EclipseReading(Inquiry3.2)
TrueorFalse:
Whichofthefollowingstatementsistrue?
• AneclipseoftheSunoccurswhenaninvisibledragoneatstheSun.
• Duringeclipses,poisonsdropfromtheSky
• Aneclipseisasignthattheworldiscomingtoanend.
Theanswer?Noneofthesestatementsaretrue.But,peoplefromculturesallovertheworld
createdthese,andotherstoriestoexplainthemysteriousdisappearanceoftheSunandMoon
fromthesky.
Today,weknowhowandwhyeclipsestakeplace.Whileeclipseshavenothingtodowith
dragons,poisons,ortheendoftime,theyareamazingcelestialspectacles.
SolarEclipse
AsolareclipseoccurswhentheMooncomesdirectly
betweenEarthandtheSun.Thekeywordis
“directly”becausetheMoonorbitsEarthevery
month,andeverymonththeMooncastsashadow.
Wedon’thaveasolareclipseeverymonthbecause
theMoon’sshadowfallseitherabove,orbelow
Earthduringmostmonths.Butonrareoccasions,
whentheSun,Earth,andMoonarealignedjustright,theMoon’sshadowfallsdirectlyonEarth.
Duringasolareclipse,thedarkestpartoftheMoon’sshadowcone,calledtheumbra,is
oftenonlyabout250kilometersindiameter.AstheEarthspins,differentpartsofitfallwithinthe
umbra.People,whohappentobeintheumbra,canseeatotalblockingoftheSun,oratotalsolar
eclipse.Duringatotalsolar
eclipse,theaircoolsanddaylight
disappears.Itbecomesdark
enoughtoseestars!Forafew
breathlessminutes,wecansee
whatit’sliketoliveinasunless
world.
Outsidethenarrowpathof
theumbra,theMoonblocksonly
partoftheSunandcreatesa
partialsolareclipse.Ashadowiscast,butitisn’tasdarkastheumbra.Thislighterpartofthe
shadowconeiscalledthepenumbra.Becausethepenumbraismuchlargerthantheumbra,a
greaterareaofEarthexperiencesapartialeclipsethanatotaleclipse.
LunarEclipse
Inalunareclipse,Earthcomesdirectly
betweentheSunandMoon–analignment
thatputstheMooninEarth’sshadow.When
theentirefullmoonfallswithinthecenterof
Earth’sshadow,orumbra,wehaveatotal
lunareclipse.Everyoneontherightsideof
theMoon(halftheglobe!)canseesuchan
eclipse.
Apartiallunareclipseoccurs
whenonlypartoftheMoonpasses
troughtheEarth’sumbra.Apenumbral
lunareclipseoccurswhentheMoon
passesthroughonlythelighterpartof
Earth’sshadowcone–thepenumbra.
Neitheroftheselunareclipsesisas
colorfulasatotaleclipse.
ColorfulMoon
Haveyoueverwonderedwhythemoonismoreorangeor
yellowincolorwhenitfirstrisesatnight?Thiseffectiscaused
bytheatmosphereoftheearth.Thereasonfortheorangecolor
isduetothescatteringoflightbytheatmosphere.Whenthe
moonisnearthehorizon,themoonlightmustpassthrough
muchmoreatmospherethanwhenthemoonisdirectly
overhead.Bythetimethemoonlightreachesyoureyes,theblue,
green,andpurplepiecesofvisiblelighthavebeenscattered
awaybyairmolecules.That’swhyyouonlyseeyellow,orange,
orred.
Themooncanhaveanorangecoloratanytimeoftheyear.
Sometimesthemoonappearsorangeevenwhenit’sdirectly
overhead.Thisoccurswhenthere’salotofdust,smoke,orpollutionintheatmosphere.Thesize
ofthoseparticleswilldeterminethetypeofcoloryouwillsee.
ViewingCauseandEffect
Lookfirstatthewhitemoondirectlyoverhead.Seetheredpartofthearrowpointingtothewhite
moon?Thisredpartofthearrowshowsthepartoftheatmospherewearelookingthroughtosee
themoon.Nowlookattheorangemoonjustrisingintheeast.Lookattheblueportionofthe
arrowpointingtotheorangemoon.Seehowmuchlongerthebluelineisthantheredline?This
showsthatwearelookingthroughaboutthreetimesasmuchatmosphereatarisingorsetting
moon.