Chapter 20 Earth Sun Moon

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

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

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)

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)

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

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

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

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

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

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

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)

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

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)

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

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

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

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

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

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

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

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

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