2.1 Understand how the occurrence of
and the conditions related to day and
night and the seasons are caused by
the earth’s movement in space.
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2.1.1 Distinguish between the
terms rotation and revolution.
Rotation:
• The earth spins on its own axis.
• The earth rotates 360 degrees, or one complete
rotation, on its own axis in one day.
• The earth rotates from west to east, in a
counterclockwise motion.
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Revolution:
• The earth circles the sun.
• It takes the earth 365.25 days to orbit the
sun.
• The earth travels in a counterclockwise
direction around the sun.
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Earth’s Revolution:
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In Summary:
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Video Earth’s Rotation:
http://www.youtube.com/watch?v=CEe
8vzJjj3M
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Animation: Earth’s Revolution
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2.1.2
Explain how cloud cover
influences the range of temperature
from day to night.
• Nightly cloud cover reduces the range
of temperature from day to night.
• Clouds reflect heat waves
• Heat below clouds is reflected back to
earth.
• Without clouds heat escapes, giving
colder nights
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2.1.3
1.
2.
3.
4.
Define the terms Equinox &
Solstice
Solstice:
Occurs Dec 21 & June
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Longest amount of
daylight/dark in the
year!
Sun is directly over
head @ 12 noon on
23.5o North or South.
From Latin for sun
stand still
1.
2.
3.
4.
Equinox:
Occurs Sept. 21 &
March 21
Equal length of
daylight AND dark
everywhere on earth!
Sun is directly over
head @ 12 noon on
the equator.
From Latin for equal
day & night.
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2.1.3
Define the terms Equinox &
Solstice
Equinox
Solstice
Adapted from “World
Geography” p. 56
Solstice
Equinox
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2.1.4 Changes in Seasons Relate to Earth’s
Revolution around the Sun
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Describe how the Seasons are related to the
Earth’s Revolution around the Sun
Seasons are directly related to the
earth’s revolution around the sun
Because of the tilt, different places
receive different lengths of day and
night
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The tilt in the earth cause sunlight to hit
the earth at different angles
When the sun is directly overhead, the
sun’s rays are more intense
As the earth revolves around the sun;
1. the length of day changes 2. the
intensity of the sun’s rays change
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2.1.4 As seasons change, so does the amount of
direct sunlight
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The length of day and intensity of
sunlight changes gradually as each
hemisphere leans toward or away from
the sun.
The seasons are characterized by
gradual transitions, as each hemisphere
receives more or less sunlight
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Check for Understanding!
Chapter 4
Read pages 55-57
Do questions on page 55: #’s 6, 7, 8
and 9
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The Earth in its Revolution around the Sun!
2.1.4
•September 21st
•North is in Fall
•12 hrs day & 12 hrs night
•Noon Sun 900 @ Equator
•Dec 21st
•South is in Spring
•North is in Winter
•June 21st
•Less sun hours
•North is in
Summer
•Less direct sun
•More sun hours
•South is in Summer
•More direct sun
•More sun hours
•Noon Sun 900 @
Tropic of Cancer
•More direct sun
•Noon Sun 900 @
Tropic of Capricorn
•South is in Winter
•March 21st
•Less sun hours
•North is in Spring
•Less direct sun
•12 hrs day & 12 hrs night
•Noon Sun 900 @ Equator
•South is in Fall
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2.1.5 Differences in Length of day as Seasons
Change.
The tilt of the earth’s axis, plus the earth’s
rotation in orbit around the sun, gives the
earth different lengths of daylight!
The pole pointed towards the sun receives
more hours of exposure to the sun. This
feature gives this hemisphere longer days.
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Differences in Length of Day…June
In June, because of
the tilt on the
earth's axis, the
north pole points
towards the sun.
It receives more
hours of exposure to
the sunlight hence
giving it longer days.
June Solstice
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Differences in Length of Day…June
Northern
hemisphere only
rotates out of the
sunlight for a short
period each day
i.e. Daylight at 5:30
am and dark at
10:00 pm
June Solstice
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Differences in Length of Day…December
In December,
because of the tilt
on the earth's axis,
the north pole points
away from the sun.
It receives fewer
hours of exposure to
the sun hence giving
it shorter days.
December Solstice
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Differences in Length of Day…December
Northern
hemisphere rotates
out of the sunlight
for a long period
each day
i.e. Daylight at 8:30
am and dark at 4:30
pm
December Solstice
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Differences in Length of Day…equinoxes
(Mar 21 & Sept 21)
On March 21 and
September 21,
because of the tilt
on the earth's axis,
all parts of the earth
receive equal
amounts of sunlight.
Day and night are of
the same length.
March 21 and Sept 21
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2.1.6
Differences in Temperature as
Seasons Change.
Two factors:
1. Longer summer
daylight hours means
there are more heating
hours and fewer cooling
hours.
2. More direct sunlight
gives greater intensity of
heat!
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2.1.6 Common Misconception!
Misconception : The
difference in summer and
winter is due to the earth
getting closer or further
from the sun.
Actually we are further
from the sun in our
summer!
The difference in summer
and winter is due to the tilt
of the earth on its axis!
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Remember!
The earth’s rotation in orbit around the sun
accompanied by the tilt of the earth on its axis,
gives the earth different day lengths,
differences in temperatures, and ultimately
different seasons!
The pole pointed towards the sun receives
more hours of exposure to the sun. This tilting
gives the pole pointed toward the sun longer
days and warmer temperatures.
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