Vulcan | 
pick(2015) In the 19th century, Newton's laws were applied to astrophysics, but failed to explain the orbit of Mercury ... unless there were an undiscovered planet even closer to the sun. A generation of astronomers searched for (and sometimes sighted) a planet which it turns out doesn't exist. Levenson describes their efforts, with lessons about how science proceeds when observations don't match theory. Interesting, brief, and accessible (math-free!)
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