Earth's oval orbit

[beilzabob]

What causes earth's orbit to change over time from a round orbit to an oval orbit;wich in my mind would cause ice ages?When it goes into a round orbit does it speed up then slingshot into an oval orbit slowing down to repeat the process?

 

[harmonicaman]

Are you referring to the Milankovitch Cycles? He's a web page which discusses their possible effects on the Earth's environment and ice ages. <br /><br />http://aa.usno.navy.mil/faq/docs/seasons_orbit.html

 

[mlorrey]

Earth does not "go into a round orbit". Its orbit is very circular, but is still an ellipse like every other orbiting body, as Kepler's law dictates.<br /><br />The precession of the orientation of earths orbit has several components: <br />a) lunar tide: the tidal influence of the moon on earth causes the majority of the precession, as it essentially is draining Earths angular velocity slowly over time. This process causes the mantle to rotate slightly slower than earths core. This differential is the dynamo that generates earth's van allen belts and electromagnetic fields.<br />b) Solar tide: the gravitational tidal influence of the sun is a small fraction of the moons influence, but is real and measurable<br />c) Solar frame dragging: as gravity is a relativistic phenomenon, the spinning of the sun causes space-time distortion known as frame dragging. This is most pronounced in the perturbation of the orbit of Mercury, which precesses rather rapidly over a few decades. Each planet further out experiences frame dragging influence to a decreasing degree with distance.<br />d) Jupiters tidal influence.