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How Analog Tide Predictors Changed Human History ( 37

szczys writes: You'd think tide prediction would be quite easy: it comes in, it goes out. But of course it's driven by gravity between the moon and earth and there's a lot more to it. Today, computer models make this easy, but before computers we used incredible analog machines to predict the tides. The best of these machines were the deciding factor in setting a date for the Allies landing in Europe leading to the end of the second world war. From the Hackaday story: "In England, tide prediction was handled by Arthur Thomas Doodson from the Liverpool Tidal Institute. It was Doodson who made the tidal predictions for the Allied invasion at Normandy. Doodson needed access to local tide data, but the British only had information for the nearby ports. Factors like the shallow water effect and local weather impact on tidal behavior made it impossible to interpolate for the landing sites based on the port data. The shallow water effect could really throw off the schedule for demolishing the obstacles if the tide rose too quickly. Secret British reconnaissance teams covertly collected shallow water data at the enemy beaches and sent it to Doodson for analysis. To further complicate things, the operatives couldn't just tell Doodson that the invasion was planned for the beaches of Normandy. So he had to figure it out from the harmonic constants sent to him by William Ian Farquharson, superintendent of tides at the Hydrographic Office of the Royal Navy. He did so using the third iteration of Kelvin's predictor along with another machine. These were kept in separate rooms lest they be taken out by the same bomb.
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How Analog Tide Predictors Changed Human History

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  • This may have affected the timing of the invasion somewhat, but IIRC the days were determined primarily by the moon and the weather. You had a window each month where you had minimal light because the moon wasn't lit or was barely lit. Then there was bad weather, so they called off one planned date.

    • Re:Moon... (Score:5, Interesting)

      by techno-vampire ( 666512 ) on Thursday October 08, 2015 @05:07PM (#50689209) Homepage
      Yes, a full moon was important, as well as acceptable weather conditions. However, the state of the tides [] was also important. The planners wanted the landing to take place before dawn, on a rising tide. Not only did that expose more of the beach obstacles, it meant that grounded landing craft would be afloat again sooner, making them able to bring in reinforcements sooner. And, if the landings didn't take place on June 6, the next time the tides would be right would be in two weeks, without a full moon.
      • Dice (Score:3, Funny)

        by fyngyrz ( 762201 )

        They think we'll just lap this stuff up. But I'm here to wave it off. Not just to rip tides, but to surf something else entirely. This kind of article-fishing eventually turns into website breakers. Which is to say, the editors are all wet.

  • by fahrbot-bot ( 874524 ) on Thursday October 08, 2015 @05:10PM (#50689251)

    You'd think Tide prediction would be quite easy, it comes in, it goes out.

    Unless you're Bill O'Reilly []:

    “Tide goes in, tide goes out. Never a miscommunication. You can’t explain that. You can’t explain why the tide goes in.”

    Not trolling; just sayin' apparently not as easy as one might think - even way back in 2011.

    • Re: (Score:3, Informative)

      Obviously the more important followup [] questions are: "How did the moon get there? . . . How come we have that and Mars doesn't have it? . . . "
  • by 140Mandak262Jamuna ( 970587 ) on Thursday October 08, 2015 @05:36PM (#50689439) Journal
    In the evolution of humans, genetics show a bottleneck about 75000 years ago. Some catastrophic global event, probably a volcanic eruption, nearly wiped out all the hominids that were ancestors of Homo sapiens, in Africa. The best evidence suggests the only bands that survived the event clung to life in the east African coast near the southern end of the continent. They seem to have subsisted on shell fish and other crustaceans collected during the low tide. There are some telltale marks of intelligence about that band. Scratches on stone tools that could be decorations or ownership marks, shells with holes punched through them to make garlands of shells, using fire to sharpen and temper their stone tools etc.

    In hardly 30,000 years they expanded all across Africa, broke out of Africa, set up nascent populations all across Arabia, Persia, India, Andaman Nicobar Islands (this is important), Malaysia, Java, Sumatra, Papua New Guinea and reached Australia.

    Andaman islands is important because the first clade in the cladogram of world languages is Andamanese and Non-Andamanese. It is very clear to me, as a layman, not a strict scientist, the Great Leap Forward that happened 75000 years ago in our history was the development of abstract language and the ability to exploit coastal resources.

    So yeah, tide prediction changed our history. But not 75 years ago in Europe, but 75000 years ago in South Eastern Africa.

    • by slew ( 2918 )

      It is very clear to me, as a layman, not a strict scientist, the Great Leap Forward that happened 75000 years ago in our history was the development of abstract language and the ability to exploit coastal resources.

      So yeah, tide prediction changed our history. But not 75 years ago in Europe, but 75000 years ago in South Eastern Africa.

      Although this is all very interesting, I submit that it is merely serendipity to take advantage of the benefits of tide, but not the actual *prediction* of tides that changed human history in this case.

      Although prediction of future events has been very useful in human history, we should not overstate it. Lest we devolve in to the shadow of practice like numerology, astrology, and other such fortune telling nonsense, because of course stopped clocks are still right twice a day...

    • Great Leap Forward!! What?!!!? Please tone down the sensitivity, man! More people died in the Great Leap Forward than the Holocaust. Let's not re-use the name for something else because it doesn't fit. Seriously, you do not mess with things like this, man.
      • by 140Mandak262Jamuna ( 970587 ) on Friday October 09, 2015 @06:26AM (#50692009) Journal
        I did not know Nazi's were using this phrase. I give rats tail to Nazis. I have seen "Great Leap Forward" being used in this context, to the unknown combination of traits that changed our species from anatomically modern H sapiens to behaviorly modern H sapiens. It is not something I coined. I'm not going to abandon it and cede permanent ownership to the Nazis. [] [] []

        But I did know the Nazis were using the Swastika symbol. So what? I will proudly and happily use the Swastika for what it is, a Hindu symbol and a decorative motif from ancient India. I recently ran into a group Indians and their priest in the Starbucks (@ State College PA) The women were wearing white saris with ornate decorative borders. The motifs in their border? The Swastika and the Star of David alternating in a series!

        Not sure how many noticed the irony!

        • Um, "Great Leap Forward" refers to Mao Zedong's agricultural revolution, which is thought to have killed tens of millions of people.

          Nothing to do with the Nazis.

          • Realized it after posting it. Still, commies, nazis the principle is the same. They are propagandists, and they would usurp very good phrases and symbols. If we eschew them for ever, they win.
  • put them in separate buildings?

    That seems like doubling the probability of getting screwed by a bomb. Was there some reason they could replace either machine but not both of them?
    • by Anonymous Coward

      Our (United States) No. 2 tide prediction machine was kept in the basement of the Dept. of Commerce during the war.
      It is now on display at the National Ocean Service headquarters in Silver Spring, Maryland.
      I worked in the tide prediction office for more than 30 years. One of my coworkers was the last person to actually use the machine in the early 1960's.

  • " it's driven by gravity between the moon and earth and there's a lot more to it."

    I'm pretty sure the gravity of the Sun has something to do with it as well.

  • "Laplace’s hydrodynamic approach to tide prediction was first put into use by William Thomson, who would later become Lord Kelvin."

    Dude scienced so hard he leveled up like motherfucking Gandalf.

I THINK MAN INVENTED THE CAR by instinct. -- Jack Handley, The New Mexican, 1988.