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Earth, Moon, and Sun. S8.D.3.1.1-3. Earth’s 2 Motions. Great Site. 2. Revolution (orbit) – go around the Sun. Rotation – Spin (rotate) on its axis. Rotation. The turning of a planet on its axis. 23.5 0. Axis. Axis: - PowerPoint PPT Presentation
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Earth, Moon, and Sun
S8.D.3.1.1-3
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Earth’s 2 Motions
1.Rotation
– Spin (rotate) on its axis
2. Revolution (orbit)
– go around the Sun
Great Site
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Rotation• The turning of a planet on its
axis
• We have days and nights because of Earth rotating in and out of sunlight
•Axis:–Imaginary line that runs from the North Pole, through the center of Earth, to the South Pole.–Earth’s axis is tilted at 23.5 0
Axis23.5 0
Table of Planets day
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Rotation• The direction of Earth’s
rotation is counterclockwise (when looking from above the North Pole)
• Because Earth rotates counterclockwise, it appears the Sun rises in the East and sets in the West
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Rotation• It takes Earth 24 hrs to complete one
rotation
• One complete rotation of any planet is called a Day
• At the Equator, Earth rotates 1,000 mph
• The faster a planet rotates, the shorter the day is on that planet
Cool Fact: Earth is slowing down at a rate of 0.0018 seconds per century
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Revolution• Movement of a planet around the Sun• Counterclockwise (from above NP)• One complete revolution of any planet
around the Sun is called a year• Earth rotates 365 ¼ times during one
revolution around the Sun (There are 365 ¼ days in a year)
We make up for that extra ¼ day by adding a day to our calendar (Feb 29th) every 4 years Leap Year
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Revolution
• The closer a planet is to the Sun, the shorter its year is , because:
1. It has to travel a shorter distance
2. Its speed is greater due to the Sun’s gravity
**Earth Revolves at an average of 67,000 mph
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Revolution• Orbit - The path a planet follows around the
Sun
- Shape is elliptical (Oval) with the Sun off-center (not in the middle!)
91 million miles95 million miles
Average= 93 million miles
Perihelion
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2 Forces that Keep Earth in Orbit:
1. Inertia(A) Body in motion will remain in motion
(B) Body at rest will remain at rest
**Inertia is why the planets keep moving ( in a straight line)
Unless acted upon by an outside force
2. Gravity• The Sun’s gravity pull planets toward the Sun and
keeps them in their orbital path
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Tropic of Cancer
Equator
Equator
Tropic of Capricorn~9hrs
~12 hrs
~15hrs
~12 hrs
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24 hrs daylight
24 hrs daylight
24 hrs darkness
24 hrs darkness
Why is there More Hrs of Daylight in Summer?
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Seasons• The seasons in one hemisphere are
opposite of the seasons in the other Hemisphere
**Seasons in the Southern Hemisphere are more extreme than in the Northern Hemisphere
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Tropic of Capricorn (23.50 below Equator)
Tropic of Cancer (23.50 above Equator)
Equator
Northern Hemisphere
Southern Hemisphere
Bill Nye- seasons
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Seasons Animations:
• http://projects.astro.illinois.edu/data/Seasons/seasons.html
• http://esminfo.prenhall.com/science/geoanimations/animations/01_EarthSun_E2.html
• http://astro.unl.edu/naap/motion1/animations/seasons_ecliptic.html
Video clipVideo clip #2
Bill Nye Seasons
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The Moon• Revolves around Earth
• ¼ Earth’s diameter (2,159 miles)
• 1/6 of Earth’s gravity
• Frozen water ice at the poles (in deep shadowed craters)
• Mainly rock and dust (brought back 840lbs of rock to Earth
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The MoonNO atmosphere therefore NO weather
•Temp range is large since it lacks an atmosphere
250F = high during the day-250F = low at night
• Lots of craters from impacts because it lacks an atmosphere
•Old and unchanged because it lacks an atmosphere
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Our Moon Has 2 Motions:
1. Rotation• counterclockwise• 10.7 mph on its axis (6.70)• Takes 28 days to rotate once • Lunar Day = 28 Earth days
2. Revolution• counterclockwise• Around Earth at 2,300 mph• Orbit is Tilted (5º)• Orbit is elliptical (Perigee and apogee)• Average distance to the moon is 238,000 miles• Lunar Year = 28 Earth days
A Day is as long as a Year on the Moon!
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Why Don’t We See the Far Side?
• The Moon rotates 1 time around its axis as it makes 1 revolution around Earth.
• It finishes a rotation at the same time it finishes a revolution
• Period of Rotation = Period of Revolution28 Earth Days Dark
Side
FACT:
The Moon does not rotate and revolve at the same speed!
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Phases of the Moon
• The Moon reflects sunlight
• It does NOT produce its own light
• We see different phases (shapes) depending on where the moon is in its orbit
• It takes the Moon about 28 Earth days to complete one revolution around Earth and go through all of its phases
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New Moon
• During a New Moon we can’t see the moon from Earth
• The side hit by sunlight is facing AWAY from Earth
• Occurs when the Moon passes between the Earth and Sun
Moon is above or below Earth’s plane
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Full Moon
• After a New Moon, the Moon continues to revolve in a counterclockwise direction allowing us to see more and more of the side facing us. (Waxing Phases)
• When it gets halfway around Earth, we see ALL of the side facing us
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Full Moon (cont.)
• Earth is between the Moon and Sun
Moon is above or below Earth’s plane
•As the Moon continues to revolve from a full moon position, we see less and less of the side facing us (Waning Phases), until we have another New Moon
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Animation Animation
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Eclipses1. Lunar Eclipse
• Moon is being eclipsed (blocked from our sight)
2. Solar Eclipse• Sun is being eclipsed by the moon (blocked from
our sight)• Moon is 400 x smaller than the Sun• Moon can perfectly block out sun because the
moon is 400x closer to us than the sun is
•Earth is 4x bigger than Moon
•Sun is 100x bigger than Earth
FACTS:
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Lunar Eclipse• Earth is directly between the Sun and a Full Moon
(all 3 bodies are in line)• Moon is in the shadow of Earth (no sunlight hitting it)
• Only happens 2-4 times a year (not all total)
Whole back side of Earth can see Lunar Eclipse
Zone of partial shadow
Zone of complete shadow
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Solar Eclipse• When a New Moon is directly between the Earth
and Sun (all 3 bodies are in line)• Sunlight is blocked (by the moon) from reaching a
small area of Earth, so only people living in that area see the solar eclipse
• At least 2 a year (not all total)
People in penumbra see partial solar
People in umbra see total solar
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Tides• Rising and falling water levels
of our oceans• Moon’s and Sun’s gravity
makes water bulge out on Earth• The Moon’s gravity has a
greater effect because it’s closer than the Sun
• The area aligned with the moon High Tide
• The area not aligned with the moon Low Tide
Neap tides
Spring tides
Bill Nye- Moon