Dot Physics

Scale Model of the Solar System

The solar system is difficult to show correctly. Why? It is difficult because the size of things are vastly different. Let me use units common in solar-system astronomy, the Astronomical Unit (or AU). One AU is the distance from the Sun to the Earth. If I want to look at all the planets, I would need to go out to about 30 AU (to Neptune – remember that Pluto is not a planet). That is not a problem but then if I want to look at the size of even the Sun, it is just 0.001 AU across. And the Earth is even smaller, at 0.0001 AU. So that is the problem. The distance from the Sun to Neptune is like 5 orders of magnitude greater than the scale of Earth. You can’t really show that on paper.

Normally, what textbooks do is to show two separate scales. One scale showing the orbits of the planets and another scale showing the size of the planets. Unfortunately, this way you don’t get a good sense of how far apart these things are. One way is to show the model of the solar system in one web page – as shown here. Another way is to build a scale model in the real world.

Real world solar system models can be found in lots of places, the one that inspired us was the Maine solar system model. We originally tried to make something similar to this, but it was logistically very difficult (property issues and everything). Eventually we (by we I mean some people in our university) decided to make one that went just around our campus. For our scale, the sun is about 1 meter across and 1 AU is about 100 meters.

For each planet, there is a circular poster the size of the Sun (in 2-d). On this circle, there is another circle representing the size of that particular planet. On the side, there are some informational-type posters with more info. These are designed to be “temporary” and are made with some type of plastic printed stuff glued on some type of foam backing (clearly, I had very little to do with that part). In fact, this project was a collaboration between our department (Chemistry and Physics) and the Department of Visual Arts. The stands and posters were designed by students (Stacy Kest, Shalayne Heffner, Brett Blanchard, and Daniel Ippolito).

Here is a map showing the location of the planets.

i-3bfd70b9c4e6cc1267e75e84cacb98f3-2009-12-14_i_photo.jpg

And here is a sample poster.

i-b3fe35557367c6473183d6657ae30c57-2009-12-14_i_photo_4.jpg

Finally, as a way of documenting the scale, I walked around campus with a video camera. Here is the movie that I made (time-compressed to prevent too much boredom). Unfortunately, some parts get a little shaky – enough that it might make you barf. Please don’t blame me. I would make another one, but it just won’t stop raining here.

Other Scale Solar System Resources

Comments

  1. #1 Who Cares
    December 14, 2009

    Good solution you (as a group) came up with.
    What I really like is that this is the first one that directly compares the different planets to the sun (that said others generally have a sun the size of a 3 to 4 story building).

  2. #2 Lassi Hippeläinen
    December 14, 2009

    In 1992 Finnish amateur astronomers completed an outdoor model (scale 1:1’000’000’000) in Helsinki.
    http://www.ursa.fi/ursa/aurinkokuntamalli/eng/solarsystem-en.html

    You will notice that Pluto has been missing since 2000…

  3. #3 FrauTech
    December 14, 2009

    Neat! Do kids still make styrofoam models in school? I haven’t seen one in a while. That should be a third grade Science requirement. Either a styrofoam solar system model, or a volcano.

  4. #4 andy
    December 14, 2009

    A comparative scale of extrasolar systems would be an interesting thing to consider. Before you’ve got as far as Mercury, you would have passed the fourth planet of Gliese 581, located on the outer edge of its star’s habitable zone. The planetary systems of HR 8799 and Fomalhaut on the other hand are built on a rather larger scale than our own.

  5. #5 Gray Gaffer
    December 14, 2009

    We used to have one on the jogging path around Battle Point Park, where we built the Ritchie Observatory (http://www.bpastro.org/). The planet and sun models are inside the building now, but the posts are still up (or were last time I walked around). The Sun was about 12″ in our version. Earth was IIRC a marble.

  6. #6 CS
    December 14, 2009

    The 110 meter diameter Globe Arena in Stockholm is used as the Sun for a scaled model of the solar system in Sweden. Pluto is 300 km away.

    http://en.wikipedia.org/wiki/Ericsson_Globe
    http://ttt.astro.su.se/swesolsyst/englishsum.html

  7. #7 Shawn Smith
    December 14, 2009

    Gray Gaffer,

    If the Sun is only 12 inches across, then Earth would only be about an eighth of an inch across. I think “BB” or “Buckshot” or “Skateboard Ball Bearing” would be a better description than “marble.” And the Earth in that case would be somewhere between 120 and 130 feet away.

  8. #8 Shawn Smith
    December 14, 2009

    And, I just noticed…Ths Sun is closer to 0.01 AU (4.5 light seconds wide vs. 500 light seconds per AU), not 0.001 AU in diameter.

  9. #9 Robert
    December 14, 2009

    Does this scale model let you see why the Moon and Sun have the same apparent sizes when viewed from Earth?

    Seems to me that animations or software like Starry Earth can do this stuff much better than models.

  10. #10 Robert
    December 14, 2009

    I meant Starry Night.

    Sorry about that.

  11. #11 mandas
    December 14, 2009

    If you want a really good scale model of the solar system, you need to go to the Coonabarabran Observatory in New South Wales (Australia). Here is a link to their website:
    http://www.solarsystemdrive.com/

  12. #12 Shawn Smith
    December 14, 2009

    Robert, let’s take a look at the relevant numbers:

    Moon: 2150 miles diameter, 239,000 miles away.
    Sun: 865,000 miles diameter, 93,200,000 miles away.

    865,000 / 2150 = 402.
    93,200,000 / 239,000 = 390.

    That’s pretty close (about 3.1% difference). If by scale model, I suppose that means that looking at a 1/8″ ball bearing from 16 inches away looks an awful lot like looking at a beach ball that’s 4’8″ (56 inches) across from 500 feet (almost a tenth of a mile) away.

  13. #13 Gray Gaffer
    December 15, 2009

    @7: the jogging loop is 1 1/2 miles. I could be wrong, maybe it was Jupiter that was the marble. 130 ft sounds about right. End to end then was around 3000 ft. I was not the one who laid it out, so I am going on visual memory.

  14. #14 santa chen
    February 19, 2010

    in what way can i scaled model of the solar system , any example

  15. #15 Our Solar System
    May 30, 2010

    The effort! No sound on the video, is that just me? Anyway its encouraged me to do my own scale model, right where’s the scotch tape?

The site is currently under maintenance and will be back shortly. New comments have been disabled during this time, please check back soon.