transcript
658
The Sun-Earth-Moon System
Full Moon RisingmdashThe Real StoryWhy does the Moonrsquos appearance change throughout the monthDo the Sun and Moon really rise You will find the answers tothese questions and also learn why we have summer and winter
Rotation or revolutionmdashwhich motion of Earth brings morningand which brings summer Science Journal
Many common observationssuch as seasons eclipsesand lunar phases are causedby interactions between theSun Earth and the Moon
SECTION 1EarthMain Idea Earth is asphere that rotates on atilted axis and revolvesaround the Sun
SECTION 2The MoonmdashEarthrsquos SatelliteMain Idea Eclipses andphases of the Moon occur asthe Moon moves in relationto the Sun and Earth
SECTION 3Exploring Earthrsquos MoonMain Idea Knowledge of the Moonrsquos structureand composition has been increased by manyspacecraft missions to the Moon
S6E1 Students will explore current scientific views of the universe and how those viewsevolved S6E2 Students will understand the effects of the relative positions of the Earthmoon and sun Also covers S6CS1ndash4 6 8ndash9
Chad EhlersStoneGetty Images
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Earth and the Moon All onEarth can see and feel the move-ments of Earth and the Moon as
they circle the Sun Make the following Foldableto organize what you learn about these move-ments and their effects
Fold a sheet of paper in half lengthwise
Fold paper down25 cm from the top(Hint From the tip ofyour index finger toyour middle knuckleis about 25 cm)
Open and drawlines along the25-cm foldLabel as shown
Summarize in a Table As you read the chaptersummarize the movements of Earth and theMoon in the left column and the effects of thesemovements in the right column
STEP 3
STEP 2
STEP 1
Model Rotation and RevolutionThe Sun rises in the morning at least itseems to Instead it is Earth that moves Themovements of Earth cause day and night aswell as the seasons In this lab you willexplore Earthrsquos movements
1 Hold a basketball with one finger at thetop and one at the bottom Have a class-mate gently spin the ball
2 Explain how this models Earthrsquos rotation
3 Continue to hold the basketball and walkone complete circle around anotherstudent in your class
4 How does this model Earthrsquos revolution
5 Think Critically Write a paragraph inyour Science Journal describing how thesemovements of the basketball modelEarthrsquos rotation and revolution
Start-Up Activities
Preview this chapterrsquos contentand activities at earthmssciencecom
Movements Effects
659Chad EhlersStoneGetty Images
660 A CHAPTER 23 The Sun-Earth-Moon System
Apply It Practice summarizingas you read this chapter Stop after each section and write a brief summary
Learn It Summarizing helps you organize informationfocus on main ideas and reduce the amount of information to rememberTo summarize restate the important facts in a short sentence or para-graph Be brief and do not include too many details
Practice It Read the text on page 664 labeled SolsticesThen read the summary below and look at the important facts from that passage
The solstice is the day whenthe Sun reaches its greatestdistance north or south ofthe equator
Summary
Important Facts
In the northern hemispherethe summer solstice occurs inJune and the winter solsticeoccurs in December
In the southern hemispherethe winter solstice occurs inJune and the summer solsticeoccurs in December
Summer solstice is about thelongest period of daylight ofthe year
Winter solstice is about theshortest period of daylight ofthe year
660 B
Before You Read Statement After You ReadA or D A or D
1 Earthrsquos revolution around the Sun causes dayand night to occur
2 Earthrsquos magnetic poles are aligned on Earthrsquosrotational axis
3 Summer occurs in the northern hemispherewhen Earth is closest to the Sun
4 During an equinox the number of daylighthours is nearly equal with the number of night-time hours all over the world
5 When observing the phases of the Moon theMoonrsquos lighted surface area is daylight on the Moonand the dark portion is nighttime on the Moon
6 The length of one Moon day is about the sameamount of time as the length of one Earth day
7 A lunar eclipse occurs when the Moon comesbetween Earth and the Sun
8 Humans first walked on the Moon during theApollo spacecraft missions
Print out a worksheetof this page at earthmssciencecom
Reread your summary to make
sure you didnrsquot change the
authorrsquos original meaning
or ideasUse this to focus on the main ideas as you read the chapter
Before you read the chapter respond to the statements
below on your worksheet or on a numbered sheet of paper
bull Write an A if you agree with the statement
bull Write a D if you disagree with the statement
After you read the chapter look back to this page to see if yoursquove
changed your mind about any of the statements
bull If any of your answers changed explain why
bull Change any false statements into true statements
bull Use your revised statements as a study guide
Properties of Earth You awaken at daybreak to catch the Sun ldquorisingrdquo from the
dark horizon Then it begins its daily ldquojourneyrdquo from east to westacross the sky Finally the Sun ldquosinksrdquo out of view as night fallsIs the Sun movingmdashor are you
It wasnrsquot long ago that people thought Earth was the centerof the universe It was widely believed that the Sun revolvedaround Earth which stood still It is now common knowledgethat the Sun only appears to be moving around Earth BecauseEarth spins as it revolves around the Sun it creates the illusionthat the Sun is moving across the sky
Another mistaken idea about Earth concerned its shapeEven as recently as the days of Christopher Columbus manypeople believed Earth to be flat Because of this they were afraidthat if they sailed far enough out to sea they would fall off theedge of the world How do you know this isnrsquot true How havescientists determined the true shape of Earth
Spherical Shape A round three-dimensional object is calleda sphere (SFIHR) Its surface is the same distance from its cen-ter at all points Some common examples of spheres are basket-balls and tennis balls
In the late twentieth century artificial satellites and spaceprobes sent back pictures showing that Earth is sphericalMuch earlier Aristotle a Greek astronomer and philosopherwho lived around 350 BC suspected that Earth was sphericalHe observed that Earth cast a curved shadow on the Moonduring an eclipse
In addition to Aristotle otherindividuals made observationsthat indicated Earthrsquos sphericalshape Early sailors for examplenoticed that the tops of ap-proaching ships appeared first onthe horizon and the rest appearedgradually as if they were comingover the crest of a hill as shownin Figure 1
Examine Earthrsquos physicalcharacteristics
Differentiate between rotationand revolution
Discuss what causes seasonsto change
Your life follows the rhythm ofEarthrsquos movements
Review Vocabularyorbit the path taken by an objectrevolving around another
New Vocabulary
bull sphere bull ellipse
bull axis bull solstice
bull rotation bull equinox
bull revolution
Earth
Figure 1 For many years sailorshave observed that the tops ofships coming across the horizonappear first This suggests thatEarth is spherical not flat as wasonce widely believed
660
S6E1d Explain the motion of objects in the daynight sky in terms of relative position S6E2c Relatethe tilt of the Earth to the distribution of sunlight throughout the year and to its effect on climate Alsocovers S6E1a S6CS5a 8c
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SECTION 1 Earth 661
Additional Evidence Sailors also noticed changes in how thenight sky looked As they sailed north or south the North Starmoved higher or lower in the sky The best explanation was aspherical Earth
Today most people know that Earth is spherical They alsoknow all objects are attracted by gravity to the center of a spher-ical Earth Astronauts have clearly seen the spherical shape ofEarth However it bulges slightly at the equator and is somewhatflattened at the poles so it is not a perfect sphere
Rotation Earthrsquos axis is the imaginary vertical line aroundwhich Earth spins This line cuts directly through the center ofEarth as shown in the illustration accompanying Table 1 Thepoles are located at the north and south ends of Earthrsquos axis Thespinning of Earth on its axis called rotation causes day and nightto occur Here is how it works As Earth rotates you can see theSun come into view at daybreak Earth continues to spin makingit seem as if the Sun moves across the sky until it sets at nightDuring night your area of Earth has rotated so that it is facingaway from the Sun Because of this the Sun is no longer visible toyou Earth continues to rotate steadily and eventually the Suncomes into view again the next morning One complete rotationtakes about 24 h or one day How many rotations does Earth com-plete during one year As you can infer from Table 1 it completesabout 365 rotations during its one-year journey around the Sun
Why does the Sun seem to rise and set
AxisTable 1 Physical Properties of Earth
Diameter (pole to pole) 12714 km
Diameter (equator) 12756 km
Circumference (poles) 40008 km
Circumference (equator) 40075 km
Mass 598 1024 kg
Average density 552 gcm3
Average distance to the Sun 149600000 km
Period of rotation (1 day) 23 h 56 min
Period of revolution (1 year) 365 days 6 h 9 min
Earthrsquos RotationSuppose that Earthrsquosrotation took twice aslong as it does now Inyour Science Journal pre-dict how conditions suchas global temperatureswork schedules plantgrowth and other factorsmight change underthese circumstances
Rotation
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662 CHAPTER 23 The Sun-Earth-Moon System
Magnetic FieldScientists hypothesize that the movementof material inside Earthrsquos core along with
Earthrsquos rotation generates a magnetic field This magnetic fieldis much like that of a bar magnet Earth has a north and a southmagnetic pole just as a bar magnet has opposite magnetic polesat each of its ends When you sprinkle iron shavings over a barmagnet the shavings align with the magnetic field of the mag-net As you can see in Figure 2 Earthrsquos magnetic field issimilarmdashalmost as if Earth contained a giant bar magnetEarthrsquos magnetic field protects you from harmful solar radiationby trapping many charged particles from the Sun
Magnetic Axis When you observe a compass needle point-ing north you are seeing evidence of Earthrsquos magnetic fieldEarthrsquos magnetic axis the line joining its north and south mag-netic poles does not align with its rotational axis The magneticaxis is inclined at an angle of 115deg to the rotational axis Ifyou followed a compass needle you would end up at the mag-netic north pole rather than the rotational north pole
The location of the magnetic poles has been shown to changeslowly over time The magnetic poles move around the rotational(geographic) poles in an irregular way This movement can besignificant over decades Many maps include information aboutthe position of the magnetic north pole at the time the map wasmade Why would this information be important
Figure 2 Earthrsquos magnetic fieldis similar to that of a bar magnetalmost as if Earth contained a giantmagnet Earthrsquos magnetic axisis angled 115 degrees from itsrotational axis
Axis
S
N
North magnetic pole
South magnetic pole
Making Your OwnCompassProcedure
WARNING Use care whenhandling sharp objects1 Cut off the bottom of a
plastic foam cup to makea polystyrene disk
2 Magnetize a sewingneedle by continuouslystroking the needle in thesame direction with amagnet for 1 min
3 Tape the needle to thecenter of the foam disk
4 Fill a plate with water andfloat the disk needle sideup in the water
Analysis1 What happened to the
needle and disk when youplaced them in the waterWhy did this happen
2 Infer how ancient sailorsmight have used magnetsto help them navigate onthe open seas
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SECTION 1 Earth 663
What causes changing seasonsFlowers bloom as the days get warmer The Sun appears
higher in the sky and daylight lasts longer Spring seems like afresh new beginning What causes these wonderful changes
Orbiting the Sun You learned earlier that Earthrsquos rotationcauses day and night Another important motion is revolutionwhich is Earthrsquos yearly orbit around the Sun Just as the Moon isEarthrsquos satellite Earth is a satellite of the Sun If Earthrsquos orbitwere a circle with the Sun at the center Earth would maintain aconstant distance from the Sun However this is not the caseEarthrsquos orbit is an ellipse (ee LIHPS)mdashan elongated closedcurve The Sun is not at the center of the ellipse but is a littletoward one end Because of this the distance between Earth andthe Sun changes during Earthrsquos yearlong orbit Earth gets closestto the Sunmdashabout 147 million km awaymdasharound January 3The farthest Earth gets from the Sun is about 152 million kmaway This happens around July 4 each year
What is an ellipse
Does this elliptical orbit cause seasonal temperatures onEarth If it did you would expect the warmest days to be inJanuary You know this isnrsquot the case in the northern hemi-sphere something else must cause the change
Even though Earth is closest to the Sun in January thechange in distance is small Earth is exposed to almost the sameamount of Sun all year But the amount of solar energy any oneplace on Earth receives varies greatly during the year Next youwill learn why
A Tilted Axis Earthrsquos axis is tilted235deg from a line drawn perpendicularto the plane of its orbit It is this tilt thatcauses seasons The number of daylighthours is greater for the hemisphere orhalf of Earth that is tilted toward theSun Think of how early it gets dark inthe winter compared to the summer Asshown in Figure 3 the hemisphere thatis tilted toward the Sun receives morehours of sunlight each day than thehemisphere that is tilted away from theSun The longer period of sunlight isone reason summer is warmer thanwinter but it is not the only reason
North Pole
Figure 3 In summer the north-ern hemisphere is tilted toward theSun Notice that the north pole isalways lit during the summer Observe Why is there a greaternumber of daylight hours in thesummer than in the winter
Topic EllipsesVisit for Weblinks to information about orbitsand ellipses
Activity Scientists compareorbits by how close they come tobeing circular To do this they usea measurement called eccentricityA circle has an eccentricity of zeroEllipses have eccentricities that aregreater than zero but less thanone The closer the eccentricity isto one the more elliptical theorbit Compare the orbits of thefour inner planets List them inorder of increasing eccentricity
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664 CHAPTER 23 The Sun-Earth-Moon System
Radiation from the Sun Earthrsquos tilt also causes the Sunrsquosradiation to strike the hemispheres at different angles Sunlightstrikes the hemisphere tilted towards the Sun at a higher anglethat is closer to 90 degrees than the hemisphere tilted awayThus it receives more total solar radiation than the hemispheretilted away from the Sun where sunlight strikes at a lower angle
Summer occurs in the hemisphere tilted toward the Sunwhen its radiation strikes Earth at a higher angle and for longerperiods of time The hemisphere receiving less radiation experi-ences winter
SolsticesThe solstice is the day when the Sun reaches its greatest dis-
tance north or south of the equator In the northern hemispherethe summer solstice occurs on June 21 or 22 and the wintersolstice occurs on December 21 or 22 Both solstices are illus-trated in Figure 4 In the southern hemisphere the winter sol-stice is in June and the summer solstice is in December Summersolstice is about the longest period of daylight of the year Afterthis the number of daylight hours become less and less untilthe winter solstice about the shortest period of daylight of theyear Then the hours of daylight start to increase again
Figure 4 During the summersolstice in the northern hemi-sphere the Sun is directly over thetropic of Cancer the latitude lineat 235deg N latitude During thewinter solstice the Sun is directlyover the tropic of Capricorn thelatitude line at 235deg S latitude Atfall and spring equinoxes the Sunis directly over the equator
Tropic of Cancer
Equator
Tropic of Capricorn
Tropic of Cancer
Equator
Tropic of Capricorn
Tropic of Cancer
Equator
Tropic of Capricorn
Tropic of Cancer
Equator
Tropic of Capricorn
Summer solstice for northern hemisphere
Winter solstice for northern hemisphere
Fall equinox
Spring equinox
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SECTION 1 Earth 665
Self Check1 Explain why Aristotle thought Earth was spherical
2 Compare and contrast rotation and revolution
3 Describe how Earthrsquos distance from the Sun changesthroughout the year When is Earth closest to the Sun
4 Explain why it is summer in Earthrsquos northern hemisphereat the same time it is winter in the southern hemisphere
5 Think Critically Table 1 lists Earthrsquos distance from theSun as an average Why isnrsquot an exact measurementavailable for this distance
SummaryProperties of Earth
bull Earth is a slightly flattened sphere that rotatesaround an imaginary line called an axis
bull Earth has a magnetic field much like a barmagnet
bull The magnetic axis of Earth differs from itsrotational axis
Seasons
bull Earth revolves around the Sun in an ellipticalorbit
bull The tilt of Earthrsquos axis and its revolution causethe seasons
bull Solstices are days when the Sun reaches itsfarthest points north or south of the equator
bull Equinoxes are the points when the Sun isdirectly over the equator
6 Classify The terms clockwise and counterclockwise areused to indicate the direction of circular motion Howwould you classify the motion of the Moon aroundEarth as you view it from above Earthrsquos north poleNow try to classify Earthrsquos movement around the Sun
EquinoxesAn equinox (EE kwuh nahks) occurs when the Sun is directly
above Earthrsquos equator Because of the tilt of Earthrsquos axis the Sunrsquosposition relative to the equator changes constantly Most of thetime the Sun is either north or south of the equator but twotimes each year it is directly over it resulting in the spring and fallequinoxes As you can see in Figure 4 at an equinox the Sunstrikes the equator at the highest possible angle 90deg
During an equinox the number of daylight hours and night-time hours is nearly equal all over the world Also at this timeneither the northern hemisphere nor the southern hemisphereis tilted toward the Sun
In the northern hemisphere the Sun reaches the spring equinox on March 20 or 21 and the fall equinox occurs onSeptember 22 or 23 In the southern hemisphere the equinoxesare reversed Spring occurs in September and fall occurs in March
Earth Data Review As you have learned Earth is a spherethat rotates on a tilted axis This rotation causes day and nightEarthrsquos tilted axis and its revolution around the Sun cause theseasons One Earth revolution takes one year In the next sec-tion you will read how the Moon rotates on its axis and revolvesaround Earth
Topic SeasonsVisit for Weblinks to information about theseasons
Activity Make a posterdescribing how the seasons differin other parts of the world Showhow holidays might be celebrateddifferently and how farming mightvary between hemispheres
earthmssciencecom
earthmssciencecomself_check_quiz
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Moonrsquos orbit
Moonrsquos rotation
Northpole
Motions of the MoonJust as Earth rotates on its axis and revolves around the Sun
the Moon rotates on its axis and revolves around Earth TheMoonrsquos revolution around Earth is responsible for the changesin its appearance If the Moon rotates on its axis why canrsquot yousee it spin around in space The reason is that the Moonrsquos rota-tion takes 273 daysmdashthe same amount of time it takes torevolve once around Earth Because these two motions take thesame amount of time the same side of the Moon always facesEarth as shown in Figure 5
You can demonstrate this by having a friend hold a ball infront of you Direct your friend to move the ball in a circlearound you while keeping the same side of it facing youEveryone else in the room will see all sides of the ball You willsee only one side If the moon didnrsquot rotate we would see all ofits surface during one month
The MoonmdashEarthrsquos Satellite
Identify phases of the Moon andtheir cause
Explain why solar and lunareclipses occur
Infer what the Moonrsquos surfacefeatures may reveal about itshistory
Learning about the Moon can teachyou about Earth
Review Vocabularymantle portion of the interior ofa planet or moon lying betweenthe crust and core
New Vocabulary
bull moon phase bull waning
bull new moon bull solar eclipse
bull waxing bull lunar eclipse
bull full moon bull maria
Figure 5 In about 273 daysthe Moon orbits Earth It alsocompletes one rotation on itsaxis during the same periodThink Critically Explain how thisaffects which side of the Moon facesEarth
666 CHAPTER 23 The Earth-Sun-Moon System
S6E2a Demonstrate the phases of the moon by showing the alignment of the Earth moon and sunS6E2b Explain the alignment of the Earth moon and sun during solar and lunar eclipses Also covers S6E1a 1d S6CS5a 8c
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SECTION 2 The MoonmdashEarthrsquos Satellite 667
Reflection of the Sun The Moon seems to shine because itssurface reflects sunlight Just as half of Earth experiences day asthe other half experiences night half of the Moon is lightedwhile the other half is dark As the Moon revolves around Earthyou see different portions of its lighted side causing the Moonrsquosappearance to change
Phases of the Moon Moon phases are the different forms that the Moon takes in
its appearance from Earth The phase depends on the relativepositions of the Moon Earth and the Sun as seen in Figure 6on the next page A new moon occurs when the Moon isbetween Earth and the Sun During a new moon the lighted halfof the Moon is facing the Sun and the dark side faces Earth TheMoon is in the sky but it cannot be seen The new moon risesand sets with the Sun
Why canrsquot you see a new moon
Waxing Phases After a new moon the phases begin waxingWaxing means that more of the illuminated half of the Mooncan be seen each night About 24 h after a new moon you cansee a thin slice of the Moon This phase is called the waxing cres-cent About a week after a new moon you can see half of thelighted side of the Moon or one quarter of the Moonrsquos surfaceThis is the first quarter phase
The phases continue to wax When more than one quarter isvisible it is called waxing gibbous after the Latin word forldquohumpbackedrdquo A full moon occurs when all of the Moonrsquos sur-face facing Earth reflects light
Waning Phases After a full moon the phases are said tobe waning When the Moonrsquos phases are waning you seeless of its illuminated half each night Waning gibbous beginsjust after a full moon When you can see only half of thelighted side it is the third-quarter phase The Moon continuesto appear to shrink Waning crescent occurs just beforeanother new moon Once again you can see only a small sliceof the Moon
It takes about 295 days for the Moon to complete its cycle ofphases Recall that it takes about 273 days for the Moon torevolve around Earth The discrepancy between these two num-bers is due to Earthrsquos revolution The roughly two extra days arewhat it takes for the Sun Earth and Moon to return to theirsame relative positions
Comparing the Sunand the MoonProcedure1 Find an area where you
can make a chalk mark onpavement or similarsurface
2 Tie a piece of chalk to oneend of a 200-cm-longstring
3 Hold the other end of thestring to the pavement
4 Have a friend pull thestring tight and walkaround you drawing acircle (the Sun) on thepavement
5 Draw a 1-cm-diametercircle in the middle of thelarger circle (the Moon)
Analysis1 How big is the Sun com-
pared to the Moon2 The diameter of the Sun
is 139 million km Thediameter of Earth is12756 km Draw two newcircles modeling the sizesof the Sun and EarthWhat scaledid you use
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668 CHAPTER 23 The Sun-Earth-Moon System
EclipsesImagine living 10000 years ago You are foraging for nuts
and fruit when unexpectedly the Sun disappears from the skyThe darkness lasts only a short time and the Sun soon returnsto full brightness You know something strange has happenedbut you donrsquot know why It will be almost 8000 years beforeanyone can explain what you just experienced
The event just described was a total solar eclipse (ih KLIPS)shown in Figure 7 Today most people know what causes sucheclipses but without this knowledge they would have been terrify-ing events During a solar eclipse many animals act as if it is night-time Cows return to their barns and chickens go to sleep Whatcauses the day to become night and then change back into day
What happens during a total solar eclipse
Figure 6 The phases of the Moon change during a cycle that lasts about 295 days
New
1st qtr
3rd qtr
Waxinggibbous
Waxingcrescent
Waninggibbous
Waningcrescent
Earth
Full
Sunlight
Figure 7 The outer portion ofthe Sunrsquos atmosphere is visibleduring a total solar eclipse It lookslike a halo around the Moon
Photographs of moon phasesare as seen from Earth
(bl)Richard J WainscoatPeter Arnold Inc (others)Lick Observatory
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SECTION 2 The MoonmdashEarthrsquos Satellite 669
What causes an eclipse The revolution of the Mooncauses eclipses Eclipses occur when Earth or the Moon tem-porarily blocks the sunlight from reaching the otherSometimes during a new moon the Moonrsquos shadow falls onEarth and causes a solar eclipse During a full moon Earthrsquosshadow can be cast on the Moon resulting in a lunar eclipse
An eclipse can occur only when the Sun the Moon andEarth are lined up perfectly Because the Moonrsquos orbit is not inthe same plane as Earthrsquos orbit around the Sun lunar eclipsesoccur only a few times each year
Eclipses of the Sun A solar eclipse occurs when the Moonmoves directly between the Sun and Earth and casts its shadowover part of Earth as seen in Figure 8 Depending on where youare on Earth you may experience a total eclipse or a partialeclipse The darkest portion of the Moonrsquos shadow is called theumbra (UM bruh) A person standing within the umbra experi-ences a total solar eclipse During a total solar eclipse the onlyvisible portion of the Sun is a pearly white glow around the edgeof the eclipsing Moon
Surrounding the umbra is a lighter shadow on Earthrsquos sur-face called the penumbra (puh NUM bruh) Persons standingin the penumbra experience a partial solar eclipse WARNINGRegardless of which eclipse you view never look directly at the SunThe light can permanently damage your eyes
Area of total eclipse
Umbra
Penumbra
Area of partial eclipse
Distances are not drawn to scale
Figure 8 Only a small area ofEarth experiences a total solareclipse during the eclipse event
Topic EclipsesVisit for Weblinks to information about solarand lunar eclipses
Activity Make a chart showingthe dates when lunar and solareclipses will be visible in your areaInclude whether the eclipses willbe total or partial
earthmssciencecom
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670 CHAPTER 23 The Sun-Earth-Moon System
Eclipses of the Moon When Earthrsquos shadow falls on theMoon a lunar eclipse occurs A lunar eclipse begins when theMoon moves into Earthrsquos penumbra As the Moon continues tomove it enters Earthrsquos umbra and you see a curved shadow onthe Moonrsquos surface as in Figure 9 Upon moving completelyinto Earthrsquos umbra as shown in Figure 10 the Moon goes darksignaling that a total lunar eclipse has occurred Sometimes sun-light bent through Earthrsquos atmosphere causes the eclipsed Moonto appear red
A partial lunar eclipse occurs when only a portion of theMoon moves into Earthrsquos umbra The remainder of theMoon is in Earthrsquos penumbra and therefore receives somedirect sunlight A penumbral lunar eclipse occurs when theMoon is totally within Earthrsquos penumbra However it is dif-
ficult to tell when a penum-bral lunar eclipse occursbecause some sunlight con-tinues to fall on the side ofthe Moon facing Earth
A total lunar eclipse canbe seen by anyone on thenighttime side of Earth wherethe Moon is not hidden byclouds In contrast only alucky few people get towitness a total solar eclipseOnly those people in the smallregion where the Moonrsquosumbra strikes Earth can wit-ness one
Figure 9 These photographsshow the Moon moving from rightto left into Earthrsquos umbra thenout again
Figure 10 During a total lunareclipse Earthrsquos shadow blocks lightcoming from the Sun
Umbra
Penumbra
Dr Fred EspenakScience Photo LibraryPhoto Researchers
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SECTION 2 The MoonmdashEarthrsquos Satellite 671
The Moonrsquos Surface When you look at the Moon as shown in Figure 12 on the
next page you can see many depressions called cratersMeteorites asteroids and comets striking the Moonrsquos surfacecreated most of these craters which formed early in the Moonrsquoshistory Upon impact cracks may have formed in the Moonrsquoscrust allowing lava to reach the surface and fill up the largecraters The resulting dark flat regions are called maria (MAHRee uh) The igneous rocks of the maria are 3 billion to 4 billionyears old So far they are the youngest rocks to be found on theMoon This indicates that craters formed after the Moonrsquos sur-face originally cooled The maria formed early enough in theMoonrsquos history that molten material still remained in theMoonrsquos interior The Moon once must have been as geologicallyactive as Earth is today Before the Moon cooled to the currentcondition the interior separated into distinct layers
Inside the Moon Earthquakes allow scientists to learn about Earthrsquos interior
In a similar way scientists use instruments such as the one in Figure 11 to study moonquakes The data they have receivedhave led to the construction of several models of theMoonrsquos interior One such model shown in Figure 11suggests that the Moonrsquos crust is about 60 km thick onthe side facing Earth On the far side it is thought to beabout 150 km thick Under the crust a solid mantle mayextend to a depth of 1000 km A partly molten zone ofthe mantle may extend even farther down Below thismantle may lie a solid iron-rich core
Crust
Upper mantle
Core
Lower mantle
SeismographControl center
Figure 11 Equipment such asthe seismograph left on the Moonby the Apollo 12 mission helpsscientists study moonquakes
Models of the Moonrsquos interior were created fromdata obtained by scientists studying moonquakes
Seismology A seismologistis an Earth scientist whostudies the propagation ofseismic waves in geologicalmaterials Usually thismeans studying earth-quakes but some seismolo-gists apply their knowledgeto studies of the Moon andplanets Seismologists usu-ally study geology physicsand applied mathematics incollege and later specializein seismology for anadvanced degree
BettmannCORBIS
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Figure 12
VISUALIZING THE MOONrsquoS SURFACE
672 CHAPTER 23
By looking through binoculars you can see many of the features on the surface of the Moon These include craters that are hundreds of kilometers wide light-colored mountains and darker patches that
early astronomers called maria (Latin for ldquoseasrdquo) However as the NASA Apollomissions discovered these so-called seas do not contain water In fact maria (singular mare) are flat dry areas formed by ancient lava flows Some of theMoonrsquos geographic features are shownbelow along with the landing sitesof Apollo missions sent toinvestigate Earthrsquosclosest neighborin space
Sea ofSerenity
(Mare Serenitatis)
Sea of Rains (Mare Imbrium)
Sea of Clouds
(MareNubium)
Sea of Moisture(Mare
Humorum)
Sea of Fertility(Mare
Fecunditatis)
Sea ofNectar
(Mare Nectaris)
Sea ofVapor
(Mare Vaporum)
Sea of Crisis (Mare Crisium)
Sea ofTranquility
(Mare Tranquillitatis)
S e a o f C o l d ( M a r e F r i g o r i s )
APOLLO 15
APOLLO 17
APOLLO 11
APOLLO 16
APOLLO 12APOLLO 14First major
scientificexperimentsset up onthe Moon
Longestand finalApollomission to the Moon
First landing in thelunar mountains
First astro-naut sets footon the Moon
Crew exploresmountains
Oc
ea
no
fS
to
r ms
(Oce
an
us
Pr
oc
el l a
r um
)
Plato Crater
EndymionCrater
Copernicus CraterKeplerCrater
PythagorasCrater
AristotelesCrater
First wheeled-vehicle excursions
NASAastronaut
NASA
The Moonrsquos Origin Before the Apollo space missions in the 1960s and 1970s
there were three leading theories about the Moonrsquos originAccording to one theory the Moon was captured by Earthrsquos grav-ity Another held that the Moon and Earth condensed from thesame cloud of dust and gas An alternative theory proposed thatEarth ejected molten material that became the Moon
The Impact Theory The data gathered by the Apollo mis-sions have led many scientists to support a new theory knownas the impact theory It states that the Moon formed billions ofyears ago from condensing gas and debris thrown off whenEarth collided with a Mars-sized object as shown in Figure 13
Figure 13 According to theimpact theory a Mars-sized objectcollided with Earth around 46 bil-lion years ago Vaporized materialsejected by the collision beganorbiting Earth and quickly con-solidated into the Moon
SECTION 2 The MoonmdashEarthrsquos Satellite 673
A Mars-sizedobject collidedwith Earth
The blast ejectedmaterial from bothobjects into space
A ring of gasand debris formedaround Earth
Particles in thering joined togetherto form the Moon
What will you use to survive on the Moon
You have crash-landed on the Moon It will take one day to reach a mooncolony on foot The side of the Moon that you are on will be facing away from
the Sun during your entire trip You manage to salvage the following items fromyour wrecked ship food rope solar-powered heating unit battery-operated heat-ing unit oxygen tanks map of the constellations compass matches water solar-powered radio transmitter three flashlights signal mirror and binoculars
Identifying the Problem The Moon lacks a magnetic field
and has no atmosphere How do theMoonrsquos physical properties and the lackof sunlight affect your decisions
Solving the Problem 1 Which items will be of no use to you
Which items will you take with you 2 Describe why each of the salvaged
items is useful or not useful
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674 CHAPTER 23 The Sun-Earth-Moon System
Self Check1 Explain how the Sun Moon and Earth are positioned
relative to each other during a new moon and howthis alignment changes to produce a full moon
2 Describe what phase the Moon must be in to have alunar eclipse A solar eclipse
3 Define the terms umbra and penumbra and explainhow they relate to eclipses
4 Explain why lunar eclipses are more common thansolar eclipses and why so few people ever have achance to view a total solar eclipse
5 Think Critically What do the surface features andtheir distribution on the Moonrsquos surface tell you aboutits history
SummaryMotions of the Moon
bull The Moon rotates on its axis about once eachmonth
bull The Moon also revolves around Earth aboutonce every 273 days
bull The Moon shines because it reflects sunlight
Phases of the Moon
bull During the waxing phases the illuminatedportion of the Moon grows larger
bull During waning phases the illuminated por-tion of the Moon grows smaller
bull Earth passing directly between the Sun andthe Moon causes a lunar eclipse
bull The Moon passing between Earth and the Suncauses a solar eclipse
Structure and Origin of the Moon
bull The Moonrsquos surface is covered with depres-sions called impact craters
bull Flat dark regions within craters are called maria
bull The Moon may have formed as the result of acollision between Earth and a Mars-sized object
6 Solve Simple Equations The Moon travels in itsorbit at about 3400 kmh Therefore during a solareclipse its shadow sweeps at this speed from westto east However Earth rotates from west to east atabout 1670 kmh near the equator At what speeddoes the shadow really move across this part ofEarthrsquos surface
The Moon in History Studyingthe Moonrsquos phases and eclipses led tothe conclusion that both Earth andthe Moon were in motion around theSun The curved shadow Earth castson the Moon indicated to early scien-tists that Earth was spherical WhenGalileo first turned his telescopetoward the Moon he found a surfacescarred by craters and maria Beforethat time many people believed thatall planetary bodies were perfectlysmooth and lacking surface featuresNow actual moon rocks are availablefor scientists to study as seen inFigure 14 By doing so they hope tolearn more about Earth
How has observing the Moon been importantto science
Figure 14 Moon rocks collectedby astronauts provide scientistswith information about the Moonand Earth
earthmssciencecomself_check_quizRoger RessmeyerCORBIS
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2004
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In this lab you will demonstrate the positions ofthe Sun the Moon and Earth during certainphases and eclipses You also will see why only asmall portion of the people on Earth witness atotal solar eclipse during a particular eclipse event
Real-World QuestionCan a model be devised to show the positionsof the Sun the Moon and Earth during variousphases and eclipses
Goals Model moon phases Model solar and lunar eclipses
Materialslight source (unshaded) globepolystyrene ball pencil
Safety Precautions
Procedure1 Review the illustrations of moon phases and
eclipses shown in Section 2
2 Use the light source as a Sun model and apolystyrene ball on a pencil as a Moonmodel Move the Moon around the globe toduplicate the exact position that would haveto occur for a lunar eclipse to take place
3 Move the Moon to the position that wouldcause a solar eclipse
4 Place the Moon at each of the followingphases first quarter full moon third quar-ter and new moon Identify which if anytype of eclipse could occur during eachphase Record your data
5 Place the Moon at the location where a lunareclipse could occur Move it slightly towardEarth then away from Earth Note theamount of change in the size of the shadow
6 Repeat step 5 with the Moon in a positionwhere a solar eclipse could occur
Conclude and Apply1 Identify which phase(s) of the Moon
make(s) it possible for an eclipse to occur
2 Describe the effect of a small change in dis-tance between Earth and the Moon on thesize of the umbra and penumbra
3 Infer why a lunar and a solar eclipse do notoccur every month
4 Explain why only a few people have experi-enced a total solar eclipse
5 Diagram the positions of the Sun Earthand the Moon during a first-quarter moon
6 Infer why it might be better to call a fullmoon a half moon
Mhhn Phases and Elipses
Communicate your answers to other students
LAB 675
Moon Phase Observations
Moon Phase Observations
First quarter
Full moon
Third quarter
New moon
S6E2a Demonstrate the phases of the moon by showing the alignment of the Earthmoon and sun S6E2b Explain the alignment of the Earth moon and sun during solarand lunar eclipses Also covers S6CS1a 2bndashc 6c 9a
Do not write inthis book
522-S2-MSS08 11907 624 AM Page 321
July 20 1969Apollo 11 lands on the MoonNeil Armstrong becomes thefirst human to set foot onanother celestial body
Lunarlander
April 11 1970Apollo 13 launchedExplosion causes missionto abort Astronautsbarely make it home
July 30 1971Apollo 15 lands on theMoon Crew deploysfirst lunar roving vehicle
December 11 1972Apollo 17 lands on theMoon The first geologistvisits on the last crewedMoon mission
August 1966ndashAugust 1967Five Lunar Orbiters launched by US photograph virtually the entire Moon
June 2 1966Surveyor 1 first ofseven US Surveyormissions makes aperfect soft landingon the Moon
July 31 1964US receives perfectphotos from uncrewedprobe Ranger 7 beforeit crash lands onthe Moon
October 7 1959Russian space probeLuna 3 returns firstpictures of the Moonrsquosfar side
1959 1964 1965 1967 19681966 1969 1970 1971 1972 1973
December 24 1968Apollo 8 along withits crew becomes the first mission to orbit the Moon
Missions to the MoonThe Moon has always fascinated humanity People have
made up stories about how it formed Childrenrsquos stories evensuggested it was made of cheese Of course for centuriesastronomers also have studied the Moon for clues to its makeupand origin In 1959 the former Soviet Union launched the firstLuna spacecraft enabling up-close study of the Moon Two yearslater the United States began a similar program with the firstRanger spacecraft and a series of Lunar Orbiters The spacecraftin these early missions took detailed photographs of the Moon
The next step was the Surveyor spacecraft designed to takemore detailed photographs and actually land on the Moon Fiveof these spacecraft successfully touched down on the lunar sur-face and performed the first analysis of lunar soil The goal ofthe Surveyor program was to prepare for landing astronauts onthe Moon This goal was achieved in 1969 by the astronauts ofApollo 11 By 1972 when the Apollo missions ended 12 USastronauts had walked on the Moon A time line of these impor-tant moon missions can be seen in Figure 15
Describe recent discoveriesabout the Moon
Examine facts about the Moonthat might influence futurespace travel
Continuing moon missions may resultin discoveries about Earthrsquos origin
Review Vocabularycomet space object orbiting theSun formed from dust and rockparticles mixed with frozenwater methane and ammonia
New Vocabulary
bull impact basin
Exploring Earthrsquos Moon
Figure 15 This time line illustrates some of the most important events inthe history of moon exploration
676 CHAPTER 23 The Sun-Earth-Moon System
S6E1a Relate the Nature of Science to the progression of basic historical scientific models (geocen-tric heliocentric) as they describe our solar system and the Big Bang as it describes the formationof the universe
522-S3-MSS08 11907 629 AM Page 322
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Surveying the Moon There is still much to learn about theMoon and for this reason the United States resumed its studiesIn 1994 the Clementine was placed into lunar orbit Its goal wasto conduct a two-month survey of the Moonrsquos surface Animportant aspect of this study was collecting data on the min-eral content of Moon rocks In fact this part of its mission wasinstrumental in naming the spacecraft Clementine was thedaughter of a miner in the ballad My Darlinrsquo Clementine Whilein orbit Clementine also mapped features on the Moonrsquos sur-face including huge impact basins
Why was Clementine placed in lunar orbit
Impact Basins When meteorites and other objects strike theMoon they leave behind depressions in the Moonrsquos surface Thedepression left behind by an object striking the Moon is knownas an impact basin or impact crater The South Pole-AitkenBasin is the oldest identifiable impact feature on the Moonrsquos sur-face At 12 km in depth and 2500 km in diameter it is also thelargest and deepest impact basin in the solar system
Impact basins at the poles were of special interest to scien-tists Because the Sunrsquos rays never strike directly the crater bot-toms remain always in shadow Temperatures in shadowed areasas shown in Figure 16 would be extremely low probably nevermore than 173degC Scientists hypothesize that any ice depositedby comets impacting the Moon throughout its history wouldremain in these shadowed areas Indeed early signals fromClementine indicated the presence of water This was intriguingbecause it could be a source of water for future moon colonies
Figure 16 The South Pole-Aitken Basin is the largest of itskind found anywhere in the solarsystem The deepest craters in thebasin stay in shadow throughoutthe Moonrsquos rotation Ice depositsfrom impacting comets arethought to have collected at thebottom of these craters
Topic The Far SideVisit for Weblinks to information about the farside of the Moon
Activity Compare the image ofthe far side of the Moon with thatof the near side shown in Figure 12Make a list of all the differences younote and then compare them withlists made by other students
earthmssciencecom
677BMDONRLLLNLScience Photo LibraryPhoto Researchers
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678 CHAPTER 23 The Sun-Earth-Moon System
Mapping the MoonA large part of Clementinersquos mission included taking high-
resolution photographs so a detailed map of the Moonrsquos surfacecould be compiled Clementine carried cameras and otherinstruments to collect data at wavelengths ranging from infraredto ultraviolet One camera could resolve features as small as 20 macross One image resulting from Clementine data is shown inFigure 17 It shows that the crust on the side of the Moon thatfaces Earth is much thinner than the crust on the far sideAdditional information shows that the Moonrsquos crust is thinnestunder impact basins Based on analysis of the light data receivedfrom Clementine a global map of the Moon also was createdthat shows its composition as seen in Figure 18
What information about the Moon did scientistslearn from Clementine
The Lunar Prospector The success of Clementine opened thedoor for further moon missions In 1998 NASA launched the desk-sized Lunar Prospector shown in Figure 18 into lunar orbit Thespacecraft spent a year orbiting the Moon from pole to pole onceevery two hours The resulting maps confirmed the Clementinedata Also data fromLunar Prospector con-firmed that the Moonhas a small iron-richcore about 600 km indiameter A small coresupports the impact the-ory of how the Moonformedmdashonly a smallamount of iron could beblasted away from Earth
Figure 17 This computer-enhanced map based onClementine data indicates thethickness of the Moonrsquos crust Thecrust of the side of the Moon facingEarth shown mostly in red is thin-ner than the crust on the far side ofthe Moon
Figure 18 Lunar Prospector per-formed high-resolution mappingof the lunar surface and had instru-ments that detected water ice atthe lunar poles
(t)Zuber et alJohns Hopkins UniversityNASAPhoto Researchers (b)NASA
null
2004
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eng - iTunPGAP0
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Self Check1 Name the first US spacecraft to successfully land
on the Moon What was the major purpose of thisprogram
2 Explain why scientists continue to study the Moon longafter the Apollo program ended and list some of thetypes of data that have been collected
3 Explain how water ice might be preserved in portionsof deep impact craters
4 Describe how the detection of a small iron-rich coresupports the theory that the Moon was formed from acollision between Earth and a Mars-sized object
5 Think Critically Why might the discovery of ice inimpact basins at the Moonrsquos poles be important tofuture space flights
SummaryMissions to the Moon
bull The first lunar surveys were done by Lunalaunched by the former Soviet Union andUS-launched Ranger and Lunar Orbiters
bull Five Surveyor probes landed on the Moon
bull US Astronauts landed on and explored theMoon in the Apollo program
bull Clementine a lunar orbiter mapped the lunarsurface and collected data on rocks
bull Clementine found that the lunar crust is thin-ner on the side facing Earth
bull Data from Clementine indicated that water icecould exist in shaded areas of impact basins
Mapping the Moon
bull Lunar Prospector orbited the Moon frompole to pole collecting data that confirmClementine results and that the Moon has asmall iron-rich core
bull Data from Lunar Prospector indicate the pres-ence of large quantities of water ice in cratersat the lunar poles
6 Infer why it might be better to build a future moonbase on a brightly lit plateau near a lunar pole in thevicinity of a deep crater Why not build a base in the crater itself
Icy Poles In addition to photographing thesurface Lunar Prospector carried instrumentsdesigned to map the Moonrsquos gravity magneticfield and the abundances of 11 elements in thelunar crust This provided scientists with datafrom the entire lunar surface rather than just theareas around the Moonrsquos equator which hadbeen gathered earlier Also Lunar Prospectorconfirmed the findings of Clementine that waterice was present in deep craters at both lunarpoles
Later estimates concluded that as much as3 billion metric tons of water ice was present atthe poles with a bit more at the north poleUsing data from Lunar Prospector scientists prepared mapsshowing the location of water ice at each pole Figure 19 showshow water may be distributed at the Moonrsquos north pole At firstit was thought that ice crystals were mixed with lunar soil butmost recent results suggest that the ice may be in the form ofmore compact deposits
SECTION 3 Exploring Earthrsquos Moon 679
Figure 19 The Lunar Prospectordata indicates that ice exists incrater shadows at the Moonrsquos poles
earthmssciencecomself_check_quizNASA
null
2004
56868355
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eng - iTunSMPB 00000000 00000210 00000504 000000000013BD2C 00000000 00072564 00000000 00000000 00000000 00000000 00000000 00000000
If you walk on blacktop pavement at noon you can feel the effect ofsolar energy The Sunrsquos rays hit at the highest angle at midday Nowconsider the fact that Earth is tilted on its axis How does this tilt affectthe angle at which light rays strike an area on Earth How is the angleof the light rays related to the amount of heat energy and the chang-ing seasons
Real-World QuestionHow does the angle at which light strikes Earth affect the amountof heat energy received by any area on Earth
Procedure1 Choose three angles that you will use to aim the light at the paper
2 Determine how long you will shine the light at each angle beforeyou measure the temperature You will measure the temperatureat two times for each angle Use the same time periods for eachangle
3 Copy the following data table into your Science Journal to recordthe temperature the paper reaches at each angle and time
4 Form a pocket out of a sheet of black construction paper and tapeit to a desk or the floor
5 Using the protractor set the gooseneck lamp so that it will shineon the paper at one of the angles you chose
Goals Measure the tempera-
ture change in a surfaceafter light strikes it atdifferent angles
Describe how theangle of light relates toseasons on Earth
Materialstapeblack construction paper
(one sheet)gooseneck lamp
with 75-watt bulbCelsius thermometerwatchprotractor
Safety Precautions
WARNING Do not touchthe lamp without safetygloves The lightbulb andshade can be hot evenwhen the lamp has beenturned off Handle thethermometer carefully If itbreaks do not touch any-thing Inform your teacherimmediately
680 CHAPTER 23 The Sun-Earth-Moon System
Temperature Data
Angle of Initial Temperature at Temperature atLamp Temperature ___ MinutesSeconds ___ MinutesSeconds
First angle
Second angle
Third angle
AND TEMPERATURETILT
S6E2c Relate the tilt of the Earth to the distribution of sunlight throughout the year andits effect on climate Also covers S6E4c S6CS1a 2andashc 3d 4bndashc 6c 8a 9andashc
Do not write in this book
522-S3-MSS08 11907 631 AM Page 326
6 Place the thermometer in the paper pocket Turn on the lamp Use the ther-mometer to measure the temperature of the paper at the end of the first timeperiod Continue shining the lamp on the paper until the second time periodhas passed Measure the temperature again Record your data in your datatable
7 Turn off the lamp until the paper cools to room temperature Repeat steps5 and 6 using your other two angles
Conclude and Apply1 Describe your experiment Identify the variables in your experiment Which
were your independent and dependent variables
2 Graph your data using a line graph Describe what your graph tells you aboutthe data
3 Describe what happened to the temperature of the paper as you changed theangle of light
4 Predict how your results might have been different if you used white paper Explain why
5 Describe how the results of this experiment apply to seasons on Earth
Compare your results with those of otherstudents in your class Discuss how thedifferent angles and time periods affectedthe temperatures
LAB 681Matt Meadows
Most people take for granted that aweek is seven days and that a year is12 months However there are other
ways to divide time into useful units Roughly1750 years ago in what is now south Mexicoand Central America the Mayan peopleinvented a calendar system based on carefulobservations of sun and moon cycles
In fact the Maya had several calendars thatthey used at the same time
Two calendars were most importantmdashonewas based on 260 days and the other on 365days The calen-dars were so accu-rate and usefulthat later civiliza-tions includingthe Aztecsadopted them
The 260-Day CalendarThis Mayan calendar called the Tzolkin
(tz uhl KIN) was used primarily to time plantingharvesting drying and storing of cornmdashtheir maincrop Each day of the Tzolkin had one of 20 namesas well as a number from 1 to 13 and a Mayan godassociated with it
The 365-Day CalendarAnother Mayan calendar called the Haab
(HAHB) was based on the orbit of Eartharound the Sun It was divided into 18 monthswith 20 days each plus five extra days at theend of each year
These calendars were used together makingthe Maya the most accurate reckoners of timebefore the modern period In fact they were onlyone day off every 6000 years
Drawing Symbols The Maya created picture symbols for eachday of their week Historians call these symbols glyphs Collaboratewith another student to invent seven glyphsmdashone for each weekdayCompare them with other glyphs at mssciencecomtime
For more information visitearthmssciencecomtime
SCIENCEAND
HISTORYSCIENCE
CAN CHANGE THE COURSE OF HISTORY
THE
MayanCalendar
Africa
SouthAmerica
NorthAmerica
Australia
Asia
Europe
UNITED STATES
GULF OF MEXICO
MEXICO CUBA
SChicheacuten Itzaacute
These glyphs represent four differentdays of the Tzolkin calendar
The Kukulkan builtaround the year
1050 AD in what isnow Chicheacuten ItzaacuteMexico was usedby the Maya as a
calendar It had fourstairways each with
91 steps a total of365 including the
platform on top
Cosmo CondinaStone
Copy and complete the following concept map on the impact theory of the Moonrsquos formation
Earth
1 Earth is spherical and bulges slightly atits equator
2 Earth rotates once per day and orbits theSun in a little more than 365 days
3 Earth has a magnetic field
4 Seasons on Earth are caused by the tilt ofEarthrsquos axis as it orbits the Sun
The MoonmdashEarthrsquos Satellite
1 Earthrsquos Moon goes through phases thatdepend on the relative positions of the Sunthe Moon and Earth
2 Eclipses occur when Earth or the Moontemporarily blocks sunlight from reachingthe other
3 The Moonrsquos maria are the result of ancientlava flows Craters on the Moonrsquos surfaceformed from impacts with meteoritesasteroids and comets
Exploring Earthrsquos Moon
1 The Clementine spacecraft took detailedphotographs of the Moonrsquos surface and col-lected data indicating the presence of waterin deep craters
2 NASArsquos Lunar Prospector spacecraft foundadditional evidence of ice
part of Earthrsquos crust and mantle to be vaporized and ejected into space
the Moon when particlesin the ring join together
causing
which leads to
which forms
earthmssciencecominteractive_tutor CHAPTER STUDY GUIDE 683
Fill in the blanks with the correct vocabularyword or words
1 The spinning of Earth around its axis iscalled
2 The is the point at which theSun reaches its greatest distance north orsouth of the equator
3 The Moon is said to be whenless and less of the side facing Earth islighted
4 The depression left behind by an objectstriking the Moon is called a(n)
5 Earthrsquos orbit is a(n)
Choose the word or phrase that best answers thequestion
6 How long does it take for the Moon torotate onceA) 24 hours C) 273 hoursB) 365 days D) 273 days
7 Where is Earthrsquos circumference greatestA) equator C) polesB) mantle D) axis
8 Earth is closest to the Sun during whichseason in the northern hemisphereA) spring C) winterB) summer D) fall
9 What causes the Sun to appear to riseand setA) Earthrsquos revolutionB) the Sunrsquos revolutionC) Earthrsquos rotationD) the Sunrsquos rotation
Use the photo below to answer question 10
10 What phase of the Moon is shown in thephoto aboveA) waning crescent C) third quarterB) waxing gibbous D) waning gibbous
11 How long does it take for the Moon torevolve once around EarthA) 24 hours C) 273 hoursB) 365 days D) 273 days
12 What is it called when the phases of theMoon appear to get largerA) waning C) rotatingB) waxing D) revolving
13 What kind of eclipse occurs when theMoon blocks sunlight from reaching EarthA) solar C) fullB) new D) lunar
14 What is the darkest part of the shadowduring an eclipseA) waxing gibbous C) waning gibbousB) umbra D) penumbra
15 What is the name for a depression onthe Moon caused by an object striking itssurfaceA) eclipse C) phaseB) moonquake D) impact basin
684 CHAPTER REVIEW
axis p 661ellipse p 663equinox p 665full moon p 667impact basin p 677lunar eclipse p 670maria p 671moon phase p 667
new moon p 667revolution p 663rotation p 661solar eclipse p 669solstice p 664sphere p 660waning p 667waxing p 667
earthmssciencecomvocabulary_puzzlemakerLick Observatory
CHAPTER REVIEW 685
16 Predict how the Moon would appear to anobserver in space during its revolutionWould phases be observable Explain
17 Predict what the effect would be on Earthrsquosseasons if the axis were tilted at 285deginstead of 235deg
18 Infer Seasons in the two hemispheres areopposite Explain how this supports thestatement that seasons are NOT caused byEarthrsquos changing distance from the Sun
19 Draw Conclusions How would solar eclipsesbe different if the Moon were twice as farfrom Earth Explain
20 Predict how the information gathered bymoon missions could be helpful in thefuture for people wanting to establish acolony on the Moon
21 Use Variables Constants and Controls Describea simple activity to show how the Moonrsquosrotation and revolution work to keep thesame side facing Earth at all times
22 Draw Conclusions Gravity is weaker on theMoon than it is on Earth Why mightmore craters be present on the far side ofthe Moon than on the side of the Moonfacing Earth
23 Recognize Cause and Effect During a newphase of the Moon we cannot see itbecause no sunlight reaches the side facingEarth Yet sometimes when there is a thincrescent visible we do see a faint image ofthe rest of the Moon Explain what mightcause this to happen
24 Describe Earthrsquos magnetic field Include anexplanation of how scientists believe it isgenerated and two ways in which it helpspeople on Earth
25 Display Draw a cross section of the MoonInclude the crust outer and inner mantlesand possible core based on the informationin this chapter Indicate the presence ofimpact craters and show how the thicknessof the crust varies from one side of theMoon to the other
26 Poem Write a poem in which you describethe various surface features of the MoonBe sure to include information on howthese features formed
27 Orbital Tilt The Moonrsquos orbit is tilted at an angleof 5deg to Earthrsquos orbit around the sun Using aprotractor draw the Moonrsquos orbit around EarthWhat fraction of a full circle (360deg) is 5deg
Use the illustration below to answer question 28
28 Model to Scale You are planning to make ascale model of the Lunar Prospector spacecraftshown above Assuming that the three instru-ment masts are of equal length draw a labeleddiagram of your model using a scale of 1 cmequals 30 cm
29 Spacecraft Velocity The Lunar Prospector space-craft shown above took 105 hours to reach theMoon Assuming that the average distance fromEarth to Moon is 384000 km calculate its aver-age velocity on the trip
13 m13 m
14 m14 m
25 m25 m
13 m
14 m
25 m
earthmssciencecomchapter_reviewNASA
CRCT PracticeCRCT Practice
686 CRCT PRACTICE
These CRCT questions also provide practice for the NAEP science test
Record your answers on the answer sheetprovided by your teacher or on a sheet of paper
1 Which of the following terms would youuse to describe the spinning of Earth onits axisA revolutionB ellipseC rotationD solstice
Use the illustration below to answer questions 2 and 3
2 Which season is beginning for the southernhemisphere when Earth is in this positionA springB summerC fallD winter
3 Which part of Earth receives the greatesttotal amount of solar radiation when Earthis in this positionA northern hemisphereB South PoleC southern hemisphereD equator
Use the illustration below to answer questions 4 and 5
4 Which letter corresponds to the moonphase waning gibbousA GB CC ED A
5 The Moon phase cycle lasts about 295 daysGiven this information about how longdoes it take the Moon to wax from newmoon to full moonA about 3 daysB about 1 weekC about 2 weeksD about 4 weeks
6 Where have large amounts of water beendetected on the MoonA highlandsB lunar equatorC mariaD lunar poles
Time
DA B C E F G
North Pole
Eliminate Choices If you donrsquot know the answer to amultiple-choice question eliminate as many incorrect choicesas possible Mark your best guess from the remaining answersbefore moving to the next question
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7 Which term describes the dark flat areason the Moonrsquos surface which are made ofcooled hardened lavaA spheresB moonquakesC highlandsD maria
8 In what month is Earth closest to the SunA MarchB SeptemberC JulyD January
9 So far where on the Moon have theyoungest rocks been foundA lunar highlandsB mariaC lunar polesD lunar equator
Use the illustration below to answer question 10
10 What type of eclipse is shown aboveA total eclipseB lunar eclipseC solar eclipseD partial eclipse
Record your answers on a sheet of paper
Use the illustrations below to answer questions 11ndash12
11 As a ship comes into view over the hori-zon the top appears before the rest of theship How does this demonstrate thatEarth is spherical
12 If Earth were flat how would anapproaching ship appear differently
13 Explain why eclipses of the Sun occuronly occasionally despite the fact that theMoonrsquos rotation causes it to pass betweenEarth and the Sun every month
14 Recent data from the spacecraft LunarProspector indicate the presence of largequantities of water in shadowed areas oflunar impact basins Describe the hypoth-esis that scientists have developed toexplain how this water reached the moonand how it might be preserved
15 Compare the impact theory of lunarformation with one of the older theoriesproposed before the Apollo mission
16 Describe how scientists study the interiorof the Moon and what they have learnedso far
17 Explain why Earthrsquos magnetic north polesmust be mapped and why these mapsmust be kept up-to-date
Umbra
Penumbra
Moon
Earth
Sun
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