[Orange (OP)]

Hello,
Since the Earth is slightly distorted by its rotation (oblate spheroid shape) I was wondering, is there a greater amount of mass between a place on the surface at the equator and the center of the Earth or between a place on the surface at the North Pole (or South Pole) and the center of the Earth?

Thank you!

[Kryptid]

I would have intuitively thought that there would be more mass along the equator than at the poles, but the actual mass distribution seems to be more random than that: https://en.wikipedia.org/wiki/Gravity_of_Earth#/media/File:Gravity_anomalies_on_Earth.jpg

[evan_au]

The NASA GRACE gravity map of the Earth (link from Kryptid above) shows deviations from an ideal Earth ellipsoid.
- They expect the equator to be farther from the axis of rotation (and it is, as surmised in the OP)
- They have subtracted that out, leaving only the deviations from a perfect ellipsoid.

However, because water flows downwards, the gravitational acceleration felt at mean sea level is fairly uniform around the world.
- Although there is more mass between the Sri Lanka and the center of the Earth than beneath Oslo...
- Sri Lanka gets a lift from Centrifugal force
- And Sri Lanka is farther from Earth's dense iron center

If there was some place in the ocean with higher surface gravity, the water would flow from there to a place with lower surface gravity (if you ignore things like ocean density differences and the effect of ocean gyres)...

[Orange (OP)]

Thank you for your explanations!

I imagine that this greater mass between the surface at the equator and the center of the Earth participates at least in part in the nodal precession of artificial satellites in orbit around the Earth?

[evan_au]

Gravitational tugs from the Moon and the Sun also distort the orbits of satellites, even those in geostationary orbit, where the equatorial bulge has no impact.

[Zer0]

Follow-up...

Does Earth's Gravity modulate or fluctuate with Time?

[Eternal Student]

Hi.

Follow-up...

Does Earth's Gravity modulate or fluctuate with Time?

    I think this question may have got overlooked or missed.

Anyway,  the rough or practical answer is "no":   It's fairly constant and consistent.

More complicated answers exist.   For example, the earth rotates on it's own axis every 24 hours (while the moon stays fairly still by comparison).   The most obvious effect is the ocean tides (bulges in the ocean) which move around the earth.    Beneath the outer crust of the earth there will be a lot of molten rock which can move (e.g. due to convection currents).   We know the magnetic field lines of our planet do move around instead of staying constant   (see for example:   https://en.wikipedia.org/wiki/North_magnetic_pole    which discusses the movement of the Magnetic North pole thought to be due to changes in the movement of molten ferro-magnetic material in the outer core).    So there will be some movement of various material  (surface water and molten rock inside the earth) which can affect the gravitational field local to a fixed place on the surface of the earth.

Best Wishes.

[Zer0]

Thanks for Answering.

Yes, roughly, fairly Constant & Consistent.

Perhaps only if We push for extra Decimals(is that what it's called?) then Modulating/Changing with respect to Time.

9.807 m/s2 is Totally Fine.

But what about SLAC or LIGO or VIRGO?
They have to be pretty precise in measurements.
They must be taking all this into account, isn't it.

I've also read the Moon is slowly drifting apart.
& Space junk also matters.

That might be affecting Measurements on scales like 9.807605403201