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    Re: NASA and celestial navigation
    From: Frank Reed
    Date: 2018 Mar 6, 08:39 -0800

    Geoffrey Kolbe, you wrote:
    "Its a space sextant which works using xrays..... obviously. The mirror shades are only clear in visible light."

    Ha ha ha. Yes, exactly. Now I'm just waiting for someone to think you were being serious...

    Moving on from the sextant in the pointless image, which is clearly a paperweight or a decorative objet, we could look at the text of the article. For example, there's this:
    "The astrolabe was a simple sphere made of brass"

    Yes, a simple sphere! A sphere so simple they even took out the third dimension.

    And then:
    "But determining the longitude remained a serious challenge. Navigators can only determine longitude by comparing the time-of-day difference between the mariner's starting location and new location. In the early days, navigators kept time with sand-filled hourglasses that had to be watched and turned hourly."

    The turning of hourglasses is, of course, completely irrelevant to the determination of longitude unless we count dead reckoning longitudes (which we shouldn't!).

    "In 1764, British clockmaker John Harrison invented the seafaring chronometer, which was the most important advance in marine navigation in the 3,000 years that mariners had taken to the sea. Over the next 40 years, he improved on the technology, making his chronometers more and more accurate."

    Oh, so Harrison improved on his chronometers from 1764 to 1804. That's a pretty good trick for a man who died in early 1776! Of course the author here has confused the end of the story with the beginning... Also, calling it the most important advance in 3000 years is over-the-top. It's the sort of hyperbole, over-stating the importance of one single contribution, that has become standard in NASA's reality-warping public affairs office.

    There's more... who's next?

    Frank Reed

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