 Using these disks, with balls representing the Earth and Moon, and using the snake-light sun, we can show why eclipses don't happen every month. For the best shadows, use just the light without the ping-pong ball. You can also use a regular light bulb. Now the size of the Earth and the Moon are to scale, but they're too close to each other. They'd have to be about 30 inches apart on this scale. We're also exaggerating the tilt of the Moon's orbit, so it's easier to see. This model is tilted about 30 degrees. The Moon's orbit around the Earth is actually tilted only about 5 degrees from Earth's orbit around the Sun. So why don't eclipses happen every month? Well, the Moon's orbit is tilted compared to the Earth's orbit around the Sun. Let's see what that means. See, the Moon orbits the Earth like this as the Earth orbits the Sun. Now, the Earth orbits the Sun once every year. And the Moon orbits the Earth once every month. Now, here's one for each of you. So let's place each of you at a particular place. Let's put you about here, you're about here, you're right about there, and I'll be right here. Now, we want all of our tilts to be in the same direction. You see that little dark black stripe on your Earth? Everybody point them in this direction, so they're all parallel. So pointing in that direction. Got it, got it. Let's get yours just tilted perfect a little bit more, about like that. Good, good. Okay, we're all tilted the same way, because it keeps that same tilt throughout the year. Now, let's see if anyone has a lunar eclipse. Now, what position does the Moon have to be in order for there to be a lunar eclipse? In other words, what phase does it have to be in? Full Moon. Full Moon, right, that's right. So let's move your, see, I've got to move mine over here so that the Moon is opposite the Earth from the Sun. So everybody move your Moon opposite the Earth from the Sun. Good, this is of course the Sun. This is representing the Sun. Very good. Okay, you've all got the right position. Now let's see, let's check for lunar eclipses. Let's see if I have a lunar eclipse. Let's see. Oh, you see where my Moon shadow is here? And my Earth shadow is above it? Yeah. So my Earth shadow does not hit the Moon, right? Right. The Moon shadow is below the Earth shadow, so I'm not going to get a lunar eclipse here. Now, let's check your shadow. Here's your Moon, and we'll get it into, let's get your Earth nice and perpendicular. There you go. And there's your Moon. There it is at full position. Look, your shadows are aligned. Your Moon is in Earth shadow, so you have a lunar eclipse. You're right. Good. Now let's check yours. Now, why don't you hold that there, and let's see if we can find your shadow here. There it is. And we see that here's your Earth shadow, and there's your Moon shadow. Are you going to have a lunar eclipse? No. No, because your Moon shadow is above your Earth shadow. Right. So the tilt of Earth's orbit, so the tilt of the Moon's orbit, compared to the Earth's orbit around the Sun, is the reason that we don't have eclipses every month. Now, you can continue this by having your visitors move their Moon around to new position and check for solar eclipses. There are more tips and suggestions in the manual.