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The Boston Globe

Ideas

Brainiac

How lights define a city

And other recent highlights from the Ideas blog

You’ve likely seen nighttime satellite pictures of Earth before—images that show Tokyo and New York blazing away and a swath of darkness over the ­Sahara.

These images offer a vivid picture of human activity around the world, and now it turns out they may be instrumental in solving a practical problem in the social sciences: how to define where metropolitan boundaries begin and end.

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