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Old 17-June-2008, 04:40 PM
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Miketmbt Miketmbt is offline
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Default Childish Gravity question

Hello all,

I had one question that I should of thought about in middle school but im 30 now.

Does the rotation of earth make us feel gravity weaker than if it wasnt rotating?

What I mean is does the rotation try to throw us off and counter some of the force holding us on?
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Old 17-June-2008, 04:48 PM
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Originally Posted by Miketmbt View Post
Does the rotation of earth make us feel gravity weaker than if it wasnt rotating?
Not detectably feel it, but there is a slight measurable difference.

Wikipedia: Earth's gravity

Quote:
Gravity is weaker at lower latitudes (nearer the equator), for two reasons. The first is that in a rotating non-inertial or accelerated reference frame, as is the case on the surface of the Earth, an object's velocity vector will be perpendicular to the axis of rotation, but will be prevented from following this vector by centripetal force. The gravitational force on a body is partially offset by this resulting force (known as the pseudo-force centrifugal force), reducing its weight. This effect is smallest at the poles, where the gravitational force and the centrifugal force are orthogonal, and largest at the equator. This effect on its own would result in a range of values of g from 9.789 m·s−2 at the equator to 9.832 m·s−2 at the poles.
(The second is due to the equatorial bulge that places the surface there farther from the Earth's center.)
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Old 17-June-2008, 06:45 PM
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Originally Posted by 01101001 View Post
Not detectably feel it, but there is a slight measurable difference.

Wikipedia: Earth's gravity



(The second is due to the equatorial bulge that places the surface there farther from the Earth's center.)

The third is the transverse doppler shift of the neutrinos coming through the Earth, due to the rotating reference frame which has it's largest value also at the equator...see:http://en.wikipedia.org/wiki/Transverse_Doppler_effect
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Old 17-June-2008, 06:54 PM
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I was once told that the "lightest" place on Earth is some point near the Equator in the Andes which is the highest point on the equator. I don't know what the total difference between this point and the north or south pole is, but I suspect that it is measurable.
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Old 17-June-2008, 06:59 PM
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Quote:
Originally Posted by Miketmbt View Post
Hello all,

I had one question that I should of thought about in middle school but im 30 now.

Does the rotation of earth make us feel gravity weaker than if it wasnt rotating?

What I mean is does the rotation try to throw us off and counter some of the force holding us on?

If you're 30 now, by the time you are 40 or 50 you will begin to think that gravity has increased quite a lot since you were 30.
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Old 17-June-2008, 07:05 PM
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If you're 30 now, by the time you are 40 or 50 you will begin to think that gravity has increased quite a lot since you were 30.
To be fair, the equitorial bulge does get bigger.
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Old 18-June-2008, 12:13 AM
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To be fair, the equitorial bulge does get bigger.
Very true. When I was in high school, my body didn't even have an "equitorial bulge". Now it does.
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Old 18-June-2008, 12:16 AM
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So your saying I should donate all those pants I was hoping to wear again someday..
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Old 18-June-2008, 12:43 AM
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So your saying I should donate all those pants I was hoping to wear again someday..
Well, I suppose it depends on the individual. For me, I keep them about 10 years, then when I later find them and I can’t even get my foot into them, then I give them to the local thrift store.

By the way, one time I wanted to find out if I would weigh less if I moved to the top of a tall Andes mountain somewhere along the equator. Turns out I wouldn’t even weigh an ounce less (or some small number like that) so I gave up my Andes project.
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Old 18-June-2008, 06:18 AM
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Originally Posted by Miketmbt View Post
Does the rotation of earth make us feel gravity weaker than if it wasnt rotating?
Simply answer: yes. Obviously not if you are on one of the poles, of course. The effect gets stronger as you approach the equator.
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Old 19-June-2008, 01:00 AM
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Quote:
Originally Posted by Miketmbt View Post
Hello all,

I had one question that I should of thought about in middle school but im 30 now.

Does the rotation of earth make us feel gravity weaker than if it wasnt rotating?

What I mean is does the rotation try to throw us off and counter some of the force holding us on?
Hi Mike.

Yes, the rotation of earth does counter the gravitational force slightly. Especially on the equator. At the equator the acceleration is reduced by V^2/R = about .034 meters/sec^2. So your weight is reduced by about 1/3rd of one percent. Nothing to worry about. you will not fly off. You are stuck here .

That is a good question. You are not too old to lern. I am much older.

Wo
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Old 19-June-2008, 05:29 AM
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omg the earth spins
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Old 20-June-2008, 01:08 AM
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Quote:
Originally Posted by trinitree88 View Post
The third is the transverse doppler shift of the neutrinos coming through the Earth, due to the rotating reference frame which has it's largest value also at the equator...see:http://en.wikipedia.org/wiki/Transverse_Doppler_effect
Why do You think tranverse dopler shift has something to do with making earth gravity different? May be you do not understand the question.

Wo
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Old 20-June-2008, 07:36 AM
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omg the earth spins
Yeah! Since when?


Welcome to BAUT Mr. Napolean, Mr. Fong.

May your stay be long and fruitfull
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Old 20-June-2008, 03:32 PM
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Why do You think tranverse dopler shift has something to do with making earth gravity different? May be you do not understand the question.

Wo
The "neutrino sea" is his little pet theory that he throws out any chance he gets, relevant or not!
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Old 20-June-2008, 03:53 PM
grant hutchison grant hutchison is offline
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Quote:
Originally Posted by jfribrg View Post
I was once told that the "lightest" place on Earth is some point near the Equator in the Andes which is the highest point on the equator. I don't know what the total difference between this point and the north or south pole is, but I suspect that it is measurable.
If you travel from the pole to the equator, your weight is reduced by 0.5%. If you climb to the summit of Chimborazo, in Ecuador, which is near the equator and the farthest point from the centre of the Earth, you'll get a small additional reduction in weight. So, yes, it's a readily measurable difference: pendulum clocks run noticeably slower at the equator than at higher latitudes, for instance.

Grant Hutchison
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