19-10-27
1
NoviceAstronomyClassesPeterboroughAstronomicalAssociation
TheSun,Earth&MoonSystemTheSun,Earth&Mooncompriseourimmediatepartoftheuniverse. Theirrelativemotionsgiveusday&night,theseasons,thephasesofthemoon,eclipses&tides. Itisawonderfuldance,choreographedbyMotherNatureandNewtonianphysics.
TheSun,Earth&MoonSystem
RelativeSizesoftheSun,Earth&Moon
Relativesizesanddistancesapartaretoscale.
Earth Moon
Thesunis334,000timesmoremassivethanearth.
Theearth&sunare150millionkilometersapart. 150millionkilometers=1AstronomicalUnit(AU)
Thesun’slighttakes8½minutestoreachearth.
Alargepumpkin&asmallpeaseparatedbythelengthofafootballfield.
Thispictureistoscale.
Earth’sRotation&itsOrbitoftheSun
Day&Night.SunRisesinEast, SetsinWest.
Circularorbit in365days.
Earth’stiltis23.4° toorbitalplane.
19-10-27
2
HowObliquitycausestheSeasonsEarth’stilt(obliquity)is23.4°
Obliquitycausestheseasons
Angleofincidenceismaincauseofsummerwarmth&wintercold(2.5Xhigherinsummer)
Lengthofdayissecondarycause
Closenesstosundoesnotchangesignificantly
Stability:Overtime,theobliquityhaschanged:22.0°to24.5°
AnnualDaylightVariations
AtSummerSolstice AtWinterSolstice
AttheSpring&FallEquinoxes InPeterborough(10hrsvs16hrs)
�Shadowsmovefromrighttoleft�
OrbitoftheMoonaroundtheEarth
Lunarmonth=28days Distancevariesfrom362,000kmto405,000km
TheMoonorbitstheEarth&rotatesonitsownaxisonceeverylunarmonth
PhasesoftheMoon
CCWinfigure.
DarksidevsFarside
OnceinaBlueMoon
Hourlatereachday
TracktheMoon’smonthlycycleat http://sciencenetlinks.com/tools/lunar-cycle-1-calendar/
19-10-27
3
TidesandotherFunkyStuff
BayofFundy: 16metertides 160Btonnesofseawater
LongerDays: 2ms/100yrs In1Myrsnoleapyear 6hourdays
MoonRetreating: 1.5”/year 4.5Byearsago>15Xcloser
Nottoscale!
ProfileofaLunarEclipseEarthbetweenSun&Moon
MooninEarth’s‘shadow’
Threeforms: Total,PenumbralorPartial
VisibleoverwideareaofEarth&lasts~5hours
OccursonlyduringafullMoon.
TheMooninTotalEclipse
TotalLunareclipseinPeterborough,January20/21,2019 PhotobyPAAmemberRickStankiewicz
Asthelunareclipseprogressescolourschangefromdeepbrowns&darkgraystoshadesofbrilliantredandbrightorange
ThenexttotallunareclipsevisibleinPtbowillbeMay15,2022
Eyeprotectionnotrequiredtoviewalunareclipse
ProfileofaSolarEclipse
MoonbetweenSun&Earth.OccursonlyatNewMoonphase
Moon’sshadowonEarthisverysmall,diameter<200km
Totaleclipselastsshorttime,<10minutes
19-10-27
4
TotalEclipse
PartialEclipse
AnnularEclipse
TheDifferentFormsofSolarEclipse
TotaleclipseshowsSun’scorona.
Annulareclipseshowsaringoffire.
PartialeclipseshowsonlyapartoftheSun’sglobeblockedbytheMoon.
Eyeprotectionisrequiredtoviewasolareclipse.
ImagesofTotalSolarEclipses
PhenomenaofaTotalSolarEclipse
TotalSolarEclipsewithSpectacularCorona
Itisworththetriptoseeatleastoneoftheseinyourlifetime!
Duringtheeclipse,birdsdon’tchirpandbeesstopflying.
TheNextNorthAmericanTotalEclipseoftheSunis…
…inOurBackyard!
April8,2024�…NiagaraFalls,PrinceEdwardCounty,Kingston,Cornwall…
