Is Gravity Lower at the Earth’s Equator and What Does This Have to Do With the Moon’s Orbit?

the Earth is not actually a perfect sphere and it doesn’t have perfectly spherical symmetry. Different parts of the Earth have different densities (because of variations in rocks and stuff). It’s possible to map these gravitational variations using satellites. <img alt="" src="https://miro.medium.com/v2/resize:fit:350/0*_YD4v4jX2XI6oQnR.jpg" style="height:216px; width:350px" /> Image: NASA. <a href="https://earthobservatory.nasa.gov/features/GRACE/page3.php" rel="noopener ugc nofollow" target="_blank">Variations in the gravitational field using the GRACE</a> There’s also the effective gravitational field. This is the sum of the effects due to the Earth’s mass and the rotation of the Earth. Recall that an object moving in a circle at a constant speed still has an acceleration. We call this the centripetal (center-pointing) acceleration. It has the following magnitude. <a href="https://rjallain.medium.com/is-gravity-lower-at-the-earths-equator-and-what-does-this-have-to-do-with-the-moon-s-orbit-e0a6c2b37073">Website</a>