Question

the person who discovered that the earth is spherical in shape

Answer 1

It was a Greek scientist Pythagoras who called earth as sphere in shape for the very first time 

Answer 2

Diogenes Laertius says that Pythagoras was the first Greek who called the Earth round. But there are others like Theophrastus who says that Parmenides was the first one to discover this. Zeno says that Hesiod was the first one to do so.