April 25th, 2006

Fishy Circumstances

Teaching with maps

Today, for the first time, I taught graduate students.
And it went well.

The class was on medieval maps, a niche more usually filled by a class on astrolabes. (I was guest-teaching one class in a semester-long seminar on Ancient and Medieval Science.) Since astrolabes are maps, albeit with extra add-ons, I reworked the topic to focus on world view, on what was important to the map makers of both terrestrial and celestial maps in the period.

Playing around with medieval maps is fun. Many of them are really hard to decipher, which makes looking at them an educational group exercise. The world often doesn't look at all like the world, even if it's a layout closely related to the map before. Seeing the abstractness of a labelled T-O map with east at the top is all well-and-good, but it doesn't help a huge much when then confronted by the Hereford mappamundi. (mappamundi is Latin for "world map".)

I wasn't actually talking about Christian medieval world maps today, but Islamic ones. Still, the T-O style maps, with Jerusalem at the center of the world, make a good comparison with the Islamic world maps, which have Mecca at the center. When confronted with a seriously abstract world map, it sure is helpful to know what the center is meant to be. Pretty much all the maps we worked through today were in the Ptolemaic tradition. This means that
  • The data points all have latitude and longitude, whether or not the grid is marked.
  • The Nile probably has all its headwaters in the mountains
  • Southern Africa is entirely uninhabitable and connects with South-east Asia, quite possibly without a break in landmass.

Al-Idrisi's world map, made for Roger of Sicily over the course of 15 years, and based, in part on the Ptolemaic tradition, makes a fair amount of sense, especially if you don't go assuming that north is up and you keep in mind that it's Ptolemaic. (To see the map, go here and scroll down.)

The al-Balkhi school of mapmakers? Well... their goal wasn't to make earthlike maps so much as geometrically elegant maps of caravan routes. This results in maps with perfect circles representing towns and lakes, rivers represented by parallel lines, and everything looking very abstract. It does not lend itself sensibly to world maps. If you've already had a go deciphering the al-Idrisi map, then you can move on to working on figuring out the map below the cut. Really. Do the other as a warm up.

Anyways, the lecture went well, covered more than maps and schools of geographers, and the students had lots of good, thought-provoking questions.

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