Scale Models of the Solar System
Three things from watching students make scale models of the Solar System:
We all bend the rules to make things “look better”
Perspective view changes everything
A reminder that: The geocentric model was often more an act of humility than arrogance.
Bending the Rules
When we first work to make a scale model of the Solar System, it takes a while to realize how difficult it will be to use one scale to show both the orbit sizes and the planet sizes. Making the Earth the size of a golf ball tends to put Neptune somewhere in the neighboring town. Once the students see the difficulty I might say to just do the orbits, getting something like this:
They have already calculated that the planet sizes are just fraction of a millimeters, and hence invisible on this scale. But they cannot leave the drawing as-is, and will invariably draw in planets that they think- somehow- are- maybe- the- right- size- just- to- give- the- right- idea…
I try discussing the idea of scale, and how the planets would be points - the students nod, but then opt for leaving the false picture.
Perspective view changes everything
I never before realized that when you stand at the Sun, perspective makes all the planets look pretty much the same distance apart. In the image below the camera is sitting at the Sun. The black weights are the planets. I drew red boxes around Uranus, Neptune, Pluto so you can see them better. Before today, I would emphasize for myself the geometric increase of orbit distances, and ponder all that might imply. See the bottom of this post for links to my other posts on this topic. But today I am struck by the simple fact of perspective, of the fore-shortening. If you wanted to built a system which, from its center, appeared equally spaced, you would need to lay it out with geometrically increasing distances. (Reminder that the asteroid belt lies in that gap between Mars & Jupiter.)
A Reminder that the Geocentric model was for many an act of humility, not of arrogance.
I was taught by school and many history books that those silly, primitive people centuries ago placed the Earth at the center of the universe and thought everything revolved around us. This explanation was further mixed up with a messy assault on the arrogance of the Church, and jabs at the self-centeredness of people.
I had the good fortune to speak with my friend who seriously studies Elizabethan Cosmology. During those “previous years”, the people who really pondered the place of the Earth and humanity would laugh at our interpretation of their Cosmology. The Earth was far from the Divine; the Earth was dense and difficult. The Earth was far down in the great chain of being. As you went up from the Earth matter became finer, more intelligent. Each higher realm included all the lower because each higher realm was more Divine, and the Divine encompasses all. Seeing a diagram with the Earth at the center was not an act of arrogance, it was an act of humility.
Here are my other posts on the spacings of planet orbits: