Chapter 8: Planet Earth and Its Moon

Lesson 1How Does Earth Move?

EllipseA shape that is like a circle stretched out in opposite directions

RotationSpinning of a planet, moon, or star around its axis

EclipseEvent in which one object in space gets between the sun and another object

RevolutionMovement of one object around another object

VOCABULARY WORDS

Lunar eclipse

Event in which the moon passes through Earth’s shadow

Orbit Path an object follows as it revolves around another object

Solar eclipse

Event in which the moon passes between the sun and Earth

NASA The government agency that runs the U.S. space program

VOCABULARY

Earth, Sun, and Moon- The sun always illuminates half of the moon’s surface. As the moon orbits Earth, the moon’s position in relation to the sun changes. The positions of Earth, the moon, and the sun cause the moon’s phases. When the moon is positioned between the sun and Earth, the unlighted side of the moon faces Earth. The moon is not visible because its sunlit side is facing the sun. This phase is called a new moon. When Earth is between the sun and moon, the half of the moon that faces Earth is sunlit and visible. This phase is called a full moon.

Earth MovesYou cannot feel Earth’s movement, but you are moving along with Earth. Even though you cannot sense its motion, you can make observations to know that it does.

Cause/EffectBecause the Earth is tilting…

1. The sun and stars seem to move across the sky.

2. I cannot feel Earth’s movement.

Predict- If Earth did not rotate on its axis or move around the sun, what would be the sun’s position?The sun would be in one position and stay there.

Apply- How do you know you are moving when you are riding in a car?You can see objects move past you outside your window. You can also feel the car change speed and direction.

What is the Earth’s axis?

The axis is an imaginary line that runs from the Earth’s North Pole, through Earth’s center, and to the South Pole.

What would happen to the length of day and night if Earth rotated more slowly?

Both day and night would last longer.

Earth’s Rotation

The spinning of a planet, moon or star around its axis is called its rotation. Each time Earth makes a full turn around its axis, it makes one rotation. Earth takes 23 hours and 56 minutes to make one rotation. When Earth rotates, it turns from west to east. Earth’s rotation causes day to change into night and night into day. When a place on Earth is turned toward the sun, it has daylight.

SHADOWS

When light shines on an object and does not pass through it, the object cast a shadow. As Earth rotates, sunlight shines on an object from different angles.

Shadows are the shortest around noon because the sun is directly overhead.

Earth’s Revolution*An orbit is the path that the moon follows around the Earth. *As the Earth rotates, it travels around the sun. The movement of one object around another is called revolution.*Earth takes one year, or about 365 days, to complete one revolution. *Gravity is a force that pulls two objects toward each other. The gravity between Earth and sun keeps Earth revolving around the sun.

The tilt of Earth’s axis affects how directly the sun shines on Earth as it travels in its orbit.

March- Neither pole is tilted toward the sun.

June- The Northern Hemisphere is tilted toward the sun.

September- Neither pole is tilted toward the sun.

December- The Northern Hemisphere is tilted away from the sun.

SEASONS

As the Earth revolves around the sun, it is tilted on its axis. Its tilt affects how places on Earth receive sunlight. When places tilt toward the sun, it is summer. When places tilt away from the sun, it is winter.

Questions/Answers1. During which seasons are daylight and darkness

closest to being equal? Spring and Fall

2. What causes winter in the Northern Hemisphere? The North Pole is tilted away from the sun.

3. How is the relationship between the Northern Hemisphere of Earth and the sun different in June and December? In June, the Northern Hemisphere of Earth faces toward the sun. In December, it faces away from the sun.