## Tuesday, May 17, 2011

### Solar System Beads

In this activity, students create a scale model of the distances between planets and get a feel for just how much space there is in space.  (Note: planet size is not to scale in this activity, just the distance - there is no scale in which you could both fit it in the classroom and still be able to see the planets).

Even if you don't have the time or resources to have students make the models, I might recommend that you make one for demonstration purposes.

This activity is based on an activity, from COSI, and I found it by way of HowToSmile.org.  You can find other, similar activities, by searching "solar system bead distance."

For each model, you'll need about 5 meters of string or yarn and 11 * (one to represent each planet (Pluto was included in this model), one for the sun and one for the asteroid belt).  You'll also need rulers or meter sticks available.

First you need to determine how far each planet is from the sun.  Here are the distances in astronomical units (AU).  1 AU = the distance between the Earth and the sun, about 150 million kilometers.
Mercury: 0.4 AU
Venus: 0.7 AU
Earth: 1.0 AU
Mars: 1.5 AU
Asteroid belt: 2.8 AU
Jupiter: 5.0 AU
Saturn: 10.0 AU
Uranus: 19.0 AU
Neptune: 30.0 AU
Pluto: 39.0 AU
For this model, we'll use a scale of 1 AU = 10 cm.  Students need to convert the above distances to cm.  (The original activity includes a nice table, with a space to put the scaled values.)

Now you're ready to create.

Slide the sun bead on the string and tie it in place, near one end of the string.

Now measure 4 cm (scaled distance for Mercury) and slide on the bead for Mercury.  Tie the bead in place, being careful to maintain the correct distance (you may want to find a partner to help make sure everything stays in the correct place).

For Venus, you'll need to measure 7 cm from the sun (be careful, the distances above are from the sun to each planet, not the distances between planets).  Slide the bead on and tie in place.

Continue in the same manner until all the beads have been added and secured.

You'll quickly notice that the first four planets are quite close to one another:

But as you move further out in space, the planets become spaced further and further apart.
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 Sorry to make you follow the wavy lines, but there's no way to get a picture of the whole thing spread out!
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If you want to take the conversation a bit further... travelling at the speed of light (300,000 km/s), it would take 8 minutes to travel from the sun to the Earth.  How long would it take to travel from the Earth to each of the other planets?  At the same speed, it would take 4.3 years to reach the next nearest star (Alpha Centauri).  How far away is that star?

*I used the bead colors recommended in the original version, but I would have no problem allowing students to select their own colors.  I particularly like the idea of allowing students to choose what they deem an appropriate color after you've shared a bit of information about each planet - if the student makes a connection between the color they've chosen and a fact about the planet, it's likely to make the experience and the finished model all the more meaningful.