Falmouth Public SchoolsA Community Committed to Excellence: Every Student. Every Day.

The solar system is huge! And that’s an understatement. Even traveling at the speed of light, it would take about four hours to get from the Sun to Neptune – a distance of about 2.8 billion miles. Because of the great distances between planets and the planets’ relatively small sizes compared to those distances, it’s difficult and sometimes impossible to create a visual representation on a computer screen or the page of a book that accurately represents the size of the planets and the distances between them.

A scale model – a model with sizes and distances proportionally reduced or enlarged – is a great way to correctly display the size of and distance between planets, giving people a better visual representation of the solar system than they could otherwise get from an image in a book or on a computer.

Some scale models show just scale distances, some show just scale planet sizes, while some display both. An accurate size and distance scale model in which Mercury, the smallest planet, is 1 mm across would require about half a mile to properly display the distance from the Sun to Neptune. There are scale solar systems all over the world. Some are just a few blocks long, but the largest, in Sweden, stretches more than 140 miles (http://www.swedensolarsystem.se/en/)!

Here are links to some other scale models:

• Ithaca NY: https://saganplanetwalk.com/
• Maine: https://pages.umpi.edu/nmms/solar/
• Nevada: https://www.youtube.com/watch?v=zR3Igc3Rhfg

Because the distances between planets are so great, astronomers sometimes describe distances in terms of astronomical units (au). One au is equal to the average distance between the Sun and Earth, about 150 million kilometers. This allows scientists to describe distances using smaller relatable numbers rather than tens of millions, hundreds of millions, or even billions of kilometers. For example, Mars is 1.5 au from the Sun and Neptune is 30 au from the Sun.

(from Jet Propulsion Laboratory website)

This scale model stretches from Woods Hole to North Falmouth along the Shining Sea Bikeway.  The total distance is 14.4 km (8.9 miles).  At that scale, the Sun is 3.4 m (11.1 feet) in diameter and Pluto is only 5mm in diameter.

On a mobile device, follow the links in the menu above to get more information about each planet.  In a web browser, links to each planet are in the left-hand menu.