The Moon

Atmosphere? There is none! The gravity of the Moon is too low to hold on to the molecules of an atmosphere. There is water on the moon though—ice at the poles.

Interior Mostly made of relatively low density materials Has a small, solid core that is also low density The crust on the far side of the Moon from the Earth is thicker, because the mantle and core were pulled towards Earth by gravity.

Lunar Surface Maria: large, roughly circular dark areas caused by the flow of lava when the Moon was still volcanic. Made of basalt—a dark colored, high density rock from the Moon’s mantle

Lunar Surface Lunar highlands: light colored areas elevated several kilometers above the maria. Made of rocks that are light in color, rich in aluminum, and low density Probably part of the original lunar crust—thrust up by the impact of meteoroids

Cratering Impact craters are created when meteoroids, asteroids, and comets strike the moon The crater is usually about 10 times the diameter of the impactor This is the only form of erosion on the Moon—it creates a thick layer of dust known as the regolith

Cratering Two crater types: Simple crater—small and deep with smooth bowl shape Complex crater—large, shallow, with central peak

The Moon’s Origin Before the Apollo missions in the 1960’s and 70’s, there were three leading theories to the moon’s origin: The Earth’s gravity captured it. The Moon and the Earth condensed from the same cloud of dust

3. When it is still molten, a large object strikes the Earth 3. When it is still molten, a large object strikes the Earth. (Impact Theory) Material from both objects flies off. That material condenses and forms the moon

Phases of the Moon (1) New Moon The general locations and orientations for the phases of the moon. Phases of the Moon (7) Third Quarter (6) Waning Gibbous (8) Waning Crescent Sunlight Earth (1) New Moon (5) Full Moon Sunlight Note: If you have internet explorer 5.0 and beyond you will need to Use the mouse button to advance through these slides. For Netscape Navigator the graphics show as a static picture. Earth spins on its axis in the same direction as the moon’s orbit. (4) Waxing Gibbous (2) Waxing Crescent (3) First Quarter

Perspective & The Moon’s Face How much of the moon’s face does the person see? Sunlight Earth (1) New Moon Note: If you have internet explorer 5.0 and beyond you will need to Use the mouse button to advance through these slides. For Netscape Navigator the graphics show as a static picture. NEW MOON Wherever the person looks all they see is shadowed moon. What time of day is it for the observer? Noon!!

Perspective & The Moon’s Face How much of the moon’s face does the person see? Sunlight Earth (2) Waxing Crescent WAXING CRESCENT When you look up you see only a small crescent brightly lit. (Right Side) Note: If you have internet explorer 5.0 and beyond you will need to Use the mouse button to advance through these slides. For Netscape Navigator the graphics show as a static picture. What time of day is it for the observer? 3PM!!

Perspective & The Moon’s Face How much of the moon’s face does the person see? What time of day is it for the observer? Sunset - 6PM!! Sunlight Earth (3) First Quarter Note: If you have internet explorer 5.0 and beyond you will need to Use the mouse button to advance through these slides. For Netscape Navigator the graphics show as a static picture. FIRST QUARTER When you look up you see one half of the front face of the Moon brightly lit. (Right side)

Perspective & The Moon’s Face How much of the moon’s face does the person see? Sunlight Earth (4) Waxing Gibbous Note: If you have internet explorer 5.0 and beyond you will need to Use the mouse button to advance through these slides. For Netscape Navigator the graphics show as a static picture. WAXING GIBBOUS When you look up you see only a small crescent, darkly shadowed, on the left. What time of day is it for the observer? 9PM!!

Perspective & The Moon’s Face How much of the moon’s face does the person see? Sunlight Earth (5) Full Moon Note: If you have internet explorer 5.0 and beyond you will need to Use the mouse button to advance through these slides. For Netscape Navigator the graphics show as a static picture. FULL MOON When you look up you see the entire face of the Moon brightly lit. What time of day is it for the observer? Midnight-12AM!!

Perspective & The Moon’s Face How much of the moon’s face does the person see? Sunlight Earth (6) Waning Gibbous WANING GIBBOUS When you look up you see only a small crescent, darkly shadowed, on the right. Note: If you have internet explorer 5.0 and beyond you will need to Use the mouse button to advance through these slides. For Netscape Navigator the graphics show as a static picture. What time of day is it for the observer? 3AM!!

Perspective & The Moon’s Face How much of the moon’s face does the person see? Sunlight Earth (7) Third Quarter THIRD QUARTER When you look up you see one half of the front face of the Moon brightly lit. (Left side) Note: If you have internet explorer 5.0 and beyond you will need to Use the mouse button to advance through these slides. For Netscape Navigator the graphics show as a static picture. What time of day is it for the observer? Sunrise - 6AM!!

Perspective & The Moon’s Face How much of the moon’s face does the person see? Sunlight Earth (8) Waning Crescent Note: If you have internet explorer 5.0 and beyond you will need to Use the mouse button to advance through these slides. For Netscape Navigator the graphics show as a static picture. WANING CRESCENT When you look up you see only a small crescent brightly lit. (Left Side) What time of day is it for the observer? 9AM!!

Eclipses Although the Sun is about 400 times larger than the Moon, it is also about 400 times further away. As a result of this coincidence, the Moon can completely cover the Sun, producing a total solar eclipse.

Eclipses The shadow of any body consists of two parts: The umbra is the darkest part of the shadow--in the center. The penumbra a lighter shadow—on the outer edges.

Total Solar Eclipse Penumbra Umbra

Solar Eclipse A total solar eclipse occurs about once every 18 months somewhere in the world. At any given location, a total solar eclipse occurs once every 360 years. The next total solar eclipse in the U.S. is on Aug. 21 2017.

Total Solar Eclipse

Solar Corona During Eclipse

Total Solar Eclipse As the Moon orbits the Earth, its apparent size varies. Only when the Moon is closest to the Earth can it completely block the Sun. If the Moon does not completely cover the Sun we get an annular eclipse.

Lunar Eclipses A lunar eclipse occurs when the Moon passes into the shadow of the Earth. The lunar eclipse is visible to everyone on the night side of the Earth.

Lunar Eclipse

Lunar Eclipse

NASA Eclipse Page The best web page on eclipses is: http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html

One reason we know the Earth is round: Early scientists determined that the Earth was round, because they recognized that its shadow was being cast on the moon during a lunar eclipse. The shadow is curved.

The Tides  12-hour cycle Caused by the difference of the Moon’s gravitational attraction on the water on Earth Excess gravity pulls water towards the moon on the near side Excess centrifugal force pushes water away from the moon on the far side

Spring and Neap Tides The Sun is also producing tidal effects. Near Full and New Moon, the Sun’s gravity combines with the moon’s gravity to cause spring tides. Spring tides Neap tides

Spring and Neap Tides Near first and third quarter, Sun and Moon’s gravity are at a right angle, causing neap tides.

Effects of tides Friction slows down the rotation Slow down the rotation of earth Friction slows down the rotation The day was 18 hours long 900 mya

The Tidally-Locked Orbit of the Moon Earth exerts tidal forces on the moon’s rocky interior that slow down its rotation. It is rotating with the same period around its axis as it is orbiting Earth (tidally locked). This is why we always see the same side of the Moon.

Acceleration of the Moon’s Orbital Motion Gravitational force pulls the moon slightly forward along its orbit.