Unit 6 Lesson 1 How Do the Sun, Earth, and Moon Interact? Copyright Houghton Mifflin Harcourt Publishing Company

Transcription

1 Unit 6 Lesson 1 How Do the Sun, Earth, and Moon Interact?

2 Night and Day Earth rotates, or turns like a top. Earth s rotation causes day and night. Earth rotates around an imaginary line called an axis, which runs through its center from the North Pole to the South Pole. Earth completes one rotation around its axis once every 24 hours, or once a day.

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4 Night and Day As Earth rotates, one side of Earth faces the sun. This side of Earth has daytime. The other side of Earth faces away from the sun. This side of Earth has night time.

5 Q1

6 Q2

7 The-Sun-Earth-Moon System The Sun, Earth, and the moon form a system in space. This system is held together by gravity.

8 The-Sun-Earth-Moon System Gravity is a force that pulls objects toward each other. Gravity pulls Earth toward the sun, holding Earth in an orbit around it.

9 The-Sun-Earth-Moon System An orbit is the path an object takes around another object in space. Earth revolves, or travels, around the sun. It takes Earth about 365 days to complete one revolution. (1 year)

10 The-Sun-Earth-Moon System While Earth revolves around the sun, the moon revolves around Earth. Like Earth, the moon turns on its axis. It takes about one month for the moon to complete one rotation. During the same period of time, the moon makes one complete revolution around Earth. Because the moon s rotation and revolution take the same amount of time, the same side of the moon always faces Earth.

11 The-Sun-Earth-Moon System

12 Q3

13 The-Sun-Earth-Moon System The sun has the largest diameter of all bodies in the solar system. The sun is a hot, glowing ball of gas that is composed mostly of helium and hydrogen. It is about 4.6 billion years old.

14 The-Sun-Earth-Moon System

15 The-Sun-Earth-Moon System

16 The-Sun-Earth-Moon System Earth and the moon both have rocky surfaces. Earth s surface has large oceans, and it has a thick atmosphere of nitrogen and oxygen. It has life forms. Unlike Earth, the moon has no atmosphere or water. The moon experiences extreme cold and heat. It has no known life forms.

17 Seasons

18 Seasons As Earth revolves around the sun, the direction of its tilted access does not change. The tilt of Earth s axis and its orbit cause the seasons. Earth is divided into halves called hemispheres. The Northern Hemisphere extends from the equator to the North Pole. The Southern Hemisphere extends from the equator to the South Pole.

19 Seasons When one of the hemispheres tilts toward the sun, it has summer. When one of the hemispheres tilts away from the sun, it has winter. As Earth orbits the sun, the two hemispheres alternate between tilting toward and away from the sun. ( That s why seasons occur )

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23 Our Place in Space Long ago, astronomers believed Earth was the center of the universe. It took hundreds of years, new technology, and new observations for this idea to change. In the 1500s, a Polish astronomer named Nicolaus Copernicus designed a new model, or system, of the universe. He suggested that Earth and the planets revolved around the sun. In the 1600s, scientists gathered more evidence to support this sun-centered model.

24 Our Place in Space (My Very Excellent Mother Just Served Us Noodles)

25 Our Place in Space Galileo Galilei was the first to see moons orbiting Jupiter, using a telescope he made. His observation showed that all objects in space did not orbit Earth. Johannes Kepler correctly described the shape of the planets orbits around the sun. His calculations showed that the planets revolved around the sun in elliptical orbits. All these scientists observations changed our ideas about Earth s place in space.

26 Patterns in the sky Constellation is a group of stars that seems to form a picture in the night sky. The early Greeks named constellations after animals or people from stories called myths. The big dipper is part of constellation called Ursa major or great bear. Orion is a constellation named after a hunter in Greek myth.

27 Patterns in the sky

28 Patterns in the sky

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