The Moon makes no light of its own. It glows with reflected sunlight, and the Sun always lights exactly half of it. The Moon orbits Earth about once a month, so we see that lit half from a changing angle. That is why its shape seems to change from new to crescent to quarter to full and back. Earth's shadow is not the cause. This week the crew models the phases with a lamp, a head for Earth and a small ball for the Moon, and starts the nightly Moon log.