How come I can see the moon and sun at the same time and yet it is not a full moon, when it seems that the sun can shine directly on the moon?

Answer

Dear Tim,

at full moon we see the moon fully lit. The side that is turned towards us is therefore turned towards the sun, so that it is completely illuminated by it. Usually at such a moment the moon is illuminated from something ‘above’ or ‘below’ the Earth. When the sun is really exactly behind the Earth, we see a lunar eclipse. With a full moon you can never see the sun and the moon together.

With other moon phases, such as half moon, it can happen that the sun and moon are together in our field of view. You will then see e.g. on the left the sun and on the right the moon with the left half illuminated. That left half that we see is indeed illuminated directly by the sun, together with the left ‘back’ half of the moon, which we cannot see from our position.