Theory of Mutuality

Since the Universe is expanding, it could be because the stars having a very high temperature repel each other. Gas molecules also repel each other at temperatures above the boiling or liquifaction temperature. With apology to Newton, it seems that the mutual force existing between two bodies is related to their masses, temperatures and mutual distance, and can be either attractive or repulsive (positive or negative) depending on these three (or more?) factors. The problem is that we have calculated the mass of the Sun based on the gravitational constant derived from forces between brass balls at earth temperature. It is possible that the actual mass of the Sun is many times greater and the specific force of mutuality between the Earth and Sun as may times smaller. Now don't ask me to fit the Big Bang into my Theory of Mutuality.