Anastronomicalpotpourri

Szydagis02.07.2018

1/11

¡  Nearlyallgravitationalorbitsareoneofafewpossiblecross-sectionsoftwoofwhatshape?§  A.Cylinder§  B.Football§  C.Egg§  D.Cone

¡ Whendoesthefirstdayofspringseasonoccur?§  A.March20always(Gregoriancalendar)§  B.Dependswhichhemisphereyouarein§  C.Itisnotadayitisatime,andchanges

2/11

Onthesecondquestionbelow:DisbothB.&C.

¡  Trueofanyforcedecreasingwithinversesquareofdistance¡  Therearetwomorenotpicturedhere:radialorbit(straight-line

inorout)andade-stabilizingspiral(general-relativisticeffect)3/11

Prof.AmandaW.Peet,UniversityofToronto

Parabolaistippingpointbetweenellipseandhyperbola.Meansyouloseyourkineticenergy(comingtorestatinfinity)

Hyperbolicorbitmeanscomeandgo,butstillgoingatinfinitedistance

Circularorbitisnotstable(tooperfect)

Anellipseisamathematical-lypreciseobject.Itisnotjustan“oval.”

Parabolaisthatshapeyoulearnedaboutinalgebraclass(quadraticpolynomial:x2ishighestpowerinit)&projectiletrajectories

¡  Contrarytopopularbelief,theEarth’sorbitisNOTahighlyexaggeratedellipse§  It’squitecircular

¡  Ourseasonsarenotcausedbyorbitalshape/proximitytoSun§  CausedbytiltofEarth’saxis

§  Planet-wide!4/11

TheseseasonlabelsreferonlytotheNorthernHemisphere

SouthernHemispherehasOPPOSITEseasons.Isclosesttosuninsummer

Exactdatesvary-March19-22-June20-22-Sept.21-24-Dec.20-23

Itisaprecisemomentintime.Forexample,thisyearspringwillbegin6:29aEDT3/20(common)

Firstdaysofseasonscalled:vernalequinox,summersolstice,autumnalequinox&wintersolstice.Differentdatesinplaces.

¡  TheEarth‘wobbles,’likeatop,asitrotatesaboutitsownaxis,andrevolvesaroundSun§  1cycletakes~26,000yearstocomplete

§  CausedbytidalforceofSunonequatorialbulge

¡  ThubannotPolariswasthePoleStarduringtimeoftheGreatPyramid§  NextVegain12millennia. 5/11

http://earthobservatory.nasa.gov

http://www.intoxicatedonlife.com

6/11

http://ap.io/mpip/03/

Stigmatellaaurantiaca

Tidallocking

¡  https://www.youtube.com/watch?v=ouRbkBAOGEw(PresidentJohnF.KennedyspeechabouttheMoon:WeChoosetoGo…)

7/11

Notetoself,iflowontime:skiptothebestpart,~8minutesin

¡ Moonismuchsmallerthansun,butmuchcloser,sothatcompensates,makingtotalsolareclipsespossible§  PartialeclipsesoccurwhenMoonjustclipstheSun

§  Annulareclipsesoccurwhensizesnotquitematchedup

¡  Usuallyverybrief.Invisiblesolarfeaturesmayappear§  Solarflaresandprominences

8/11

Picture:JayPasachoff/ScienceFaction/Corbis

Eclipseisatypeofsyzygy,moregeneraltermforstraight-linealignmentofcelestialobjects.Transitissmallerobjectinfrontoflarger;occultationotherway

¡ Mercury:0¡  Venus:0¡  Earth:1¡ Mars:2¡  Jupiter:67(16)¡  Saturn:62(18)¡  Uranus:27(15)¡  Neptune:14(8)¡  [Pluto:5(1)]

9/11

Inparenthesesarenumbersknowninmyoldbookfrom1992.Ourdatahaveimproved.

solarsystem.nasa.gov

Wehavetoaddword“natural”nowbecauseofthemanyartificialoneswe’veputinorbitoftheEarth!http://nssdc.gsfc.nasa.gov/planetary/factsheet/

¡  Planetsareorbitingatdifferentspeedsattheiruniqueradii§  Theyareveryrarely(thousandsofyears)inanicelinelikeintextbookillustration

§  CanattimesbeonoppositesidesofSun(badformissions)

¡  Canaligninourskyand/orfromspace

10/11

Friday,May5th,2000(nottoscaleofcourse)

http://www.goagil.com/seattle.html

Crazypeoplethoughtthiswouldendtheworld

¡  Quiz#7¡  Purposeofhaving1perclassistoenhancelearning,preventcram¡  Clearwhoarenotdoingthereading:bi-modaldistribution

11/11