Introduction to the Moon

The phase of the moon we see depends on from what the direction the sunlight's hitting it, and the angle we see that from Earth.

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The moon goes through all its phases 29.5 days.

The word moon can be traced to the word mona, an old English word from medieval times. The moon is called the moon because it is used to measure the months.

​​The Moon

Multiple Choice

How many days does it take for the moon to go through it's phases?

• 29.5 days
• 365 days

• 24 hours

• 12 months

Moon Phases

​New Moon
New moon happens when the Sun, Moon and Earth are all more or less in a line. The Moon's orbit is actually tipped a bit to the Earth. New Moon happens when the Moon is below the sun or above it. The Moon appears to be as close to the Sun as it can.

The Moon is between the Earth and the Sun, so from our perspective we only see the dark half, the unilluminated half of the Moon.

​First Quarter Moon


The Moon is 90 degrees away from the Sun in the sky. The Moon is half lit, with the sunward side of the Moon visible and the other side dark. The Moon is 1/4 of the way to its orbit around the Earth.

Full Moon comes 2 weeks after new Moon, when it moves halfway through it's orbit. It is now opposite the Sun in the sky, 180 degrees around. The Earth is between the Moon and the Sun so we're looking at fully illuminated half of the Moon. This is the full Moon.

​Full Moon

​Third Quarter Moon

The Moon is 3/4 away to its cycle. It's a lot like first quarter but the side that was lit is now dark and vice versa. It's 270 degrees around the sky from the Sun. It rises at midnight and sets at noon.

Multiple Choice

Why does the moon appear to change its shape over the course of a month?

• The sun orbits the moon.

• The moon orbits the earth as the earth orbits the sun.

• The earth orbits the moon.

• Both the sun and the moon orbit the earth in one month.