Transcript Astronomy Unit Chapter One: Earth, Moon, and Sun

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 waysrotation and revolution
A.
Rotation
1. axis- imaginary line that passes through
Earth’s center and the North and South poles
2. rotation- spinning of Earth on it’s axis
a. causes night and day
b. rotates East to West
c. Takes about 24 hrs. for Earth to
rotate once = 1 day
B. Revolution
1. Revolution- movement of 1 obj. around
another
2. 1 complete revolution of Earth around sun
= 1 yr.
3. Orbit- elongated path Earth moves in
around sun
C. Calendars
1. 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 Earth
A. 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 Axis
1. 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 June
1. North end of Earth’s axis tilted toward sun
(summer in northern hemisphere and
winter in southern)
D. Earth in December
1. Southern hemisphere receives the most
direct sunlight (summer in southern
hemisphere and winter in northern
hemisphere)
E. Solstices
1. Happen twice/yr in June and December
2. Solstice- Sun is farthest north or south of
equator
3. Farthest north, summer solstice in
northern Hemisphere and winter in
southern hemisphere
4. Sun farthest south, winter solstice in
northern hemisphere and summer solstice
in southern hemisphere
F. 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.