A Final Word: Gravity.
Isaac Newton discovered that Kepler's 3 laws would automatically occur if gravity had the form:
Force of gravity
|
|
=
| |
Mass1 x Mass2
R2
|
Force of gravity depends only on Mass1, Mass2 and R (distance).
As either mass increases, force of gravity is stronger.
As distance increases, force of gravity gets *much* weaker.