1. Unit 8 Lesson 1 How Do Earth and the Moon Move?
Copyright © Houghton Mifflin Harcourt Publishing Company 1

2. Turning Through the Day
Unit 8 Lesson 1 How Do Earth and the Moon Move?
Turning Through the Day
Looking at the Earth from above the North Pole, we see that Earth turns in the opposite direction to a clock.
As Earth turns, half of it gets light from the sun, and half of it is in darkness.
It is day on the lit half of Earth, and night on the dark half. Day changes to night as Earth turns.
Copyright © Houghton Mifflin Harcourt Publishing Company 2

3. Turning Through the Day
Unit 8 Lesson 1 How Do Earth and the Moon Move?
Turning Through the Day
Picture a line going through Earth from the North Pole to the South Pole. This imaginary line is Earth’s axis.
Like a wheel on a bike, Earth rotates, or turns, on its axis.
Earth’s rotation causes the cycle of day and night. One full rotation takes 24 hours, or one full day.
Copyright © Houghton Mifflin Harcourt Publishing Company 3

4. Unit 8 Lesson 1 How Do Earth and the Moon Move?
Reasons for Seasons
As Earth turns on its axis, it also moves around the sun.
Each complete trip around the sun is one revolution.
Each revolution takes about 365 days, or one year.
Copyright © Houghton Mifflin Harcourt Publishing Company 4

5. Unit 8 Lesson 1 How Do Earth and the Moon Move?
Reasons for Seasons
How does Earth’s tilt on its axis affect the amount of sunlight different parts of the planet receive?
Copyright © Houghton Mifflin Harcourt Publishing Company 5

6. Unit 8 Lesson 1 How Do Earth and the Moon Move?
Reasons for Seasons
The part of Earth that points toward the sun gets more direct sunlight. The part with the most direct sunlight experiences summer.
The part of Earth that points away from the sun gets less sunlight. The part with the least direct sunlight experiences winter.
During fall and spring, neither the top nor the bottom half of Earth is tilted toward or away from the sun.
Copyright © Houghton Mifflin Harcourt Publishing Company 6

7. Unit 8 Lesson 1 How Do Earth and the Moon Move?
Winter Days!
What is winter like for kids in the United States? That depends on where you live.
In Phoenix, Arizona, winter temperatures are usually in the 60s or 70s.
But someone in Madison, Wisconsin, would be used to temperatures in the 20s or 30s.
Copyright © Houghton Mifflin Harcourt Publishing Company 7

8. Phases of the Moon Does moonlight really come from the Moon? No!
Unit 8 Lesson 1 How Do Earth and the Moon Move?
Phases of the Moon
Does moonlight really come from the Moon? No!
The moon doesn’t produce its own light. Moonlight reflects from the sun.
The reflected light is what we see from Earth. At any time, half of the moon is lit by the sun.
Copyright © Houghton Mifflin Harcourt Publishing Company 8

9. Unit 8 Lesson 1 How Do Earth and the Moon Move?
Phases of the Moon
As the moon revolves around Earth, different amounts of its lit side can be seen. This is what causes the different shapes, or phases, of the moon.
Eight moon phases make up one cycle. A full cycle happens in about one month. Then the cycle repeats.
Copyright © Houghton Mifflin Harcourt Publishing Company 9

10. Unit 8 Lesson 1 How Do Earth and the Moon Move?
Phases of the Moon
The four main moon phases are new moon, full moon, and both quarter moons.
A first-quarter moon looks like a half-circle and is lit on the right side.
Copyright © Houghton Mifflin Harcourt Publishing Company 10

11. Unit 8 Lesson 1 How Do Earth and the Moon Move?
Phases of the Moon
As we see more of the moon’s lit side, we say that the moon is waxing.
As we see less of the moon’s lit side, we say that the moon is waning.
Copyright © Houghton Mifflin Harcourt Publishing Company 11

12. Unit 8 Lesson 1 How Do Earth and the Moon Move?
Daily Highs and Lows
The pull of the moon’s gravity causes ocean tides.
Tides are changes in the height of ocean water.
When the moon is above an ocean, the moon causes high tide on that part of Earth and on the opposite side, too.
Copyright © Houghton Mifflin Harcourt Publishing Company 12

13. Unit 8 Lesson 1 How Do Earth and the Moon Move?
Daily Highs and Lows
In the parts of the ocean between the two areas of high tide, the water level is lower.
At those places, a low tide occurs.
At most beaches, there are high tides and low tides every day. The tides make a cycle.
Copyright © Houghton Mifflin Harcourt Publishing Company 13