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Q & A: Is there a net gravitional foce at the center of the earth?

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Most recent answer: 08/04/2018
Q:
If gravity is emergent solely from mass, then shouldn't gravity be zero at the center of a massive body such as the Earth; having ~equal mass in all directions about the vertex?This one has driven me nuts for years.
- John Gilmour (age 63)
L2A 3R1
A:

Rest easy John,  your intuition and reasoning are correct.

Lee H


(published on 07/30/2018)

Follow-Up #1: where is gravity zero in Earth?

Q:
I don't think this is correct because it implies that the Earth's mass is distributed perfectly uniformly, which isn't the case as revealed by Earth's gravitational anomalies. Although mathematically, such a vector field must have a null point which wouldn't be the exact Earth's center but pretty much next to it.
- Anonymous
A:

That's true. It's not necessary for the Earth to have uniform density, however, for the zero to occur at the middle. The density varies a great deal with radius, but any spherically symmetrical density will have zero field in the center. Any cylindrically symmetrical field with inversion symmetry on the axis will also have the zero at the center. Those asymmetrical anomalies you mention are real but small. 

Mike W.


(published on 08/04/2018)

Follow-up on this answer.