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Introduction This Instructor’s Guide provides information to help you get the most out of Planets, Stars, and Gal-axies, part of the five-part series Physics in Action. The contents of the guide will allow you to prepare your students before using the program and to present follow-up activities to reinforce the program’s key learning points.
Can the study of physics be fun? This clever five-part series answers “Yes!” by presenting essential facts, formulas, and laws of physics through real-world examples, illustrative animations, and a like-able field guide named Mr. Physics who makes complicated concepts easier to understand. End-of-section reviews are included throughout each program, and equations are worked out, step by step, on-screen.
The series includes the following titles: •Energy •ForcesandMotion •Planets,Stars,andGalaxies •ProcessesThatShapetheEarth •TheNatureofMatter
Learning Objectives After viewing the program, students will be able to: • Understandearlytheoriesofcosmology• Understandvelocity,gravity,andacceleration,andhowtheyrelatetoeachother• UnderstandthebasicsofKepler’sLaws,andNewton’sLawofUniversalGravitation• Understandparallax,apparentandintrinsicbrightness,andthelifecycleofstars• UnderstandthebasicsofEinstein’stheoriesofSpecialandGeneralRelativity• UnderstandtheCosmologicalPrinciple,Hubble’sLaw,andtheBigBang
Instructor’s Guide
Physics in Actions PLANETS, STARS, AND GALAXIES Instructor’s Guide
Educational StandardsBENCHMARKS FOR SCIENCE LITERACY STANDARDSThis program correlates with the following standards from BenchmarksforScienceLiteracy, by the AmericanAssociationfortheAdvancementofScience,forgrades9through12. The Nature of Science: TheScientificWorldview• Fromtimetotime,majorshiftsoccurinthescientificviewofhowthingswork.Moreoften,
however, the changes that take place in the body of scientific knowledge are small modifications of prior knowledge. Continuity and change are persistent features of science.
The Nature of Science: ScientificInquiry• Intheshortrun,newideasthatdonotmeshwellwithmainstreamideasinscienceoften
bythescientificestablishment;sometimesspringfromunexpectedfindings;andusuallygrowslowly, through contributions from many investigators.
The Physical Setting: TheUniverse• Thestarsdifferfromeachotherinsize,temperature,andage,buttheyappeartobemadeupof
the same elements found on earth and behave according to the same physical principles. • Onthebasisofscientificevidence,theuniverseisestimatedtobeovertenbillionyearsold.The
current theory is that its entire contents expanded explosively from a hot, dense, chaotic mass. • Starscondensedbygravityoutofcloudsofmoleculesofthelightestelementsuntilnuclear
fusionofthelightelementsintoheavieronesbegantooccur.Fusionreleasedgreatamountsofenergy over millions of years.
• Eventually,somestarsexploded,producingcloudscontainingheavyelementsfromwhichotherstars and planets orbiting them could later condense. The process of star formation and destruc-tion continues.
• Mathematicalmodelsandcomputersimulationsareusedinstudyingevidencefrommanysources in order to form a scientific account of the universe.
The Physical Setting: Motion• Thechangeinmotion(directionorspeed)ofanobjectisproportionaltotheappliedforceand
inversely proportional to the mass. • Allmotionisrelativetowhateverframeofreferenceischosen,forthereisnomotionlessframe
• Wavescansuperimposeononeanother,bendaroundcorners,reflectoffsurfaces,beabsorbedby materials they enter, and change direction when entering a new material. All these effects vary with wavelength.
The Physical Setting: ForcesofNature• Gravitationalforceisanattractionbetweenmasses.Thestrengthoftheforceisproportionalto
the masses and weakens rapidly with increasing distance between them.
ematical model of the universe based on continuous motion in perfect circles, and in circles on circles.Withthemodel,hewasabletopredictthemotionsofthesun,moon,andstars,andevenof the irregular “wandering stars” now called planets.
• Inthe1500s,aPolishastronomernamedCopernicussuggestedthatallthosesamemotionscould be explained by imagining that the earth was turning around once a day and orbiting aroundthesunonceayear.Thisexplanationwasrejectedbynearlyeveryonebecauseitviolatedcommonsenseandrequiredtheuniversetobeunbelievablylarge.Worse,itflewinthefaceofthe belief, universally held at the time, that the earth was at the center of the universe.
• Usingthenewlyinventedtelescopetostudythesky,Galileomademanydiscoveriesthat supportedtheideasofCopernicus.ItwasGalileowhofoundthemoonsofJupiter,sunspots,craters and mountains on the moon, and many more stars than were visible to the unaided eye.
• TheworkofCopernicus,Galileo,Brahe,andKeplereventuallychangedpeople’sperceptionoftheir place in the universe.
unified view of force and motion in which motion everywhere in the universe can be explained by thesamefewrules.Newton’ssystemwasbasedontheconceptsofmass,force,andacceleration;histhreelawsofmotionrelatingthem;andaphysicallawstatingthattheforceofgravitybetweenanytwoobjectsintheuniversedependsonlyupontheirmassesandthedistancebetweenthem.
ity, which brought about revolutionary changes in human understanding of nature. Among the counterintuitive ideas of special relativity is that the speed of light is the same for all observers no matter how they or the light source happen to be moving. In addition, nothing can travel faster than the speed of light.
• Undereverydaysituations,mostofthepredictionsofspecialrelativityarenearlyidenticaltothose of classical mechanics. The more counterintuitive predictions of special relativity occur in situations that humans do not typically experience.
ENGLISH LANGUAGE ARTS STANDARDS The activities in this instructor’s guide were created in compliance with the following standards from NationalStandardsfortheEnglishLanguageArts,fromtheNationalCouncilofTeachersofEnglish.• Studentsadjusttheiruseofspoken,written,andvisuallanguage(e.g.,conventions,style,vocabulary)
to communicate effectively with a variety of audiences and for different purposes. • Studentsemployawiderangeofstrategiesastheywriteandusedifferentwritingprocesselements
appropriately to communicate with different audiences for a variety of purposes. • Studentsconductresearchonissuesandinterestsbygeneratingideasandquestions,andbyposing
TECHNOLOGY STANDARDSThe activities in this instructor’s guide were created in compliance with the following standards fromTheISTENationalEducationTechnologyStandards(NETS•S)andPerformanceIndicatorsforStudents.• Creativity and Innovation:Studentsdemonstratecreativethinking,constructknowledge,and
develop innovative products and processes using technology. • ResearchandInformationFluency:Studentsapplydigitaltoolstogather,evaluate,anduse
Program Overview Beginningwiththehistoryofastronomy(Ptolemy,Copernicus,GiordanoBruno,Galileo),thisprogramconsidersthemathematicsofmotion(velocity,acceleration);gravity(Kepler’sdiscoveries,Newton’slaws,centerofgravity,astronomicalunits);thepropertiesofstars(parallax,flux,luminosity,color,Hertzsprung-Russelldiagram);relativity(Einstein’stheories,speedoflight,space-time);andthelarge-scalestructureoftheuniverse(BigBang,CosmologicalPrinciple,Hubble’slaw).Humankindhascomealongwayinourunderstandingofthecosmos—butwe’restillonlyscratchingthesurfaceof astrophysics, with discoveries of incalculable value still waiting to be made.
Main TopicsChapter 1: The Universe (and Welcome to It!)AfterareviewofthecosmologicaltheoriesofPtolemy,Copernicus,andGiordanoBruno,viewerslearn the importance of Galileo and the impact the telescope had on astronomy.
Chapter 2: The Mathematics of MotionThis section provides an overview of velocity, gravity, and acceleration. It demonstrates how under-standing the relationship of these three to each other has allowed us to put satellites into orbit and send spacecraft to the moon and beyond.
Physics in Actions PLANETS, STARS, AND GALAXIES Instructor’s Guide
Chapter 3: Newton, Kepler, and GravityKepler’sthreelawsdescribingtheorbitofplanets,whichleadtoNewton’sLawofUniversalGravita-tion,isthesubjectofthissection.Alsoincluded:astronomicalunits.
Chapter 4: Observing the Night SkyThis section explains how astronomers determine parallax, apparent and intrinsic brightness, and thetemperatureandenergyofastar.TheHertzsprung-Russelldiagramandthelifecycleofstarsisalso covered.
Chapter 5: RelativityEinstein’stheoriesofSpecialRelativityandGeneralRelativityarepresentedhere,withthehelpofMr. Physics, spaceships, and the Twin Paradox.
Chapter 6: The Large-scale Structure of the UniverseAfteranexplanationoftheCosmologicalPrincipleandHubble’sLaw,theprogramendswitha descriptionoftheBigBangandthecreationofthefirstprotons,neutrons,electrons,andatoms—andhowtheyeventuallyformedthelarge-scalestructuresoftheuniverse.
Fast Facts • AccordingtoancientHinduscriptures,theuniversewasbornfromasinglecosmicseed(which
• Intheearly17thcentury,GalileoGalileiperfectedthetelescope,andwasabletouseittoseemountainsonthemoon,theringsofSaturn,andeventhetinysatellitesclearlyorbitingJupiter.Hisobservationsledhimtoquestionthen-currentteachingsonthesolarsystem.Helivedtherest of his life under house arrest because of his challenge to the geocentric model of the universe.
• Thegravitationalpullfromalltheplanetsonthesungivesitatinywobbleasit,too,rotatesaround the solar system’s true center of gravity. This wobbly motion is what astronomers use to detect the presence of planets in distant solar systems.
• Starshaveslightlydifferentcolors.Thisisbecauselightemittedatacertaintemperaturealsohas acertaincolor.Starsintheredandorangeendofthelightspectrumarecooler,whilestarsontheblue end are hotter.
• AccordingtoEinstein’sTheoryofSpecialRelativity,speeditselfcandistortspaceandtime,asillustrated by the Twin Paradox. If one twin boards a spaceship, accelerates at nearly the speed of light,andtravelsfor20yearsaccordingtoaclockonhisship,whenhereturnstoearth20yearswillhavepassed,andhewillappear20yearsolder.But,forthetwinwhostayedbehind,46yearswill have passed!
• Whiletheotherplanetsinthesolarsystemrotatecounter-clockwise,Venusrotatesclockwise.Astronomers think this may be due to tidal effects on its thick atmosphere.
• Marsishometothelargest-knownvolcanointhesolarsystem.Atalmost17milestall,OlympusMons is about three times the height of Mount Everest.
Big Bang: A model of the initial conditions and subsequent development of the universe. The theorydeducestheexplosionofasmall(smallerthanadime!),hot,densemassabout13billionyearsago which eventually resulted in the scattering of elements that then formed the stars and planets. Theideawasfirstproposedin1927,andisbasedontheobservedexpansionoftheuniverse,cosmicbackground radiation, abundance of the elements, and the laws of physics.
Big Bang nucleosynthesis: Era in the early universe when elementary particles first combined to form atomic nuclei.
center of gravity:Theweightedaverageofthepositionsofallobjectsinagivengravitational system, for instance, the solar system.
Copernicus, Nicolaus: 1473-1543,Polishastronomerwhoproposedtheheliocentrictheorythatthe earth and the other planets move around the sun, and that the stars are fixed.
cosmological principle: The principle that states that the universe has no center, and that it appears the same in every direction from every point in space.
Hertzsprung-Russell diagram: A graph that shows the life cycle of a star. It has axes for temperature, color, and brightness.
Hubble’s Law: NamedafterEdwinHubble,anAmericanastronomerwhofirstdiscoveredthattheuniverse was expanding, it is a formula that helps us measure the rate of expansion of the universe. Hubble’sLawstatesthattherecessionalvelocityofagalaxyisproportionaltoitsdistancefromus.
intrinsic brightness: Also called luminosity, it is the amount of light a star emits at a given time.
Physics in Actions PLANETS, STARS, AND GALAXIES Instructor’s Guide
Kepler, Johannes:1571–1630,Germanastronomer,astrologer,andmathematician.Consideredthe founder of modern astronomy, he formulated three laws to describe how the planets revolve around the sun.
Law of Universal Gravitation: A law of physics that describes the gravitational attraction between bodies with mass.
main sequence: AnarrowbandintheHertzsprung-Russelldiagraminwhich90percentofallobserved stars are plotted.
orbit: The curved path, usually elliptical, of a planet, satellite, etc., around a celestial body, for instance the sun.
parallax: An angle used for measuring the distance of a star from Earth.
period: In astronomy, one full orbit. A period of rotation is the time in which a body rotates once on its axis. A period of revolution is the time in which a planet or satellite revolves once about its primary.
red giant: Astarofgreatsizeandbrightness,withareddishhue,thathasarelativelylowsurfacetemperature.AredgiantwouldbefoundintheupperrightoftheHertzsprung-Russelldiagram.
Theory of General Relativity: Einstein’s theory stating that gravity is a kind of curvature of space andtime,orspace-time.Wherevermatterexists,itbendsspace-timearoundit,creatingtheinflu-ence of gravity. General relativity explains that space and time are bound together.
Theory of Special Relativity: Einstein’stheorystatingthat(a)allobserversarethesameinrespecttoalllawsofphysics(inotherwords,thereisnosuchthingasaspecialperspective;ifyouareina closed box moving at constant velocity, no experiment you do inside the box can tell you how fasttheboxismoving);and(b)thespeedoflightisalwaysthesameinavacuum(forinstance,thespeed of light will remain the same for an observer inside the closed box, even if the box itself is movingatalargefractionofthespeedoflight).Specialrelativityexplainsthenatureoftheuniverseat high speeds.
white dwarf:Astar,approximatelythesizeoftheearth,thathasundergonegravitationalcollapseand is in the final stage of evolution for low-mass stars, beginning hot and white and ending cold anddark.AwhitedwarfwouldbefoundinthelowerleftoftheHertzsprung-Russelldiagram.
Physics in Actions PLANETS, STARS, AND GALAXIES Instructor’s Guide
Student ProjectsPresentanexplanationoftheBigBang,includingevidence,unresolvedissues,andimplications•for the future. Your presentation can be in the form of a written report, chart, series of labeled drawings,orevenavideoorsong.(Youmayalsowanttoincludedescriptionsandcomparisonsofothercosmologicalmodelsandoriginmyths.)
Researchandreportongalaxies.Includeinformationontheclassificationofgalaxies,howthey•form, what they are composed of, how many galaxies astronomers estimate exist, how large they are,andhowfarapartfromeachother.Howdoastronomersobtainthisinformationongalax-ies?Includevisuals,orlinkstoWebsitesthatcontainimagesofdifferentgalaxies.
Explore space at www.nasa.gov. Create a report on the history of the space program, including •thelatestNASAmissions.Or,reportonthevarietyofcareeropportunities,internships,andcooperativeprogramsavailableatNASA.DidyouknowthatNASAneedshistorians,writers,educators, and lawyers, along with mathematicians, technicians, and astronauts?
Physics in Actions PLANETS, STARS, AND GALAXIES Instructor’s Guide
UsingthelibraryandInternet,learnmoreaboutsomeofthetopicstouchedonin• Planets, Stars, and Galaxies.Presentyourfindingsintheformofanewsstoryormagazinearticle,andincludeillustrations.Possibletopics:spacetourism;sunspots;lightpollution;theHerschelSpaceObser-vatory;thephysicsoftimetravel;blackholes.
Shouldwecontinuetoexplorespace?Or,doesthespaceprogramdivertfundsfromurgentprob-•lemsstilltobesolvedonEarth?Whathasthespaceprogramachieved,andwhatareitspossiblefuturebenefits?Workwithotherstudentstoconductadebateonthis.Participantsshouldbackuptheir positions with statistics and information from a variety of reputable sources.
Physics in Actions PLANETS, STARS, AND GALAXIES Instructor’s Guide
2._____statedthatplanets—includingtheEarth—movearoundthesun,challengingthegeocentricmodelofthesolarsystem.BecausetheBiblestatesthattheEarthdoesnotmove,hewasplaced under house arrest for heresy. a)GiordanoBruno b)NicolausCopernicus c)JohannesKepler d)Galileo
11.Theuniversebeganasdenseenergy,whichthenexpandedandcooled,eventuallycreating protons, neutrons, and electrons. Then atomic nuclei were formed, and later, hydrogen atoms, at which point gravity drew larger and larger masses together, forming the universe as we know ittoday.Thisisknownas_____.
2._____statedthatplanets—includingtheEarth—movearoundthesun,challengingthegeocentricmodelofthesolarsystem.BecausetheBiblestatesthattheEarthdoesnotmove,hewasplaced under house arrest for heresy. a)GiordanoBruno b)NicolausCopernicus c)JohannesKepler d)GalileoA: (d) Galileo
11.Theuniversebeganasdenseenergy,whichthenexpandedandcooled,eventuallycreating protons, neutrons, and electrons. Then atomic nuclei were formed, and later, hydrogen atoms, at which point gravity drew larger and larger masses together, forming the universe as we know ittoday.Thisisknownas_____.