unit 3: chapter 7: the earth-moon-sun system i. earth in space a. earth’s size and shape 1. early...
TRANSCRIPT
UNIT 3: Chapter 7: The Earth-Moon-Sun System
I. Earth in Space
A. Earth’s Size and Shape
1. Early astronomers like Aristotle said Earth was spherical in shape
a. Evidenced by shadow of Earth on Moon during eclipseb. People in different parts of world see different stars above their horizons
B. Earth’s Magnetic Field
1. Earth has magnetic field similar to a bar magnet
a. Protects us from harmful radiation from Sun
b. Magnetic field concentrated at the poles
2. Location of poles changes slowly over time
3. Aurora borealis (northern lights) caused by reaction of charged particles from sun and Earth’s magnetic field
a. Distance of Earth to sun varies during year
b. Closest to the Earth in January and furthest away in July
2. Earth is considered a planet like Venus, Mars, and Jupiter.
a. Conditions on different planets depend on how far from the Sun they are and their size
b. Mars is most like the Earth
II. Time and Seasons
A. Measuring Time on Earth
1. People have used the position and movements of Sun and Moon to measure time for thousands of years
3. The spinning (rotation) motion of Earth enables you to measure the passing hours of the day.
4. The motion (revolution) of Earth around the Sun enables you to measure passing of years
3. Angle at which sunlight hits the Earth determines warming effect
a. Higher angles produce more warming
b. Lower angles produce less warming
4. More hours of sunlight in summer than winter
5. Equinox- when number of daylight hours equals number of nighttime hours
a. Spring equinox- March 21st
b. Fall equinox- September 22
6. Solstice- sun reaches greatest distance north or southof equator
a. Summer solstice- June 21st
b. Winter solstice- December 21st
III. Earth’s Moon
A. Movement of the Moon
1. The Moon revolves around the Earthevery 27.3 days (a sidereal month)
2. The same side of the moon faces Earth because it also rotates one complete revolution in 27.3 days
B. How does the Moon affect the Earth?
1. Tides- caused by gravitational pull of the Sun and Moon
a. Moon’s gravity has more effect than Sun because it is much closer to Earth
b. As Earth rotates, different locations pass through high and low tides
C. Moonlight
1. Moon phases- are changing appearances of the Moon as seen from Earth
a. New Moon- occurs when Moon is between Earth and Sun. Moon is in sky,but cannot be seen
D. Eclipses
1. Solar eclipses- occurs when Moon moves directly between Sun and Earth and casts shadow on part of Earth
E. The Moon’s Surface
1. Moon’s surface includes many different surface features
2. Craters- depressions on the Moon formed by impact of meteorites, asteroids, and
comets
F. Moon’s Interior- Model shows crust 60 km - 150 km thick with solid mantle 1000 km deep with partially molten core
H. Origin of the Moon
1. Prior to Apollo mission there were 3 different theories
2. After Apollo mission all three theories found incorrect