Another gravity Q

Station yourself at the center of the Earth. Walk towards the surface, and where is Gm/r^2 the greatest? I assume stratifies density layers in the earth contribute…

If you are asking a general question, not relating to some specific geographic location on the globe, then the obvious answer is at the surface.

Although you may be thinking that the deeper parts of the planet are denser and that proximity to that material will override the additional mass involved as you move closer to the surface, remember that the additional mass increases as a factor of r^3 while the G value drops off as r^2.

But…that’s exactly what happens. The force of gravity stays approx. constant, increasing a little, down to the core-mantle boundary, where it is greatest, then it decreases steadily to the center of the Earth.

We’ve talked about this before…I’ll see if I can dig up the threads.

Well look at that…you learn something new everyday. But do you have a cite?

is this a stupid question? if you were positioned exactly in the center of all the earth’s mass, wouldn’t you be weightless? since the gravitational pull would be the same all around you?

But that’s not what the OP is asking. The question is: as you move outward from the center of the earth, at what point is the force of gravity the greatest?


The second figure on this page is a bit hard to read, but the line labeled g essentially duplicates a figure on page 253 (Chapter 5) of Stacey’s Physics of the Earth, which is referenced just below the figure. The peak, a bit over 10m/s/s, is at the core-mantle boundary.