of Earth’s axis?
Revolution
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Movement of one object around another
Earth revolves around Sun
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counterclockwise
Earth’s orbit is almost circular rather than oval shaped but
is still referred to as an elliptical orbit
365 ¼ days to revolve once around the Sun (~ a year)
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The imaginary line that runs through the
north and south poles of the Earth is
called the
A. Equator
B. Axis
C. Longitude
D. Latitude
Decide weather each example is of
A. Rotation or B. Revolution
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The Earth spinning on it’s axis.
A baseball player running around
the infield.
Takes 1 year
A top spinning
Causes day and night.
Takes 24 hours
The moon circling the Earth
Location and Distance in Orbit
Two Primary Reasons for the
Seasons (on Earth)
1. angle of Sun in the sky at a given time and
latitude
2. number of hours of daylight at a given
time and latitude.
Handout available at http://www.uwm.edu/~kahl/CoVis/Seasons/
Seasons
Seasons
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Northern hemisphere tilts towards Sun =
warmer (Summer)
Seasons
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Northern hemisphere tilts away from Sun
= cooler (winter)
Seasons
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In the Spring and the Fall, the tilt of the
Earth is such that the spread of sunlight
shines on the Earth approximately equally
Seasons
Southern hemisphere seasons
opposite Northern hemisphere
seasons
 If its Winter here, then Australia is
having _?_.
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Solstices
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Occur twice yearly when the Sun is directly over
“Tropics” (23.5°N and 23.5°S Latitude)
 winter solstice = shortest day of the year for
Northern Hemisphere (Sun directly over Tropic of
Capricorn-23.5°S-at noon)
 Summer Solstice is the longest day of the year in
the Northern Hemisphere (Sun directly over Tropic
of Cancer-23.5°N-at noon)
Equinox
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equal night & day
Occurs twice each
year
Half-way between
solstices
noon sun directly over
equator
Sun will be at its
highest point in our
sky at noon but never
directly overhead in
Texas… why do you
think this is true?
Your answer should refer to Godley, TX.
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This occurs because the Earth’s
axis is tilted as it moves around
the sun.
This occurs when the Northern
hemisphere is tilted towards the
sun.
This is when the length of day and
night are equal.
The shortest and longest days of
the year when the noon sun is
directly overhead at 23.5 degrees.
This occurs when the Northern
hemisphere is tilted away from the
sun.
A.
B.
C.
D.
E.
Winter
Summer
Solstice
Equinox
All of the
above
Based on this Night and Day Map…
• What season do you think it is in Godley?
• What time do you think it is in Godley?