Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: benep on 05/05/2008 19:12:18

Title: Does gravity change depending on where you are on Earth?
Post by: benep on 05/05/2008 19:12:18

gravity... probably the weirdest thing about our planet but to make it weirder is gravity stronger in depending on where or what country you are in? egis gravity stronger i america then here in britain?

Title: Re: Does gravity change depending on where you are on Earth?
Post by: JP on 05/05/2008 19:30:08

I assume you're talking about the strength of the Earth's gravitational field here.  If the earth were a perfectly round and symmetric sphere of matter, the gravitational field would be the same everywhere.  However, the earth isn't quite a sphere (it's fatter around the equator), and has mountains, seas, etc.  These variations are incredibly small compared to the size of the earth, so gravity is practically the same everywhere (~9.8 N/kg).  If you want to be incredibly picky, however, the gravitational field does vary from place to place depending on the composition of what you're standing on and your elevation.

Title: Re: Does gravity change depending on where you are on Earth?
Post by: LeeE on 05/05/2008 21:18:56

For more info have a look at:

http://en.wikipedia.org/wiki/World_Geodetic_System
http://en.wikipedia.org/wiki/Physical_geodesy

Title: Re: Does gravity change depending on where you are on Earth?
Post by: lyner on 05/05/2008 22:32:14

Why is the difference surprising? Work out the force on  1kg due to all the individual bits of the Earth, each of which produce their own gravitational force on that kg (simple Newtonian stuff) and you get different answers, depending where you are.
The presence of the Moon and Sun affect its weight, too; enough to cause the tides. All calculable to a reasonable degree of accuracy.

Title: Re: Does gravity change depending on where you are on Earth?
Post by: benep on 06/05/2008 20:11:58

thanks guys helped me to undestand much better thanks