How did Copernicus and Kepler change peoples view of the world?

They were the first 'modern' (well, medieval) scientists to come up with the "heliocentric" view of the universe: the concept that the Earth revolves around the Sun and is not the center of the Universe itself.

It should be mentioned that ancient Greek scientist had already discovered that some 1,500 years earlier, but their writings had been more or less forgotten by then. Well, not quite: it was much later discovered that Copernicus referred specifically to those earlier Greek findings in the draft of his book, but left it out in the final text.