[Centurion2000]

The other is more or less catastrophic and involves either earth’s crust or the whole planet tipping over. That might have happened as recently as 12,000 years ago and be a regular event.

Considering the angular momentum generated by a spinning PLANET I think I'm going to have to call BS on that one.

Or is there any evidence that this has ever happened in history? I know that the earth precesses on it's rotation axis every 14,000 years which shoots the pole star from Polaris to Vega, but an actual turnover of the Earth??

[RightWhale]

is there any evidence that this has ever happened in history?

Not in history. When this happens history ends. Maybe later history starts up again, but the old history would be wiped, as if a Great Flood had happened. Evidence abounds. The precession is more like 26,000 years, also known as the Great Year, which would not be affected.

[SunkenCiv]

“the earth precesses on it’s rotation axis every 14,000 years”

[snip] Like a wobbling top, the orientation of the Earth’s axis is slowly but continuously changing, tracing out a conical shape in a cycle of approximately 25,765 years [end]

http://en.wikipedia.org/wiki/Precession_(astronomy)

[happygrl]

See the book cited in my post #125.

[21twelve]

The MAGNETIC poles flip periodically and often (geologically speaking). Do a google on “magnetic bands seafloor spreading” and it will probably come up with info. I think it was in WWII in developing submarine detection that they noticed fairly regular bands in the ocean floor. The basalt comes up in the middle ridge, pushes the other rock to the side, and cools. When the iron-rich magma cools the iron aligns itself to the pole. When the poles reverse themselves, the magma iron points in the opposite direction, giving a magnetic anomaly. This has happened thousands of times just remember what the band maps look like. This also contributed to the theory of plate tectonics.

It has happened so often without catastrophic die-outs or whatever, so I think it is fairly benign. And I think it does happen fairly quick (geologically speaking). But now the concern is what will happen to electronics, satellites, etc. Does the magnetic force weaken for a short time when it flips - thus allowing the sun's ionic wind to enter in to our realm?