Who the heck is "we"?
You don't know the size or shape of the earth. I don't think you have verified the ancient Greek mathematics, nor have you verified the bogus mathematics of Copernicus. And anyone who studies science seriously knows that all science is theoretical, which means it mainly relies on consensus for its validity. Almost nothing is "proven", and theories change.
You believe what you believe because it's what you've been told for a long time. But, alas, you have no proof of your own, just ancient rumors and theories about life.
Cheers!