Academic journal article Science Scope

The Dimensions of the Solar System

Academic journal article Science Scope

The Dimensions of the Solar System

Article excerpt

We have added a few new wrinkles to the popular activity of building a scale model of the solar system. The new activity takes advantage of some of the special features of Google Earth. Our goal was to create an activity that would give a much more powerful sense of the enormity and emptiness of the solar system and, at the same time, provide an opportunity to make connections with the community.

Traditional models

Historically, solar-system models are built by choosing objects of the appropriate relative sizes as the Sun and planets, and then laying them out along a line from the Sun outward. Unfortunately, the sizes of the Sun and planets often need to be exaggerated relative to their distances to make them visible. This may seem inevitable given the huge difference in the distances versus the sizes, but we see this as an obstacle to students gaining a deeper insight into the scale of the solar system. The problem can be solved if we expand our model sufficiently, so that we can have realistic separations between the solar-system bodies and still have an Earth that is not microscopic.

The second problem with traditional models is the practice of laying out the planets along a straight line. Again, this is understandable as a convenience, but what if we could make a scale model that reflected the essentially two-dimensional character of the solar system? When everything is placed along a line, it is not hard to find even small objects. However, imagine trying to find a grain of rice somewhere in the outskirts of your community. That gives a clearer idea of the challenge facing astronomers who are hunting for dwarf planets in the Kuiper belt.

Middle school students are expected to have some understanding of the solar system, the Sun, and planets and may even be able to name them in their order from the Sun (NRC 1996). However, as one middle-school teacher stated, "I have learned over the years that middle schoolers have zero concept of distance." In addition, at the middle level, students' attention needs to shift from the properties of particular celestial objects toward an understanding of the place of the Earth in the solar system (Massachusetts Department of Education 2006). Thus, building an accurate model helps students grasp the size of the solar system.

We have found a fun way to design a more-realistic "2-D" model of the solar system where students can learn about maps and scaling using easily accessible online resources that include satellite images. This activity also invites reaching out to a school's community in a way that will engage and educate.

Using Google Earth

Google Earth is a wonderful, free resource for looking at our planet (see Resources). Once installed, play with the program to learn how to zoom in and out, select layers to show different information on top of the images, and tilt the landscape to see it in 3-D. Under "Tools/ Options" you can change to metric units.

For this project, we suggest using Google Earth to focus on the landscape around your school. Type in your school address and Google Earth will take you there. Now "back out" using the zoom controls until the image encompasses the community surrounding your school. This article is based on a scale in which the Sun is 1 meter in diameter, but you might decide to rescale the numbers we provide so you can make the solar system reach to local landmarks and stores that students are familiar with.

An overlay of the solar system

The next thing we want to do is to lay a map of the solar system on top of the bird's-eye view of your community. To do this, we created two transparent GIF images (Figure 1) that you can download to your computer. These diagrams show the orbits of the planets (and dwarf planets) in the inner and the outer solar systems--it is almost impossible to show both on the same map because of the huge difference in distances.


To incorporate these images in Google Earth, adjust the zoom until you are at an "Eye alt[itude]" of about 1. …

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