Friday, February 21, 2014

Buckminster-Fuller inspires a new classroom demo

One of the challenges in teaching Plate Tectonics to introductory students is that - along with being spread out over a huge scale - most of the maps we use are flat, whereas the plates are actually distributed across a sphere (oblate spheroid, technically).

With most map projections, the polar regions are heavily distorted and much larger in comparison to equatorial regions. So, for instance, if you want to reverse tectonic motions and reassemble the continents into Pangaea, you run in to issues of mis-matched continents. Even worse, students begin to assume that Greenland is really that big and there must be some active tectonic boundaries around such a huge land mass.

A globe tackles the issues of projection and relative scale, but then students can't see what's happening on the back side. After a little digging around, I stumbled upon this graphic on Wikipedia, based on Buckminster Fuller's "Dymaxion" globe - the earth projected onto an icosahedron, but done in a way that minimizes distortion of the land masses.

The next part was deciding how big to make it. I wanted to be able to remove the continents and shuffle them around on the board, so they had to be big enough to be visible from across a classroom. I settled on 20 inches (~500 cm) for the sides of my equilateral triangles (based in part on globe size, but it was also the largest size that would allow for multiple whole triangles from a single piece of black foamcore. I got out my 30/60/90 triangle and meter stick and began cutting. I ended up with about eight half triangles in addition to 16 full triangles.


The finished stack, with reference map/model.

Testing out the fit.

I laid out the panels to form two halves, each pentagonal pyramid half has five triangles dangling below it that would fit between the five from the other half.

I printed out full-size continents (taping many sheets of paper together) to line them up. I flipped the sheets over and traced the outlines in soft pencil. Flipping the sheets back right-side up, I retraced the outlines, transferring some of the soft pencil underneath onto the board.

I went over the outlines with a silver marker and taped up each of the pentagonal pyramids.

Here are the two taped up halves. The "northern hemisphere" is also outlined, but I had yet to ink the other one.

Backsides of the pyramids were color-coded so I knew which edges should line up.

And the whole thing assembled. I lucked out because the narrowest dimension of the icosahedron was about an inch less than the width of our door.

I re-covered the colored tape with black to blend everything together.

Adding latitude/longitude lines in a bronze/copper color. Some of these were transferred using the soft pencil technique for the continent outlines, others were sketched in based on measurements scaled up from a reference print of each triangle.

A "western hemisphere" view of the finished globe.

"Southern hemisphere"

"Northern hemisphere." Incidentally, the pink flamingo in the background is about 22" tall.

A closer view of North America. I really like how the silver stands apart from the bronze and both show up well against the black background.

It is large.

"Atlas, it's done" (pun shamelessly borrowed from a friend).


  1. Part of my extended history/critique of the Fuller map: how I labeled his triangles: