Features:
This change in circumpolar stars is consistent with the spherical Earth theory.
The behavior of the Sun on the celestial sphere in the course of the solar year = 365.2421897 days (J2000) as function of latitude is also consistent with thte spherical Earth theory.
Another perspective on the same point is that the horizon is always on average the same distance away no matter where you are on Earth. It moves with you. Again a spherical Earth explains this.
Perhaps for sailors on Mediterranean Sea, it may have been noticeable that the horizon is the same distance away whether you are at the eastern or western end.
But what if the Mediterranean Sea was just so remote from the edge of the flat Earth, that the varying distance to the horizon was too small to notice. But in this case, solar time should be almost the same throughout the Mediterranean Basin. However, the ancient Greek astronomers eventually knew this was NOT the case since the stages of lunar eclipses happen at different solar times at different locations even though the stages happen, of course, at the same absolute time. So either the Sun AND the horizon were NOT so remote (in which case you would notice varying distance to the horizon which you do NOT) or the Earth was NOT flat and the horizon (which was NOT so remote actually) moved as you moved on the Earth.
Credit/Permission: ©
David Jeffery,
2003 / Own work.
Image link: Itself.
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File: Ancient Astronomy file:
parmenides_earth.html.