Final answer:
The Earth was never flat according to scientific discoveries. Copernicus challenged the Ptolemaic model with his heliocentric theory.
Step-by-step explanation:
The idea that the Earth was flat was a common belief in ancient times, but it was eventually disproven. The Ptolemaic model, which was widely accepted before the discoveries of Kepler, Copernicus, Galileo, Newton, and others, believed that the solar system revolved around the Earth. However, Copernicus challenged this view with his heliocentric theory, which proposed that the sun, not the Earth, was at the center of the universe.