How many times has planet earths axels been tilted and when could it happen again?

Question

How many times has planet earths axels been tilted and when could it happen again?

Answer 1

Three or four, opinions vary. It could happen again on April 14, 2029. Or not. Nobody knows, really.

Cheers

Answer 2

The Earth's axis is constantly shifting, since as our planet slows down it creates a wobble - which is what causes the axis to migrate.  Our axis, while it currently points to the star Polaris, once pointed towards the star Vega, and is currently moving back in that direction (and will be there in about 11-13 thousand years).

Two good links:  

http://www.earthsky.org/radioshows/48335...

http://www.earthsky.org/radioshows/48335...

Since the tilt changes on average every 26-28 thousand years, and the Earth is approximately 4.5 billion years, then the axis has changed over 16,000 times (4.5 billion divided by 28 thousand).

Imagine the Earth as a top (that spin toy you play with as a kid).  You spin it, and as it slows down you can see how the stick part at the top that you used to spin wobbles.  That's analogous to what's happening to the Earth and its axis.

Here's a video of a spinning top to help you visualize what's happening to our axis:

http://video.google.com/videoplay?docid=...