The Earth, Moon, and Sun System

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The Earth, Moon, and Sun System

• SOL 6.8

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Introduction

• In this presentation we will learn
• About the relative sizes, motions, locations, and
  characteristics of the earth, sun and moon.
• Vocabulary includes rotation, revolution, axis
  of rotation, orbital plane,
• periods of rotation and revolution, mass,
  diameter, radius of orbit, density, composition,
  surface, core, atmosphere.
• The effects of their motions and positions on our
  seasons, tides, eclipses, and the measurement of
  time.
• Vocabulary includes seasons, high and low
  tides, phases of the moon, equinoxes, solstices,
  perihelion, aphelion, day, night, month, year,
  solar and lunar eclipses.

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• Lets compare all three
• heavenly bodies
• for a minute!!
• Well start with the Sun

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The Sun

• A G2 typical yellow dwarf star
• Diameter 1.4 million kilometers
• Contains 99.8 of the mass of the solar system
• Composition 75 hydrogen, 25 helium
• Surface Temperature 5500 oC
• Core Temperature 15 million degrees Celsius

• Rotates on its own axis once every 25.4 days at
  the equator.
• Revolves around the center of the Milky Way
  Galaxy once every 225 million years.

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The Earth

• Diameter 12.7 thousand kilometers
• Mass 6.0 x 1024 kilograms or six sextillion
  metric tons
• Composition water, silicon, heavy metal
  iron-nickel core
• Atmosphere nitrogen, water vapor, oxygen, carbon
  dioxide
• Surface Temperature -13 37oC
• Called the Blue Planet because of the color of
  nitrogen in its atmosphere.

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Earths Movement

• The Earth rotates on an axis that is tilted 23 ½
  degrees relative to the orbital or ecliptic
  plane.
• Its period of rotation is one day or 23 hours
  and 56 minutes.
• The period of revolution around the Sun is a year
  or 365 and one-quarter days.
• Why do we have leap years every four years?
• The earth completes this elliptical orbit at an
  average radius of 150,000,000 kilometers from the
  Sun.
• It travels through 942 million kilometers of
  space during its elliptical orbit, and travels at
  a speed of 100,000 km per hour to finish that
  path in one year.
• The earth is also wobbling back and forth along
  its orbit because of the movement of the moon.

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The Moon

• Diameter 3.4 thousand kilometers (about ¼ of the
  diameter of the earth)
• Mass 7.36 1022 kilograms or about 1/80 of the
  mass of the earth
• Composition similar to the earths crust
• Atmosphere because of little gravity the moon
  basically has no atmosphere
• Surface covered with craters and mares (flat seas
  of rock)
• Surface Temperature -233 123 oC
• The moon always shows the same side to Earth
• What is the collision theory about how the moon
  was formed?

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The Movements of the Moon

• The Moon rotates on an axis that is not tilted
  very much relative to the Earth.
• Its period of rotation is 27.3 days.
• The period of revolution around the Earth is 27.3
  days as it completes a near circular orbit at an
  average radius of 384,000 kilometers.
• What do these last two facts mean?
• Thats right. We are always looking at the same
  side of the moon from the Earth. Actually we can
  see a little more around the edges, but only 55
  of the lunar surface is visible from the earth.
• It travels through 2.4 million kilometers of
  space during its slightly elliptical orbit, and
  travels at a speed of 3700 km per hour to finish
  that path in one month.
• The moon looks as much as 11 bigger or smaller
  because of the apogee, perigee, and tilt of its
  orbit relative to the earth.
• The moons orbital plane is 5 degrees tilted
  compared to the Earths ecliptic plane.

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Lets see what you know!!

• Which one is the smallest?
• Which one is the densest?
• Which one has the greatest mass?
• Which is spinning fastest on its axis?
• Which one is spinning slowest?
• Which one has the longest orbit?
• Which is moving fastest? Be careful on this
  one!!
• Now lets see how they are related!!

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• The moon is constantly revolving around the Earth
  as the Earth revolves around the Sun.
• The appearance of the lit side of the moon causes
  a change in the appearance of the moon called a
  phase.
• Lets look closer at phase changes and other
  things related to this movement.

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Phases of the Moon
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The Moon Phases and Tides

• Tides are periodic rises and falls of large
  bodies of water. Tides are caused by the
  gravitational interaction between the Earth and
  the Moon.
• The gravitational attraction of the moon causes
  the oceans to bulge out in the direction of the
  moon. Another bulge occurs on the opposite side,
  since the Earth is also being pulled toward the
  moon (and away from the water on the far side).
• Since the earth is rotating while this is
  happening, two tides occur each day.
• Isaac Newton (1642 -1727) was the first person to
  explain tides scientifically. His explanation of
  the tides (and many other phenomena) was
  published in 1686, in the second volume of the
  Principia.

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Take a Look!!
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Variations in Tides
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What two dates would have the highest tides?
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How many times a day do high tide and low tide
happen?

• Tides at the Chesapeake Bay Bridge Tunnel

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• Besides tides and phases, the moons movement
  is also responsible for two common events called
  solar and lunar eclipses.

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Facts about Eclipses

• Eclipses are caused by a shadow being cast on the
  moon or the earth.
• When the moon cast a shadow on the Earth it is a
  solar eclipse (The sun is blocked from view)
• When the Earth casts a shadow on the moon it is
  called a lunar eclipse (we can not see the moon)
• Lunar eclipses do not occur as frequently as
  total solar eclipses, but they are visible from
  anywhere on the side of Earth facing the Moon
  during the evening. (seen most often)
• A total solar eclipse can only be seen from a
  narrow band about a hundred miles wide at most,
  and while up to seven of these a year are not
  unusual, they frequently occur over the most
  inaccessible regions on the planet.
• (most common) (least seen)

• Even when 99 of the Sun's surface is obscured
  during the partial phases of a total eclipse, the
  remaining crescent is intensely bright and cannot
  be viewed safely without eye protection. Failure
  to use appropriate filtration may result in
  permanent eye damage or blindness.

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Eclipse Schedules - 2004

• Apr. 19. Partial eclipse of the Sun. Visible in
  Antarctica, southeast Atlantic Ocean, southern
  half of Africa and Madagascar.
• May 4. Total eclipse of the Moon. The beginning
  of the umbral phase visible in Asia except
  extreme northeast, Europe except western region,
  Africa except northwestern part, Indonesia,
  Australia, New Zealand, Antarctica except part of
  the peninsula, the eastern South Atlantic Ocean,
  the Indian Ocean, and the western Pacific Ocean
  the end visible in Africa, Europe, western Asia,
  western Australia, Antactcia, South America
  except the southwestern part, the eastern North
  Atlantic Ocean, the South Atlantic Ocean, the
  Indian Ocean, and the extreme southeastern South
  Pacific Ocean.
• Oct. 14. Partial eclipse of the Sun. Visible in
  Northeast Asia, Japan, western Pacific Ocean,
  Hawaiian Islands, and the western part of Alaska.
• Oct. 28. Total eclipse of the Moon. The beginning
  of the umbral phase visible in Africa, Europe,
  Greenland, the Arctic region, North America
  except the extreme northwest, Central America,
  South America, extreme western Asia, part of
  Queen Maud Land and the peninsula of Antarctica,
  the Atlantic Ocean, the eastern South Pacific
  Ocean, and the western Indian Ocean the end
  visible in North America, the Arctic region,
  Greenland, Central America, South America,
  Europe, western Africa, Antarctic peninsula, the
  eastern Pacific Ocean, and the Atlantic

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Models of Solar Eclipses
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Model of a Lunar Eclipse
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• The Earth is moving around the Sun and is tilted
  on an axis relative to the orbital plane.
• What kinds of things does this cause?

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What Causes the Seasons?
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Check this out!!

• In the below animation, you can see the Earth
  during one full year (the animation then starts
  over again), as you would if you looked straight
  at it from the Sun. As you can see, the part of
  the Earth that is directly facing the sun changes
  with the time of the year. It is the northern
  half for a while, then moves south of the
  equator, only to move back to the north again.

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Kind of makes you dizzy thinking about it,
doesnt it?

• A common myth is that the seasons are caused by
  the changing distance between the Earth and the
  Sun.
• The info below disproves that myth.
• The aphelion is the furthest distance from the
  Sun, and the perihelion is the closest distance
  to the Sun.
• Notice that the perihelion happens during the
  winter and the aphelion in the summer.

Perihelion Jan 4 18 Aphelion July 5 11
Equinoxes Mar 20 06 49 Sept 22 16 30
Solstices June 21 00 57 Dec 21 12 42
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Equinoxes and Solstices

• The official date beginnings of the seasons are
  the equinoxes and the solstices.
• Summer begins on the summer solstice (the longest
  day of the year)
• Fall begins on the autumnal equinox. (equal night
  12h/12h)
• Winter begins on the Winter solstice (the
  shortest day of the year)
• Spring begins on the vernal equinox. (equal
  night)
• In 2004 these occur on
• Equinoxes Mar 20 06 49 Sept 22 16 30
• Solstices June 21 00 57 Dec 21 12 42

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What would happen if

• the earths axis was not tilted toward or away
  from the sun?
• the earths axis was tilted more than 23.5
  degrees?
• The earths axis was tilted less than 23.5
  degrees?

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Time Goes On

• A day is the time it takes for the Earth to
  complete one rotation on its axis.
• A year is the time it takes for the Earth to
  complete one revolution around the sun.
• A month is the time it takes for the moon to
  complete one revolution around the earth and one
  rotation on its axis.
• A week is 7 days long, which is the time it takes
  to go through one phase of the moon.
• Monday is moon day, and Sunday is Sun day
• What would happen to time measurement if the
  earth started rotating twice as fast on its axis?

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Do You Understand?

• What causes the seasons?
• Tides are caused by the tilt of the Earth. T or F
• What are the highest tides called?
• If your days are shorter than twelve hours long
  and getting shorter all the time what season are
  you?
• What do we call the longest day?

• If your days are longer than twelve hours and
  getting longer all the time, what season are you?
• What type of eclipse happens most often?
• What type of eclipse is seen more often?
• What calendar time periods are related to the
  movement of the moon?

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September
Summer
October
Fall
August
Autumnal Equinox Sept. 22
November
July
Aphelion July 5
December
Summer Solstice June 21
Winter Solstice Dec. 21
June
Perihelion Jan. 4
March 6,1959
Winter
May
Vernal Equinox Mar 20
Spring
January
April
February
March