earth slowing down

Fr0st2k · #1 29th November 2003, 06:19 PM

i remember watching some video where someone was arguing about god existing, and at the time the points seemed valid. one point just popped in my head so i wanted to ask about it..he said that he earth was slowing down in its rotation. now of course, i have no reason not to believe this, so i do. with that point, he said, if the earth was billions of years old, the things living on it would have been thrown off, he even had a little picture that he showed. He then concluded that statement by saying something like ..."thats why the earth is onlyl 4-6 thousand years old"
Now is there any more information on this whole earth slowing down thing? Its pretty interesting, like will the earth stop 1 day? or maybe the earth spins 1 way, stops and spins the other way, maybe thats what causes ice ages! wow, i really have no idea, so if you know lemme know! thanks

pureone · #2 29th November 2003, 06:21 PM

Originally Posted by Fr0st2k

i remember watching some video where someone was arguing about god existing, and at the time the points seemed valid. one point just popped in my head so i wanted to ask about it..he said that he earth was slowing down in its rotation. now of course, i have no reason not to believe this, so i do. with that point, he said, if the earth was billions of years old, the things living on it would have been thrown off, he even had a little picture that he showed. He then concluded that statement by saying something like ..."thats why the earth is onlyl 4-6 thousand years old"
Now is there any more information on this whole earth slowing down thing? Its pretty interesting, like will the earth stop 1 day? or maybe the earth spins 1 way, stops and spins the other way, maybe thats what causes ice ages! wow, i really have no idea, so if you know lemme know! thanks

Hovind again....

Hands&Feet · #3 29th November 2003, 06:23 PM

I don't know, but the theory sure makes a great excuse for me not moving as quickly as I once did.

PhantomLlama · #4 29th November 2003, 06:24 PM

If I recall correctly there is some evidence that the earth spun faster in the past, but 'spun faster in the past' equates to 400days/year around about the time of the dinosaurs. And it may not have been slowing at the same rate.

Or I may be misremembering and it is actually speeding up. Or it's all bunk and I have just wasted 2 minutes making a post on a vague memory of something I read once.

pureone · #5 29th November 2003, 06:28 PM

May the physics guys correct me if I am wrong, but it has something to do with the moon as well. the moon gets closer, the earth slows down. Sometime in the future, the moon will head back out, and the earth will "speed up" again. the two things are linked...

MartinM · #6 29th November 2003, 06:29 PM

Yes, the Earth's rotation is slowing. No, not enough to be a problem for an old Earth. In fact, there's a good example of consistency checking here. Corals lay down a layer of lime every day, and the thickness of those layers varies with season, so it's possible to determine how many days there were in any given year of the coral's life. TalkOrigins (I think) have an article on this where it is shown that if we use radiometric dating to get an age for a coral, then project backwards the decrease in the rate of the Earth's spin, we can work out how many days in the year there should have been back then, and compare it to the number we get from studying the coral's layers. The two numbers check out.

Edited to add: ahh, here we go: http://www.talkorigins.org/faqs/hovi...good-yea2.html

Take a look at #20

MartinM · #7 29th November 2003, 06:34 PM

Originally Posted by pureone

May the physics guys correct me if I am wrong, but it has something to do with the moon as well. the moon gets closer, the earth slows down. Sometime in the future, the moon will head back out, and the earth will "speed up" again. the two things are linked...

Not quite right. The Earth's slowing down because it loses energy to the Moon, which is boosted up to a higher orbit because of this. The Moon's recession and the Earth's slowing spin are part of the same process.

Neither, of course, is in any way whatsoever problematic for an old Earth.

ForeRunner · #8 29th November 2003, 06:44 PM

I thought I read something about the earth slowing slightly because of the oceans as well, is there any merit to this?

pureone · #9 29th November 2003, 06:46 PM

Originally Posted by MartinM

Not quite right. The Earth's slowing down because it loses energy to the Moon, which is boosted up to a higher orbit because of this. The Moon's recession and the Earth's slowing spin are part of the same process.

Neither, of course, is in any way whatsoever problematic for an old Earth.

Thank you. I thought they were connected.

MartinM · #10 29th November 2003, 07:05 PM

Originally Posted by ForeRunner

I thought I read something about the earth slowing slightly because of the oceans as well, is there any merit to this?

Yeah, it's all part of the same thing. The Moon raises tidal bulges in the Earth's oceans. Strictly speaking, the location of these bulges is due to the position of the Moon, and so the Earth ought to rotate while the bulges stay where they are - one pointing towards the Moon, one pointing away. But the Earth's rotation tends to drag the bulges along with it, moving them slightly out of line with the Moon. Since the Moon orbits in the same direction as the Earth rotates, this means that the bulge nearest to the Moon tends to pull it forwards in its orbit, accelerating it and driving it out to a higher orbit.

Of course, the same friction which drags the bulges out of line also slows the Earth's rotation. So the net effect is to transfer some of the Earth's angular momentum to the Moon.