1. Chapter 20
Earth
Sun
Moon

2. Lesson 1 Earth rotates on a tilted imaginary axis and orbits the sun
Earth’s rotation causes day and night
Earth’s gravity pulls objects toward the center-south is down everywhere
About half the Earth is in sunlight while the other half is dark

3. Earth’ tilt and orbit cause seasons
Earth’s rotation defines day and night
Earth’s orbit defines seasons
Earth makes one revolution around the sun a year (365 days-12 months)
Earth’s orbit is not a perfect circle

4. Seasonal Patterns
Hemisphere is half of the globe (northern and southern)
Patterns of temperature and weather trends change throughout a year and are called seasons (summer, winter, fall, spring)

5. Equinox vx Solstice
September Equinox-Sun shines equally on 2 hemispheres-Fall/Spring
December Solstice-North leans away from sun-Winter/Summer (shortest day)
March Equinox-Sun shines equally on 2 hemispheres-Spring/Fall
June Solstice-North leans toward sun-Summer/Winter (longest day)

6. Length of Days
The farther you get away from the equator, the more extreme changes in day and night
The closer you get to the equator, the more equal amounts of time in day and night
On equator=12 day 12 night hours
On poles=20+ day/6 months changes

7. Angles of Sunlight
When the sun is high in the sky (directly above you), the sunlight is concentrated in one area-right angle-shadows are short- between 10 and 2
When the sun is low in the sky, the sunlight strikes the ground at an obtuse or acute angle-not concentrated-shadows are long-early morning or late afternoon

8. Lesson 2 The moon is Earth’s natural satellite
The moon rotates once per orbit of Earth
Gravity keeps the moon in orbit
The moon is Earth’s closest neighbor
It takes astronauts 3 days of travel to reach the moon

9. Moon’s craters show history
Mare-dark area on the moon
Lunar means moon
All the features that can be seen on the moon are different types of solid or broken rock
Moon has no air, no oceans, no clouds, no life

10. Craters Light colors designate high altitude-highlands
Have many round features called craters that formed when small objects from space hit the surface
Moon’s lighted side has many large dark colored spots
Moon’s dark side has mostly highlands

11. Moon Rocks Different ages (some 4.5 billion years)
The older rocks are found in the highlands
The new rocks are found in the dark maria areas
Rock covers the entire moon surface
Basalt is a common rock on the moon

12. Layers of the Moon Remains mostly unchanged for billions of years
Structure: Crust, mantle and core
Similar materials in Earth and the moon but in different proportions
Evidence from rocks show that the moon was once closer to Earth (3.8 cm yearly)

13. Lesson 3 Positions of the Sun and Moon affect Earth Eclipse Tides
Waxing vs Waning
Phases-orbits the Earth monthly

14. Waxing and Waning Waxing is1-2 week of the month
Waning is 3-4 week of the month
New moon-when the Earth, moon and sun are all lit in the same direction
Full moon-half way through cycle/month when the whole near side of the moon is in sunlight-the moon and sun are in opposite directions (p. 701)

15. Waxing means growing and waning means shrinking
The appearance of the moon depends on the positions of the sun, moon, and Earth

16. Crescent and Gibbous
Crescent moons occur when the moon appears close to the sun in the sky-visible during daytime or around sunrise or sunset
Gibbous and full moons appear far from the sun in the sky-more noticeable at night

17. Lunar eclipse
Moon becomes dark during a lunar eclipse because it passes through Earth’s shadow
Just before a lunar eclipse, sunlight streaming past Earth produces a full moon
A total lunar eclipse occurs when the moon passes completely into shadow

18. Solar Eclipse
Solar eclipse occurs when the moon passes directly between the Earth and sun
The sun seems to darken because the moon’s shadow falls onto part of Earth
Moon covers the sun and the sky becomes as dark as night
Do not ever look at a solar eclipse

19. Ocean Tides
Average ocean water level rises slowly for about 6 hours to high tide
Then it lowers for about 6 hours to low tide
Entire pattern takes about 24 hours
2 high and 2 low tides per day

20. Tides
Tides occur because the moon’s gravity changes the shape of Earth’s oceans
Moon pulls on different parts of Earth with different amounts of force
Earth’s crust is hard enough to resist being pulled into a different shape, but Earth’s oceans do change shape

21. Tides
Moon’s pull produces a bulge of thicker ocean water on the side of Earth nearest to the moon (picture on page 706)
Another bulge of water is produced on the side of Earth farthest from the moon because the moon pulls the center of Earth away from that side
Thin layers of water run in between bulge

22. Chapter Review page 709
Earth rotates on a tilted axis and orbits the sun (day/night and seasons)
Moon is Earth’s natural satellite with many similar characteristics as Earth
Positions of the sun and moon affect Earth

23. Time to test …..
Study vocabulary and pictures noted throughout the chapter
Keep notes neat and organized in binder
Complete and study chapter review on page 709