The MoonThe Moon

Chapter 6Chapter 6

Characteristics of the MoonCharacteristics of the Moon

The ___________ neighbor in spaceThe ___________ neighbor in space No atmosphereNo atmosphere Marked with craters Marked with craters The earth also has craters, but most The earth also has craters, but most

have been erased by erosion and have been erased by erosion and tectonic activity.tectonic activity.

General FeaturesGeneral Features The Moon is 1/4The Moon is 1/4thth the size of Earth the size of Earth 868.5 km diameter868.5 km diameter 384403 km away from the Earth384403 km away from the Earth CratersCraters – – Craters diameters on the moon range from Craters diameters on the moon range from

centimeters to several hundred kilometers. centimeters to several hundred kilometers. Most craters on bodies such as the Moon are Most craters on bodies such as the Moon are formed by the impact of solid bodies, such as formed by the impact of solid bodies, such as asteroids.asteroids.

See figure 6.13 for “Birth of the Moon”See figure 6.13 for “Birth of the Moon”

Other Surface FeaturesOther Surface Features

_________ – Pronounced – A vast, _________ – Pronounced – A vast, smooth, dark, and congealed lava flow filling smooth, dark, and congealed lava flow filling a basin on the Moon and on some planets. a basin on the Moon and on some planets. Maria often have roughly circular shapes.Maria often have roughly circular shapes.– Examples – Mare Serenitatis (Sea of Serenity), Examples – Mare Serenitatis (Sea of Serenity),

Mare Tranquillitatis (Sea of Tranquility) – site Mare Tranquillitatis (Sea of Tranquility) – site where astronauts first landed. where astronauts first landed.

These “Seas” are not associated with waterThese “Seas” are not associated with water Maria are believed to have formed in a Maria are believed to have formed in a

relatively complex manner. relatively complex manner.

Maria formationMaria formation Maria were formed as the moon first formed.Maria were formed as the moon first formed. As it cooled iron rich dense material sank As it cooled iron rich dense material sank

into the interior, lighter material formed on into the interior, lighter material formed on the surface.the surface.

Large objects crashed into the surface and Large objects crashed into the surface and pushed large amounts of lunar crusts up, pushed large amounts of lunar crusts up, which formed mountains.which formed mountains.

This allowed the release of molten material This allowed the release of molten material onto the lunar surface. It cooled relatively onto the lunar surface. It cooled relatively recently in lunar formation.recently in lunar formation.

Most of the stellar debris that formed Most of the stellar debris that formed craters would have been attracted to the craters would have been attracted to the Earth because of it gravity and therefore Earth because of it gravity and therefore remain smooth and unmarked with craters.remain smooth and unmarked with craters.

Lunar landscapeLunar landscape

– – Old, heavily cratered Old, heavily cratered regions on the Moon.regions on the Moon.

– – Long, narrow light colored Long, narrow light colored markings on the moon or other bodies markings on the moon or other bodies that radiate out from young craters. that radiate out from young craters. Rays are debris splashed out of Rays are debris splashed out of craters by the impact that formed it.craters by the impact that formed it.

RillesRilles - -

Lunar AtmosphereLunar Atmosphere

Most of the Earth’s atmosphere is a Most of the Earth’s atmosphere is a result of early volcanic eruptions and a result of early volcanic eruptions and a large enough surface gravity to keep large enough surface gravity to keep the gases close to the planet.the gases close to the planet.

Two Reasons there is NO lunar Two Reasons there is NO lunar atmosphere: atmosphere:

1. 1.

2. 2.

Lunar RotationLunar Rotation

The moon rotates on its axis, but it is The moon rotates on its axis, but it is equal to its orbital period.equal to its orbital period.

This means that we always see the This means that we always see the same side of the moon.same side of the moon.

As the moon rotates, it is also As the moon rotates, it is also orbiting around the earth.orbiting around the earth.

rotationrotation – The condition – The condition that a body’s rotation period is the that a body’s rotation period is the same as its orbital period. same as its orbital period.

EclipsesEclipses

EclipseEclipse – Occurs when one astronomical – Occurs when one astronomical body casts its shadow on another.body casts its shadow on another.

eclipseeclipse – The passage of the – The passage of the moon between the sun so that our view moon between the sun so that our view of the sun is partially obscured.of the sun is partially obscured.

eclipseeclipse – The passage of the – The passage of the Earth between the Sun and the Moon so Earth between the Sun and the Moon so that the Earth’s shadow falls on the that the Earth’s shadow falls on the Moon.Moon.

Schedule of upcoming Schedule of upcoming EclipsesEclipses

Solar EclipsesSolar Eclipses Lunar EclipsesLunar Eclipses– February 7, 2008February 7, 2008 - February 21, - February 21,

20082008– August 1, 2008August 1, 2008 - August 16, 2008- August 16, 2008

Images of Lunar EclipsesImages of Lunar Eclipses

TidesTides Caused by the gravitational pull of Moon Caused by the gravitational pull of Moon

on water.on water. The pull is strongest on the side of the The pull is strongest on the side of the

Earth that is facing the moon. This pulls Earth that is facing the moon. This pulls the water, creating a bulge near the the water, creating a bulge near the equator.equator.

The rotation of the Earth causes us to The rotation of the Earth causes us to spin in and out of the higher water spin in and out of the higher water zones and in and out of low water zones. zones and in and out of low water zones. This occurs about every 6 hours along This occurs about every 6 hours along the coast. Giving us High and low tides. the coast. Giving us High and low tides.

Go over figures 6.20, 6.21, 6.22Go over figures 6.20, 6.21, 6.22

Solar TidesSolar Tides The Sun is much more massive than the The Sun is much more massive than the

moon, but it is a mush greater distance moon, but it is a mush greater distance from the Earth. It does have an effect on from the Earth. It does have an effect on the tides, but not to the intensity of the the tides, but not to the intensity of the Moon. Moon.

Spring Tides illustrate the effect of the Spring Tides illustrate the effect of the sun on tides Have nothing to do with sun on tides Have nothing to do with spring, rather the observation of water spring, rather the observation of water “SPRINGING up the beach” “SPRINGING up the beach”

During spring tides the earth and moon During spring tides the earth and moon are opposite each other and enhance the are opposite each other and enhance the gravitational pull causing a greater than gravitational pull causing a greater than normal tidal surge. Fig 6.23normal tidal surge. Fig 6.23

Tidal BrakingTidal Braking If the day seems longer that is because it is!If the day seems longer that is because it is! Tidal braking – Is the slowing of the Earth’s Tidal braking – Is the slowing of the Earth’s

rotation as a result of the gravitational force rotation as a result of the gravitational force exerted on it by another.exerted on it by another.

The pull on the water gradually slows the The pull on the water gradually slows the rotation of the Earth. Thus, increasing the rotation of the Earth. Thus, increasing the length of the day .002 seconds per century!length of the day .002 seconds per century!

Newton’s 3Newton’s 3rdrd law explains that just as the law explains that just as the moon exerts a force on the water, the water moon exerts a force on the water, the water also exerts a force on the moon. It is actually also exerts a force on the moon. It is actually enough to push the moon 3 cm away from enough to push the moon 3 cm away from the earth each year.the earth each year.

This change is detectable by lasersThis change is detectable by lasers

Tidal brakingTidal braking

After Billions of years of tidal braking, the After Billions of years of tidal braking, the Earth and the Moon will have synchronous Earth and the Moon will have synchronous rotation.rotation.

This means only half of the planet will see This means only half of the planet will see the moon.the moon.

The effects of the moon on the tides also The effects of the moon on the tides also stabilize our climate and weather patterns.stabilize our climate and weather patterns.

If we are still around when the earth and If we are still around when the earth and moon’s rotations are synchronized, then moon’s rotations are synchronized, then we will really have some severe weather!we will really have some severe weather!

Phases of the MoonPhases of the Moon The lunar cycle is a result of differing amounts of The lunar cycle is a result of differing amounts of

the moon’s surface being illuminated by the sun. the moon’s surface being illuminated by the sun. It has NOTHING to do with the Earth’s shadow!It has NOTHING to do with the Earth’s shadow!

The lunar cycle is approximately 28 daysThe lunar cycle is approximately 28 days The new moon occurs when the moon is in The new moon occurs when the moon is in

between Earth and the Sun the back side of the between Earth and the Sun the back side of the Moon is facing the SunMoon is facing the Sun

A full moon occurs when the moon is on the A full moon occurs when the moon is on the opposite side of the Earth from the sun. The opposite side of the Earth from the sun. The moon’s lit half is facing the Earth and the Sun.moon’s lit half is facing the Earth and the Sun.

See figure 1.13 and animations on the computer. See figure 1.13 and animations on the computer.

Phases of the MoonPhases of the Moon – – nothing to seenothing to see

– – Moon’s face begins to increase in size.Moon’s face begins to increase in size.

– – The quarter away from the sun is lit. The quarter away from the sun is lit. Appears to be half of the lunar Appears to be half of the lunar

face.face. – – Lunar face increasing ¾ illuminatedLunar face increasing ¾ illuminated

– – Entire face illuminatedEntire face illuminated

– – Lunar face toward the sun lit. Lunar face toward the sun lit. Illuminated Illuminated surface is decreasing in size. surface is decreasing in size. (¾ (¾ illuminated)illuminated)

– – Lunar face toward the sun is lit. Lunar face toward the sun is lit. Appears Appears to be half of the lunar face.to be half of the lunar face.

– – Side closest to the sun is illuminated, Side closest to the sun is illuminated, lunar face is increasing in size.lunar face is increasing in size.