Section One:Earth in Space

What effects are caused by the motions of Earth and the moon?

1. Demonstrate how Earth moves in space.

Explain what causes the cycle of the seasons.

Astronomy-study of moon, stars, and other space objects

I. How Earth Moves in Space-Earth moves through space in two major ways- rotation and revolution

A. Rotation

1. axis- imaginary line that passes through Earth’s center and the North and South poles2. rotation- spinning of Earth on it’s axisa. causes night and dayb. rotates East to Westc. Takes about 24 hrs. for Earth to

rotate once = 1 day

B. Revolution1. Revolution- movement of 1 obj. around

another2. 1 complete revolution of Earth around sun

= 1 yr.3. Orbit- elongated path Earth moves in

around sunC. Calendars1. Calendar- system of organizing time that

defines beginning, length, and divisions of a yr.

2. 365 days = 1 yr.3. Earth orbits sun in about 365 ¼ days 4. Every 4 yrs there is an extra day

added (leap year) to make up for this.

II. The Seasons on EarthA. How Sunlight Hits Earth

1. Sunlight hits Earth most directly near equator *warmer weather

2. Near poles of Earth, sunlight arrives at steep angles, so it is spread out over a greater area

B. Earth’s Tilted Axis1. Earth has seasons because its

axis is tilted as it revolves around the sun

2. It is tilted at an angle of 23.5 degrees

3. As Earth revolves around sun, north end

of its axis is tilted away from sun for part

of yr.

C. Earth in June1. North end of Earth’s axis tilted toward

sun (summer in northern hemisphere and winter in southern)

D. Earth in December1. Southern hemisphere receives the most

direct sunlight (summer in southern hemisphere and winter in northern hemisphere)

E. Solstices1. Happen twice/yr in June and December2. Solstice- Sun is farthest north or south of

equator

3. Farthest north, summer solstice in northern Hemisphere and winter in

southern hemisphere4. Sun farthest south, winter solstice in

northern hemisphere and summer solstice

in southern hemisphereF. Equinoxes

1. Happen twice a yr in March and September

2. Equinox- “equal night” day and night are

ea. about 12 hrs. long

Explain what effects are caused by the motions of the Earth and moon.

Explain the two ways Earth moves in space.

Explain what causes the cycle of seasons on Earth.