Lessons / Space

Moon Phases

Half of the Moon is always lit by the Sun. Move the Moon around Earth and watch how much of that lit half you can see. Learn to tell waxing from waning.

Free

Moon lab

Drag the Moon, pick a phase, or press Play

Seen from above the North Pole · not to scale

Half of the Moon that faces Earth (always the same half) You, with the Moon highest in your sky

Position 60°

Seen from

Speed 2 days/s

When is the Moon up?

Rises about 10 AM, highest about 4 PM, sets about 10 PM.

Rough times: the Sun rises at 6 AM and sets at 6 PM (as at an equinox), and times are rounded to the hour. The Moon rises about 50 minutes later each day. Real times shift by an hour or two with your latitude and the season.

Phases

Jump to a phase

Each picture shows the phase as seen from the Northern Hemisphere. Day = days since new moon.

Live readout

Moon position60° Days since new moon4.9 of 29.5 PhaseWaxing Crescent Waxing or waningWaxing (growing) Lit part you see25%

What you're learning

Half of the Moon is always lit by the Sun, just as half of Earth always has daytime. The phase is how much of that lit half faces you.

Waxing: the lit part grows each night. Waning: it shrinks. Crescent: less than half lit. Gibbous: more than half lit.
From the Northern Hemisphere a waxing Moon is lit on the right. From the Southern Hemisphere the Moon looks upside down, so it is lit on the left.
A full cycle of phases takes about 29.5 days. Measured against the stars, the Moon circles Earth in 27.3 days. Earth moves along its own orbit meanwhile, so lining up with the Sun again takes about 2 more days.
The Moon turns once for each trip around Earth, so the same side always faces us (the red-orange edge in the lab).

Myth: "Earth's shadow makes the phases."
Reality: Earth's shadow only reaches the Moon during a lunar eclipse, which can happen only at full moon.

Practice

Name the phase from a picture of the Moon or from its place in orbit

Score: 0 Streak: 0 Attempted: 0

Choose the phase

Score counts answers you get right on the first try.