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Originally posted by apache:
If you have a black hole with the mass of the sun, it will definitely be a few million times denser than the sun. However, the gravitational force on the earth from the black hole will be exactly the same as the force the sun has on the earth, if the earth orbited a black hole at the same distance it orbits the sun.
Your statement is correct but you are missing the point. The AVERAGE density of the mass INSIDE the earth's orbit is the SAME for the sun and the black hole.
quote:
Originally posted by apache:
Now, if you were at the center of Jupiter, theoretically you would either experience infinite gravity or gravitational force based on the mass of the planet. Logic says its no gravity, but then again, there cannot be zero gravity, in fact there would at least have to be a force completely pulling you apart because you are completely surrounded by the mass of Jupiter.
I'm sorry, but I cannot give you even partial credit for this answer. You could have either used integral calculus or else used Green's Theorem and symmetry arguments. Either way, the correct answer is that the gravitational force at the center of a planet is zero.
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Originally posted by apache:
But then again, we really do not know since we have never been to the center of any planet or moon or anything to see what the gravitational forces would be.
We do not need to go there and measure it. We have known the answer from theory since Newton's Principia was published.