The Earth is round. Circles mean the earth is round.
Why did Columbus think the earth was flat? Why did anyone think the earth was flat?
All they had to do was read the Bible; it's right there."
It was right there all the time. I guess we could save ourselves a lot of trouble and gain so much if we would take the time to read the Bible and process what we read.
God sits above the circle of the earth. The people below seem like grasshoppers to him! He spreads out the heavens like a curtain and makes his tent from them. Isaiah 40:22 NLT