How Analog Tide Predictors Changed Human History (hackaday.com) 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.
Moon... (Score:2)
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)
Dice (Score:3, Funny)
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.
You can't explain that... (Score:3, Funny)
You'd think Tide prediction would be quite easy, it comes in, it goes out.
Unless you're Bill O'Reilly [newser.com]:
“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.
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Re:Summary fail (Score:5, Informative)
Or you could, you know, look it up: https://en.wikipedia.org/wiki/... [wikipedia.org]
It isn't like somebody threw out a specialized acronym and expected people to understand the subject matter instantly. You could get a pretty good guess what was going on from the context and the details are secondary to the story.
After that, if you want to know specifically what Kelvin's Predictor was or how it works, it's not to hard to look it up.
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Here's how you do it:
Highlight a term that you want to look up, such as "Kelvin's Predictor". Right-click, and select "search google" from the popup menu. A new tab will open up, and google will present various hits. Wikipedia entries are typically at the top of the list and often gives and adequate explanation of the term. If not, a review of all the hits and what the links point to gives an idea of what the term is. Total time spent to find the information should be under 5 seconds, longer if there is no
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Oops, didn't go far enough, it *was* on the wiki page: American Mathematical Society/Bill Casselman (2009), animated JAVA simulation based on Kelvin's Tide Predicting Machine (the animation shows computing 7 harmonic components).
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> she lifts oceans,
Actually, no, the moon does not lift oceans.
If gravity did 'lift oceans' then a pressure gauge on the sea bed would show the same reading whether the tide was in or out. It actually shows the exact correct reading for the depth of the water regardless of where the moon is. So, no, the moon's gravity does not pull the water up.
The moon does not go around the earth. They both go around a common centre of gravity which is not the centre of the earth. This offset around which the earth wob
Tide prediction probably saved the human race (Score:5, Interesting)
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.
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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...
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Great Leap Forward,it is. (Score:4, Interesting)
http://www.pbs.org/wgbh/nova/e... [pbs.org]
http://schools.yrdsb.ca/markvi... [yrdsb.ca]
http://www.ncbi.nlm.nih.gov/pm... [nih.gov]
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!
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Nothing to do with the Nazis.
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or perhaps... "other elegant computers" (Score:2)
Not to say that they are more elegant, but they are elegant, and another example thereof. Sorry English is such a shitty language that it routinely introduces serious ambiguity with as few as three words.
FWIW, English only allows you to be ambiguous, you could have written "other elegant computer"...
Wait, they had two irreplaceable machines and they (Score:1)
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?
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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.
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It's basic, layered security principles.
Neither machine was irreplaceable, however neither machine was *easily* replaceable either.
Also, either machine could do *part* of the job needed, but not the *whole* job needed. There were other, similar (though less accurate/precise) machines elsewhere that could be pressed into service if needed while one destroyed machine was being replaced. You can use those other machines either to generate the inputs for the second machine, or process the outputs of the first
Some still don't get it (Score:1)
https://www.youtube.com/watch?... [youtube.com]
Cpmplex gravitation (Score:2)
" 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.
covered in PBS "secrets of Normady" last year (Score:2)
Back when Science was Metal \m/. .\m/ (Score:1)
"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.