Post on 07-Mar-2018
Unit 4 Lesson 1 Part I Earth’s Days, Years, and Seasons
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
Florida Benchmark
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• SC.8.E.5.9 Explain the impact of objects in space on each other including: 1. The Sun on the Earth including seasons and gravitational attraction, 2. The Moon on the Earth, including phases, tides, and eclipses, and the relative position of each body.
Spinning in Circles
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What determines the length of a day?
• Each planet spins on its axis. • The spinning of a body, such as a planet, on its
axis is called rotation. • The time it takes a planet to complete one full
rotation on its axis is called a day.
Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
What determines the length of a day?
• Earth rotates in a counterclockwise motion around its axis when viewed from above the North Pole.
• As a location on Earth’s equator rotates from west
to east, the sun appears to rise in the east, cross the sky, and set in the west.
• Only one-half of Earth faces the sun at any given
time.
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
What determines the length of a day?
• People on the half of Earth facing the sun experience daylight, and this period is called daytime.
• People on the half of Earth facing away from the
sun experience darkness, and this period is called nighttime.
• Earth completes one rotation on its axis in 24
hours, or one day.
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
What determines the length of a year?
• As Earth rotates on its axis, it also revolves around the sun.
• The motion of a body that travels around another
body in space is called revolution. • Earth completes a full revolution around the sun in
365 ¼ days, or about one year. We have divided the year into 12 months, each lasting 28 to 31 days.
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
What determines the length of a year?
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
Tilt-a-Whirl
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What conditions are affected by the tilt of Earth’s axis? • Earth’s axis is tilted at 23.5°. During each
revolution, the North Pole may be tilted toward the sun or away from the sun.
• When the North Pole is tilted toward the sun, the
Northern Hemisphere has longer periods of daylight than does the Southern Hemisphere.
• When the North Pole is tilted away from the sun,
the opposite is true.
Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
What conditions are affected by the tilt of Earth’s axis?
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
What conditions are affected by the tilt of Earth’s axis? • The angle at which the sun’s rays strike each part
of Earth’s surface changes as Earth moves in its orbit.
• When the North Pole is tilted toward the sun, the
sun’s rays strike the Northern Hemisphere more directly, and this region is warmer.
• When the North Pole is tilted away from the sun,
the sun’s rays strike the Northern Hemisphere less directly, and this region is cooler.
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
What conditions are affected by the tilt of Earth’s axis? • The spherical shape of Earth also affects how the
sun warms up an area. • At a point near the equator, the sun’s rays hit
Earth’s surface more directly, so temperatures are higher there.
• At a point near one of the poles, the sun’s rays hit
Earth’s surface less directly, so temperatures are lower there.
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
What conditions are affected by the tilt of Earth’s axis? • Compare the area over which the sun’s rays are
spread at the equator and at the poles.
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
What conditions are affected by the tilt of Earth’s axis? • The number of daylight hours on any given day of
the year varies with location. • Areas around Earth’s equator receive about 12
hours of light a day.
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
What conditions are affected by the tilt of Earth’s axis? • Areas on Earth’s surface that are tilted toward the
sun have longer than 12-hour days, as they travel a longer path through the lit part of Earth.
• Areas on Earth’s surface that are tilted away from
the sun have shorter than 12-hour days, as they travel a shorter path through the lit part of Earth.
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
What conditions are affected by the tilt of Earth’s axis?
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons
• Which place has the longest days? Which has the shortest?
What conditions are affected by the tilt of Earth’s axis? • During summer in the Northern Hemisphere,
areas north of the Arctic Circle receive 24 hours of daylight.
• At the same time, areas south of the Antarctic
Circle receive 24 hours of darkness. • In winter in the Northern Hemisphere, the polar
areas experience the reverse conditions.
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Unit 4 Lesson 1 Earth’s Days, Years, and Seasons