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Posted By: Rallem Will The Planet? - 03/29/08 07:55 PM
Let's say for the sake of this question that the Polar Caps will melt and our Oceans will rise. I was watching "Universe" on the "History Channel," and they say that the moon has such an effect on our oceans that it actually slows our Planet's rotation and keeps us to a 24 hour day. If our oceans rise up will the Moon's effect on our oceans cause our Planet's rotation to slow even more?
Posted By: redewenur Re: Will The Planet? - 03/30/08 12:52 AM
Good question - which has had me googling a lot!

It seems reasonable to suppose that more water in the oceans would slow the rotation more, but to what degree I've not yet discovered.

It's worth noting that the tidal force applies to the whole of the Earth, not just the water. The dry bit bulges by about a foot up and down twice daily -

http://www.badastronomy.com/bad/misc/tides.html

- because the Moon's gravity acts more strongly on the side of the Earth nearest to it, and less strongly on the far side. The friction thus generated converts rotational energy to heat. That same effect accounts for our seeing only one side of the moon, since it too has been subjected to tidal force.

As mentioned, Rallem, I haven't found figures regarding your question, nor figures comparing rotation retardation through tidal effects on the water v. rock. I'm hoping for informative posts to follow.

As a matter of interest, according to the geological record, 620 million years ago the solar day was about 22 hrs.
Posted By: Rallem Re: Will The Planet? - 03/30/08 06:26 PM
On the show I was watching about the moon it did say that when the moon was still molten and was a lot closer to Earth that the high tides instead of being 10 feet different were probably 10k feet higher, and that the drag from the moon significantly slowed the earth’s rotation. I don't really know how this applies to my question and your answer except maybe to show an extreme case, and I would like to ask if you think it is likely our planet could enter a vicious cycle? Could it enter a cycle where the polar caps melt raising the ocean level thus slowing the rotation of the planet making the days longer and hotter thus melting the polar caps more and more until there is no more ice?
Posted By: paul Re: Will The Planet? - 03/31/08 02:50 AM
Rallem

the gravitational attraction between the earth and the moon
causes tides , also the rotation of the earth itself causes tides , not many people are aware of this fact.

it is the gravity between the two that causes the tides on the side that faces the moon and it is the rotational acceleration that causes the tides on the side that faces away from the moon.

think of the earth and moon attached together by a string.
or think of a basketball and a softball in the same scenario.
if you spin the two they will develope a orbit around each other.

it is not that the earth follows a precise path as it travels around the sun , but more like a wave form as the two tug on each other as they orbit each other and the sun..

our sun and planets also have a degree of attraction along with everything else in this universe that influences our tides yet the two above are the main influences.

when a part of the earths mass moves further away from its
center this will slow down the earths rotation.

its basic physics.

you could try this example.
get two 1 gallon jugs of water and spin around holding them as close to you as you can.

then before your rotation decelerates , extend the two juggs of water.

your rotation will slow down , just as the earth will.

then try the same without extending the juggs.

and then bring the juggs in even closer , and your rotation will accelerate as you bring them in closer to your center of mass.

you can feel the resulting speed increases and decreases.

of course we should not leave out that the melting ice will have moved closer to the center of the earths mass as it melts , speeding up the earths rotation to that degree.

which will add to the height of the tides.

Posted By: redewenur Re: Will The Planet? - 03/31/08 05:57 AM
Rallem: "Could it enter a cycle where the polar caps melt raising the ocean level thus slowing the rotation of the planet making the days longer and hotter thus melting the polar caps more and more until there is no more ice?"

All other things being equal, it's a plausible scenario but, again, all other things being equal, the total solar energy received would be the same, the longer daytime being balanced by the longer night time.

But we should remember the timescale. Lengthening the solar day by just a couple of hours takes several hundred millions years - and all other things are not necessarily equal. During that time a gradual increase in solar radiation is expected, which would cause evaporation of the oceans and actually reduce their depth. After a billion years (some estimate ~ 3.5 billion) they could evaporate completely. See: http://www.spaceref.com/news/viewpr.html?pid=908
Posted By: samwik Re: Will The Planet? - 03/31/08 06:42 AM
Originally Posted By: paul
think of the earth and moon attached together by a string.
...
of course we should not leave out that the melting ice will have moved closer to the center of the earths mass as it melts , speeding up the earths rotation to that degree.


Paul, thanks for that description.
As soon as you mentioned the string, I got the "opposite-side" tide thing.

I have to ask about the last paragraph though. I was just thinking about the melting ice too; but thought it would carry mass away from the CG (axis?), and hence slow rotation down a bit.
I was thinking an analogy might be a spinning ice skater shifting a mouthpiece from mouth to an extended hand. Probably it'd be perceptible, but only measurable with atomic clocks.

Which of us is missing something (or centrifugally dyslexic)?
grin
Posted By: paul Re: Will The Planet? - 04/01/08 05:48 PM
Samwik
Quote:
I have to ask about the last paragraph though. I was just thinking about the melting ice too; but thought it would carry mass away from the CG (axis?), and hence slow rotation down a bit.


I was refering to the [ ICE ] caps.
the [ ICE ] that is currently above sea level.

as the ice above sea level melts , its mass moves closer to
the center of the earth.

and as the ice skater brings in their arms [ closer ] to the center of rotation the skater [ speeds up ].

so the earths rotation like the skater will also increase in speed.

there are very large amounts of ice remaining to melt ,

and this melting of ice [ WILL ] speed up the earths rotation.

of course there are other things to explore such as the thermal expansion of the seas and oceans which will place mass further away from the center of the earth , yet this mass is expanded water and its weight to volume ratio is not the same as that of normal temperature water , so you cannot get a precise weight unless you know its temperature.

many things are in play that need to be included into any forecast or program that will forcast the upcomming climatic changes.

Quote:
Which of us is missing something (or centrifugally dyslexic)?


I say neither , this is a direct result in our education system that refuses to teach centrifugal force.

the education system tells us that there is no outward force in rotation.

[sarcasm]
perhaps this is why the ozone hole moved closer to the center of rotation and is still there today !!!

instead of moving to the equator.

[end sarcasm]

because we are taught that the only force is towards the center of rotation.






Posted By: paul Re: Will The Planet? - 04/01/08 06:07 PM
Quote:
Let's say for the sake of this question that the Polar Caps will melt and our Oceans will rise. I was watching "Universe" on the "History Channel," and they say that the moon has such an effect on our oceans that it actually slows our Planet's rotation and keeps us to a 24 hour day. If our oceans rise up will the Moon's effect on our oceans cause our Planet's rotation to slow even more?


YES...this would happen.

and the melted ice would tend to speed up the earth first.

maybe a balance will be reached ?

maybe not.

best thing to do is either use your brain and cut down on your energy consuption.
or pray.

since GOD gave me a brain to think with , I choose to cut down on my energy consumption , and pray.

Posted By: Rallem Re: Will The Planet? - 04/02/08 09:03 PM
I'll increase my power consumption and beginning claiming to be the one who killed the human species. Some say that mankind is overly pretentious in thinking it can destroy the world. I look at that as a challenge and gladly accept.
Posted By: paul Re: Will The Planet? - 04/04/08 05:12 AM
Quote:
I'll increase my power consumption and beginning claiming to be the one who killed the human species. Some say that mankind is overly pretentious in thinking it can destroy the world. I look at that as a challenge and gladly accept.


OH NO , your waaaaay toooo late for that Rallem !!!

Quote:
mankind is overly pretentious


in thinking that they cannot harm the climate .

maybe you should just move to china and breath the
nice fresh air that is caused by those who think like you.

Quote:
overly pretentious


Im sure that when your lungs clogg up with all the added
ingredients that you would be getting in their air they
would conpensate you and pay for the damages. LOL

of course you would then be the one that is

Quote:
overly pretentious
sick








Posted By: Rallem Re: Will The Planet? - 04/04/08 09:49 PM
Why move to China, won't their environment come to me?
Posted By: paul Re: Will The Planet? - 04/05/08 04:17 AM
Quote:
Why move to China, won't their environment come to me?


LOL ... just like everything else they make!!

it just takes awhile for it to get here.

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