Scaling down

Natural History, Feb, 2003 by Robert (American businessman and engineer) Anderson

It's a pretty safe bet that you're never going to travel more than a few thousand miles from home--how could you, without becoming an astronaut and leaving the Earth itself? So how can you hope to get an intuitive grasp of the size of the solar system? Given the distances, measured in millions and billions of miles, my guess is it's nearly impossible. You might as well try to conjure a visceral sense of geologic time--surely a quixotic exercise, when you think about the seconds ticking by as life evolves from jellyfish to human.

But still, you can try. And if you have any interest in astronomy, the wow factor is well worth the effort of thinking about how the solar system would scale down to a more manageable size. Now the Exploratorium in San Francisco has introduced a Web site (www.exploratorium.edu/ronh/solar_system/index.html) that will blast you off to a great start. You type in how big you want your model sun to be, and the site does the rest, calculating the size of each planet and its distance from the Sun. I typed in 9.5 inches for my model, the diameter of a basketball, and was surprised to learn that the Earth would be the size of a peppercorn, eighty-five feet from the Sun, and Pluto would be almost two-thirds of a mile away. The Web site also calculates such things as the distance to Alpha Centauri--after the Sun, the nearest bright star. On my chosen scale its distance would be 4,351 miles. Much beyond that, though, and the model quickly becomes almost as unmeaningfully large as the real thing.

If you want to find out about large-scale solar system models, check out the links at the bottom of the Exploratorium Web page. My favorite, the most ambitious project in North America but still a work in progress (unless more funding can be found), has been laid out across 200 miles of central Kansas (www.fhsu.edu/solarsystem/). The planets are roughly aligned along Interstate 70, running east from the city of Hays, where the enormous dome of the Sternberg Museum of Natural History stands in for the Sun. A project much closer to completion can be found in northern Maine (www.umpi.maine.edu/info/nmms/solar/index.htm), where three-dimensional scale models of the planets adorn forty miles of U.S. Route 1, from Presque Isle to Houlton.

Robert Anderson is a freelance science writer living in Los Angeles.