Why does the moon appear to change shape throughout the month?
AClouds cover different parts of the moon each night
BThe moon shrinks and grows each month
CAs the moon orbits Earth, we see different amounts of its sunlit side from our viewpoint
DEarth's shadow covers different parts of the moon each night
The moon is always half-lit by the sun (the sun always illuminates one side). As the moon orbits Earth over 29.5 days, our viewing angle changes, so we see different amounts of that lit half. At full moon, we see the entire lit side. At new moon, the lit side faces away from us and we see the dark side. In between, we see partial views -- crescents, quarters, and gibbous shapes.
Question 2 True / False
The moon produces its own light, which is why it glows at night.
TTrue
FFalse
Answer: False
The moon has no light source of its own. What we see as moonlight is actually sunlight bouncing off the moon's surface and reaching our eyes. The moon's surface is rocky and gray, but it reflects enough sunlight to light up the night sky. If the sun were to disappear, the moon would go completely dark.
Question 3 Short Answer
What is the difference between a full moon and a new moon?
Think about your answer, then reveal below.
Model answer: During a full moon, the entire sunlit side of the moon faces Earth, so we see a fully bright, round moon. During a new moon, the sunlit side faces away from Earth and we see the dark side -- so the moon is essentially invisible in the sky. Full moon and new moon are opposite points in the moon's monthly orbit around Earth.
Understanding full moon and new moon as opposite viewing angles (not as the moon growing or shrinking) is the key insight. The moon is always half-lit; the question is how much of that lit half we can see from Earth.