[beloveds]

I´m just wondering,
has there ever been a world wide test to see if Gravity has the exact same force/pull independent of the location on earth ?

[quottrethew]

Not sure, but since the earth is not perfectly round I would imagine the places it is more oblong it would be somewhat lesser... I don't know.

[Goseciwx]

I would have thought that gravitational field strength what not constant for all points on the earths surface as the earth is not a sphere. I can't back that up with experimental evidence however.

[Kamendoriks]

Sure has and yes, the gravity differs. Generally gravity equally measured at sea level is weakest at the Equator and strongest at the Poles, but there are regional fluctuations too, probably because of the unbalance of the masses on the surface (land,sea) and in the Core itself.

[JOR4qxYH]

The exact gravitational force is inversely proportional to the distance to the centre of mass squared.

Force = G M m / (R^2)

Where force is in Newtons, G is the gravitational constant, M is the mass of the earth, m is the mass of the object you're measuring the interaction of and R is the distance between the object and the Earth's centre of mass.

So... for example, if you're at the top of mount everest, there will be a smaller gravitational pull on you than if you were at the bottom.

To give you an idea of how much it would differ....

Average radius of the earth = 6371km, everest height ~= 9km

So distance to centre of the earth from bottom of everest would be 6371 and from top would be 6380km

Ratio of gravitational pull

BOTTOM : TOP

0.0000000246368279 : 0.0000000245673686

1.002827299 : 1

... so the gravitational pull at the top of everest is approximately 0.3% weeker than it is at the bottom

This suggests the centre of mass is exactly at the centre of the earth & makes quite a few assumptions - but you get the idea & the actual figure will be very close to that.

The radius of the earth varies around the globe...

the radius at the equator is about 6378km, whereas it's about 6357km at the poles



That should answer your question in plenty of detail


... the basic answer is - no - the pull of gravity is not exactly the same everywhere. Heck... if you take a single step it probably changes (a very minute amount of course)

[JonatonM]

Probably doesn't, but I doubt you'd feel the difference anyway.

[minowz]

The exact gravitational force is inversely proportional to the distance to the centre of mass squared.

Force = G M m / (R^2)

Where force is in Newtons, G is the gravitational constant, M is the mass of the earth, m is the mass of the object you're measuring the interaction of and R is the distance between the object and the Earth's centre of mass.

So... for example, if you're at the top of mount everest, there will be a smaller gravitational pull on you than if you were at the bottom.

To give you an idea of how much it would differ....

Average radius of the earth = 6371km, everest height ~= 9km

So distance to centre of the earth from bottom of everest would be 6371 and from top would be 6380km

Ratio of gravitational pull

BOTTOM : TOP

0.0000000246368279 : 0.0000000245673686

1.002827299 : 1

etc..

yes indeed. Around the equator a pack of sugar weigts less when it is weight than on the arctic poles.

I dont know you mathemetics though, but I trust they are right.

[sisimelanyk]

Long answer, Crowhorse, and not entirely accurate.
Gravitational force does vary on the earths surface as the differing heights above sea level allow greater mass below, sea water is less dense than rock so there'll be a defference between above the Marianas trench (particularly Challenger Deep) and Everest, the distribution of the different materials in the earth - and differing temperatures will further affect the densities.
Centripetal force at the equator, Vs the poles, will also affect the apparent gravitation force.

[Maserati]

Surely the moon has an affect too - if it can cause huge waves, surely it cancels out a bit of earth's gravity at the position its closest to.

[Grennios]

Yes, the Moon does have an effect on the overall gravitational field of the Earth; the tides are indeed the result of this. Every particle on/in Earth experiences the Moon's gravity and if the entire planet was made from water, we'd noticed the planet bulge into an ellipsoid. However, since most of the Earth is rock/iron and very rigid (and more importantly, our frame of reference is attached to this rigid foundation), it stays put - only the water on the surface noticeable responds.

Don't forget that the Sun also has the same effect on the Earth too, but to a lesser extent.

[Suentiend]

did you not watch mythbuster? there is a device that is design to calculate gravity... it is accurate enough to detect a change cause by the people sitting in a stadium! it basically calculate the difference in time it takes of the laser beam to reach a target...

so there you have it! it is NOT constant because everything has mass! as you move around the planet, you are effecting gravity around you, only detectable to mr. beam of light!
[rofl]