Astro 5 Lectures .docx

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Department
Astronomy
Course
ASTR 5
Professor
Karlan
Semester
Spring

Description
LifeIntheUniverse05202014hallmarksofthescientificapproachtointerpretingnaturerepeatabilityorverifiabilityselfconsistencylogicalbasedondeductiveorinductivereasoningbasedonevidenceanecdotalevidenceoflittlevalueincorporatesuncertaintyanderrorinexactitudeinmeasurementswehavenoreasontobelievethatanyofthestepsintheevolutionofthecosmosthesolarsystemtheearthandlifeontheearththroughitsmodernmanifestationsisimprobableandevenifsomeofthestepsareimprobablenaturecanwieldastronomicalnumberstocounteractsuchnaturalreluctanceastrobiologyorexobiologythescienceoflifebeyondtheearthasciencewithlittledatabutmanyinvestigatorseveniftheneareststarweretohaveaplanetwithateemingbiospherewewouldntyetbeabletoknowiteachstarinastarclusterorinagalaeachstarinastarclusterorinagalaxycanpotentiallyhaveitsownplanetarysystemjustasourownstarthesundoesdistancescalesusinglightasareferenceearthmoon1lightsecondearthsun8lightyearsplanetsofthesolarsystem8lighthoursdistancetoneareststar13lightyearstypicalsizeofstarcluster10lightyearsdistancetocenterofmilkyway25000lightyearsdistancetoAndromedagalaxy2500000lightyearsdistancetomostdistantgalaxyknown20000000000lightyearstimescalesageoftheuniverse137billionyearsageoftheearth455billionyearsfirstappearanceoflife354billionyearsagoCambrianexplosion545520millionyearsago17Galacticyear200millionyears125Thelastdinosaur65millionyearsago170Emergenceanddevelopmentofthehominidline16millionyearsago14000Lastmajoriceage12000yearsago1380000Recordedhistory4500years11000000EvolutionoftheUniversefromtheBigBangtotheEarth05202014EdwinHubble1930theexpansionoftheuniversethatremarkablediscoveryhadafewimmediateimplications1AnythingthatexpandscoolssotheuniversewasonceveryhotHowhotIthasbeencookingeversinceOriginallysohotthatmattercouldonlybeionizedgasCurrently3Kionanatominwhichoneormoreelectronshavebeenstrippedoffcausingittohaveapositivechargesoionizedagasofchargedparticleselectronsandionsextheinteriorofthesunplasma2Theuniverseusedtobemuchdenserandisnowrelativelyrarified3Everythinginourpresentlyvisibleuniversewasinitiallyinthesameplaceatthesametimeinatinyvolume4TherewasaspecialtimewhentheexpansionstartedthemomentofthebigbangwhentheuniversebegantheelementsthatweandtheeartharemadeoutofcarbonsiliconetcwerenotthereTheywerecreatedlaterinstarsbutstarswerenotbeginningtoformfor100000000yearsorsoThebigbangonlycreatedhydrogenandheliumsowestartwithanexpandinghotgasAfewthingshadtohappen1Theuniversehadtochillabit2GravityhadtohavetimetooperatetheuniversewasfillednotonlywithionizedgasattheoutsetbutalsowithelectromagneticradiationtheradiationisstilltherefillingouruniversebutlikeeverythingelseithascooledandisnowpresentintheformofmicrowavesthecosmicmicrowavebackgroundthecoolingoftheuniverseallowedfortheformationofatomsoutofionsandelectronswhentheuniversebecameneutralitbecametransparenttoelectromagneticradiationThisradiationscattersoffofchargedparticlesionsandelectronsbutitessentiallydoesnotseeinteractwithneutralatomssolightdropsoutofthepictureattherecombinationepochthisisimportantbecauselighthadpreviouslyexertedaradiationpressureonthematterthatpreventedgravityfrommakinganythinghappensowhenlightdropsoutgravitykicksin
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