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V ari a tions in E arth ’ s Orbit

V ari a tions in E arth ’ s Orbit. Our s olar s y st em f ormed when a su p ern o v a se n t ene r gy th r ough a la r g e neb u la of g as, du s t, and ice, c aus i ng the m a t erial t o spin and c ollect i n t o the Sun a nd the plan e t s .

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V ari a tions in E arth ’ s Orbit

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  1. Variations inEarth’s Orbit

  2. Our solar system formed whena supernovasent energythrougha largenebulaof gas,dust,andice, causing the materialto spin andcollectinto theSunandthe planets.

  3. Thenine planets arelocated invery predictablepatternsas they orbitthe Sun. Dueto conflicting gravitybetween Jupiter andthe Sun,there isalso anasteroidbelt betweenMars and Jupiter

  4. JohannesKepler’s ThreeLaws of Planetary Motion The orbitofeveryplanet is anellipsewiththe sunatone focus. Aline joininga planet andthe sunsweeps outequalareasduringequalintervalsoftime. The square of the time taken for aplanettocompleteone orbitis proportionalto thecubeofits mean distancefrom the Sun.

  5. 1. Theorbitofeveryplanetis an ellipsewiththesunat one focus.

  6. 2. A linejoining aplanetandthesunsweepsoutequalareasduringequalintervalsoftime. Theplanets travelfasterwhenclosertotheSun(perihelion)andslowestwhenfurthestfromthe Sun(aphelion)

  7. 3. Thesquareofthetimetaken for aplanetto completeoneorbitis proportionaltothecube ofits meandistance fromtheSun. Theclosertheplanetis totheSun,theshortertimeittakestoorbit theSun

  8. Thepathonwhich theplanets, includingEarth, orbittheSunis calledthe PlaneoftheEcliptic.

  9. BoththeMoonandthe Sunexerta gravitational "tug" onthe Earth'sequatorialbulge,trying topull theEarth's equatorialregionintoalignmentwith theEclipticplane.

  10. This tug,alongwith the rotational motionofthe Earth onits axis, the revolutionofthe Eartharoundthe Sun, andthe revolutionofthe Moonabout the Earth, causethe Earth towobbleaboutitsaxisofrotation, similar tothe motionofa spinningtop.This motionis calledPrecession.

  11. During precession, the angle of Earth’stiltdoesnotchange. What arechanges isourviewofthe stars. Currently,Polarislies directlyover the north pole, butin about 12,000years,Vega will beoverthe northpole.

  12. Thetime it takes for Earth to completeone precession periodis 26,000years. During aprecession period,the vernalequinox travels through each ofthe zodiac constellations. Thisis theDawningoftheAgeofAquarius

  13. Just as Earth’s equatorial plane is inclinedatan angle,the moon’s“equatorial” planeisalso tiltedorinclinedona5degreeangle in respect to itsorbit aroundEarth.

  14. TheMoondoesnot orbitthecenterofthe Earth,rather,theybothrevolvearoundthe centeroftheirmassescalled thebarycenter. Noticethat howthe Earthis also movingslightly http://www.youtube.com/watch?v=uGBANgbRkws

  15. Thesunactsontheearth andits moonasone entitywithits centeratthebarycenter.Sincethe earthrevolvesaroundthebarycenter,whichin turnorbitsthesun,theearthfollows a wobblypatharoundthesun. Dueto thiswobbly path, thedistances betweenthe Sunand Moon,inrelationto Earthvary resulting in a variationintheir forcesontheEarth.

  16. Whentheforce from theMoononthe Earthis at it greatest,the Moon tries toalignEarth’s equatorial plane withitsownequatorialplane, causinga slight changeinthetiltofEarth’saxis ofabout½ degree eachway onan18.6yearcycle.

  17. This periodic change inEarth’stiltiscallednutation andleads toperiodicharsherseasons.

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