When we look at the moon, the light that we see is actually the light of the sun reflected by the moon. Half of the moon is always in sunlight and half is always in darkness. Even though half of the moon stays lit, or illuminated, by the sun, the moon appears to have different shapes on different nights. These shapes are called phases. Different phases occur because we see different amounts of the lighted half of the moon on different days. The more of the illuminated side of the moon we see, the larger the moon appears to be. The less of the illuminated side of the moon we see, the smaller the moon appears. For example, during the full moon phase, all of the lighted part of the moon is seen from Earth and the moon appears fully lit. During the new moon phase, when the whole moon appears very dark, only the non-lit part of the moon is visible to Earth. The names of all the phases of the moon are shown below.

Question

When we look at the moon, the light that we see is actually the light of the sun reflected by the moon.  Half of the moon is always in sunlight and half is always in darkness. Even though half of the moon  stays lit, or illuminated, by the sun, the moon appears to have different shapes on different nights.  These shapes are called phases. Different phases occur because we see different amounts of the lighted  half of the moon on different days. The more of the illuminated side of the moon we see, the larger  the moon appears to be. The less of the illuminated side of the moon we see, the smaller the moon  appears. For example, during the full moon phase, all of the lighted part of the moon is seen from  Earth and the moon appears fully lit. During the new moon phase, when the whole moon appears  very dark, only the non-lit part of the moon is visible to Earth. The names of all the phases of the  moon are shown below.

GPT-4o mini · Answer

The phases of the moon represent the different ways the moon looks as it orbits Earth. Here are the main phases of the moon:

New Moon: The moon is between the Earth and the Sun, and the illuminated side is facing away from us, making it nearly invisible.
Waxing Crescent: A small, thin crescent of the moon starts to be illuminated as it moves away from the Sun, increasing in visibility.
First Quarter: Half of the moon is illuminated (the right half is lit in the Northern Hemisphere), and it appears as a semicircle.
Waxing Gibbous: More than half of the moon is illuminated, but it is not yet full. It continues to grow in appearance.
Full Moon: The entire illuminated side of the moon is visible from Earth, making it appear bright and round.
Waning Gibbous: After a full moon, the amount of illumination begins to decrease, but more than half of the moon’s surface is still lit.
Last Quarter: Similar to the first quarter, but the left half is illuminated (in the Northern Hemisphere).
Waning Crescent: Only a small crescent of light is visible as the moon approaches the new moon phase again.

These phases cycle approximately every 29.5 days, resulting in the moon's changing appearance throughout the month.