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Yourwebbrowser(Safari7)isoutofdate.Formoresecurity,comfortand thebestexperienceonthissite: Updateyourbrowser Ignore Activitydevelop EducatorVersion THE REASON FOR THE SEASONS HowdoesthesuncauseEarth'sseasons? OVERVIEW Studentsusepolystyrenefoamballsandlightbulbstoinvestigatethesun's intensityonthesurfaceoftheEarth. Forthecompleteactivitywithmediaresources,visit: http://www.nationalgeographic.org/activity/the-reason-for-the-seasons/ Program DIRECTIO NS 1.Activatepriorknowledgeaboutseasonsandsunlight. ExplaintostudentsthattheEarthorbitsanidealdistancefromthesun,andthis affectstheweatherweexperiencehereonEarth.Ask:Whatarethedifferent seasons?Writethesequenceoftheseasonsontheboardforstudents’ reference:winter,spring,summer,autumn.Ask:Whatistheweatherlikeduring thedifferentseasons?Whatisthesameordifferentabouttheseasons?Prompt studentstoincludesimilaritiesanddifferencesinweather,temperature,and lengthofdaylight.Writetheirideasontheboard.Thenexplaintostudentsthat 1of12 theanswertothatquestionisdifferentforthosewholiveinadifferent hemisphere,orhalfoftheEarth.Ask:Whatdoyouthinkcausesthedifferencein seasons?Whatdoyouthinkcausesthedifferenceinwhattimeitgetsdark outside? 2.Buildbackgroundaboutwhatcausesseasons. Useaglobeandgesturetointroducethevocabularytermstiltandaxis,the imaginarylinebetweentheNorthandSouthPoles.Thenexplainthefollowingto students:TheEarthrotatesonanaxisthatistilted.Inotherwords,ourplanet neverstandsupright—itisalwaysleaningtotheside.Thedirectionofthislean doesnotchangesignificantlyoverthecourseofayear,butitdoesshift graduallyovermillennia.AstheEarthtravelsalongitsorbit,itsometimesleans towardthesunandsometimesawayfromthesun.Displaythediagram “Seasons”forstudents,andpointtothepartsofthediagramasyouexplainthe following:IfyouliveintheNorthernHemisphere,youliveonthepartofthe EarththatisnorthoftheEquator.WhentheNorthernHemisphereistilted towardthesun,youexperiencesummer.WhentheNorthernHemisphereis tiltedawayfromthesun,youexperiencewinter.Ask:Howwouldthischangeif youlivedintheSouthernHemisphere?(Theoppositewouldhappen.Whenthe Earth'saxisistiltedtowardthesunfortheNorthernHemisphere,thepeoplein theNorthernHemisphereexperiencesummer,whileatthesametime,the SouthernHemisphereistiltedawayfromthesunandthepeoplethere experiencewinter.WhentheNorthernHemisphereexperienceswinter,the SouthernHemisphereexperiencessummer.) 3.Introducethehands-onactivity. Dividestudentsintosmallgroupsofthree.Provideeachgroupwithone polystyrenefoamball,onemarker,oneflashlight,andtwopushpins.Have groupschoosewhowillholdthefoamballthatrepresentstheEarthandwhowill holdtheflashlightthatrepresentsthesun.AskthestudentholdingtheEarthto drawacirclearounditsmiddletorepresenttheEquator,anddotsontheNorth 2of12 PoleandSouthPole.Havethethirdgroupmemberplaceapushpin, representingaperson,midwaybetweentheEquatorandtheNorthPole,and anotherbetweentheEquatorandSouthPole.Makesurestudentsplaceboth pushpinsonthesamesideoftheirEarth.TellstudentsthattheEarthmoves aroundthesuninanellipticalorbitandistiltedonitsaxis.ExplainthatasEarth orbitsthesun,itrotatesonitsaxis,andtheaxisisalwayspointedinthesame direction.HavethestudentsrepresentingtheEarthandsunineachgroupstand approximately5-7feetapart.Dimorturnoffthelights. 4.Useguidedinquirytohavestudentsinvestigatedirectandindirectsunlight. First,havethestudentactingasthesunkeeptheflashlightpointedstraightat therepresentationofEarthwhilethestudentholdingEarthwalksinacircle aroundthesun.TheEarthshouldstopwhenthepushpinrepresentingaperson intheNorthernHemispherecan"see"thesun.AskthestudentholdingEarthto tilttheEarthsothatthesun,withoutmovingtheflashlight,isshiningdirectly overheadofthepushpin/personinthenorth.Ask:Isthesunmoredirectforthe personatthetoporthepersonatthebottomoftheEarth?(top)Doyouthinkitis warmerforthepersonatthetoporthepersonatthebottomoftheEarth?(top) Whydoyouthinkso?Addressanystudentmisconceptions.Onecommon studentmisconceptionisthatthisisduetotheNorthernHemispherebeing closertothesun.Notethatthereisnosignificantdifferenceinthedistanceof thesuntotheNorthernandSouthernHemispheres.Thedifferenceisdueto directandindirectsolarradiation.Thehemispherethatispointedtowardthe sunreceivesmoredirectsolarradiation,thusitiswarmer.Nowaskthestudent holdingEarthtoorbitthesun,makingsuretoholdthetiltinthesamedirection untilthetiltoftheEarthispositionedsothatthesunisdirectlyoverheadofthe pushpin/personintheSouthernHemisphere.Ask:Isthesunmoredirect,or bright,forthepersonintheNorthernHemisphereortheSouthernHemisphere? (SouthernHemisphere)Whichpersondoyouthinkfeelswarmertemperatures? (thepersonintheSouthernHemisphere)Why?(duetodirectsolarradiation) 3of12 5.Useguidedinquirytohelpstudentsinvestigatetheroleofaxisandtiltin thesun-Earthrelationship. Whilethesunisstillshiningdirectlyoverheadofthepushpin/personinthe SouthernHemisphere,havestudentslocatewhereintheclassroom,suchasa wallorceiling,theNorthPolepointsto.Tapeablackcircletothewallatthat locationtohelpstudentskeeptheaxispointedinonedirection.Next,askthe Earthtoresumeorbitingthesun,whilekeepingtheNorthPolepointedatthe blackcircle.RemindstudentstokeepthesunstationaryandpointedatEarth. HavetherestofthegrouphelptomakesuretheEarth’stiltdoesn'tchange. ExplaintostudentsthattheEarth'stiltdoesnotchangesignificantlyoverthe courseofayear,butdoesshiftgraduallyovermillennia.Havestudentsstopthe Earthafterone-halfofanorbitsothatitisoppositeofwhereitstarted.Then askonegroupmembertomakeitdaytimeforthe“top”and“bottom”people.It shouldbenightforthemiftheEarthhasorbitedcorrectly,sothestudentwill havetospintheEarth.Finally,askgroupstomovetheEarthhalfanorbit aroundthesunagain,makingsuretokeeptheNorthPolepointedattheblack circle.Makesurethesundoesnotmove.Also,ensureastheEarthorbitsthe sun,theaxisdoesnotchangeorientationandcontinuespointingtotheblack circle.Haveagroupmembermakeitdaytimeforthe“top”and“bottom” people.Ask: DoesthesunshinemoredirectlyonthepersononthetophalfoftheEarth,or thepersononthebottomhalf?(bottomhalf,orSouthernHemisphere) Whichpersonfeelswarmertemperatures?(thepersonintheSouthern Hemisphere) Whichpersonisexperiencingsummer?(thepersonintheSouthern Hemisphere)Winter?(thepersonintheNorthernHemisphere)Howdoyou know?(ThepersonintheSouthernHemisphereisreceivingmoredirect sunlight,soitiswarmerthereandisthesummerseason.) Isthesunbrighterormoreconcentratedforthepersoninsummerorthe personinwinter?(thepersoninsummer) 4of12 6.Havestudentsmakeamathconnection. Askforavolunteerfromoneofthegroupstocometothefrontofthe classroomwiththeir“sun”(flashlight).Havetherestofthestudentssitonthe floorinasmallareanearthecenteroftheclassroombutfacingthesun.Ask studentstoimaginethattheflooristheNorthernHemisphereoftheEarth.In thewinter,theNorthPoleoftheEarthispointingawayfromthesun,sothesun appearsfarthersouthintheskytous.Havethestudentholdthesuncloserto thefloor.Havetherestoftheclassplacetheirhandsclosetothefloorandpoint towardthesun.Ask:Doyourfingerandthefloorformalargeorsmallangle? (smallangle)Tellstudentstheyareforminganacuteangle.Thenhavethe studentholdingthesunholditupashighasheorshecan.Havetherestofthe classkeeptheirhandsclosetothefloorandagainpointtothesun.Ask:Isthe angleyouhaveformedwithyourfingerandfloorlargerorsmaller?(larger)Tell studentstheyareforminganobtuseangle.Ask:Whatseasondoesthis represent?(summer) 7.Haveawhole-classdiscussionabouthowthesunaffectsEarth’sseasons. Pointouttostudentsthattheseasonsareoppositeforpeopleonthetop(north) oftheEarthandonthebottom(south)oftheEarth.Ask: Whenitiswinteronthetop(north)oftheEarth,whatseasonisitonthe bottom(south)oftheEarth?(summer) Whenitiswinteronthebottom(south)oftheEarth,whatseasonisitonthe top(north)oftheEarth?(summer) Howcanweuseanglestohelpotherstounderstandseasons?(Inthesummer, theangleofthesunismoredirectlyoverus,andlarger,providingmore directsolarradiationandmakingitwarmer.Inthewinter,theangleofthe sunissmallerandwereceivelessdirectsolarradiation,soitiscolder.) TipGoingGreen Tomakethisactivitymore"green,"useroundfruitinsteadofpolystyrenefoam balls. 5of12 Modification Foradvancedstudents,introducetheconceptsofthewintersolstice,summer solstice,autumnalequinox,andvernalequinox.Havethemmakeconnections betweenthehands-onactivityandthesespecialdaysthatcorrespondto differentpointsintheEarth'sorbit. Modification InStep4,addressanystudentmisconceptionsaboutdirectversusindirect sunlight.Dimthelights.Adjustasmallflashlighttoitsmostconcentratedbeam andshinethelightondarkpaperorawall.Explainthatthisissimilarto concentrated,directsunlightduringsummermonths.Thenadjusttheflashlight tothewidebeamanddescribeitasdispersed,orindirectsunlightduringwinter months. InformalAssessment AskstudentstoorallyexplainhowtheinteractionbetweenthesunandEarth affectsseasonshereonEarth,andwhathappenswiththesun'sraysduringthe differentseasons.Encouragethemtousevocabularytermsaxis,tilt,direct sunlight,andindirectsunlightintheirresponses. ExtendingtheLearning Explaintostudentsthateveryplanetinoursolarsystemhasseasons.Butthe seasonsthatoccuronotherplanetsareextremelydifferentfromthetraditional spring,summer,autumn,andwinterthatweexperienceonEarth.Remind studentsthatthetworeasonsseasonsoccurarethetiltofaplanet’saxisandits orbitaroundthesun.Ask:Aplanet’saxismighthaveasmallerorlargertiltthan Earth’s.Whichwouldcausemoreextremeseasons—asmallerorlargertilt? (larger)Aplanet’sorbitmightbeclosertoorfartherawayfromthesunthan Earth.Whichwouldcausemoreextremeseasons—beingcloserorfartheraway? 6of12 (closer)Havestudentsexplaintheiranswersusingevidencefromthehands-on activity.ThenhavethemreadalistfromNASAaboutthelengthofseasonson otherplanetsinoursolarsystem. O BJECTIVES Subjects&Disciplines InformalEducation AcademicEnrichment Mathematics Geometry Science Astronomy Physicalsciences Spacesciences LearningObjectives Studentswill: explaintherelationshipbetweenthesunandEarth describehowthetiltandpositionoftheEarthaffectstheseasons explaindifferencesindirectandindirectsunlight TeachingApproach Learning-for-use TeachingMethods Cooperativelearning Demonstrations 7of12 Discussions Hands-onlearning Inquiry Multimediainstruction SkillsSummary Thisactivitytargetsthefollowingskills: 21stCenturyStudentOutcomes LearningandInnovationSkills CommunicationandCollaboration CriticalThinkingSkills Analyzing Applying Understanding NationalStandards,Principles,and Practices N C T M P RI N C I P LE S A N D S TA N DA RDS F O R S C H O O L M AT H E M AT I C S •Geometry(3-5)Standard4: Usevisualization,spatialreasoning,andgeometricmodelingtosolveproblems N AT I O N A L S C I E N C E E DU C AT I O N S TA N DA RDS •(K-4)StandardB-2: Positionandmotionofobjects 8of12 •(K-4)StandardD-3: Changesinearthandsky I S T E S TA N DA RDS F O R S T U DE N T S (I S T E S TA N DA RDS *S ) •Standard2: CommunicationandCollaboration •Standard4: CriticalThinking,ProblemSolving,andDecisionMaking PREPARATIO N WhatYou’llNeed M AT E RI A LS YO U P RO V I DE Blackconstructionpaper Flashlights Globe Markers Polystyrenefoamballsorroundfruit Pushpins Rulers Scissors Toothpicks Transparenttape RE Q U I RE D T E C H N O LO G Y InternetAccess:Optional TechSetup:1computerperclassroom,Projector,Speakers Plug-Ins:Flash 9of12 P H Y S I C A L S PA C E Classroom Home SETUP Beforestartingthisactivity,cutalarge,blackcircleoutofblackconstruction paper. G RO U P I N G Large-groupinstruction Small-groupinstruction RE S O U RC E S P RO V I DE D: I M A G E S Seasons BACKGRO U ND & VO CABU L ARY BackgroundInformation Onecommonmisconceptionthatstudentshaveaboutseasonsisthatseasons areduetohowcloseorfartheEarthistothesun.Thechangingpositionofthe Earth’stiltisthereasonforthedifferencesintemperatureandlengthof daylightthatdistinguishtheseasons.WhentheNorthernHemisphereofthe Earthisleaningtowardthesun,itreceivesdirectsunlight.Thewarmthofdirect rayscausesspringandthensummerinthatpartoftheglobe.Whenthe NorthernHemisphereoftheEarthisleaningawayfromthesun,itreceives moreindirectsunlight.Thecoolingeffectsofmoreindirectsunlightcause autumnandwinter.BecauseoftheEarth’sapproximately23.5ºtilt,theseasons intheNorthernandSouthernHemispheresarereversed,aboutsixmonths 10of12 apartfromeachother. PriorKnowledge ["theEarthorbitsthesunandrotatesonitsownaxis"] RecommendedPriorActivities None Vocabulary Term Partof acuteangle noun angle autumnal equinox noun noun axis noun Equator noun hemisphere noun Northern Hemisphere NorthPole obtuse angle noun noun noun orbit noun season noun solar radiation Definition Speech noun anglemeasuringbetween0and90degrees. slantingspacebetweentwolinesthatultimatelymeetina point. autumnday,usuallyaroundSeptember22,whendayand nightareofgenerallyequallength. aninvisiblelinearoundwhichanobjectspins. imaginarylinearoundtheEarth,anotherplanet,orstar runningeast-west,0degreeslatitude. halfofasphere,orball-shapedobject. halfoftheEarthbetweentheNorthPoleandtheEquator. fixedpointthat,alongwiththeSouthPole,formstheaxison whichtheEarthspins. anglemeasuringmorethan90degrees,butlessthan180 degrees. pathofoneobjectaroundamoremassiveobject. periodoftheyeardistinguishedbyspecialclimatic conditions. lightandheatfromthesun. 11of12 Term Southern Hemisphere Partof noun SouthPole noun summer solstice vernal equinox winter solstice halfoftheEarthbetweentheSouthPoleandtheEquator. fixedpointthat,alongwiththeNorthPole,formstheaxison whichtheEarthspins. dayoftheyearwiththemosthoursofsunlight,June20or noun 21intheNorthernHemisphereandDecember21or22in theSouthernHemisphere. temperaturenoun tilt Definition Speech verb noun degreeofhotnessorcoldnessmeasuredbyathermometer withanumericalscale. toleanorslant. day,usuallyaroundMarch21,whendayandnightareof generallyequallength.Alsocalledthespringequinox. (December22intheNorthernHemisphere,June22inthe noun SouthernHemisphere)longestnightoftheyearandthe beginningofwinter. ForFurtherExploration Websites NASA:EducatorFeatures—PlanetarySeasons NationalGeographicScience:Space NASA:SolarSystemExploration—Kids NatGeoMovies:WildestWeatherintheSolarSystem FU NDER ©1996–2017NationalGeographicSociety.Allrightsreserved. 12of12