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    Re: Physics Today: Trigonometry for the heavens
    From: Frank Reed
    Date: 2017 Dec 1, 08:02 -0800

    Yes, the article is visible. Thanks for sending the link! The author, Glen Van Brummelen, while he has some considerable expertise in the pre-modern history of spherical trigonometry, has only a modest background in celestial navigation and its history in the past 250 years (hence the highly formulaic re-telling of the Sumner story which he has apparently pulled from Peter Ifland's old book for some reason). You'll notice he credits NavList member Joel Silverberg at the end of the article. :)

    Here's a little funny thing. To set up the concept of a spherical triangle, Van Brummelen writes: "Imagine you and a friend are at the north pole of a sphere. You each head off on a trek to the equator, departing along paths at right angles to each other. When you reach the equator, you both turn toward each other and walk until you meet." And in another message this morning, Bob Crawley posted a BBC puzzle which reads in part, "Father Christmas always celebrates his birthday by waking up at sunrise and going for a walk. This year he was staying at his home in the Arctic. When he woke up he walked ten miles south, ten miles east and ten miles north, only to find himself back where he started. " Same geometry, smaller triangle. :) By the way, what was Santa's change in longitude, expressed in minutes of arc, on the second leg of his walk?

    Frank Reed

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