Mooning

We did a science class on the moon. Well, about the moon anyway!

We started out talking about satellites and moons and how many each planet had. This segued into an interesting conversation about why the planets closest to the sun had no moons, and the relationship of gravity to mass and distance.

In other words, Mercury is too close to the sun to have a moon (because the sun would pull the moon out of mercury's orbit), but he further out you go, the less the sun's pull becomes an issue.


My personal favorite moment was asking our visiting 7 year old how many moons Jupiter had and, without hesitation, he gave the (correct) answer, "63." Dude, I had to look that one up!

We moved on to eclipses. These are easy to demonstrate with a dark room and an unshaded light bulb. We set up the lamp and used our globe for the earth and an apple on a stick for the moon.

The first trick was to use the apple to block the bulb, giving the effect of a solar eclipse. This worked pretty well (you could see the light rays shining around the blocked bulb) as long as you remembered to close one eye. The distance between the lamp and the apple varied with the kid holding the apple.

We then looked at the "solar eclipse" by casting the apple shadow on the globe. I explained that everyone in the shadow would see the eclipse, but people far from the shadow wouldn't see anything.

On the Earth, of course, the shadow has fuzzy edges where people can see partial eclipses.

While we had the room dark, we did the moon phases. We kept the lamp (as our sun) stationary. The kids took turns being the Earth, a few feet from the sun. They stayed in one place, but pivoted to face me. I held a softball as the moon and I walked around them slowly. As they turned to watch, the light on the ball went through all the phases of the moon.

While we were at it, I showed them the lunar eclipse behind them, and they could see why a lunar eclipse can only happen during a full moon.

Then we talked about gravity. Why does the moon orbit the Earth? (Gravity) What would happen if the moon were closer to the size of the Earth? (They would orbit each other like Pluto and Charon) How much smaller is the moon? (1/6 the size of Earth) Does the moon pull on the Earth, too? (Yes, but just the water moves and that causes tides)

I wanted to come up with an experiment to show why the moon could pull the water, but not the rocks. I filled a cup 1/3 full of pebbles, and another cup 1/3 full of water, and had the kids try tipping the cups slightly. The rocks moved very little to not at all, but the water moved freely.

One sixth the size means 1/6 the gravity, means you could jump 6 times as far. So we went outside and the kids took running leaps from the carport into the driveway. I marked and measured where they had landed (yay, sidewalk chalk!) and then I marked where they would have landed on the moon. Woah! Mxyl could jump clear across the street! All the kids loved this project, but I had saved the best for last...

The crater experiment! I filled a large pan with a few inches of flour and then dusted the top with cocoa powder. It's the opposite color scheme of the actual moon, but I wasn't about to fill the pan with cocoa and dust with flour!

We started dropping small rocks. Next we stood on a chair and dropped the rocks. We went up to progressively larger rocks. Wow! The rocks ejected the flour over the dark surface. The craters overlapped, creating mountains and valleys.

So fun!