Phases of the Moon

By: Sophie Lawrence, Ph.D.

The First and Third Quarter

All moon phases are different, but some have more in common than others. Take the First and Third Quarter Moons. Both have about 50% of the total amount we can see showing, which is why most younger children call them a "Half Moon". In relation to the positions during both phases, they form at a 90 degree angle between the Earth, Sun, and Moon.

Waxing or waning?

Really, the only way we can tell the two "half moons" apart, is by which side the reflected light is on. When the moon is waxing, the 'lit' part will be on the right side. When the moon is waxing, the light will be on the left side.

the moon and me

My Time on the ISS Changed My Moon-Viewing Perspective.

When an astronaut is viewing the moon from the International Space Station, they're in a different position than those astronomers on Earth. From the ISS, you can see the sun, moon, and the Earth all at once. You're orbiting the Earth, just like the moon. Therefore, you see all sides of the moon, which makes it look like there aren't any moon phases. From Earth, you can't even see the sun and the moon at the same time, and since the moon is orbiting around you, the phases "occur" like always.

Moon View from earth vs moon view from Iss