What causes the moon to have phases?
The moon appears to have phases due to its relative position to the sun and the Earth. The phases of the moon occur as a result of the moon's orbit around the Earth.
The moon does not emit light of its own, but rather reflects the sunlight that falls on it. As the moon orbits around the Earth, different portions of the moon's illuminated side become visible to us on Earth, creating the different phases.
The four main phases of the moon are:
1. New Moon: This is when the moon is positioned between the Earth and the Sun, and the side of the moon that is illuminated by the sun is facing away from us. As a result, the moon appears dark and is not visible from Earth.
2. Waxing Crescent: As the moon moves slightly away from the sun, a small portion of the illuminated side becomes visible from the Earth, resulting in a crescent shape.
3. First Quarter: At this stage, half of the moon's illuminated side is visible from the Earth, resembling a half moon shape.
4. Waxing Gibbous: As the moon continues to orbit, more than half of the illuminated side becomes visible, resulting in a larger, almost fully illuminated moon.
These four phases are referred to as the waxing phases, as the moon's visible side is gradually increasing in size.
After the Waxing Gibbous phase, the moon enters the following phases:
5. Full Moon: The moon is now positioned opposite to the sun, with its entire illuminated side facing the Earth. It appears as a complete, round-shaped disc.
6. Waning Gibbous: As the moon starts moving closer to the sun again, its visible illuminated side decreases gradually, resulting in a slightly smaller but still mostly illuminated moon.
7. Third Quarter: Half of the moon's illuminated side is visible again, but this time in the opposite direction, resembling another half moon shape.
8. Waning Crescent: The moon continues to move closer to the sun, and only a small portion of its illuminated side is visible, once again in the shape of a crescent.
Finally, the moon returns to the New Moon phase, and the cycle starts anew.
This continuous cycle of moon phases occurs because of the moon's orbit around the Earth, combined with the sun's illumination from different angles.