Lunar Terminator Paradox

The lunar terminator paradox occurs because the Sun’s illumination on the Moon is fixed by the Sun’s position, not by the observer’s viewpoint. When the Moon rises, the illuminated portion remains constant, but the observer sees more of the Moon’s dark lower edge. The bright side then appears to point upward even after sunset. The paradox is most evident with a full or near-full Moon, where the entire disc is lit yet the observer sees a dark slice at the bottom.