Download Earth, Moon, Sun

Earth, Moon, and
Sun
S8.D.3.1.1-3
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Great Site
Earth’s 2 Motions
1. Rotation
– Spin (rotate) on its axis
2. Revolution (orbit)
– go around the Sun
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Rotation
• The turning of a planet on its
axis
23.5 0
Axis
•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
• We have days and nights because
of Earth rotating in and out of sunlight
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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!)
95 million miles
91 million miles
Average= 93 million miles
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2 Forces that Keep Earth in Orbit:
1. Inertia
Unless acted
upon by an
outside force
(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)
2. Gravity
• The Sun’s gravity pull planets toward the Sun and
keeps them in their orbital path
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~12 hrs
~15hrs
~9hrs
~12 hrs
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24 hrs
darkness
24 hrs
daylight
24 hrs
darkness
24 hrs
daylight
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 Cancer (23.50 above Equator)
Northern Hemisphere
Equator
Southern Hemisphere
Tropic of Capricorn (23.50 below Equator)
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Seasons Animations:
• http://projects.astro.illinois.edu/data/Seaso
ns/seasons.html
• http://esminfo.prenhall.com/science/geoani
mations/animations/01_EarthSun_E2.html
• http://astro.unl.edu/naap/motion1/animatio
ns/seasons_ecliptic.html
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 Moon
NO 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 Revolution
28 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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Eclipses
1. 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
FACTS:
•Earth is 4x bigger than Moon
•Sun is 100x bigger than Earth
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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)
Zone of partial
shadow
Zone of complete
shadow
Whole back side
of Earth can see
Lunar Eclipse
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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
People in
area see the solar eclipse
penumbra see
partial solar
• At least 2 a year (not all total)
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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
Spring tides
Neap tides
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