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1、Moon-Earth'sNaturalSatelliteTheMoonistheEarth'ssolecompanion,orbitingatanaveragedistanceof384,400km.ItfollowsusonourpatharoundtheSun,makingoneorbitofus(asseenagainstthebackgroundofstars)every27days,7hours,43minutes.Thisperiodisreferredtoasthesiderealmonth.TheMoon'sequatorialdiametermeasures3,4
2、76kmmakingitlessthanonethirdthediameteroftheEarth.EclipsesSolarEclipsesAstheorbitalplaneoftheMoonlieswithin5°oftheapparentorbitoftheSunasseenfromEarth,occasionallytheirpositionsintheskycoincide,givingrisetoasolareclipse.LunarEclipsesAtothertimestheMoon'sorbittakesitintotheshadowcastbytheEarthi
3、ntospace,causingalunareclipse.Unlikesolareclipses,LunareclipsesarereadilyobservedfromlargeareasoftheEarth'ssurface,duetothegreaterextentoftheEarth'sshadowthanthatoftheMoon's.ChangingPhasesAsweseetheMoononlyinreflectedlight,itshowsdistinctphases,dependingontheanglemadebetweenitself,theSunandthe
4、Earth.AtNewMoon,allthreebodiesarealigned,withtheMoonbetweentheEarthandtheSun.Duringthisphase,despitetheabsenceofdirectilluminationbytheSun,thelunarsurfaceisjustvisibleinlightreflectedfromtheEarth.FullMoonoccurswhentheEarthliesdirectlybetweentheSunandtheMoon,withfirstandlastquartersoccurringatt
5、he90°and270°positions.ThetimetakenfromNewMoontoNewMoon,calledthesynodicmonth,is29days,12hours,44minutes.Ofcourse,theEarthalsogoesthroughphasesasviewedfromtheMoon!ThephotographaboveisoftheEarthtakenbyApolloastronauts.Notethattheearthisverybrightcomparedtothemoon.LunarRoverSchematicsTheMoonwasfi
6、rstvisitedbyspacecraftfromEarthinthe1960s.OnJuly20,1969,thefirstmensteppedfootontheMoon,fromApollo11.After1972,nofurtherexplorationwasmadeforover25years.In1997,theLunarProspectorwaslaunchedtoorbittheMoon,atanaltitudeof63miles,tocarryoutaone-yearmappingmission;pavingthewayforfutureconstructiono
7、fmannedbases.—fromwww.harmsy.freeuk.com
