Any process which is spontaneous and irreversible must involve a (positive) change in entropy of the universe
This is one condition to the spontaneity of a process that the overall universe (System + Surroundings) must experience a positive entropy change.
Going back some 4.5 billion years:
- The sun is just a hot ball of gas with huge amount of debris floating around randomly in any direction
- Over a period of time a fundamental force called gravity pulls all this debris into a fiery ball of molten rock
- This ball slowly cools down and its layers start to get ordered by their own weight
Now considering all the matter on this tiny planet was once a chaotic jumble spread over many many million kilometers why would all of this rocky mess ever come together spontaneously via gravity. The earlier mess surely represents a highly chaotic state and a planet is mostly well arranged layers of solid and molten rock by their weight which by comparison seems highly ordered. So apparently a spontaneous decrease in entropy has occurred which is quite counter-intuitive to my mind. Could someone help me understand the relation between gravitational attraction, formation of planets and entropy