In reply to Mauro Lacy's message of Sun, 24 Oct 2010 22:33:48 -0300: Hi, [snip] >On 10/24/2010 06:28 PM, OrionWorks - Steven Vincent Johnson wrote: >> >From Mauro: >> >> ... >> >> >>> It is interesting to continue reading the explanation, >>> for the force exerted on points inside the sphere. >>> >> Indeed, I bet it does get interesting! In my own computer simulations, this >> is where I've had to play god, so-to-speak, and change the algorithm used >> when the orbiting body presumably passes underneath the "planetary" surface >> of the main attractor body. At that point one has to jigger a different set >> of rules since, technically speaking, a point source no longer exists. It's >> like diving into a swimming pool. The water (the source of gravity) is all >> around you.
AFAIK, that portion of the body that is at a greater radius than your own has no effect on you. IOW you can base your calculations on a that of a body with a radius equal to your own. It's effectively as though the planet shrinks with you. By the time you reach the center, there is no planet left, and the net effect is zero. Calculations would be simplified by assuming a constant fixed density for the planet. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/Project.html
