Why is this the answer?

The answer is moon because this clever riddle describes our wonderful neighbor in the sky that changes its look every night. Let us look at the first clue, which is a bit tricky: "It comes only before, it comes only after." This clue is all about the moon's place in time. The moon is always a part of the cycle of the day and night. It comes *after* the sun goes down, but it also comes *before* the sun comes up again in the morning. Even more interesting is the moon's shape. It is always changing from a tiny sliver to a bright circle, and then back again. So, every time you see the moon, it is either growing *before* it becomes a full moon or shrinking *after* it has been a full moon. It is always in a position of being next to something else. The next part is a very good clue: "Rises only in darkness, but rises only in light." Most of the time, we see the moon rising after the sun has set, when the sky is dark. That is the "rises only in darkness" part. But sometimes, if you look carefully in the late afternoon or early morning, you can see the moon rising even when the sun is still out and the sky is bright blue! This happens because the moon follows a path around the Earth, and sometimes that path brings it up over the horizon when the sun is also visible. So it can rise in darkness and light, depending on the time of the day and its location in space. Finally, the riddle says, "It is always the same, but is yet always different." The moon itself is always the exact same huge, round rock floating in space. It is always there, and its true size and shape never change! That is the "always the same" part. But the way the moon *looks* to us changes every night because of its phases. It can be a skinny, curved crescent, a half circle, or a giant, glowing full circle. These different shapes and brightness levels make it feel "always different." The moon is a constant, steady friend that just loves to wear a new outfit for us every night. It fits all the clues perfectly!