Transcript The Rotating Earth

People once believed that all planets and stars
orbited around ____.
a. Mercury
b. Earth
c. Venus
d. Mars
is a sphere, a round
3-dimensional
shape
 bulges slightly at
equator and
flattens slightly at
poles
 Radius: same from
all points on the
surface
 Axis/Tilt: imaginary
vertical line through
the north and south
poles it spins on
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Rotation: spinning of
earth on its axis, causes
days and nights

One complete rotation in
24 hours

completes 365 rotations in
a one year journey around
the Sun

rotates from west to east
Weight on a string suspended from a support and
swings freely.
 Swings in a constant direct but as earth turns it
appears the pendulum shifts orientation.

Compass always points
north is evidence of
earth’s magnetic field
 Earth’s magnetic axis and
rotational axis are not at
the same points

 Thus, your compass would
take you to magnetic
north not the north pole

Magnetic north changes
and moves around
rotational north

rotation of Earth
causes ocean
currents and wind
belts to curve to
the left or right
Revolution- the motion of a
body that travels around
another body in space;
one complete trip along an
orbit
 a satellite of Sun
 Earth’s orbit around the Sun
is an Ellipse, an elongated
closed curve
 is traveling around the sun
at an average speed of
29.8 km/s.
 Aphelion: planet is
farthest from the sun
 Perihelion: planet is
closest to the sun.
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is tilted 23.5°
causes our change
in seasons
makes daylight
longer in summer
and shorter in
winter
hemisphere tilted
toward the Sun has
longer hours of
daylight and makes
summer warmer
Equinox: occurs when the Sun is directly over the
equator; causing spring and fall
 THINK EQUAL: Hours of daylight and nighttime
 Spring equinox is Mar 21 and Fall equinox Sep 22

hemisphere tilted toward the Sun receives and
absorbs more solar radiation; causing summer
 Solstice: is the day when the Sun rays are at its
greatest/least distance from the equator
 June 21:longest daylight
 Dec 21: shortest daylight
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A natural satellite
Satellite: a natural or
artificial body that
revolves around planet.
One of more than 96
moons in our Solar
System
The only moon of the
planet Earth
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About 384,000 km
(240,000 miles) from
Earth
3,468 km (2,155 miles)
in diameter (about ¼
the size of Earth)
1/6 of Earths gravity
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3 major divisions of
the Lunar interior
Crust - average
thickness of about
70 kilometers
Mantle
Core - radius is
between 300 and
425 kilometers
Determined via
seismic data from
“moonquakes”

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No atmosphere
No liquid water
Extreme temperatures
 Daytime = 130C (265°F)
 Nighttime = -190C (-310 F)
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Mountains up to
7500 m (25,000 ft)
tall
Rilles (trenchlike
valleys)
Anorthosite: light
patches seen on the
moon’s surface
a bowl-shaped depression that forms on the
surface of an object when a falling body strikes
the object’s surface or when an explosion occurs]
 Up to 2500 km (1,553 miles) across
 Most formed by meteorite impact on the Moon
 Some formed by volcanic action inside the Moon
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Originally thought to
be “seas” by early
astronomers
Darkest parts of
lunar landscape
Filled by lava after
crash of huge
meteorites on lunar
surface 3-4 billion
years ago
Mostly basalt rock
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Revolution – Moon
orbits the Earth every
29.5days
The moon rises in the
east and sets in the west
The moon rises and sets
50 minutes later each
day
Rotation – Moon turns
on its axis every 29 days
Same side of Moon
always faces usarth

The orbit of the moon around Earth forms
an ellipse, the distance between Earth and
the moon varies over a month’s time

The illustration, based on Galileo spacecraft images, shows the approximate difference in
apparent size between a full moon at perigee (the closest point in the lunar orbit, pictured
at left) and a full moon at apogee, the farthest point in the lunar orbit.
The Moon rotates in 29.5
days.
The Moon orbits Earth in
29.5 days.
Because the Moon rotates
and revolves at the same
rate, we only see one
side
The NEAR side
There is NO DARK
SIDE
There is a FAR side….
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3 major theories
1. Capture theory: large object ventured too
near the forming earth and got trapped by
gravity
2. Simultaneous formation theory: Earth and
moon formed at the same time.
3. Impact theory: Most widely accepted.

The Giant Impact Hypothesis
 3 stages
 1. began when a large object collided with Earth
more than 4 billion years ago
 2. collision ejected chunks of Earth’s mantle into
orbit around Earth
 3. debris eventually clumped together to form the
moon.

Phase: in astronomy, the change in the
illuminated area of one celestial body as seen
from another celestial body; are caused by
the changing positions of Earth, the sun, and
the moon
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Moonlight is reflected
sunlight
Half the moon’s
surface is always
reflecting light
From Earth we see
different amounts of
the Moon’s lit surface
The amount seen is
called a “phase”
Synchronous rotation:
orbital and rotational
periods are equal.
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Waxing – lit side is getting bigger
Waning – lit side is getting smaller
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‘LEFT SIDE IS LIT, THE MOON IS LEAVING’
Left side, lit, leaving, waning
FULL
QUARTER
CRESCENT
GIBBOUS

http://www.moonconnection.com/moon_pha
ses_calendar.phtml
When only a small part of the moon is visible,
the moon may be in its
A. first-quarter phase
B. waning-crescent phase
C. new moon phase
D. last-quarter phase

MOON – SUN – EARTH: All do not travel in
the same plane of orbit

an event in which the
shadow of one
celestial body falls on
another

Bodies orbiting the
sun cast long
shadows into space
UMBRA (Latin for "shadow")
is the darkest part of the shadow
Penumbra
Umbra
Penumbra
PENUMBRA is a partial shadow,
grayish outer part of a sunspot
A solar eclipse is when the moon comes between the sun and
the Earth, so that a viewer is in the moon's shadow.
 Total eclipses rare – only once every 360 years from one
location!

Observers in the “umbra” shadow see a total
eclipse (safe to view the Sun); can see the corona
 Those in “penumbra” see a partial eclipse—not
safe to look directly at Sun
 Only lasts a few minutes
 Path of Totality about 10,000 miles long, only
100 miles wide
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Moon's orbit is tilted about 5o with respect to the
Earth's orbit (ecliptic), so the shadows usually miss!
Moon
Earth
Ecliptic
Moon’s
Orbit

the passing of the moon through Earth’s shadow at full moon
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occurs when Earth is positioned between the moon and the sun and
when Earth’s shadow crosses the lighted half of the moon
Sun
Earth
Moon’s
Path
Moon
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The Earth’s atmosphere filters some sunlight
and allows it to reach the Moon’s surface
The blue light is removed—scattered down to
make a blue sky over those in daytime
Remaining light is red or orange
Some of this remaining light is bent or
refracted so that a small fraction of it reaches
the Moon
Exact appearance depends on dust and
clouds in the Earth’s atmosphere

Tides: daily changes in the level of ocean water
 influenced by the sun and the moon
 occur in a variety of cycles
 The combination of gravity and inertia create two bulges of water.

High Tide and Low Tide: How often tides occur and the
difference in tidal levels depend on the position of the moon
as it revolves around the Earth
The gravitational attraction between the Earth
and the moon is strongest on the side of the
Earth that happens to be facing the moon,
simply because it is closer.
 This attraction causes the water on this “near
side” of Earth to be pulled toward the moon.
 As gravitational force acts to draw the water
closer to the moon, inertial force attempts to
keep the water in place.
 But the gravitational force exceeds it and the
water is pulled toward the moon, causing a
“bulge” of water on the near side toward the
moon
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On the opposite side of the Earth, or the “far
side,” the gravitational attraction of the
moon is less because it is farther away.
Here, the inertial force exceeds the
gravitational force, and the water tries to
keep going in a straight line, moving away
from the Earth, also forming a bulge
Approximately how many days does it take the
moon to go through a complete cycle?
A. 7
B. 11
C. 26
D. 29.5 ow many days does it take the moon
to go through a complete cycle?
When the visible portion of the moon is
increasing, the moon is
A. waxing
B. full
C. waning
D. waning-crescent
A solar eclipse is most likely to occur when the
A.
B.
C.
D.
sun is located between the earth and moon
moon is located between the sun and the
earth
earth is located between the sun and the
moon
earth and moon are at right angles to each
other
Earth has seasons because
A. the temperature of the sun changes
B. Earth rotates on its axis
C. Earth's axis is tilted as it moves around the
sun
D. the distance between Earth and the sun
changes
The sun appears larger than other stars because
A. it is the biggest star in the universe
B. it is a double star
C. it is the closest star to the earth
A lunar eclipse is most likely to occur when
A. sun is located between the earth and moon
B. moon is located between the sun and the
earth
C. earth is located between the sun and the
moon
D. earth and moon are at right angles to each
other
From new moon to full moon phase you see
A. a decreasing amount of the lighted side of
the moon
B. an increasing amount of the lighted side of
the moon
C. more of the lighted side, then less of the
lighted side of the moon
D. the same amount of the lighted side of the
moon
During what moon phase can a lunar eclipse
occur?
A. waxing gibbous
B. first quarter
C. new moon
D. full moon