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Putting stars in their place

The creation of the Hertzsprung-Russell diagram was a landmark advance in our understanding of the stars.
Imagine you are being given an important assignment by a taskmaster with a strange sense of humor. Your job is to study a forest, but you can only work according to a rather bizarre set of rules. For five minutes you can take all the pictures you want. You can photograph thousands of square miles of trees in any part of the spectrum. You can look north, east, south, and west. But you are not allowed to touch a tree or leaf, and after your five minutes are up, you can collect no further data. Eve...

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