Phases of the Moon: Script (30-40 minutes)

Get phase names from the audience, then have them predict how they go together. Then show in the planetarium. At each phase, where is the Sun so that the Moon is illuminated in this way?


  1. Latitude: Home
  2. Precession: Current
  3. Set Sun and sky for nearest full Moon.
  4. Time: Just before sunset.
  5. Turn on Sun, Moon
  6. Laser pointer
  7. Lights up
  8. Styrofoam ball with clay on one side to simulate the Moon with heavier maria.

Dialog is in normal type, actions for you to do are in italics, audience parts are in bold italics and indented.

Note: the following script is not meant to be followed word-by-word; rather, use it as a guide. Embellish it, change it, whatever you feel most comfortable with. We do suggest, however, that you involve your audience as much as possible. Have them predict results, explain results, use the laser pointer, make comments, ask questions. A good way to get questions: "Before we conclude this program, I need to hear 5 questions about the night sky." Also, TRY to always run the planetarium FORWARD in time when you have people in there. Otherwise, they sometimes get confused about which direction things move.

Getting Acquainted

Good morning (or afternoon)!

Introduce yourself. Remind audience that there should be no eating or drinking in the planetarium. Have them put their packs, coats, etc. under their seats.

How many people here have seen the Moon?

That's right! Nearly everyone has seen the Moon at one time or another. How many people have seen the 'Man in the Moon'? (alternatively the Energizer Bunny in the Moon---it's up to you whether you put this in their heads. Once you've seen the bunny, there's no going back!) How many times have you seen the Man in the Moon? (Pick on some people.) Can you always see the Man in the Moon when you can see the Moon? This is where the phrase 'Dark Side of the Moon' comes from. We always see the same side of the Moon! So the other side, which we don't ever see from Earth is called 'Dark', even though sometimes it's in the sunshine. Does it seem weird that we would always see the same side of the Moon, even though it's free to turn out there in space? That's right. Since it's so weird, there must be a reason, and of course there is. The near side of the Moon is quite literally heavier than the far side! That's because the near side had a thinner crust when the Moon was young, and lava flowed through the crust making big pools of dark rock called 'maria'. These are the markings that we see as the Man in the Moon. Let's investigate this a little more. Use your prop to demonstrate that if a round object has a heavy side, that heavy side will always point down towards the Earth, no matter how you twist it, as soon as you let it go, it swings heavy side down. Explain that the maria are like your lump of clay. They make the Moon heavier on the near side, so that it swings always with that side towards the Earth.

Does this mean that the Moon doesn't spin on it's own axis? Let's take a vote. How many people say 'yes'? How many people say 'no'? Well, let's check it out! I need two volunteers. Take two volunteers from the audience. Indicate one person. You are now the Earth. Hi Earth, how are you? Clown a little bit, and turn to the other person. You are the Moon. How are you, Moon? The projector is the Sun.

Now, let's pretend that the face of our Moon is really the face in the Moon. We'll start at full phase. Arrange the volunteers accordingly---Sun, Earth, Moon, with the Moon facing the Earth Here is what happens if the Moon does NOT turn on it's axis. Move the Moon around the Earth, COUNTER-CLOCKWISE. You will probably have to hold the person's shoulders in order to keep them from turning around! See how here at third quarter, the Moon still faces the Sun, so we know that it didn't turn on it's own axis. But the Earth can no longer see the whole Man in the Moon! Let's continue on to new moon. Now the Earth can't see any of the Man in the Moon! And at first quarter, the Earth can only see half of the Man in the Moon again. So this can't be what's happening. The Moon MUST rotate on it's axis! Let's try that and see what happens.

Here we are at full Moon again. Now, we will allow the Moon to turn, so that different sides may face the Sun, but the same side always faces the Earth. Move the Moon around the Earth, COUNTER-CLOCKWISE. You probably won't have to hold the shoulders this time. See! The Moon spins around it's axis once in exactly the same amount of time that it takes to go around the Earth!

Are there any questions? Take and answer questions. Some people won't have 'gotten it'. Depending on how many there are, you might ask them to pair up and all do the same thing.

Great questions everybody! Now, let's see what this looks like in the sky. Here, I've got the planetarium set up for (date), the date of the next/last full Moon. Notice that the Sun is there in the west, and the Moon is in the east, just rising. In our previous example, the machine was the Sun. But what does it really represent? That's right, the machine is in the place where the Earth should be! Now, looking at this setup, can you see that the Sun, the Earth and the Moon are all approximately in a line? What do you think will happen as the month progresses? Let's find out! Run the planetarium forward in time, slowly, so that they can see the Moon becoming less illuminated. Stop about halfway between full and third quarter and point out that they can still see the Man in the Moon, even here at Waning Gibbous phase. Continue to third quarter.

Here is the Moon at third quarter. It's called third quarter because it's three quarters of the way between one new moon and the next. Which side of the Moon is illuminated, right or left? That's right, the LEFT side is illuminated when the Moon is getting "smaller", or waning. Now look where the Sun is. You may need to adjust the time of day slightly so they can see both at once. I need two volunteers. Take two audience members, and position one as the Earth, and name the other the Moon. The machine in the center is the Sun. Where should the Moon stand so that the Earth sees the left side illuminated, but not the right? Start moving the Moon around the Earth, and asking the audience 'here?', 'here?' until they figure it out.

Ok. Have a seat! Well done! Let's continue through the month to new Moon. Advance the Moon to a tiny crescent. We're about to lose the Moon, so that we can't see it, because we are looking at the unilluminated side. How are the Moon, Sun and Earth oriented now? Great! Now we've gone halfway around the phases. We'll continue forward through the waxing phases. Advance through waxing crescent to first quarter. Here's first quarter, one quarter of the way through the phases from new Moon. Which side is illuminated, right or left? That's correct! When the Moon is waxing, the right side is illuminated, and when it's waning, the left side is illuminated. So now you can always tell, just by looking at the Moon, which phase it's in. Full Moon is easy, and crescents are just slivers of illuminated Moon. The quarters show half the visible face in sunlight, and gibbous Moons are closer to full. Waxing means it's illuminated on the right, and getting bigger, and waning means it's illuminated on the left and getting smaller. Let's practice a little bit! Run the planetarium forward, stopping once in a while to identify the phase. This can be a little tricky, because sometimes you want the Sun in one place, and sometimes you want it in another, and so it will probably take more time than you think!

Now, I'm going to start turning up the lights. Start turning up the lights. As I do, let's do one more thing. Let's put all these phases in order. First comes new Moon. And after that comes Waxing Crescent. What comes next? That's right! And then? And so on. Sometimes, depending on how much the group knows, it's easier to get volunteers, or to have a bunch of cards that show the different phases, and have the audience help put the people holding the cards in order.

You've been a terrific audience everyone, and I hope you learned something today! Are there any questions before you go out in the world where you can see the Moon for real? Take questions.

Be sure to reset the planetarium properly before you leave. You are probably far from the correct date, since you were moving forward at least several months during the practice portion of the show.