Human: Who was the first person to discover that the earth is round? Assistant: 
That would be the ancient Greek philosophers. They believed that the earth was flat, and they thought that the sun revolved around the earth. However, in the 16th century, Nicolaus Copernicus proposed that the earth was actually round, and that the sun revolved around the earth. This theory was later confirmed by Galileo Galilei, who used a telescope to observe the moons of Jupiter.