chapter 28 minor bodies of the solar system the moon
TRANSCRIPT
Chapter 28 Minor Bodies of the Solar System
The Moon
Lunar Facts• Earth’s only natural satellite
• The Moon orbits the Earth at a distance of about 384,000 km (240,000 miles)
• The Moon is about 3,468 km in diameter- about ¼ the size of Earth.
• The Moon orbits the Earth at a 5o angle with respect to the Earth’s orbit around the Sun.
Earth’s orbital plane
Moon’s orbital
plane
Space Exploration
• 1957- the Soviet Union launches, Sputnik, the first artificial satellite
• 1958- the U.S. launched its first, Explorer 1
• Thousands now orbit the Earth
Lunar Missions
• July 20, 1969 Neil Armstrong became the first man on the Moon
• Between 1969 and 1972, the U.S. accomplished six Apollo missions
• 12 Americans have walked on the moon
Apollo 11 MissionFirst Lunar Landing Footage
The Lunar Surface
• No atmosphere• Extreme
temperatures– Daytime =
130C (265°F)– Nighttime = -
190C (-310 F)• 1/6 Earth’s
gravity
• Mountains up to 7500 m (25,000 ft) tall
• Ridges- long, narrow elevations of rock that crisscross the moon’s surface.
Highlands
The Lunar SurfaceHighlands
The Lunar SurfaceMaria
• Dark areas made chiefly of basalt
• Galileo named them for there “sea”-like appearance
• Formed 3-4 billion years ago by magma resulting from massive impacts or radioactive decay
Mare
Lunar FeaturesRilles
Long, deep ancient lava channels leftover from the formation of maria
Lunar FeaturesCraters
•Most formed by meteorite impact on the Moon
•Young craters characterized by bright streaks, called rays
Lunar FeaturesRegolith
Fine layer of dust and rock that covers the moon’s surface
Lunar FeaturesRocks
• Similar to igneous rocks found in Earth’s crust
• Breccia- contain fragments of other rocks fused together
Comparison of the Near and Far Sides
So where did the moon come from?
The Spin or Fission Theory
The Capture Theory
Failed Planet Theory
The Giant Impact Theory
Giant Impact Theory
• Formed 4-5 billion years ago
• Caused by impact of Mars-sized “planetesimal” on Earth
• Debris melted together to form the Moon
Movements of the Moon
• Revolution: the Moon orbits the Earth every 27.3 days
• Rotation – Moon turns on its axis every 27.3 days
• We always see the same side of the Moon because its period of rotation equals its revolution!
• This is called synchronous rotation.
Earth
Moon
MoonPlane of earth’s orbit
Plane of lunar orbit
Orbital Planes of the Earth and Moon
The Earth-Moon System
• Apogee- point at which the Moon is farthest from Earth
• Perigee- point at which the Moon is closest to Earth
Illumination of the Moon• Moonlight is reflected sunlight• Half the moon’s surface is ALWAYS
reflecting light
Illumination of the Moon
• Waxing- occurs when the size of the lighted part of the Moon is increasing
• Waning- occurs when the size of the lighted part of the Moon is decreasing
Phases of the Moon• From Earth we see different amounts of the
Moon’s lit surface• The amount we can see is called a “phase”
starchild.gsfc.nasa.gov/docs/StarChild/questions/phases.html
Phases by Day
Phases
PHASEAPPROXIMATE
DURATION
NEW 1 DAY
WAXING CRESCENT
SEVERAL DAYS
1ST QUARTER 1 DAY
WAXING GIBBOUS
SEVERAL DAYS
FULL 1 DAY
WANING GIBBOUS
SEVERAL DAYS
LAST QUARTER 1 Day
WANING CRESCENT
SEVERAL DAYS
Moon Phases Video
Eclipses• Eclipses are caused when one celestial
body passes through the shadow of another
• The Sun and Moon occasionally line up with the Earth so that an eclipse occurs
• A solar eclipse occurs when the Moon passes between the Earth and the Sun and the shadow of the Moon falls on the Earth
• A lunar eclipse occurs when the Earth passes between the Sun and the Moon and the shadow of the Earth falls on the Moon
Solar Eclipses• When the Moon’s shadow covers part of the
Earth• Only happens at New Moon• Observers in the “umbra” see a total eclipse
(corona is visible)• Those in the “penumbra” see a partial eclipse• Save the date! The next U.S. total solar eclipse
will occur 21 August 2017!
Total Solar Eclipse
• When the Earth’s shadow covers the Moon• A total lunar eclipse occurs when the entire
Moon passes into the Earth’s umbra• A partial lunar eclipse occurs when only part
of the Moon passes into the Earth’s umbra• A penumbral eclipse occurs when the entire
Moon passes into the Earth’s penumbra
Lunar Eclipses
Lunar Eclipses
• Even during a total lunar eclipse, sunlight is bent around Earth through the atmosphere
• The Moon is visible and appears to have a reddish tint
• Save the date! The next U.S. total lunar eclipse will occur 21 December 2010!
The Tides• The Moon’s gravity
tugs on the Earth. – It pulls the most on
the part of Earth closest and least on the farthest causing tidal bulges
• High tide –– Side facing Moon and
side away from Moon
• Low tide –– On sides of Earth
Tidal Patterns
Time for reflection!
Think back to your lunar modeling activity…
Have your preconceptions changed? How?
THE END