Anyone can see that Earth looks like a circle from outer space since the Moon looks like a circle from Earth.
Seattle:
How would anyone, prior to the 20th century "see" that earth looks like a circle from outer space, based upon their view of the moon? The moon and the earth are two entirely different planets.
People on earth can see that the moon is a circle, because the moon is far enough above for them to see it in its entirety. But there was no opposing viewpoint in the 8th century B.C.E. when Isaiah stated correctly that earth appears as a circle when viewed from outer space. Why so? Because there was no space shuttles in the 8th century so that people could hover in outer space, far above earth. Isaiah was earthbound.
Alter2Ego