Does the gravitational rate of acceleration increase within a planet?

AI Thread Summary
The discussion centers on the gravitational effects within a planet, particularly regarding the density distribution and gravitational acceleration near the center. It is noted that if 80% of a planet's density is concentrated in the innermost 20% of its radius, the gravitational acceleration would be significantly higher than at the surface. However, the shell theorem indicates that gravity at the exact center of a spherical mass is zero due to symmetrical forces canceling each other out. Participants debate the implications of linear versus nonlinear models of gravity, with some arguing that gravity should increase towards the center, while others maintain that it cannot exceed zero at the center. The conversation highlights the complexities of gravitational physics and the importance of precise definitions in discussing theoretical models.
  • #51
sjbauer1215 said:
I don't believe we will ever reach the extreme density of a black hole.
Why don't you simply write down the formula for density as function of radius that you have in mind?
 
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  • #52
sjbauer1215 said:
This corresponds to a gravitational acceleration of about 10.7 m/s2 (which is comparable to the gravity at the surface of Saturn!). For comparison, the gravitational acceleration at Earth’s surface is 9.81 m/s2.
Saturn may be physically large but it is not very dense. Given a sufficiently large bathtub, it would float.
I weigh 85kg. On Saturn, I would only weigh 8kg more.
 
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  • #53
sjbauer1215 said:
I don't believe we will ever reach the extreme density of a black hole.
The idea that black holes have a density at all is problematic. You could divide a black hole mass by ##\frac{4}{3}\pi r^3## where r is its Schwarzschild radius. But this turns out not to be a constant. The larger the hole, the lower the "density" in this sense.

You could consider the local density in the interior of a black hole. But black holes are "vacuum solutions". They are vacuum everywhere. Zero density everywhere. There is no mass anywhere. Just space-time curvature.

You could consider what happens as one gets closer and closer to the singularity. But the geometry of a black hole is strange. Its interior volume is infinite. That ##\frac{4}{3}\pi r^3## formula works for Euclidean geometry, not for the curved pseudo-Riemannian manifold of the Schwarzschild solution.
 
  • #54
Thread is closed for Moderation...
 
  • #55
To the extent I can discern a coherent question that the OP is asking, it appears to be answered.

Thread will remain closed.
 
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