Solarconstant
Measurementsonthesurfaceoftheearthmusttakeintoaccounttheatmosphericinfluenceandthecorrectionofseasonalchangesinthedistancefromthesun.Thevalueofthesolarconstantisapproximately2caloriespersquarecentimeterperminute,orapproximately1.8horsepowerpersquaremeter;itcanvaryslightlywithsolaractivity.Anysubstantialchangeswillhaveamajorimpactonlifeontheearth.
Precessionandnutation
Undertheactionofexternalforce,therotationaxisoftheearthdoesnotmaintainafixeddirectioninspace,butconstantlychanges.Thelong-termmotionoftheearth'saxisiscalledprecession,anditsperiodicmotioniscallednutation.Precessionandnutationcausethemovementofthecelestialpoleandthevernalequinoxonthecelestialsphere,andaffectthepositionofthestars.
InthesecondcenturyBC,theancientGreekastronomerHipparchuswastheearliestdiscovererofthephenomenonofprecession.InthefourthcenturyAD,theChineseJinDynastyastronomerYuXiindependentlydiscoveredprecessionbasedonobservationsofthestarsonthewintersolsticeanddeterminedthewintersolsticepointtoretreatonceevery50years.Newtonwasthefirsttopointoutthatthecauseofprecessionwastheattractionofthesunandmoontotheequatorialupliftoftheearth.Underthegravitationalforceofthesunandthemoon,theearth'srotationaxisrotatesaroundtheverticalaxisoftheeclipticplane,drawingaconeinspace,andittakesabout26,000yearstomakeafullcircle.
Onthecelestialsphere,thecelestialpolecirclestheyellowpoletodrawasmallcirclewitharadiusofabout23.5°(yellow-redangle),thatis,thevernalequinoxrotatesonceevery26,000years.Thislong-termmovementoftheearth'saxiscausedbythesunandthemooniscalledsun-moonprecession.TheGermanastronomerBesselcalculatedforthefirsttimethatthesun-moonprecessionwas5,035".05(epoch1755.0),andthecurrentvalueis5,029".0966(epoch2000.0).
BritishastronomerBradleyfoundthenutationafteranalyzingtheobservationaldataofstarpositionsfrom1727to1747in1748.Thechangeinthepositionofthemoon'sorbitalsurface(whitesurface)isthemaincauseofnutation.Theascendingnodeofthewhiteroadmoveswestwardalongtheecliptic,orbitingonecircleinabout18.6years,sothegravitationalactionofthemoonontheearthalsochangesinthesamecycle.Onthecelestialsphere,itappearsthatthecelestialpole(truecelestialpole)movesaroundtheyellowpolewhilealsomovingarounditsaverageposition(flatcelestialpole)foraperiodof18.6years.Similarly,thegravitationalforceofthesunontheearthalsohasperiodicchangesandcausescorrespondingperiodicnutation.Thecombinedeffectofprecessionandnutationmakesthetruecelestialpoledrawawavycurveonthecelestialspherearoundtheyellowpole.
Inadditiontothegravitationalpullofthesunandthemoon,theearthisalsoattractedbyotherplanetsinthesolarsystem,whichcausesconstantchangesinthepositionoftheecliptic.Thedisplacement(thedirectionisoppositetotheprecessionofthesunandthemoon),thisdisplacementofthevernalequinoxiscalledplanetaryprecession.Planetaryprecessionmakesthevernalequinoxmoveeastwardalongtheequatorbyapproximately0".13everyyear.
TheMysteryofLife
Wheredidthevoicecomefrom?Therearetwothinslicesontheupperendofourtrachea.Thisisthevocalcords.Thesoundsofspeakingandsingingareproducedbytheairflowinandoutofthetracheathatvibratethevocalcords.Byadjustingthedistancebetweenthetwovocalcordsandthespeedoftheairflowinandout,thelevelofthesoundcanbecontrolled.
TheVirgoGalaxy
ThenearestirregulargalaxyclusterisnamedforitslocationinthedirectionofVirgo.Itoccupiesatleast12h~13hrightascensionand+20declinationonthecelestialsphereAlargeareaof°~-20°.Thereareatotalof34extragalacticobjectsintheMessierNebulaClusterTable,ofwhich16aremembersoftheVirgoCluster.Thesuper-giantellipticalgalaxyM87(NGC4486)islocatedinthisgalaxyThecenteroftheclusterisoneofthestrongestradiosourcesintheentiresky.Therearehundredsofmembergalaxiesinthe12°×10°ellipticalskyareainthecentralarea.Theentiregalaxyclusterhasmorethan2500galaxies.TheaveragedirectionofviewThespeedis1180kilometerspersecond.Atadistanceof19millionparsecs(60millionlight-years),itsstructureisquitecomplicatedandmaybetheprojectionofseveralgalaxyclusters.TheVirgoclusterandthelocalgalaxygroupwheretheMilkyWayislocatedbelongtothelocalsuperClustersofgalaxies.
Openclusters
Theclusterstructureofsinglestarscanbedistinguishedbytelescopes.Mostofthemarelocatednearthegalacticplane,sotheyarealsocalledgalacticclusters.TheybelongtoThecelestialbodiesofStarGroupIareroughlysphericalinshape,witharadiusrangingfromlessthan1parsectoabout10parsecs,andthenumberofstarscontainedrangesfromdozenstomorethan1000.MorethanathousandopenstarclustershavebeendiscoveredintheMilkyWay.ItisestimatedthatThetotalnumberiscloseto20,000.Becauseofthelargeinterstellarextinctionnearthegalacticplane,wecannotobservetheMilkyWaystarclustersfarawayfromthesun.OntheHeratogram,thelowerpartofthemainsequenceofeachstarclusteroverlaps,andtheupperpartisdrawntotheright.Differentdegreesofturning.Thepositionsofturningpointsofdifferentstarclustersaredifferent.Accordingtothepointofviewofstellarevolution,starswithlargermassesevolvefaster,andstarswithlowermassesevolvemoreslowly.Becausetheagesofstarsinthesamestarclusterareaboutthesame,thestarclustersMedium-massandhigh-luminositystarshaveleftthemainsequence,whichmeansthatthelowertheturningpoint,theolderthestarclusteris,andviceversa.Forveryyoungstarclusters,thehigh-luminancestarsarealreadyinthemainsequence.,Andlow-luminositystarshavenotyetarrivedandarestillontherightsideofthemainsequence.UsingtheHeratogramsofstarclustersofdifferentagestoformthestandardmainsequence,thedistancebetweentheentiregalaxyclusterandstarsofknownspectraltypescanbedetermined.
Asfortheclassificationofgalacticstarclusters,mostofthemusethemethodproposedbySwissastronomerTrompler,thatis,accordingtotheshapeoftheHerrotdiagram,thestarclustersaredividedintothreecategories,andeachcategoryisdividedintoseveralsmallertypes.ThefirstcategoryThereareonlymainsequencestars,whicharedividedintoseveralsmalltypesaccordingtothespectraltypesoftheearlieststarsinthecluster.IfastarclusterstartsfromanO-typestar,itiscalleda1otype,anditstartsfromaB-typestar,anditiscalleda1btype.Thenfollowedby1aand1ftypeandsoon.Inadditiontothemainsequencestars,therearesomeyellowandredgiantstarsinthesecondcategory,whicharefurtherdividedinto2o,2b,2a,2fandsoon.Thethirdcategoryismainlyyellowandredgiantstars,called3o,3b,3a,3f,etc.Thediscoveredstarclustersaremainlyofthreetypes:1o,1b,and2a.
Twenty-EightAltars
InancientChina,inordertounderstandthestarsandobservethecelestialphenomena,severalgroupsofstarsintheskywereassignedwithanameforeachgroup.Suchacombinationofstarswascalledastarofficial.Thenumberofstarscontainedineachstarofficialvariesfromasfewasonetoasmanyasdozens,andtheareaoftheskyisalsodifferent.Amongthemanystarofficials,31occupyaveryimportantposition.IntheTangDynasty,SanyuanTwenty-EightLakesdevelopedintotheancientChinesestarryskydivisionsystem,similartotheconstellationsinmodernastronomy.SanyuanZiweiyuan,Taiweiyuan,Tianshiyuan.Ziweiyuanincludestheskyareanearthenortherncelestialpole,whichisroughlyequivalenttothearchpolestararea;TaiweiyuanincludespartoftheconstellationVirgo,Houfa,andLion;Tianshiyuanincludesthesnakehusband,thefairy,thegiantsnake,andtheskyeagle.Etc.partoftheconstellation.
Twenty-eightstarsisalsocalledtwenty-eightstarsortwenty-eighthouses.Inthebeginning,theancientschosetwenty-eightstarofficialstocomparethemovementofthesun,moon,metal,wood,water,fire,andearth,andusedthemasmarkersforobservation.Themeaningof"Su"issimilartothe"Gong"ofthezodiac,whichmeansthepositionofthesun,moonandfivestars.IntheTangDynasty,thetwenty-eightlodgesbecamethemainbodyofthetwenty-eightcelestialareas.Thesecelestialareaswerestillnamedafterthetwenty-eightloci,whichwasdifferentfromthesituationinSanyuan.Asthecelestialareas,thetwenty-eightlodgeswereusedtodistinguishthestarofficials.Thetwenty-eightconstellationsstartfromthespicaandarearrangedfromwesttoeast,inthesamedirectionasthesunandmoon.EasternQisu:Horn,Kang,Di,Fang,Heart,Tail,Osmunda;NorthernQisu:Fighting,Niu(PornBull),Female(BustedGirl),Xu,Danger,Room(CampChamber),Bi(EastWall));WesternQisu:Kui,Lou,Wei,Subaru,Bi,Zang,Ginseng;SouthernQisu:Jing(Dongjing),Ghost(Yugi),Liu,Xing(SevenStars),Zhang,Yi,Zhen.Inaddition,therearesomestarofficialsclosetothesestarofficialsandcloselyrelatedtothem,suchastombs,ligong,fuer,cutting,yue,corpse,youxiu,zuoxiu,Changsha,andShengong,whichareattachedtoFang,Wei,andShi.,Bi,Shen,Jing,Gui,Zhen,Ouandotherplacesarecalledauxiliaryofficialsorauxiliaryseats.IntheTangDynasty,therewereatotalof183starsincludingtheauxiliaryofficialorauxiliaryconstellationstars.
Thetwenty-eightlodgesaredividedintofourgroupsaccordingtothefourdirectionsofnortheast,southwestandsouthwest.Eachgrouphassevenlodges,whichmatchthefourcolorsandfivetypesoffourgroupsofanimalimages.TheyarecalledSixiangorSilu.Thecorrespondingrelationshipisasfollows:Easternbluedragon,cyan;northernbasalt,black;westernwhitetiger,white;southernredfinch,red.
SunWave
Surfingisalsocalled"SunWave".Anejectionphenomenonofthesun'sphotosphere.Itusuallyoccursintheskyabovesunspots,andhasastrongabilitytoreappear.Whenasurffallsbehindanascendingpath,itwilltriggeranewsurftoriseintheair.Thisisrepeatedcontinuously,butitsscaleandheightaresmallerthaneachtime.Untilitdisappears.
Thesurfattheedgeofthesunsurfaceappearsasasmallandbrighthill,withthetopgrowingrapidlyoutwardintheshapeofaspike.Theheightsofascentarenotequal.Smallsurfscanonlyreachafewhundredkilometers,largesurfscanreach5,000kilometers,andthelargestonescanreach10,000to20,000kilometers.Themaximumejectionspeedcanreach100to200kilometerspersecond,whichismorethan100timesfasterthanthefastestreconnaissanceaircraft.Whentheyreachthehighestpoint,undertheinfluenceofthesun'sgravity,theybegintodescenduntiltheyreturntothesun'ssurface.Fromhigh-resolutionobservationaldata,peoplefoundthatsurfingiscomposedofaverysmallbundleoffibers,eachwithasmalldistancebetweenthem,whichshinestogetherasawholeandmovestogether.
Prominence
Prominenceisaphenomenonofsolaractivitythatprotrudesfromtheedgeofthesolarsurface.Whentheprominencesappear,theatmosphericchromosphereresemblesaburninggrassland,andtherose-redtongue-likegasriseslikeablazingfire.Ithasvariousshapes,somelikefloatingclouds,somelikearchbridges,somelikefountains,andsomelikebushesofgrass.Someareasbeautifulasfestivefireworks,butasawhole,theylooklikeearringsattachedtotheedgeofthesun,hencethename"prominence".Therisingheightofprominencesisabouttensofthousandsofkilometers.Largeprominencescanbehundredsofthousandsofkilometershigherthanthesun'ssurface,generallyabout200,000kilometersinlength,andsomecanreach1.5millionkilometers.Thebrightnessoftheprominenceismuchdimmerthanthesolarphotosphere,soitcannotbeobservedwiththenakedeyeatordinarytimes,anditcanonlybeseendirectlyduringatotalsolareclipse.
Prominenceisaverypeculiarphenomenonofsolaractivity.Itstemperatureisbetween5000and8000K.Aftermostoftheprominencematerialrisestoacertainheight,itslowlydescendstothesunsurface,buttherearealsosomeprominencematerialfloatingInthelowerpartofthecoronawithatemperatureofupto2millionK,itdoesnotattachordisintegrate.Itisasstrangeasthereisapieceoficeinaragingsteelmakingfurnace.Moreover,thedensityoftheprominenceis1000higherthanthatofthecorona.~10,000times,itisreallypuzzlingthatthetwocancoexistforafewmonths.
Humanlandingonthemoon
Theexplorationactivityofmankindlandingonthemoonbyspacecraft.Flyingtothemoonisafantasyofmankindforthousandsofyears.Withthedevelopmentofspacetechnology,in1959,the"Moon1"launchedbytheSovietUnionflewtothevicinityofthemoonandflewaroundthemoon,andbeganhumaninvestigationsonthemoon.InMay1961,USPresidentKennedyproposedinCongressaplantosendpeopletothemooninthelate1960s-the"ApolloLunarExplorationProject."Thetasksofthe"Apollo"planincludepreparationsforlaunchingtothemoon(completedby"Apollo"1-10),andmannedlunarflights(undertakenby"Apollo"11-17).OnJuly16,1969,humanbeingslandedonthemoonforthefirsttime.By1972,theUnitedStateshadsentsixgroupsofastronautstovisitthemoonintheApollospacecraft,andatotalof12peoplesetfootonthemoon.Aseriesofscientificinvestigationsonthemoonhavebeencarriedouttomakemankind'sunderstandingofthemoonmorecomprehensiveandin-depth."Apollo"from11to17,eachtimethemoonlandingflight,adifferentnumberofhigh-resolutionlunarphotoswereobtained,andtheexperimentalcontentandtechnicalequipmentofeachmoonlandingflighthavebeendeveloped.Theastronautsof"Apollo11"installedmoonseismometersandlaserrangefindersonthelunarsurface,andconductedexperimentssuchassolarwindcollection.The"Apollo12"lunarmodulecarriesatwo-wheeledvehicleforastronautstoloadtoolsandcamerasduringtheirexpeditions.Inadditiontoexperimentsonthelunarsurface,Apollo15-17alsoconductedmanymeasurementexperimentsinorbitsaroundthemoon.
Sixlandingsonthemoon,astronautsstayedonthelunarsurfaceforatotalofabout300hours,andthetotalexplorationtimeonthelunarsurfacewas80hours,ofwhich"Apollo17"stayedonthelunarsurfacefor75hours.Thedetectiontimeisabout22hours.Morethan270kilogramsoflunarrockandsoilsampleswerecollectedfromthesixmoonlandings.Somewerecollectedfromthe"sea"and"mountains"ofthemoon,andsomewereancientandsomewerenewlyborn.Theserockandsoilspecimensaretreasuresforstudyingthecomposition,structure,formationandevolutionofthelunarmaterial.
Theseismographrecordsplacedbytheastronautsonthemoonshowthatthemoon,liketheearth,hasashellwithathicknessof40-60kilometers.Thisdataisinthestormoceanandephemeris.MeasuredinLamoroandotherregions;underthemooncrustisthemoonmantle.Themoonmantleisroughlydividedintothreelayers.Theuppermoonmantleisabout240kilometersthickandismainlycomposedofheaviermaterialsdepositedintheancient"magmasea".Themiddlelunarmantleismorethan480kilometersthick,andprobablystillpreservesthe"embryonicmaterial"thatformedtheprimitivemoonintheChaosAge.Theabovetwolayersaresolid,buthaveplasticity.Theinnerlunarmantleisinapartiallymoltenstate.Thecentralpartofthemoonisthelunarcore,whosetemperatureisabout1000°C,whichisfarlesshotthantheearth'score(thetemperatureoftheearth'scoreis5000°C～6000°C).Thelunarcoreislikelytobemolten,possiblycomposedofalow-meltingironsulfidesubstance.Theexplorationofthemoonalsofoundthatthemassdistributionofthemoonisuneven,andthereareseveral“masstumors”onthenearsideofthemoon’sgravityanomaly.
Inthe"Apollo"scientificexperimentstation,averyadvancedlunarearthquakeinstrumentwasinstalled.Afterdetection,therearealsolunarearthquakesonthemoon,butthenumberoflunarearthquakesismuchlessthanthatofearthquakes,andtheenergyreleasedismuchsmallerthanthatofearthquakes.Moonquakeisveryweak,thelargestoneis1to2magnitude.Inadditiontotheshockscausedbymeteoriteimpacts,whenthemoonistheclosestorfarthesttotheearth,moonshocksoftenoccurduetothetidalforceoftheearth.
Scientistsfrommanycountrieshaveconductedjointresearchonlunarrocksamplesbroughtbackbyastronautsonvariousprojects.Accordingtolaboratoryanalysis:nearly60kindsofmineralshavebeenfoundinmoonrock,ofwhich6havenotbeenfoundontheground;allchemicalelementsontheearthhavebeendiscoveredinmoonrockandlunarsoil;noviablelunarorganicmatterhasbeenfound,Thereisnoevidenceofancientmicroorganisms;thereareweakresidualmagnetisminsomelunarrocks;therearemanytracesofsolareventsinlunarsamples;accordingtotheisotopeanalysisofthesamples,thelunarageisabout4.6billionyears.
Onthesurfaceofthemoon,whichismostlycoveredbymoondustanddebris,astronautssawrocksofvariousshapes,sizes,andfrequencies.Theyalsofoundthatthesurfaceofthemoonwasscatteredwithsomeshinyglass.substance.Thethicknessofmoondustvariesfromplacetoplace,onlyafewcentimetersinthinplacesand5-6metersinthickplaces.
Astronautswhoreachedthemoonsawthebig,luminousearthinthedarkmoonsky.Thelunarprobealsotookpicturesoftheearthinlunarspaceandpicturesofthemoonandtheearth.Theearth'slightonthemoonismorethan8timesbrighterthanthemoon'slightontheearth.
Sincethe1950s,mankind’sachievementsinlunarexplorationhavefarexceededgroundobservationsoverthecenturies.Thesuccessfullandingof"Apollo"onthemoonisthecrystallizationofhumanscienceandhasopenedaneweraformankindtounderstandthemoon.Withthedevelopmentofscienceandtechnology,humanswillbeabletobuildlaboratoriesthatflyalongthemoon'sorbit,andhugeastronomicaltelescopeswillalsoobservetheskyfromair-freespaceonthemoon;humanswillalsobeabletousethemoonasadestinationtotraveltodistantplanets.point.
Relations
Weallhavecommonsensethatlight-emittingobjectsgenerallybecomebrighterwithhighertemperatures.Sunspotsarethelowtemperatureareaonthesurfaceofthesun.Itstemperatureisusually3845-5313℃,whichis1000-2000℃lowerthantheaveragetemperatureofthesun.Accordingtoourgeneralidea,themoresunspots,thedarkerthesunshouldbe.
However,afterlong-termobservations,astronomershavediscoveredthatthemoresunspots,thebrighterthesun.Inthepeakyearofsolaractivity,thatis,whentherearemostsunspots,thesunisbrightest.Theaveragebrightnessvariationduringtheentireactivityperiodis1/2500,andthebrightnessofsunspotscanvaryupto1/500inaday.ThesedataareprovidedbytheSunPeakYearsatelliteandconfirmedbyothersatellites.
Whydoesthebrightnessofthesunincreaseduetotheincreaseofsunspots?Astronomersdiscoveredthemysteryafterstudying.Itturnedoutthatwhilesunspotsappearedinlargenumbers,manylightspotsalsoappeared.Theywerebrightspotsnearsunspotsandotherpartsofthesun'ssurface.Theirbrightnessisenoughtocompensatefortheweakenedlightofthesunspotsandmorethanenough,whichcausesthebrightnessoftheentiresuntobecomebrighterwhenthesunspotsincrease.Exploringtheuniverse-thereasonwhytherearenohighercreaturesonVegaHumanbeingshavealwayshopedtofindhighercreaturesonplanetsotherthantheearth.However,duetotheextremelyhightemperatureofstars,itisimpossibletoproduceanylife,sothefirststepinfindingaliensistofindplanets.Inadditiontothenineknownplanetsinthesolarsystem,itisreallynotaneasytasktofindothernon-luminous,smallplanetsinthevastouterspace.
InJanuary1983,apowerfulEarth-orbitinginfraredtelescopejointlymanufacturedbytheUnitedStates,Britain,andtheNetherlandswassuccessfullylaunched.Thistelescope,whichismorethan900kilometersabovethegroundandmorethan3metersindiameter,hasopenedpeople'shorizons.OnAugust9ofthisyear,theJetPropulsionLaboratoryoftheUnitedStatesannouncedtotheworldthattheremaybelifeontheplanetofVega.
However,afterscientistshavein-depthunderstandingofVega,theyfindthattheyarenotoptimistic.BecausetheformationofVegaisonlyabout1billionyearsold,andtheemergenceofhigherorganismswillhavetogothroughatleast3to4billionyearsofpracticalevolution.BecauseVegaismuchhotterthanthesunandconsumesextremelyfastenergy,itisestimatedthatVega’sownlifewillhaveendedwithoutwaitingforthebirthofintelligentlifeontheplanetsaroundit.Therefore,itisimpossibleforhigherorganismstoexistontheplanetofVega.
Invisibletothenakedeye
Generalstars,wecanseewithnakedeyesorwithatelescope.However,whensomestarshardlygeneratevisiblelightwaves,wecannotseethemdirectly,andwemustobservethemindirectlywiththehelpofinstruments.
Haveyouseentheironnuggetsbeingheated?Whentheironblockisfirstheated,itdoesnotshine,onlyheatsup.Asthetemperaturegraduallyrises,theironnuggetsbecomemoreandmorered.Whenthetemperaturerisesagain,theironblockbecomesbrighterandwhiter,withbluelightinthewhite.Whenitcoolsdownagain,itgraduallyturnsredanddarkagain,andfinallylosesitslight.Somestarsthatarebeingborn,orstarsthatareagingtothepointofdeath,areverymuchlikeironblocksthathavejustbeenheatedorabouttobecooled.Theyemitdimredlightorinfraredraysthatareinvisibletothenakedeyeandusuallydonotattractpeople'sattention.Thesestarsareinfraredstars.
Therearealsosomeinfraredstars.Theyareverybrightandhot,buttheyarewrappedinthickinterstellardustandclouds.Allowthesestarstoemitsomeinfraredraysthroughthedust,andofcoursepeoplewillnotbeabletoseethemwiththenakedeye.
DanxiaLandform
The"DanxiaLandform"israrelyfamiliartoforeigners,andeventhosewithprofessionalbackgroundsoftenonlyhearthenameandcannotseeitpersonally.Becausethistopographicstructureisuniqueandrare,itwasdiscoveredandnamedinsomeplacesinsouthernChinainmoderntimes.Thistypeoflandformisoftenrepresentedbytopographysuchaspinnacles,stonepillars,stonetowers,peaks,forests,squaremountains,castles,etc.Underthesunlight,itlookslikealayerofredgauze,shimmering,like"Danxia"andThefirstplacetostudythislandformwasDanxiaMountaininGuangdong,sogeographersnamedtheuniquelandformofredsandstoneandconglomerate"DanxiaLandform".
Thiskindoflandformisveryrareinnorthernregionsandisnotfullydeveloped,buttheDanxialandforminChengde,HebeiProvinceisverytypical.ThemountainousareasinChengdehaveverycomplexrockcomposition,includingvolcanicrock,conglomerate,sandstoneandmudstone.Duetothehardtextureofvolcanicrockandconglomerate,whilethesofttextureofsandstoneandmudstone,inthelonggeologicalage,thesun,rain,Allkindsofweatheringanderosioncausedbyfreezingandwindhavecausedthesoftrockformationstobeconstantlyerodedandcollapsed,andthehardrockshavebecomemoreandmorevisible.
Standingonahighplaceandlookingaround,youwillfeelthatthepeaksareassharpasknives,thestonesarelikehumanfigures,themountainsarelikedragonsandpythons,andthestonesarelikebirdsandbeasts.ThemostfamousTherearemorethan10landscapes.Fromthemountaincitytothewestformorethan10milestoreachtheshoreofLuanRiver,therearetwotwintowermountains.Thetwomountainsriseupfromtheground,upanddownthewater,morethan30metershigh,liketwoinvertedancienttowers,facingaway,majesticandmajestic;3kilometerstotheeastofthemountain,thereisamountainwithbothendstiltedupandresemblingingots.Lookingatthetwintowerstotheingotsfromadistance,itisingeniousandfullofinterest.
TheDanxialandformisatypicalshapelandform.OntheeastbankofthemountaincityofTowulieRiver,thereisthefamous"BangHammerMountain".Itisnarrowandround,resemblinganupside-downclothespoundingstick,standingagainsttheskyandfacingtheriverbythewater.Itseemstobespeciallysetupforthegoddesstowashclothes;halfakilometereastofthe"BangHammerMountain",thereisalargerockthatlookslikealargelyingdown.Thefrog,raisedhishead,openedhismouth,croaking.BangchuiMountainandHamaoStonestandupanddown,whichisincomparable.LuohanMountain,notfarfromthecity,hasavividappearance.Inaddition,thereareSengmaoMountain,TianqiaoMountain,ChaoyangCave,CrescentMountain,JiguanMountain,etc.,allnamedaftertheirshapes.
Distance
Inthevastuniverse,thedistancebetweencelestialbodiesandtheearthisveryfar,sohowdoweknowthedistancebetweenthemandtheearth?
Alongtimeago,astronomersdiscoveredakindofvariablestars.Theyaresometimesbrightandsometimesdark,makingitdifficulttounderstandthelawofchange.In1784,BritishamateurastronomerGoodrickfirstdiscoveredthatthebrightnessofthestar"Xianwang6"changesconstantlyinthesky,andthischangeisveryregular,withaperiodof5days,8hours,47minutesand28seconds.Thisperiodiscalledthelightvariableperiod.Sincethen,peoplehavesuccessivelydiscoveredmanyvariablestarssimilarto"Xianwang6".Theirlightcyclevariesfromlongtoshort.Astronomerscallthistypeofvariablestar"Cepheidvariablestar".
In1912,AmericanfemaleastronomerLeWittdiscoveredthatthelongerthelightcycleofaCepheidvariablestar,thegreateritsluminosity.Basedonthisrelationship,astronomerscancalculatetheluminosityoftheCepheidvariablestarbymeasuringthelightchangeperiod,andthencalculatethedistancebetweenitandtheearthfromtherelationshipbetweenluminosityandbrightness.Manyglobularstarclusters,extragalacticgalaxiesandothercelestialbodiesareveryfarawayfromtheEarth,anditisnoteasytodetermine,butaslongasthe"cepheidvariablestars"inthemcanbeobserved,thedistancebetweenthemanduscanbecalculated.
Famousquotes
Thesignificanceofcosmicexplorationisfar-reaching,andmannedspaceflightisimperative.——WangYusheng
Newmaterials,newfuelsandinnovativeconcepts,whichwillreducethecostofuniverseexplorationshouldbegivenpriority.——MichioCalais
Theexplorationofextraterrestrialcivilizationisnotonlyapartofexplorationoftheuniverse,butalsohasaprofoundimpactonhumanevolutionandtechnologicaldevelopment.——ZhouHaizhong