Answer:
When Copernicus first systematically created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model because the Catholic Church, which was the power at the time, stated it was false, and anybody who believed Copernicus and spread the "myth" were excommunicated or even executed. This was because a sun centered universe would mean that everything the Catholic Church had been teaching about how the Earth was the center of the universe would be false. If people believed it, the church would no longer be seen as the infallible authority, so they needed to stop it from spreading.
Its a chemical change. Think of it in a way of being able to change it back to its original state. You cant change something back to its original state if its a chemical change. You can however turn something back to its original state when it under goes a physical change.