<human>:  Why did the ancient Greeks think that the earth was flat?
<bot>: Well, they didn’t. They believed that the earth was a sphere, but they didn’t know why. They thought that the earth was flat because of their observations of the stars and the moon. The ancient Greeks were very interested in astronomy, and they were the first to use the telescope. They also used the telescope to study the stars and planets, which gave them a lot of insight into how the universe works.