Thread: What the heck caused the wobble of the Earth every 20 thousand years ?

I'm open for suggestions,as this is puzzling to me.Earthquake or massive meteor colliding with the planet. What actually could cause such a huge wobble,that causes the Sahara Desert to come to life and create the lakes larger than the Great Lakes ??? Had to be something big...

It's a gravitational effect, mostly "caused by the gravitational forces of the Moon and Sun on Earth's equatorial bulge" (from wikipedia). I'm pretty sure it has nothing to do, at least directly, w/ the Sahara or the Great Lakes.

Axial precession (astronomy) - Wikipedia, the free encyclopedia

Originally Posted by Lew South

It's a gravitational effect, mostly "caused by the gravitational forces of the Moon and Sun on Earth's equatorial bulge" (from wikipedia). I'm pretty sure it has nothing to do, at least directly, w/ the Sahara or the Great Lakes.

Axial precession (astronomy) - Wikipedia, the free encyclopedia

It's already been researched and archeologists uncovered the whole thing,to start with. There is now, a program on the Discovery Channel that brings all of this to light. Check it out;the show is very interesting and does'nt go into detail about why the wobble only takes place every twenty thousand years. According to what has been found out,it does cause flooding of the Sahara. There are huge aquafers under the desert and somehow the wobble causes them to swell outward.At least that's what I gathered from that particular episode on the Discovery Channel. It's all very interesting ...

It is rotating too slowly for its mass. The rotation of the earth is slowing, as it slows it begins to precess like a top spinning on the table. the slower it rotates the greater and faster the precession.

Originally Posted by Wayne Bruinekool

It is rotating too slowly for its mass. The rotation of the earth is slowing, as it slows it begins to precess like a top spinning on the table. the slower it rotates the greater and faster the precession.

Ya know, I kind of thought that might be the case. At first,when I pondered it,I was'nt thinking in geological ,global time,meaning of course,that we're just a blink in geologic time(if that,even). Considering Earth's age,it makes perfect sense to me,now. I appreciate your input and posting. At least, I know someone else out there,thinks about things, that most never contemplate. Good to know ...

Originally Posted by Wayne Bruinekool

It is rotating too slowly for its mass. The rotation of the earth is slowing, as it slows it begins to precess like a top spinning on the table. the slower it rotates the greater and faster the precession.

That's an interesting way to think about it, but it's not really applicable--the earth is not in a gravity field where it will fall down if it stops spinning.

Lew South's link probably had a good explanation. And the precession is linked to the Milankovitch cycles, so there could be weather/climate changes associated with it.

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Originally Posted by grapes

That's an interesting way to think about it, but it's not really applicable--the earth is not in a gravity field where it will fall down if it stops spinning.

As examples go it is quite applicable. Examples are, by their very nature not perfect. In this case the earth is in a gravitational field where it may not fall over, but the precession will increase as its spin slows. Like the top, the precession is the result of gravitational effects. The effects in the case of the earth are considrably more complex but the overall result is quite similar to the top.

Originally Posted by grapes

And the precession is linked to the Milankovitch cycles, so there could be weather/climate changes associated with it.

The Milankovitch cycles describe climate changes that are dependent on the precession so it is more accurate to say that the Milankovitch cycles are linked to the precession. The precession is linked to the gravitaional influences of other heavenly bodies and the climate depends heavily upon the precession.

Originally Posted by Wayne Bruinekool

As examples go it is quite applicable. Examples are, by their very nature not perfect. In this case the earth is in a gravitational field where it may not fall over, but the precession will increase as its spin slows. Like the top, the precession is the result of gravitational effects. The effects in the case of the earth are considrably more complex but the overall result is quite similar to the top.

Pretty much why I would say that that example is not applicable. Right now, the earth is slowing, because of tidal friction, and the precession seems to be increasing ( wiki ) but that wiki article says that the precession is periodic, and actually would show a decrease over the last 500 million years, and over the next 500 million years. The tilt ( the obliquity ), too, increases and decreases.

The Milankovitch cycles describe climate changes that are dependent on the precession so it is more accurate to say that the Milankovitch cycles are linked to the precession. The precession is linked to the gravitaional influences of other heavenly bodies and the climate depends heavily upon the precession.

The Milankovitch cycles include more than the cycle associated with precession. It is one of the weaker ones. But the point is that there is a reasonable (or at least arguable) connection between precession and climate.

From what I understand, the wobble of the earth is caused by the artic glacier mass. The mass of the northern glacier causes an imbalance of circular force creating a wobble. Less mass at the pole creates less wobble of the earth. I believe Einstein said this.

Originally Posted by Scott Phillips

From what I understand, the wobble of the earth is caused by the artic glacier mass. The mass of the northern glacier causes an imbalance of circular force creating a wobble. Less mass at the pole creates less wobble of the earth. I believe Einstein said this.

No.

Most of the arctic ice is floating, and is no more involved in an imbalance than ocean water. Einstein didn't really say much about geophysics, although he did give some more or less favorable reviews to some of the work of Velikovsky, I think.

The precession is mostly a result of the interaction of the tidal bulge (20 kilometers at the equator) with the moon and sun. There are other wobbles, of much smaller magnitude, but even then the sea ice doesn't have much effect.