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The Reasons for the Seasons
Rotation
Earth spins on its axis (An
imaginary line through center of
Earth from the North to South
Pole)
 Earth’s 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 is tilted on its
axis at an angle of
23.5°
Earth’s axis is currently
pointed at Polaris (the
North Star)
Rotation

Earth rotates on its axis
once every 24 hrs

Earth’s rotation causes
day & night

Earth’s rotation causes
celestial objects to
appear to move from
east to west in
Northern Hemisphere
Night and Day Map
Interactive Day-night Map
Just Checking…
THINK…PAIR…SHARE
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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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The movement of one object around another
Earth revolves around our Sun counterclockwise
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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)
Are you there yet?

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
What’s the diff????
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
Two Primary Reasons for the
Seasons (on Earth)
1. The Earth is tilted
on its axis at 23.5°
2. The angle sunlight
hits the Earth as it revolves
around the sun.
Location and Distance in Orbit
Seasons occur
due to the tilt of
the Earth’s axis &
revolution
around the Sun.
Seasons

Northern hemisphere tilts towards Sun =
summer (warmer)
Which numbered Earth represents Summer
in the Northern Hemisphere?
Seasons

Northern hemisphere tilts away from Sun
= winter (cooler)
Which numbered Earth represents Summer
in the Northern Hemisphere?
Which numbered Earth represents Winter
in the Northern Hemisphere?
Seasons
Which numbered Earth represents Fall
 in the Northern Hemisphere?

Which numbered Earth represents Summer
in the Northern Hemisphere?
Seasons
Which numbered Earth represents Spring
in the Northern Hemisphere?

Which numbered Earth represents Summer
in the Northern Hemisphere?
Seasons

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 are
opposite Northern hemisphere
seasons
 If its Winter here, then Australia is
having _?_.

Solstices

Occur twice yearly when the Sun is directly over
“Tropics” (23.5°N and 23.5°S Latitude)
 Summer Solstice is the longest day of the year in
the Northern Hemisphere (Sun directly over Tropic
of Cancer-23.5°N-at noon)
 Winter solstice = shortest day of the year for
Northern Hemisphere (Sun directly over Tropic of
Capricorn-23.5°S-at noon)
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Equinox
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Means equal amounts
of night & day
They occur twice each
year
They occur half-way
between solstices
Neither hemisphere
tilts towards or away
from the Sun
At noon, the Sun is
directly over equator
Turn and Talk
about the Equinox

The Sun will be at its highest point in our sky
at noon but never directly overhead in
Carrollton, Texas… why do you think this is
true?
Where are we?
Your answer should refer to Carrollton 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 Carrollton?
• What time do you think it is in Carrollton?