Gravity at the centre of the Earth?

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    Earth Gravity
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Discussion Overview

The discussion centers on the behavior of gravity at the center of the Earth, exploring theoretical implications and calculations related to gravitational force within a spherical mass distribution. Participants examine concepts of gravitational force, density variations, and the implications of being at the Earth's center.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants assert that at the center of the Earth, there would be no net force of gravity felt due to the symmetrical distribution of mass surrounding that point.
  • Others explain that the gravitational field within a hollowed-out space at the center would be zero, supporting the idea of weightlessness in that scenario.
  • One participant mentions that while the formula for gravity inside a sphere can be simplified by ignoring mass above the measurement point, the Earth's varying density complicates this, as gravity increases until the outer core boundary and then decreases to zero at the center.
  • Some participants inquire about the approximate value of gravitational force at its peak, with one providing a calculated acceleration of 10.88 m/s² at the mantle/outer core boundary.

Areas of Agreement / Disagreement

Participants generally agree that there would be no net gravitational force at the center of the Earth, but there are differing views on how gravity behaves as one approaches the center, particularly regarding the effects of Earth's varying density.

Contextual Notes

The discussion includes assumptions about uniform density and the simplifications made in gravitational calculations, which may not fully account for the Earth's actual structure.

Beaujolais
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I know gravity on the surface of the Earth is 9.8m/s/s from

g=GM/d^2
(6.7x10^-11)(6x10^24) / (6.4x10^6)^2 =9.81

But if you go to the center of the Earth will there be no gravity?
As the mass at the center will be nothing and the distance will be nothing?
 
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As you proceed inwards towards the center, the net force of gravity is solely provided by the INNER massive ball (with center at the Earth's center); that is the outer shell of mass contributes nothing to the net force of gravity (we may prove it cancels out).

Thus, indeed, at the center of the Earth, there won't be any net force of gravity "felt".
 
Beaujolais said:
But if you go to the center of the Earth will there be no gravity?
Correct. If you imagine a hollowed out space at the center of the earth, and if you further treat the Earth as a spherically symmetric distribution of mass, then the gravitational field within that hollowed out space will be zero.
 
Beaujolais said:
I know gravity on the surface of the Earth is 9.8m/s/s from

g=GM/d^2
(6.7x10^-11)(6x10^24) / (6.4x10^6)^2 =9.81

But if you go to the center of the Earth will there be no gravity?
As the mass at the center will be nothing and the distance will be nothing?

Assuming you could actually exist in the center of the Earth, you would essentially be surrounded by equal mass therefore, not pulled in anyone direction greater than another. In essence, you would be weightless.
 
When you calculate the gravity from somewhere inside a sphere you can as has already been stated ignore the mass that is at a higher elevation than the point where we are measuring from. That being said the gravity can be calculated by the formula g=4pG(pi)r/3 where p is the density and r is the radius from the center if the body is of uniform density. This is not quite the case with the Earth. The inner core and outer core are much denser than the mantle so the gravity of the Earth actually goes up until you reach the boundary of the outer core, from then on it declines steadily to zero at the center.
 
what (aprox) would be the value of the FoG at its peak?
 
MoonKnight said:
what (aprox) would be the value of the FoG at its peak?

Using values I found on the internet I calculated an acceleration of 10.88 m/s^2 at the mantle/outer core boundary.
 
awesome, thanks
 

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