Moon phases have captivating human imagination ever since we started looking up at the night sky. Inuit people from Greenland worshiped the Moon as a God and ancient Chinese believed that there are 12 moons around the Earth, each appearing for a month. Even today people around the world look up in the night sky, getting intrigued by our shining neighbor. But what does really cause the moon phases?
To understand why we have the different moon phases we first have to know that the Moon takes about 29.53 days to complete its orbit around the Earth. As the moon orbits around the Earth, progressing through its moon cycle, we see changes on the moon's appearance depending on how much light from the sun is reflected off the moon's surface. The amount of light reflected from the moon’s surface is depending on the position of both the sun and the moon relative to the position of Earth. The amount of light reflected gives us an easy and clear indication on how the moon is progressing through its lunar cycle, commonly known as moon phases.
- New moon
- Waxing crescent
- First quarter
- Waxing gibbous
- Full moon
- Waning Gibbous
- Third quarter
- Waning crescent
- New moon
It’s important to remember that everyone on Earth does not see the moon phases in the same way. People in the southern hemisphere will see the moon as “inverted” comparing to people observing the moon from the northern hemisphere. Reason for this is that the moon orbits around the equator of the Earth.
Key moon phases
From Earth we will see eight different phases during the lunar cycle, out of which four are recognized as key moon phases.
The moon cycle starts with a New Moon. This is the moment when the sun and moon are aligned, meaning that the Sun and the Earth are on opposite sides of the moon.
When we can observe a half of the moon from Earth we know that the moon has completed one quarter of its orbit. From earths northern hemisphere the right part of the moon is visible, while in the southern hemisphere the left part is visible. Near the equator, the moon is instead lying down where the upper part is lit during the moonrise and the lower part is the lit during moonset.
When the moon has progressed through half of its moon cycle the Sun and Moon will be on opposite sides of the Earth giving us the magnificent Full Moon. Occasionally, during the full moon we can also experience a rare phenomenon called “lunar eclipse”. Lunar eclipses only occur during the full moon and only if the moon passes through some portion of Earth's shadow.
The fourth key moon phase occurs when the opposite half of the moon is lit compared to the first quarter.
When the moon once again reaches the new moon stage the moon has fully completed its lunar cycle and progressed through all of its eight different moon phases.