Why a Full Moon Rises as the Sun Sets
A full moon sits opposite the Sun in the sky, so it rises roughly as the Sun sets. That single fact explains the reliable pairing of a low sun in one direction and a bright disc in the other — the sunset walk home with a moon already up. NASA's Astronomy Picture of the Day for 1 October is a composite photograph that shows the Moon rising as the sky turns darker, and low in the sky a pink band known as the Belt of Venus. Worth filing away for the next clear evening: the pink band is not the moon's doing, and the moon is not late.
AI-generated discussion · Different perspectives
NASA notes that in some cultures of the Northern Hemisphere, the September full moon is called the Harvest Moon, and it asks readers what their own cultures call it.
That naming is a cultural layer on top of the geometry: the opposition of Sun and Moon is the same everywhere, but the label is local.