# Why is the local gravity at the poles greater than at the equator?

Question by Guest | 2018-03-01 at 17:26

The local gravity or the gravitational acceleration is not identical at different places on earth. The biggest difference seems to be between a measurement at the poles and at the equator.

For the North Pole or South Pole, a local gravity acceleration of 9.832 m/s² is known, whereas at the equator it is only 9.787 m/s². How can that be? Where do these different values come from? I know that the local mass difference gets smaller, the higher the measure is carried out. But these values are both valid for the earth's surface.

There are two main reasons for that: The centrifugal force and the equatorial bulge.

As we all know, our earth rotates around its own axis, the axis of rotation is going through the poles. As in the case of a carousel, thereby a force is exerted to the outside. Naturally, this force is greatest at the equator.

The second point is the equatorial bulge: the earth is not circular but slightly bulging at the equator, which by the way is also the centrifugal force responsible for. Objects on the earth's surface located at the equator are therefore slightly further from the center of the earth than objects standing at the North Pole or South Pole.

These two points together lead to that we have a smaller acceleration or a smaller local gravity at the equator than at the north or south pole. At the equator we are thus 0.5% lighter than at the poles.
2018-03-02 at 13:58