Concerning the variable rate of the angular momentum transferred between the earth and moon.
I remember reading an article recently (on talkorigins.org?) which provided the theory that the shape of the land masses alter the rate at which the moon drags on the earth.
This sort of makes sense. The big bulge of water the moon is making that we call the tides is going to drag a lot less against one super continent called pangaea, then against a series of spread out continents which go almost from the north end to the south end of the earth.
Anybody heard about this/understand it/have links?
Perhaps i should let sleeping dogs lie, but I can’t resist.
Raydot14:
Gravitational attraction is a nonlinear function of distance. It is proportional to the square of the radius from one center of mass to another.
An elementary result from first-year college physics is the proof that a uniform spherical shell of matter exerts no gravitaional force on anything inside.
From these facts, it’s relatively easy to calculate the relationship of a non-black-hole star to some piece of matter (which might be part of the star):
A. Either the matter is outside the star and is far enough away that it can (but not necessarily will) escape the gravitational pull of the star, or
B. The matter is inside the star and is not affected (graitationally) by the portion of the star’s matter that is farther away from the center, and can (but not necessarily will) escape.
A black hole forms only when the star contracts enough that the mass inside a relatively small radius from the center is high enough to prevent escape.
As for the energy questions, a star radiates energy by “converting” mass to energy. (It’s more correct to say that it converts one form of mass-energy to another form). A star can lose a lot of photons without a measurable effect on the mass, but eventually the star’s mass is reduced noticably.
The process of collapse and/or explosion is complicated, because of radiation pressure and thermal effects and the size of a star (it takes a long time for something to propagagate from the center of a star to the outside).
I'm afriad I must object to the term "elementary" here. While I have the stated education, I certainly don't regard the calculation as elementary, nor was it something that was discussed. (Gravity was barely touched upon, never applied.)