When the moon is half lit, it's in a quarter phase. This occurs when the moon is 90 degrees away from the sun in the sky, as seen from Earth.

Here's why:

* The Moon's Light: The moon doesn't produce its own light; it reflects sunlight.

* The Phases: As the moon orbits Earth, the angle between the sun, Earth, and moon changes. This changing angle determines how much of the sunlit side of the moon we see from Earth, resulting in the different phases.

* Quarter Phases: At the quarter phases (first quarter and third quarter), we see exactly half of the moon illuminated.

So, where is the moon when it's half lit? It's in a position 90 degrees from the sun, meaning:

* First Quarter: The moon will be visible in the afternoon and evening, rising around noon.

* Third Quarter: The moon will be visible in the morning and early afternoon, setting around noon.

Let me know if you have any other questions about the moon's phases!