Thursday, September 24, 2009

Sidewalk astronomy

First of all, happy National Punctuation Day!

Basic celebration technique: Use proper punctuation in all your writing today.
Next level: Read a chapter of Dickens or Austen or another 19th-century book with long sentences, paying attention to the punctuation.
Advanced: Take the quick punctuation symbol quiz at Quizicon.

Yesterday we had our first astronomy class. We talked about the solar system and how it's hard to get a sense of the distances involved when you just look at numbers. We did two activities that I highly recommend, both for scientific interest and for the jaw-drop factor!

The first one was a scale model of the earth and the moon. We followed the general outline from this site. We used a basketball for the earth, measured it and calculated the diameter, then calculated the circumference needed for the moon. It turns out that a tennis ball is about the right size. Next, I asked the kids to guess how far apart the basketball and tennis ball should be placed. They moved the balls around and made different guesses, but all were between about 1 and 5 feet. Then we did the math to figure out what the distance really should be in this scale. It comes out to about 24 feet. I had someone hold the basketball at one end of the living room, then got the tape measure and showed them how far 24 feet is -- all the way across the living room, up the stairs and back along the hallway! It's amazing when you see it represented visually. Before doing this, I had never comprehended how far away the moon really is.

The second eye-opening activity was a scale model of the solar system. There are many sites online that give instructions for this, but I used this site because it has a spreadsheet where you can put in different numbers and tweak the scale however you want. I went out early that morning and measured how long our block is (with our homemade hodometer or measuring wheel, which has been surprisingly useful over the years) and then twiddled the spreadsheet until the whole solar system fit onto our block. The spreadsheet gives you all the distances from the sun, but I also wrote down the distances from each planet to the next planet.

In the class we used a ruler marked with millimeters to draw the sun and planets in the scale we were using. The sun ended up being 50 millimeters, or almost 2 inches across. Jupiter was 5 millimeters. The earth was a tiny dot, 0.4 millimeters.

We went to the end of the block and placed the sun. (We taped our sun and planets to water bottles so they wouldn't blow away.) 7 feet from the sun was Mercury, then 6 more feet to Venus, 5 more to the earth, and 9 more to Mars. The kids were fairly impressed, but then I announced the next distance: 65 feet more to Jupiter. Wow! Now jaws were dropping. 76 to Saturn, and then an incredible 170 feet more to Uranus, 192 to Neptune, and 167 to Pluto. That took us just about to the end of our block, where we could barely see the sun at the other end.

This is an amazing activity because when you see pictures of the whole solar system, the sizes of the planets and the distances between them can't be in the same scale. It wouldn't fit in a picture. So we get the impression that those distances aren't as big as they are. Seeing our tiny dots of planets and the huge distances between them made those numbers much more real.

The spreadsheet also pointed out that in the scale we used, the distance to the nearest star (other than the sun, of course) would be 901.6 miles. That puts the solar system back into perspective as a relatively close family, far from our nearest neighbors!

I had to laugh during our activity as I realized the odd picture we made. Here were 10 kids, ages 7 to 14, marching together down the sidewalk, chanting the distance aloud as we watched the arrow on the hodometer. "63, 64, 65..." I wondered if the neighbors were thinking, "Oh, it's just those homeschooled kids, practicing their remedial math."


Andrea M said...

Funny you should mention the astronomy. We went to the Puyallup Fair on Monday ( free for military/retired and a great FHE) and we were able to look at Jupiter and all of her ...not rings but...I can't remember what they are called...but anyway it was super fun to look at the giant telescope and peer a gazillion miles away. They also had a scale model of the planets and had the kids guess how far from one another they should be with the sun in a fixed position on the wall ( and measuring a meter across so that the scale of the other planets could be held by kids). Both Sasha and Jayson guessed totally wrong . It was cool seeing how wrong we all were. Enjoy your astronomy. Don't worry about what the crazy neighbors actuality, they are just a bit jealous.

Don said...

There was a show recently on Channel 7 entitled "400 Years of the Telescope." It talked about how our view of the universe has changed with advances in technology from the time of Galileo to now. Fairly recently scientists have concluded that the universe is expanding rather than contracting which surprised them. With the new telescopes being built, they expect our view of the universe to change yet again.