When was Earth discovered?

Earth was not discovered by anyone. It was here long before the first mammal set foot on the planet. Earth was eventually found to be the third planet orbiting the Sun in the solar system. Although its spherical nature was surmised by the Egyptians, Sumerians, and the Greeks, it was not until the time of Copernicus in the sixteenth century that the Earth was commonly understood to be a planet orbiting the Sun.