who discovered first that the Earth has a spherical shape?

Answer 1

Ancient civilizations knew this. Observations of lunar eclipses, plus the fact that the horizon is at equal distances no matter what direction we look made this pretty obvious. The earliest were probably the Assyrians or Babylonians, who developed the first coherent astronomical systems (claims by people that the natives of India were first notwithstanding)

The issue was not the shape of the earth, but its size, and its place in the scheme of things (at the center or off to the side.) It took thousands of years to displace the earth conceptually from the center of creation to a planet orbiting a star, which was then displaced from the center of the universe to a position in an outlying arm of our galaxy, which itself was displaced from being the entire universe to being the largest galaxy and at the center of the universe to being just another galaxy among billions. So we're just a bunch of hicks from the sticks.

Answer 2

The Greeks and Phoenicians knew it at least 2300 years ago. Then a christian mob burned the library where the information was stored and it was forgotten for about 1000 years until the Renaissance explorers rediscovered it.

Answer 3

Actually, the earth is not round, it somewhat elliptical due to centrifugal force at the equator, hence the equator circumference is
24,902 miles, while the polar equator is 24859.82 miles
Therefore the earth is NOT round at all, but a bit flattened.

So I would make the observation that no one has proven the earth to be "round".

Answer 4

Even before Ancient Egypt and before the Sphinx. People don't even know that the Sphinx is secretly 10,500 years old, no lie.

Answer 5

The ancient Greeks certainly knew it, so it is getting on for an idea that is 2500 years old.

Answer 6

Gailieo was the first one to publicly announce it but he received much criticism for this and it was still not acknowledged by the public...

Answer 7

Nicholas Copernicus
just learned about him!