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Thread: Is earth's gravity equal everywhere?

  1. #1 Is earth's gravity equal everywhere? 
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    Since the earth is spinning at about 1000 mph at the equator, the earth's gravity must be equal to the centrifugal force of the spin. But, since there is no centrifugal force at the north or south poles, shouldn't the gravitational force be much stronger?


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    Forum Professor pyoko's Avatar
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    There are gravitational anomalies everywhere on Earth, but they are not due to the spin. They are due to material variations.

    Here's a NASA link about it:

    https://earthobservatory.nasa.gov/Fe...RACE/page3.php


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    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by Speedy View Post
    Since the earth is spinning at about 1000 mph at the equator, the earth's gravity must be equal to the centrifugal force of the spin. But, since there is no centrifugal force at the north or south poles, shouldn't the gravitational force be much stronger?
    The tangential speed at the equator is ~464 m/sec at a radius of 6378000 m. The centripetal acceleration is found by V^2/r = 464^2/6378000 = ~0.034 m/sec^2 or 1/290 that due to gravity. So If you weighed 140 lbs at the poles you would weigh a bit under 1/2 lb lighter at the equator. But that is assuming the pole and equator is the same distance from the center of the Earth, and the poles are a bit closer, so in reality, you'd weigh ~ 0.7 lbs heavier at the pole. This is not a whole lot more.

    Basically, since the point moving at 1000 mph is so far from the axis of rotation, it doesn't create much of a centrifugal effect.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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