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Earth - Moon System

• I. Earths Motions

A. Earth has 2 real motions.
1. Rotation- The turning or spinning motion of an
object on an axis.
Axis-
The imaginary line around which an object spins.
Earths axis is tilted at 23 1/2 degrees from
the perpendicular to earths orbital plane.
Orbital Plane - The slice of space where an
object orbits
For earth one rotation takes 24 hours.
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Southern Night Sky from Paranal Observatory in
Chile
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Earth - Moon System

• I. Earths Motions

A. Earth has 2 real motions.
1. Rotation-
The turning or spinning motion of an object on an
axis.
Axis-
The imaginary line around which an object spins.
Earths axis is tilted at 23 1/2 degrees from
the perpendicular to earths orbital plane.
A.) Orbital Plane -
The slice of space where an object orbits.
For earth one rotation takes 24 hours.
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• 2. Revolution-The circling of one object in space
  around another object.

• Earth revolves around the sun at 107,826 Km/hr.
• Earths average distance from the sun is 93
  million miles or 150 million kilometers.

• Aphelion - When earth is farthest away from the
  sun
  (July 4th furthest away. 152 million
  km. )

• Perihelion - When earth is closest to the sun.
  (January 3rd closest to the sun. 147
  million km)

For earth one revolution takes 365.25 days.
There is a leap every 4 years, makes up for the
.25 days.
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Sidereal vs. Synodic Motion (10 pts.)

• Read through quietly to establish troublesome
  vocabulary.
• Read aloud together
• Highlight/underline key points for questions
• Answer questions.
• Answer each question using 3-4 sentences.

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Sidereal vs. Synodic Motion (10 pts.)

• Words we dont know
• Ecliptic - the great circle formed by the
  intersection of the plane of the earth's orbit
  with the celestial sphere the apparent annual
  path of the sun in space.
• Precession - A slow circular movement of the
  earth's axis around the pole of the ecliptic

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Sidereal v. Synodic

• More words we didnt know
• Gregorian - relating to Pope Gregory XIII or the
  Gregorian calendar
• Vernal Equinox - the time when daylight is equal
  to nighttime in spring, on about March 20 in the
  northern hemisphere and September 22 in the
  southern hemisphere.
• Meridian - a circle of constant longitude passing
  through a given place on the earth's surface and
  the north/south poles.

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Sidereal vs. Synodic Motion (10 pts.)

• Which one, Sidereal or Synodic, is used to define
  our day here on Earth? Describe it. (1 pt.)
• Which one do you believe should be used to define
  our day here on Earth? Why? (3 pts.)
• Should we have a leap year? Why or why not?
  (3pts.)
• How many years have been leap years since 0 A.D.?
  (3 pts.)
• Answer each question using 3-4 sentences.

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Earths Seasons

• A. Why does earth have seasons?

• B. Seasonal Dates

1. Spring Equinox or Vernal Equinox
March 20/21
First day of spring.
Hours of daylight are the same in both
hemispheres.
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2. Summer Solstice
(Latin for The Sun Stands Still)
June 21/22
First day of summer.
North Pole is tilted toward the sun.
Longest hours of sun light in the
Northern Hemisphere.
Suns direct rays are on the tropic of cancer.
(23 1/2
degrees North Latitude.)
Continual Arctic Circle day light.
Called land of the midnight sun .
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3. Fall Equinox or Autumn Equinox
September 22/23
First day of fall.

• Hours of day light are the same in both
  hemispheres.

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Stop and Think

• Should we still use daylight savings time?

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4. Winter Solstice
December 21/22
First day of winter.
North Pole is tilted away from the sun.

• Shortest hours of sun light
  in the Northern Hemisphere.

Suns direct rays are on the Tropic of
Capricorn. (23 1/2 degrees South Latitude.)
Continual Arctic Circle darkness.
Land of the Mid-Day Moon.
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Stop and Think

• What if there were no seasons?

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The Moon

• I. Moon Characteristics

• Moons Rotation and Revolution
• 1. Moons Rotation Its Revolution.
• 2. This is why the same side of the moon faces
  the earth at all times.
• 3. 29.5 days to travel around the Earth (to
  Sun).

B. Moon Structure 1. Craters cover the
surface. 2. First thought to be volcanic
craters. 3. Now we know that meteorite impacts
caused them.
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4. Rays- Streaks extending out from craters.
Caused by violent meteorite impacts 5. Maria-
(Latin for seas or oceans) Low areas of dark soil
where ancient lava flows covered the surface. 6.
Marias were first thought to be seas or oceans by
early astronomers. 7. The moon also has mountains
(terra/highlands) as large as any on earth.
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• II. Phases of the moon

• The moon takes 29 1/2 days to complete all of its
  phases.
• B. Phase Shapes
• 1. Crescent - Banana shaped.
• 2. Quarter - Half-moon.
• 3. Gibbous - 3/4 of a circle.
• 4. Full - Complete circle
• 5. New - Not visible.

• C. Phase Stages
• Waxing means to become brighter. New to full
  moon.
• 2. Waning means to become dim. Full to new moon.
  

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D. The Phases of the Moon
1. New Moon
2. Waxing Crescent
3. 1 st Quarter
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2
3
4. Waxing Gibbous
5. Full Moon
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5
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6. Waning Gibbous
7. 3 rd or Last Quarter
8. Waning Crescent
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8
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9. New Moon
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III. Eclipses
A. Eclipse- The passing of one object into the
shadow of another object.
B. Total Eclipses - When the object is fully
eclipsed.

• The eclipsed object must be completely in the
  umbra of the other object.
• 2. Umbra - The complete inner shadow of an
  object.

C. Partial Eclipses - When the eclipsed object is
partially in the umbra and partially in the
penumbra of the other object.
1. Penumbra - The partial shadow of an object.
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D. Lunar Eclipses
1. The full moon is in the earths shadow.
2. Approx. 2hrs. In length.
3. More often seen than solar eclipses.
Full Lunar Eclipse
penumbra
umbra
penumbra
Partial Lunar Eclipse
penumbra
umbra
penumbra
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E. Solar Eclipses
1. The earth is in the shadow of the new moon.

2. Length from 4 - 8 minutes.
3. Less often observed than lunar eclipses.
4. Very bright, dangerous eclipse.
5. Never look directly at it.
6. Brightest part of the sun (the corona) can be
seen. (Will permanently damage the eyes.)
Full Partial Solar Eclipse
penumbra
umbra
penumbra
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• IV. The Moons Origin

• The Fission Theory The Moon was once part of the
  Earth and somehow separated from the Earth early
  in the history of the Solar System. The present
  Pacific Ocean basin is the most popular site for
  the part of the Earth from which the Moon came.
• The CAPTURE Theory The Moon was formed somewhere
  else, and was later captured by the gravitational
  field of the Earth.
• The (CO-ACCRETION) The Moon and the Earth
  condensed together from the original nebula that
  formed the Solar System.
• The COLLISION RING Theory An object the size of
  Mars struck the earth, ejecting large volumes of
  matter. A disk of orbiting material was formed,
  and this matter eventually condensed to form the
  Moon in orbit around the Earth.

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• V. Tides

A. Tides- The periodic rise and fall of the
ocean due to the gravitational pull of the Moon
and Sun.

1.) When the ocean levels are highest it is
said to be high tide, and when they are the
lowest it is said to be low tide.
B. Tidal Range- Is the difference in water
level between high tide and low tide.
C. The moon effects tides more than the Sun
because it is closer to the Earth.
D. Because of this, the Sun either increases
the effect of the Moon or decreases the effect.

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1.) Spring Tides- A tide of large range that
occurs during the new moon phase or full
moon phase.
The Sun increases the effect of the
Moon.
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1.) Neap Tides- A tide of small range that
occurs during the 1st quarter phase or 3rd
quarter phase.
The Sun decreases the effect of the
Moon.