# Is Gravity The Same At The Equator And At The Poles? **URL:** \ **Category:** Factual Questions\ **Created:** [July 26, 2005, 11:41pm UTC](https://boards.straightdope.com/t/is-gravity-the-same-at-the-equator-and-at-the-poles/314322 "2005-07-26T23:41:59Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![JimMacMillan](https://avatars.discourse-cdn.com/v4/letter/j/7bcc69/32.png) [@JimMacMillan](https://boards.straightdope.com/u/JimMacMillan)\ **Post date:** [July 26, 2005, 11:41pm UTC](https://boards.straightdope.com/t/is-gravity-the-same-at-the-equator-and-at-the-poles/314322/1 "2005-07-26T23:41:59Z")
I had a friend tell me the following and mind you I took it with a grain salt. > [@](#): > > If the earth stopped spinning the pull of gravity would have us on our knees. In hindsight I should have asked why people at the north and South Pole are not stuck face down kissing the ground. However it left me with a question. Does centrifugal force at the equator have an effect on gravity at all? Jim ---
**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\ **Post date:** [July 26, 2005, 11:50pm UTC](https://boards.straightdope.com/t/is-gravity-the-same-at-the-equator-and-at-the-poles/314322/2 "2005-07-26T23:50:44Z")
Yes, but a miniscule amount. Less I think than the difference in gravity at the equator than the poles from the earth being a slightly flattened sphere. ---
**Author:** ![theamazingluther](https://avatars.discourse-cdn.com/v4/letter/t/f08c70/32.png) [@theamazingluther](https://boards.straightdope.com/u/theamazingluther)\ **Post date:** [July 26, 2005, 11:52pm UTC](https://boards.straightdope.com/t/is-gravity-the-same-at-the-equator-and-at-the-poles/314322/3 "2005-07-26T23:52:49Z")
> [@JimMacMillan](#): > > I had a friend tell me the following and mind you I took it with a grain salt. > > In hindsight I should have asked why people at the north and South Pole are not stuck face down kissing the ground. > > However it left me with a question. Does centrifugal force at the equator have an effect on gravity at all? > > Jim I have nothing off hand to back this up, but from what I remember of physics, gravity is slightly greater at the poles, but not (directly) because of rotation. One of the variables used to determine the acceleration of gravity is the distance from the center of the earth. Since the earth isn’t a perfect sphere, the poles are closer to the center than the equator. So there’s a bit more gravity. But not enough to notice. The same, of course, is true with varying altitudes. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [July 27, 2005, 12:25am UTC](https://boards.straightdope.com/t/is-gravity-the-same-at-the-equator-and-at-the-poles/314322/4 "2005-07-27T00:25:02Z")
[ > [@](#): > > sea-level gravitational acceleration is 9.780 m/s² at the equator and 9.832 m/s² at the poles, so an object will exert about 0.5% more force due to gravity at sea level at the poles than at sea level at the equator ]([http://en.wikipedia.org/wiki/Gravity](http://en.wikipedia.org/wiki/Gravity))Both centrifugal force and the Earth’s oblateness (flattening at the poles) contibute to the difference in acceleration. However, [this map of Earth’s gravitational field](http://antwrp.gsfc.nasa.gov/apod/ap030723.html) shows that there are other factors as well. ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [July 27, 2005, 12:35am UTC](https://boards.straightdope.com/t/is-gravity-the-same-at-the-equator-and-at-the-poles/314322/5 "2005-07-27T00:35:33Z")
I have worked at a scale shop on and off for a few years (on at the moment). We often deal with very high end balances and the differing gravitational constants occasionally come up. More often, however, it’s the difference in air boyancy from place to place that causes signifcant weighing errors. ---
**Author:** ![Punoqllads](https://avatars.discourse-cdn.com/v4/letter/p/d2c977/32.png) [@Punoqllads](https://boards.straightdope.com/u/Punoqllads)\ **Post date:** [July 27, 2005, 1:24am UTC](https://boards.straightdope.com/t/is-gravity-the-same-at-the-equator-and-at-the-poles/314322/6 "2005-07-27T01:24:31Z")
> [@JimMacMillan](#): > > I had a friend tell me the following and mind you I took it with a grain salt. > > In hindsight I should have asked why people at the north and South Pole are not stuck face down kissing the ground. > > However it left me with a question. Does centrifugal force at the equator have an effect on gravity at all? > > Jim Centripetal acceleration is w[sup]2[/sup]r, where w is the angular velocity and r is the radius of the circle. The Earth’s radius is about 6,378 km, and its angular velocity is 2 pi radians / day, or about 0.0000727 radians / second. Squaring that and multiplying by the Earth’s radius in meters gives us a centripetal acceleration of approximately 0.0337 meters per second squared; about 0.3% of the force of gravity. ---
**Author:** ![tofergregg](https://avatars.discourse-cdn.com/v4/letter/t/bbe5ce/32.png) [@tofergregg](https://boards.straightdope.com/u/tofergregg)\ **Post date:** [July 27, 2005, 1:25am UTC](https://boards.straightdope.com/t/is-gravity-the-same-at-the-equator-and-at-the-poles/314322/7 "2005-07-27T01:25:17Z")
The best answer I’ve heard to “why do you weigh more at the poles than at the equator” is > [@](#): > > because you have to wear more clothes! 😉 -Tofer (physics teacher) ---
**Author:** ![wolf\_meister](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolf_meister/32/15202_2.png) [@wolf\_meister](https://boards.straightdope.com/u/wolf_meister)\ **Post date:** [July 27, 2005, 1:56am UTC](https://boards.straightdope.com/t/is-gravity-the-same-at-the-equator-and-at-the-poles/314322/8 "2005-07-27T01:56:52Z")
Off the top of my head, I seem to remember that gravity is strongest in Northern Norway and weakest in East Africa. People have mentioned that the oblateness of the Earth and its rotation account for the variations in gravity. There is a third factor - the density variations of the Earth at differing locations. Granted, this produces slight but significant differences. As far as _scales_ showing different weights on different locations on the Earth, wouldn’t _balances_ be a more accurate determinant of mass? ---
**Author:** ![chemistrydork](https://avatars.discourse-cdn.com/v4/letter/c/7ba0ec/32.png) [@chemistrydork](https://boards.straightdope.com/u/chemistrydork)\ **Post date:** [July 27, 2005, 2:09am UTC](https://boards.straightdope.com/t/is-gravity-the-same-at-the-equator-and-at-the-poles/314322/9 "2005-07-27T02:09:42Z")
If the Earth started off as a perfect sphere, the amount of deformation due to spinning would be akin to the thickness of apple skin on an apple.