How Do Earth's Uneven Gravity Fields Affect Spacecraft Flybys?

[xyz1971]

Hi,

I rather a strange question in that I'm not a physicist and don't really understand the theories I'm about to mention fully, ok disclaimer over.

My understanding of gravity, is that a mass warps the spacetime in which it sits. Now my question is that ESA's Gravity field and steady-state Ocean Circulation Explorer (GOCE) shows gravity isn't equal all over the earth. Surely then that means spacetime isn't distorted uniformly around the earth? Surely this would have an effect on an object depending on the position of the Earth at the time flyby?

Ok maybe not quite such daft a question, but I'm sure there will be a physicist somewhere shaking their head ... :)

Mark

I think in fact I mean the GRACE project not GOCE.

 

[Ich]

Welcome o PF!

These irregularities surely have an effect. The point is: these effects are known accurately enough (or so physicists believe), and have been accounted for. The anomaly is what's left after accounting for known effects.

 

[Chalnoth]

Hi,

I rather a strange question in that I'm not a physicist and don't really understand the theories I'm about to mention fully, ok disclaimer over.

My understanding of gravity, is that a mass warps the spacetime in which it sits. Now my question is that ESA's Gravity field and steady-state Ocean Circulation Explorer (GOCE) shows gravity isn't equal all over the earth. Surely then that means spacetime isn't distorted uniformly around the earth? Surely this would have an effect on an object depending on the position of the Earth at the time flyby?

Ok maybe not quite such daft a question, but I'm sure there will be a physicist somewhere shaking their head ... :)

Mark

I think in fact I mean the GRACE project not GOCE.

Correct. Basically, it's because the Earth isn't a perfect sphere (it has mountains, valleys, etc., and has a bulge around the equator), and it isn't of uniform density (some rocks are more dense than others).

And it's precisely because these differences in the gravitational field affect these spacecraft s that we are able to measure the differences using the spacecraft in the first place.