Tuesday, March 06, 2012

Looking Inward then Outward

The Astronomy Picture of the Day (APOD) is a long-standing educational project by which NASA provides examples of the benefits -- from the practical to the sublime -- of space exploration. I use a November 2000 image -- Earth at Night -- on my home page and in many of my classes, as the lights shown in this image mosaic are a reasonable but imperfect proxy for human population patterns.

Profligate users of electricity, for example, are over-represented while the rural poor are invisible -- as they too often are in real life. Still, it is clear from this image that the majority of people live in the mid-latitudes of the northern hemisphere, that more people live near water than in the interiors of continents, and that population densities are still low in places that are extremely cold, dry, wet, or high. (The "too wet" category surprises people, but the nutrients are often so thoroughly leached from tropical soils that although they are found under lush forests, they cannot support settled agriculture -- only low-density shifting cultivation.)

Better yet, visit original APOD post to really enlarge.
This image has a lot of detail that is not visible at even double this scale.
I was pleasantly surprised to hear APOD mentioned on the radio yesterday, as one WBUR broadcaster was exclaiming how cool the image was. The image, as it turns out, was actually a time-lapse series of images (that is, an accelerated video) from the International Space Station. Set to a lively musical score, Flying Over the Earth at Night fills the screen with imagery of lights that originate from human and natural sources. We are reminded of how common lightning is, for example. We see large areas of dense human settlement but even larger areas where humans are relatively few and generally far between.

Watch this sequence a few times, looking for patterns and familiar coastlines or other locations. You can share your reactions with the "comments" button below, or on the NASA site itself.

At first glance, today's APOD image seems similar to yesterday's sequence. It is mostly dark, with some scattered blues and oranges. But as the notes for Celestial Still Life make clear, these colored lights reflect (pun intended) patterns on a much vaster scale than anything on our planet could do.

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