What happens to the moon’s visibility as it goes through its phases?

• A. It disappears completely
• B. It changes in shape and illumination
• C. It becomes larger
• D. It moves further away

Answer: (B)

As the moon goes through its phases, its visibility changes in terms of shape and illumination due to its position relative to the Earth and the Sun. The phases of the moon—from the new moon to the full moon and back—result from the changing angles at which sunlight strikes the moon, as well as how much of the illuminated part of the moon is visible from Earth.

During the new moon phase, the moon is positioned between the Earth and the Sun, making it generally invisible since its illuminated side is facing away from us. As the moon moves in its orbit, more of its illuminated side becomes visible, creating the waxing crescent, first quarter, and waxing gibbous phases leading up to the full moon, where the entire face is lit. After the full moon, the cycle continues with the waning gibbous, last quarter, and waning crescent phases, showing decreasing illumination until it returns to the new moon.

This consistent variation in shape and illumination is what characterizes the moon's cycle, making it a fascinating subject in astronomy.