The Sun-Earth-Moon System

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The Sun-Earth-Moon System

• Rotation
• Coriolis Effect
• Tides
• Revolution
• Seasons
• Moon
• Lunar Eclipse
• Solar Eclipse

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Rotation
23.5

• Earth is a round, 3-dimensional sphere
• AXIS imaginary vertical line around which earth
  spins
• 23.5 from vertical

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Rotation

• ROTATION
• the spinning of Earth around its axis

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Rotation

• Effects of ROTATION
• Night and day plants, animals, and people
• Daily change in temperature

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• Effects of ROTATION
• Earth bulges at the equator

Polar diameter 7900 miles (12,714
km) Equatorial diameter 7927 miles (12,756 km)
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Rotation

• How fast is the Earth spinning around its axis?
• At the equator, the Earth's surface moves 40,070
  kilometers in 24 hours. That is a speed of about
  1040 miles/hr (1670 km/hr or 0.5 km/sec).
• This is calculated by dividing the circumference
  of the Earth at the equator (about 24,900 miles
  or 40,070 km) by the number of hours in a day
  (24).
• As you move toward either pole, this speed
  decreases to almost zero (since the circumference
  of the spinning circle at the extreme latitudes
  approaches zero).

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Rotation

• Effects of ROTATION
• CORIOLIS EFFECT
• Earth rotates at different speeds at different
  latitudes
• Any moving solid, liquid , or gas is turned to
  the RIGHT of its intended path in the Northern
  Hemisphere
• Any moving solid, liquid , or gas is turned to
  the LEFT of its intended path in the Southern
  Hemisphere
• Winds
• Ocean currents

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• Effects of ROTATION
• CORIOLIS EFFECT

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• Effects of ROTATION
• CORIOLIS EFFECT

http//topex-www.jpl.nasa.gov/aviso/graphics/gener
al/outreach/tutorial/coriolis.mov
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• Effects of ROTATION

• CORIOLIS EFFECT

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Rotation

• Effects of ROTATION
• Tides
• The gravitational pull of the moon and the sun
  produces a rhythmic rise and fall of the oceans
  as the Earth rotates

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Tides

• Effects of ROTATION

• Result of the gravitational attraction between
  the Earth, sun, and moon.
• As the moon rotates around the Earth, it pulls
  the water on the nearest side of the Earth
  outward into a bulge.
• A similar bulge on the opposite side of the Earth
  is caused by inertia - gravitational attraction
  of the moon is less water furthest away than on
  the Earth.

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TIDES

• SPRING TIDE

• NEAP TIDE

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TIDES

• SPRING TIDE
• During time of the new moon and full moon, the
  sun and moon are in a straight line
• Combined gravitational pull produces spring tides
  
• High tides are very high and low tides are very
  low.

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TIDES

• NEAP TIDE
• When sun and moon are at right angles from the
  Earth, during the quarter phases of the moon
• Gravitational pull on the oceans is less
• A smaller difference between high and low tide

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TIDES
Nova Scotia's Hall's Harbour at high tide.

• The tides have a vertical difference, between
  high and low tide, of up to 14 metres (48 feet)!

And at low tide just six hours later.
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TIDES - WAVES

• Tides are due to GRAVITATIONAL ATTRACTION NOT wind

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TIDES

• A review of tides and the position of the sun and
  moon

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Revolution

• REVOLUTION Earths yearly orbit around the Sun
• 365.25 days
• Earths orbit is an ellipse
• Distance between the Earth and Sun changes during
  the year because the orbit is not a circle!
• Average distance is 150,000,000 km
• Earths tilt on its axis remains in the same
  direction!

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Revolution
NOTE This is not to scale in reality, the sun
is a lot bigger to scale, and Earth is a lot
further away.
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Seasons

• CAUSES of SEASONS
• Tilt of the Earths axis
• Uneven heating of Earths surface
• The hemisphere tilted toward the Sun receives
  more solar energy
• Revolution of the Earth around the sun

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Seasons
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Seasons

• Solstice
• Day when the sun reaches its greatest distance
  north or south of the equator
• Northern Hemisphere
• SUMMER June 21 or 22
• WINTER December 21 or 22

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Seasons

• Equinox
• Day when the sun is directly over the equator
• Daylight and nighttime are equal
• Northern Hemisphere
• SPRING (Vernal)
• March 21or 22
• FALL (Autumnal)
• September 21 or 22

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Seasons
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College of Alameda Physical Geography
http//members.aol.com/pakulda/emmod.htm
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MOON

• A cold, rocky body about 2,160 miles (3,476 km)
  in diameter.
• It has no light of its own - shines by sunlight
  reflected from its surface.

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MOON

• Rotates on its axis
• Rotation of the moon takes about as long as its
  revolution
• Revolves around the Earth
• once every 27? days
• The same side of the moon is facing the Earth

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Phases of the MOON

• WAXING
• When the moon is between New and Full
• Portion of moon visible is INCREASING
• WANING
• When the moon is between Full and New
• Portion of the moon visible is DECREASING

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PHASES OF THE MOON
The photographs show what the moon looks like
from Earth. The drawings show what the moon would
look like from space.
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Lunar Eclipse

• Earths shadow falls on the moon
• can only occur at Full Moon
• UMBRA darkest part of the shadow, a region
  where the Earth blocks all direct sunlight from
  reaching the Moon.
• PENUMBRA cone of shadow cast by deflected
  light, a zone where the Earth blocks part but not
  all of the Sun's rays from reaching the Moon

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Lunar Eclipse

• There is a full moon once a month why not a
  lunar eclipse?
• All 3 bodies must be in perfect alignment
• Must be nighttime when alignment occurs, only
  half the planet is experiencing night at a given
  time
• During Full Moon phase, the moon usually passes
  above or below Earth's shadows and misses them
  entirely. No eclipse takes place.
• Two to four times each year, the Moon passes
  through some portion of the Earth's penumbral or
  umbral shadows resulting in an eclipse

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MOON
Earths orbit around the sun

• The moon's orbital plane does not "lie flat"
  along the ecliptic, but forms an angle of about
  5º - affects chances of experiencing an eclipse.
• (note the distances in this diagram are not to
  scale)

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MOON
Path of moon through Earths shadow during total
eclipse in 2000.
Note the moon does not pass directly through the
center of the UMBRA
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LUNAR ECLIPSE

• Partial Lunar Eclipse
• A portion of the Moon passes through Earth's
  umbral shadow.
• These events are easy to see, even with the
  unaided eye.
• Total Lunar Eclipse
• The entire Moon passes through Earth's umbral
  shadow.
• These events are quite striking for the vibrant
  range of colors the Moon can take on during the
  total phase (i.e. - totality).

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LUNAR ECLIPSE

• When an eclipse of the Moon takes place, everyone
  on the night side of Earth can see it.
• About 35 of all eclipses are of the penumbral
  type which are very difficult to detect, even
  with a telescope.
• 30 are partial eclipses which are easy to see
  with the unaided eye.
• 35 or so are total eclipses, and these are quite
  extraordinary events to behold.

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LUNAR ECLIPSE

• Indirect sunlight still manages to reach and
  illuminate it.
• However, this sunlight must first pass deep
  through the Earth's atmosphere which filters out
  most of the blue colored light.
• The remaining light is a deep red or orange in
  color and is much dimmer than pure white
  sunlight.
• Earth's atmosphere also bends or refracts some of
  this light so that a small fraction of it can
  reach and illuminate the Moon.

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LUNAR ECLIPSE

• If the Earth had no atmosphere, then the Moon
  would be completely black during a total eclipse.
  Instead, the Moon can take on a range of colors.
• The filtering and refracting effect of Earth's
  atmosphere makes the total phase of a lunar
  eclipse interesting.
• The exact appearance depends on how much dust and
  clouds are present in Earth's atmosphere.
• Major volcanic eruptions tend to make total
  eclipses very dark, since these events dump large
  amounts of ash into Earth's atmosphere.
• During the total lunar eclipse of December 1992,
  dust from Mount Pinatubo rendered the Moon nearly
  invisible.

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SOLAR ECLIPSE

• Moon moves directly between Earth and the sun
• UMBRA Dark inner shadow total eclipses are
  seen from within this shadow. The track of the
  Moon's shadow across Earth's surface is called
  the Path of Totality. It is typically 10,000
  miles long but only 100 miles or so wide.
• PENUMBRA Faint outer shadow partial eclipses
  are seen from within this shadow.

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SOLAR ECLIPSE

• There is a NEW moon once a month why not a
  solar eclipse?
• All 3 bodies must be in perfect alignment
• During New Moon phase, the moons shadow usually
  passes above or below our planet and misses Earth
  entirely. No eclipse takes place.
• At least twice each year, the 3 bodies line up so
  that some part of the moons shadow falls on
  Earths surface
• An eclipse of the Sun is seen from that region

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SOLAR ECLIPSE
2000 Jul 31 Partial Solar Eclipse http//sunearth
.gsfc.nasa.gov/eclipse/OH/OH2000.html
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QUESTIONS

• Describe the two types of planetary motion.
• Why does the Earth have tides?
• What is the relationship between tides and waves?
• What are the characteristics of a wave?
• What causes the Coriolis Effect? What is the
  Coriolis Effect?
• Why does the Earth have seasons?
• What is the difference between a solstice and an
  equinox?

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QUESTIONS

• What is the difference between a solar eclipse
  and a lunar eclipse?
• When can you see a total solar eclipse? A total
  lunar eclipse?