I wish the aliens would come and just tell us everything. If they can travel through space at light speeds and beyond, they must know everything or damn close to everything.
Depends on your frame of reference and scale. Functionally, the earth is flat in most cases of our daily lives. Just like functionally I don't need to consider general relativity when calculating speed, distance and time. Newtonian motion is an approximation just like the earth's flatness is an approximation. Work with the approximation when it is valid and it will save you a hell of a lot of computational time. Using the approximation when it is not valid could cost you your life.
Go back to school study science then come bk and tell us if the earths round or flat..do u know what gravity is?