When Rabbi Joshua ben Hanania went to Athens to dispute with the philosophers there, they asked him many questions, and he answered them all successfully.

One of their questions was: "Where is the center of the earth?"

Rabbi Joshua pointed with his forefinger to a spot on the ground nearby, and said, "Here."

They said, "How do we know that you are right?"

He said, "Bring your measuring rods, and measure it for yourselves." (Talmud)