Astronomy_v2.notebook
November 09, 2011
ASTRONOMY
I. Earth as a part of our Solar System
A. Planets
1. Def'n: bodies, natural satellites, that orbit the sun
2. We currently have 8 planets:
a.Mercury (closest to the sun; rocky & small)
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b.Venus (rocky & small)
c.Earth (rocky & small)
d. Mars (rocky & small)
e. Jupiter (large & gas)
f. Saturn (large & gas)
g. Uranus (large & gas)
h.Neptune (large & gas)
3. The Sun is the central star in our solar system.
II. Properties of the Earth, Sun, and Moon
A. Earth
1. planet with a rocky surface, but also has water
2. it has an atmosphere of gases around it
3. It orbits millions of miles from the sun as the third planet in our solar system
B. Sun
1. Our sun is a star, a large ball of glowing gases that is extremely hot
2. It does NOT have a rocky surface, & its atmosphere glows and gives off light
3. it is located in the center of our solar system
4., earth and the other planets orbit the sun
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Astronomy_v2.notebook
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C. Moon
1. The moon is a natural satellite that orbits the earth.
2. It has a rocky, dusty surface with many craters.
3. Recently, scientists have decided there IS water on the moon.
4. It has no atmosphere.
III. Shadows
A.The objects on Earth cast shadows based on Earth's rotation.
B. The angle of the sun (how high Or how low) changes the length of the shadow of an object.
1. In the morning, the sun appears low in the sky; objects cast long shadows.
2. As Earth rotates, the sun appears higher in the sky; objects' shadows get shorter
3. At noon, the sun is located directly overhead, and the shadows are cast really small or there is no shadow at all
4. As the Earth rotates, the sun appears lower in the sky, the shadows get longer again.
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IV. Seasons
A. Earth has distinct seasons because of its tilt and its revolution around the sun.
1. It takes about 365 days for the earth to orbit the sun.
2. Earth has seasons because Earth's axis is tilted.
a. Because of the tilt, the # of daylight hours change during the seasons
3. As the earth revolves around the sun, different parts of the earth get day and night.
4. The tilt also causes the northern or southern part of the earth to point towards the sun.
a. When the tilt is toward the sun, the season is summer
b. When the tilt is away from the sun, the season is winter
c. The two hemispheres have opposite seasons.
d. The seasons do NOT depend on the distance between earth and sun.
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B. Axis
1. earth rotates around an imaginary straight line that runs from the north pole to the south pole
C. Revolution
1. The movement of earth as it makes an orbit around the sun in one year
D. The tilt of Earth's axis causes the change of amount in sunlight
1. Summer occurs when the Earth is tilted towards the sun.
2. Winter occurs when the Earth is tilted away from the sun
3. Autumn and Spring occur when neither part of Earth is pointed directly toward or away from the sun.
4. The order of the seasons is summer
spring
autumn/fall
winter
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Astronomy_v2.notebook
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V. Earth's rotation
A. Earth rotates (spins) on its axis and completes one rotation in about 24 hours (a day)
B. Earth rotates from west to east, therefore the sun appears to rise in the east and set in the west
C. Because of this rotation, only the side of the Earth facing the sun is lit and experiences "day;" the part not facing the sun experiences "night."
VI. Sun's effects on Earth
A. The sun gives off heat and light (that it produces itself.
B. Earth receives the heat and light after it travels through space.
C. The sun is the sources of almost all of Earth's energy.
D. Plants take the sun's energy and
use it to make food energy (photosynthesis.)
E. Heat from the sun causes the process
of evaporation of water.
F. The suns energy is stored in fossil fuels (ex: coal, oil, or natural gas) that formed from some organisms that died long ago.
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VII. The Moon
A. Because of the sun, earth, and moon positions, the moon's appearance changes every night.
B. The amount of moon's reflection of light determines the phases.
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C. Phases of the moon make the moon look like it has changed shapes
1. New Moon ­ the part of the moon facing earth is completely dark
2. Quarter Moon (sometimes called "half moon")
a. the part of the moon facing earth, half of it is lit, half of it is completely dark
b. 2 half moons per cycle
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3. Full Moon ­ the entire part of the moon facing earth is lit; the moon looks like a white circle
4. Crescent Moon ­ a small section (less than a quarter moon) is lit facing earth
D. The change in the moon's phases from new moon to new moon takes about 29 1/2 days
E. Gravity
1. the moon and earth pull on each other because of gravity
2. moon stays in orbit around earth because of earth's gravity
3. the moon's gravity makes the surface level of earth's oceans rise and fall; this is called a "tide"
4. high tide is when the water level is highest; there are about 2 high tides a day
5. low tides occur between high tides
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VIII. Telescopes
A. Telescopes are tools to help us see out in space
B. A telescope gathers more light than the eye so we can see far away objects more easily
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