Viv: i dont understand why you are so rude. yes, wikipedia use the word gravity (accurately) and i expressed the same using the word acceleration. Now you seem to claim i am wrong, or wikipedia, or both. why? I am very puzzled. You insist other should support their every claim with math, but you refuse to substantiate your point with anything but a snarl.

You offer to "help" with the math as if I am too a poor little girl stupid to do it while not even understanding the problem you are offering to "help" with and now you take offense at asking to see the math you claimed you could do? Quite an interesting notion of being rude, asking to see what was offered.

If you can't do the math, fine, but don't get upset because you made a claim you can't back up. If you HAD bothered to read the thread, you would clearly see I made a claim AND did the math AND proved myself wrong and admitted it. Sorry, that's not a snarl. Not even close.

You're right, I do need you to show me the math. While I wait, I'll go back to helping my son understand how to calculate standard deviations for his homework. The other one is working on compound functions over time, I'll get to that after dinner.

this is not the behaviour of an intelligent person pointing out a mistake, but of someone who cannot admit a mistake.

It's a shame you didn't actually read the thread. It would show how utterly wrong you are.

i only expect you to tell me what you think i have done wrong.

You brought up shell theorem without understanding it.

You hinted this had something to do with a radius and i asked the radius of what?

YOU brought the theorem up AND even included it in some rudimentary equations you wrote down. I can't read the theorem for you!

I asked because as you are hopefully aware the shell theorem is independent of the radius of the object, that is, the acceleration of an object inside a hollow sphere is zero Independent of the radius of the sphere.

The shell theorem shows that gravitational acceleration between two bodies can be calculated using the center of those bodies because, effectively, the TOTAL gravitational acceleration inside nets out to zero as can be shown using two perfectly spherical but hollow bodies and how, relative to the internal coordinates, gravitational acceleration is calculated relative to ANOTHER body either inside or external to the spherical hollow mass (that's the radius you were missing, the second body). That doesn't mean there IS NO GRAVITY or that it is not stronger inside the body in one corrdinate than in another place. It just means that it NETS to zero.

There is also a shell theorem application for electrostatic systems. A rough analogy would be that, inside the bubble of the universe, the total amount of energy = zero yet we can still utilize energy to get work done.