"How can the earth possibly change from a sphere to a flat disc?"
It didn't change. It never was a sphere. It was a theory that was rammed down the throats of the people against all logic and has instilled hopelessness in the masses ever since. The basic Heliocentric model had flaws, so ad-hoc fixes have been added to the initial error over the centuries thus creating the nonsensical model of today that most people believe to be fact. Most of the stuff taught in schools today as fact were still considered "theory" when I was in school. https://www.youtube.com/watch?v=8tFhA3ZepFs https://www.youtube.com/watch?v=C0KeDx9wGA8 https://www.youtube.com/watch?v=gu046L-dzNM