Scientific questions

I have many questions relating to many areas of science. In order that I might actually pursue answering some of these I am attempting to chronicle some of these and even lay out possible hypothesis testing for some of my ideas. So here are some of my current ideas.

Is it possible that man has mistakenly assumed that scientific laws that hold for small scale reactions, both nuclear and chemical, do not hold for large scale reactions. Is it possible that when matter is significantly large that different laws come into play that can cause a reaction to be virtually self sustaining. For instance, is it possible that a mass significantly large would generate enough force from gravity alone that it would sustain a certain amount of heat for almost eternity? Could it be that earths crust offers enough insulation that its core will remain almost indefinitely heated?

What about the sun? We are not at all sure of all the forces playing in reactions on the sun. Is it possible that chemical, nuclear and gravitational reactions simply more or less cycle? I know the second law of thermodynamics would lead us to believe otherwise. But is it possible that we have missed something? How would we test such a hypothesis?