Earth - non-spherical gravity

[Sword7]

Hello folks,

Well, I researched for more non-spherical gravity through google but learned some interesting about gravity. I have more some questions for you.

Some years ago, they launched setallite with gravimeter to measure Earth's gravity and learned results as non-spherical gravity. For example, when spacecraft orbits over big mountains (Mt. Everest) near India, it was slightly pulled downward and its gravimeter detects gravity anomaly.

For there are huge mountains by you and you fill cup with water, what happens? Does its water level slightly tilts or so?

For your curious, I found interesting article according to google search. If only two persons in universe, two persons orbits each other like planets and moons. Hmmmm. They explains about two 50kg persons and places two persons one meter separately. What happens? Two persons were pulled downward very slowly. That takes 58 minutes to touch each other. Yes, people have gravity but very very weak force.

Thanks,
Sword7

 

[Jarvitä]

You should write more intelligible sentences, but from what I understand, your question is, "Does the water surface in a cup tilt if there's a large mountain nearby?", and the answer would be "No", because the gravitational perturbations caused by Earth's mass concentrations and non-perfect shape are so minuscule you couldn't possibly detect them from the surface. If anything, the only measurable effect on the surface would be an extremely minuscule increase or decrease in the gravitational force, which would not result in a sideway force (as you asked), but in the increase or decrease in the downward force, since the gravitational force always points in the direction of the centre of mass.

 

[pattersoncr]

Actually, the answer is "yes but only by an undetectable amount"
The disruption of the local gravity from a perfect vertical due to the local topography is enough to introduce errors in the inertial navigation systems used by ships and planes.

 

[tblaxland]

Actually, the answer is "yes but only by an undetectable amount"
The disruption of the local gravity from a perfect vertical due to the local topography is enough to introduce errors in the inertial navigation systems used by ships and planes.

If it causes such errors (I'm sure it does) and the source is known, then it is not "undetectable" is it? EDIT: I guess it would be "undetectable" in the context of the original post, ie, a glass of water.

As a matter of interest, we had some discussion about this here (posts 21 to 29).

 

[Quick_Nick]

Actually, the answer is "yes but only by an undetectable amount"
The disruption of the local gravity from a perfect vertical due to the local topography is enough to introduce errors in the inertial navigation systems used by ships and planes.

With the specifics of the question (a glass of water), I'd say that surface tension and the fact that water isn't made of infintecimal particles would prevent the water from actually changing angle. Also, any change would probably be hugely dwarfed by the fact that it would be difficult to make the cup be perfectly vertical.

 

[tblaxland]

Also, any change would probably be hugely dwarfed by the fact that it would be difficult to make the cup be perfectly vertical.

Right, because how would you even measure if the glass was "vertical" (ie, parallel to a vector from the centre of mass of the Earth to the glass)?

 

[pattersoncr]

Well, water glass or not, I do know from personal experience that running parallel to a steeply sloped coastline can cause problems with an inertial navigator due to local gravity being slightly deflected from vertical.

 

[Calsir]

Well, water glass or not, I do know from personal experience that running parallel to a steeply sloped coastline can cause problems with an inertial navigator due to local gravity being slightly deflected from vertical.

If I remember correctly, inertial navigators is based on inertial platforms, which try to keep a fixed attitude in an inertial (with the usual caveats) reference frame. They don't use the gravity field to properly orient themselves, but rather gyroscopes, that are _fairly_ insensible to gravity. Of course, if I am not mistaken, there should be a very slow feedback from an accelerometer to cope with Earth curvature.