Lunar Terminator Paradox

The "lunar terminator paradox" is an optical illusion where the illuminated portion of the moon appears to point upward even after sunset, when we'd expect it to point toward the sun below the horizon. This occurs because we view the moon from below, and as it rises higher in the sky, we see more of its dark side at the bottom edge, making the bright portion appear to point up—an effect most pronounced during nearly full moons. The author created a visualization program to clarify this phenomenon, which he found existing AI tools were unable to properly explain despite having access to incomplete online descriptions.