hat percentage of the entire Earth is illuminated at any instant? (50%).
What percentage of the entire Moon is illuminated at any instant? (50%).
Is the percentage of illumination changing as the Moon revolves around the Earth? (No it is always 50%)
When any observer on the daylight side of the Earth looks at the Moon, how much illumination can they see? (0%, the dark side of the Moon is facing the Earth.)
When any observer on the nighttime side of the Earth looks at the Moon, how much illumination can they see? (100%, the dark side of the Moon is facing away from the Earth.) Thus, since 50% of the Moon is always illuminated, lunar phases are due to the changing geometry – the fact that the angle between the Sun and the Moon as seen from the Earth is changing.
What would the Moon look like from the Earth in this phase? (50% of the visible surface of the Moon is illuminated – light on
