Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: rockhopper on 20/11/2011 13:30:02

Title: Has the Earth always spun on the same axis?
Post by: rockhopper on 20/11/2011 13:30:02

rockhopper asked the Naked Scientists:
   
Has the Earth always spun on the same axis?

What do you think?

Title: Has the Earth always spun on the same axis?
Post by: RD on 20/11/2011 15:25:48

Maybe different before Theia hit it ... http://en.wikipedia.org/wiki/Giant_impact_hypothesis

The axis (poles) do move a tiny bit ... http://en.wikipedia.org/wiki/Chandler_wobble

Title: Has the Earth always spun on the same axis?
Post by: Phractality on 20/11/2011 19:05:44

Earth's polar axis presently points at the star Polaris. That is about 23.5° away from the axis of Earth's orbit around the Sun (ecliptic axis). The angle between the two axes remains constant, but the north polar axis precesses  (http://www.decodingmythology.com/precession/precession1.html) in a circle around the ecliptic axis about every 26,000 years.

The point where the polar axis passes thru Earth's crust follows a circle about 12 meters across because Earth is not a perfect sphere. It is difficult to measure this because the North Pole is under an ocean, and the ice over the South Pole is flowing about 9.9 meters per year.

Will the Real South Pole Please Stand Up? (http://astro.uchicago.edu/cara/outreach/resources/other/poles.html)

There is a theory  (http://www.google.com/url?sa=t&rct=j&q=velikovsky%20shifting%20crust&source=web&cd=1&ved=0CBsQFjAA&url=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FPole_shift_hypothesis&ei=QU_JTvisE8qciAKY3c3ZDw&usg=AFQjCNHS1ArxgTamkMmtmDFxXUqpa2IWTQ) that Earth's thin crust sometimes shifts drastically relative to the core, as much as 60° in a few thousand years. The crust is to the core as the skin is to an apple. But that theory is considered absurd by the majority of scientists.