How do we know?
↻ One of the pages with a moving picture
The Moon always shows us the same face, and a spacecraft went to see the other one.
- The Moon makes no light of its own. Sunlight always lights up half of it.
- The Moon travels around Earth about once a month.
- As it moves, we see more or less of its sunny half.
- These changing shapes are the Moon’s phases. There are 8, from new Moon to full Moon and back.
The Moon keeps the same side facing us. In 1959 a spacecraft flew past and saw the far side for the first time.
At new Moon, the far side is in full sunlight. The lit half of the Moon is simply turned away from us, so we see only a dark disk.
On 16 July 1969 Apollo 11 left Florida, taking the first people to walk on the Moon.
Wow number
29.5 days from one new Moon to the next. Then the phases start all over again.
Myth or fact?
Earth’s shadow makes the Moon’s phases. Myth. Earth’s shadow only falls on the Moon during a lunar eclipse.
You can sometimes see the Moon in the daytime. Fact. It is up by day as much as by night.
Think about it
Look at the Moon tonight. Is the lit part getting bigger or smaller each night?
Where in the world?
Kennedy Space Center, Florida where Apollo 11 left on 16 July 1969. Down in Australia the Moon shows the same phase, but upside down — 28.5729° N, 80.649° W.
Where these facts come from
Every number on page 9, and who measured it
This page tells us the Sun always lights half the Moon, and how long the phases take.
Moon Phases — NASA, the U.S. space agency
science.nasa.gov/moon/moon-phases
We checked it on 31 October 2026
This page shows how we see more or less of the Moon's sunny half.
What Are the Moon’s Phases? — NASA Space Place, NASA's science site for kids
spaceplace.nasa.gov/moon-phases/en
We checked it on 31 October 2026
This page tells us when Apollo 11 launched for the Moon.
Apollo 11 — NASA, the U.S. space agency
nasa.gov/mission/apollo-11
We checked it on 31 October 2026
This page tells us about the Moon's far side and why you can see the Moon in the daytime.
Top Moon Questions — NASA, the U.S. space agency
science.nasa.gov/moon/top-moon-questions
We checked it on 31 October 2026
This page tells us when people first saw the far side of the Moon.
Moon Facts — NASA, the U.S. space agency
science.nasa.gov/moon/facts
We checked it on 31 October 2026
Has this changed?
The Moon has gone through its phases for a very long time, so this answer is not going to change.
The 29.5 days is an average. The exact moment of each new Moon is worked out ahead of time and published by NASA.
Words from this page
- phases
- The different shapes the Moon seems to have as we see more or less of its sunny half.
- lunar eclipse
- When Earth’s shadow falls on the Moon.
Try it!
Make your own Moon phases in a dark room.
1. With a grown-up, switch on a lamp with no shade in a dark room. Don’t touch the bulb: it gets hot. 2. Hold a ball at arm’s length, just above your head. 3. Turn slowly in a circle and watch the lit part of the ball.
What happens: you see a crescent, a half and a full “Moon”. The ball is always half lit!
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