Unit 4 Lesson 1 Part I Earth’s Days, Years, and Seasonspioneerscience.weebly.com/uploads/1/3/3/1/13312494/... · • Earth rotates in a counterclockwise motion around ... of Earth’s

Unit 4 Lesson 1 Part I Earth’s Days, Years, and Seasons

Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 4 Lesson 1 Earth’s Days, Years, and Seasons

Florida Benchmark


•  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


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.



•  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.




•  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.



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.



What determines the length of a year?



Tilt-a-Whirl


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.


What conditions are affected by the tilt of Earth’s axis?



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.



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.



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.



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.



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.



What conditions are affected by the tilt of Earth’s axis?



•  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 Part I Earth’s Days, Years, and Seasonspioneerscience.weebly.com/uploads/1/3/3/1/13312494/... · • Earth rotates in a counterclockwise motion around ... of Earth’s