| MadSci Network: Physics |
Dear Vidyaranya,
As you surely know, G is the proportionality constant uniting the attraction between two bodies, their two masses, and the distance separating their centers. The numerical value and the units used will always depend upon the choices for the other five variables. The same is true for other physical constants such as the constants in the Ideal Gas Law, Coulombs Law, and the rest. Conventions may standardize those choices; but the fact remains.
You need to remember that these "constants" are the results of specific measurements on the other values. To date, they have all been done on the surface of the earth and rather recently. This does not mean that G might be some other value at a distance from us or that it didn't have a different value in another millennium.
Kepler's Laws for the Solar System imply a constant G for our planets. As we find more planets (nearly 600 discovered), we may find star systems that also follow Kepler's Laws. If so, it will imply a constant value for G at that location, but not necessarily the same as ours.
Theories abound when little is known. Cosmologists are trying to tie a lot of loose ends together. The very nature of gravity is one of them. How mass is related to gravitation is just one of the things that still needs understanding.
Look at the references available. You may want to start with the following: http://books.google.com/books?
Always remain curious,
Gene Ewald
[note added by MadSci Admin: Also Google
"gravitational constant" +changing
including the quotation marks.]
Try the links in the MadSci Library for more information on Physics.