I saw this on a show on ecuador, where it was said that we are farther away from the center of the earth so there is less gravity. I thought the more the mass the more the attraction. Which leads to another question, how come we don’t feel a lot light at the equator because of the earths centrifugal spin, and much more heavy because of none? at the poles.
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The essential answer is that the difference is so light we don’t notice it. If you’re lifting a ten gallon tank of water, are you going to notice if something drips on it?
I wikied it here .
It’s kinda “the more the mass the more the attraction” (Opposite of Lust Reactions).
Distance from Centre of Gravity is relevent reading for your questions
Yes, the more mass, the more attraction, but the Earth has the same amount of mass no matter whether you’re on the equator or the poles. Meanwhile, though, you are further from the center at the equator, too, and that’s also important.
This is also an effect. In addition to gravity itself being weaker at the equator, the centrifugal force is also partly balancing out gravity, so for this reason, also, things will effectively be lighter at the equator. We don’t feel “a lot” lighter, just because the Earth isn’t really spinning all that fast, compared to its gravity, but we do feel a little lighter there.
Chronos covered what I consider an important point. The centrfical force conters the gravity effect more on the equator. You need to get nitpick if you look for variation. Denser materials in the crust can give a minute increase to the gravity in an area.
Someone can check my math, but I calculated the centrifugal force at the equator to be 1.69 x 10^-5 m/s^2. Considering this is about 0.00017% of gravity, you might as well not worry about it.
As Captain Carrot said, the difference in weight is miniscule. If the Earth were perfectly spherical, the amount of “weight loss” due to centrifugal force is about 3.4 parts in a thousand compared to that at the poles. The oblateness of the Earth will also cause an effect; I don’t know exactly now large it is, but I’d be very surprised if it was much bigger than that. At most, you would weigh about 1% more at the poles then at the Equator.
I have a question. The equatorial bulge is about 13 miles high. If you compute the central acceleration at the equator, divide it by 32.17 and multiply by the radius of the earth the answer is 13.5 miles. Is this a coincidence or is the earth just a liquid ball held togenter by gravity?
Nope, it’s not a coincidence. The surface of the Earth will, modulo a few wrinkles here & there, shift itself around so that gravity always points perpendicular to the surface. If there’s a place where gravity isn’t perpendicular, then forces such as erosion will eventually move the lumps “downhill” until there’s no “downhill” to go to any more.
I believe the master has talked on this subject already, I’d find the thread if I weren’t so tired, so I shall leave this up to another doper…