December 29, 2004

Wobbling Weebles


{...}Richard Gross, a geophysicist with NASA (news - web sites)'s Jet Propulsion Laboratory in California, theorized that a shift of mass toward the Earth's center during the quake on Sunday caused the planet to spin 3 microseconds, or one millionth of a second, faster and to tilt about an inch (2.5 cm) on its axis.

When one huge tectonic plate beneath the Indian Ocean was forced below the edge of another "it had the effect of making the Earth more compact and spinning faster," Gross said.

Gross said changes predicted by his model probably are too minuscule to be detected by a global positioning satellite network that routinely measures changes in Earth's spin, but said the data may reveal a slight wobble.

The Earth's poles travel a circular path that normally varies by about 33 feet, so an added wobble of an inch (2.5 cm) is unlikely to cause long-term effects, he said.


Posted by Kathy at December 29, 2004 10:06 AM

Many years ago, I worked on the ground based software for the space shuttle program. The trajectory calculations involved taking into consideration precession and nutation. Precession means that the north pole moves in a little circle, and nutation means that while it's moving in a bigger circle, it's also moving in a smaller circle. Most people think of the north pole as relatively fixed, but the reality is more complex.

Posted by: Douglas at December 30, 2004 02:46 AM

Wow. Smart people are reading my blog ;)

I would have thought the north pole was static, too, but since it is just a big hunk of ice, I suppose it would be susceptible to movement.

Interesting stuff. Thanks for chiming in.

Posted by: Kathy at December 30, 2004 01:25 PM

Ok, the husband just explained what you meant to me. Meaning my previous statement about the pole being a big chunk of ice is completely wrong.

But it's still interesting.

Posted by: Kathy at December 30, 2004 01:29 PM
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