Make a globe

In another life, I might have been a locksmith. In another one, I’d have been a globe maker. Inspired by a Bellerby and Co video some years ago, I got it in mind to try to make a globe or two. Turns out it’s not that easy. But, I think these turned out pretty nice.

It started with a concrete sphere made with a plastic mold - the kind you get to make bath bombs or x-mas tree ornaments in. They’re about a dollar each and can be reused a few times. Bags of concrete are likewise pretty cheap.

concrete sphere
A concrete sphere

A little skin of plaster was added to smooth out the spheres and seal the concrete.

Next, we have to make the gores. These are the little slivers that we will glue to the sphere. You can’t just print out any old map and glue it to the sphere. Well you could, but it wouldn’t work out too well since the sphere is not flat. So, you make gores. These are sections of the map that can be made small enough to slightly bend or warp into sections of the spherical surface. And, to complicate it, there is a bit of geometry and math needed to reproject a flat, uninterrupted map into the gores. There are a number of software packages that can do this.

For example G.Projector by folks at NASA Goddard is great simple application for playing with map projections. In the end, I made some tweaks to this amazing script: Globe-Gores JS. You’ll need an equirectangular map of whatever globe you want to make. I wanted to start with a moon globe, so I went straight to the best source: Map-a-Planet by USGS/NASA/PDS groups. Here you can download large, gorgeous maps of the solar system objects.

moon gores process
Reprojection of equirectangular to gores

Then, a trip to Staples to print them out. I just used regular paper though I bet there are better choices out there. Next, you’ll have to cut them all out. Very carefully. After this you should have some nice gores ready for glueing.

moon gores
The lunar gores after printing and cutting

There are a number of various choices now about how to glue them on. It seems to help if you carefully wet the paper, then stretch them out a bit on the sphere, let them dry, then glue them.

After a day or two of glueing and drying, the globe was ready for some final coats of ModPodge. My uncle made me some nice walnut bases on his lathe (which I’d love to do myself, but am short one lathe.)

moon globe
A finished moon globe

Once you have the basic process down, you can essentially make a globe out of any 360/All Sky Image. Here’s a globe showing made with the Cosmic Microwave Background map as measured by the Planck spacecraft a decade ago.

cmb globe
CMB globe in process of glueing
moon globe
The finished CMB globe

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