The moon is the brightest celestial body in the night sky. It shines so brightly on full moon nights that some people find it difficult to sleep. It appears as big as the sun and the stars look like tiny points of light next to it. Also, the tasks are clearly divided: the sun shines during the day and the moon shines at night. But that’s not true at all: the moon can sometimes be seen during the day – how is that possible?
The moon is visible during the day for the same reason why we see it at night. Because it is illuminated by the sun. Exactly when we see the moon and in what form depends on the phase of the moon, and the position of the moon in relation to the earth and sun.
When the moon is close to ‘new moon’ cycle it is not visible during the day
Day and night have a simple cause: The earth rotates. When our location on Earth is facing the sun, it is bright, i.e. day. Later, when the earth continues to turn, our location moves to the side away from the sun. We see the sun go down and it is getting dark.
The moon also rises and sets – for exactly the same reason. But the moon also moves: it orbits the earth in 27.3 days. Half of this time its orbit runs on the side of the earth facing away from the sun. From there you can see it whenever your location is turned away from the sun – or in short: when it is night.
But two weeks later, the moon is on the side facing the sun. Then it is the other way round: You see it together with the sun during the day when your location is facing the sun. From midday to midnight the moon can be seen with its crescent widening. The full moon is visible all night, the waning moon remains above the horizon until noon. The moon is best seen during daylight in the first and last quarter of its cycle.