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  1. #1 the rivers 
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    Is the actual length of a river divided by its length at the flight of birds equal to the number Pi ?


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  3. #2  
    Time Lord Paleoichneum's Avatar
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    Gibberish much?


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    Quote Originally Posted by Paleoichneum View Post
    Gibberish much?
    Nah Paleo, you're just not on the OP's level.

    The answer is clearly: Banana because the grass is green and I ate a cookie.
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    Forum Junior anticorncob28's Avatar
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    I have no idea what the flight of birds thing means, but the length of a river divided by the distance between its endpoints is on average pi when you take all rivers in the world.
    Or at least, numberphile says that a paper pubished says so:
    https://www.youtube.com/watch?v=TUErNWBOkUM
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    I have no idea what the flight of birds thing means
    I’m guessing ‘as the crow flies’ although not sure where that might figure in. Straight line nonetheless.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
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    Quote Originally Posted by zinjanthropos View Post
    I have no idea what the flight of birds thing means
    I’m guessing ‘as the crow flies’ although not sure where that might figure in. Straight line nonetheless.
    Oh, that makes sense.
    The OP has a good question; it was just worded oddly.
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  8. #7  
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    Quote Originally Posted by anticorncob28 View Post
    Quote Originally Posted by zinjanthropos View Post
    I have no idea what the flight of birds thing means
    I’m guessing ‘as the crow flies’ although not sure where that might figure in. Straight line nonetheless.
    Oh, that makes sense.
    The OP has a good question; it was just worded oddly.
    when all else fails...google it. Checked it out here. Learned a little about sinuosity but unfortunately Pi didn’t cut.

    https://www.theguardian.com/science/...rs-truth-grime
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
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  9. #8  
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    Quote Originally Posted by zinjanthropos View Post
    Quote Originally Posted by anticorncob28 View Post
    Quote Originally Posted by zinjanthropos View Post
    I have no idea what the flight of birds thing means
    I’m guessing ‘as the crow flies’ although not sure where that might figure in. Straight line nonetheless.
    Oh, that makes sense.
    The OP has a good question; it was just worded oddly.

    when all else fails...google it. Checked it out here. Learned a little about sinuosity but unfortunately Pi didn’t cut.

    https://www.theguardian.com/science/...rs-truth-grime
    Nice!

    This is actually good science and does not belong in the Trash but in Earth Sciences. I'll report it to Dywyddyr asn see if he will move it.

    I think we were all thrown by the OP's eccentric grasp of English idiom (flights of birds = as the crow flies). I think he is francophone.
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  10. #9  
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    If the river is straight doesn't the result of the division equal 1?

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  11. #10  
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    Quote Originally Posted by geordief View Post
    If the river is straight doesn't the result of the division equal 1?

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    Yes, that's what the Grauniad article says. But the mean value of sinuosity from 258 rivers is 1.94. Nowhere near π.
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    Forum Radioactive Isotope zinjanthropos's Avatar
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    In the 3D world the shortest distance measured between river source and its end would be a straight line through the Earth so by using that measurement for ‘as the crow flies’ I think the mean would push closer to Pi? Or is it wrong to substitute a third dimension measurement for a 2D calculation? IOW sinuosity is strictly a two dimensional thing?
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
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  13. #12  
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    Well,measured that way the distance between the beginning and end of a straight river would look like a line intersecting an arc section of a circle.

    If the river did a full 180 degrees of the surface of the sphere ( a great circle?) then the distance ratio would pi/2 I think.
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  14. #13  
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    Quote Originally Posted by zinjanthropos View Post
    In the 3D world the shortest distance measured between river source and its end would be a straight line through the Earth so by using that measurement for ‘as the crow flies’ I think the mean would push closer to Pi? Or is it wrong to substitute a third dimension measurement for a 2D calculation? IOW sinuosity is strictly a two dimensional thing?
    The difference that would make would be negligible, except for the very longest rivers in the world.
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  15. #14  
    Forum Radioactive Isotope zinjanthropos's Avatar
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by zinjanthropos View Post
    In the 3D world the shortest distance measured between river source and its end would be a straight line through the Earth so by using that measurement for ‘as the crow flies’ I think the mean would push closer to Pi? Or is it wrong to substitute a third dimension measurement for a 2D calculation? IOW sinuosity is strictly a two dimensional thing?
    The difference that would make would be negligible, except for the very longest rivers in the world.
    Cant find a good scientific definition of what constitutes a river complete with minimum measurable requirements. Not really sure what qualifies as a river. I live close to a vast flowing stream of water called the Niagara River which as I understand isn’t a river at all but a strait connecting two large bodies of water. Then there are rivers that are seasonal or dry at times. I’ve seen creeks wider than rivers and meandering streams that run for very long stretches.

    Where exactly do we measure the start of a river, or it’s end?
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
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  16. #15  
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    Quote Originally Posted by zinjanthropos View Post
    Quote Originally Posted by exchemist View Post
    The difference that would make would be negligible, except for the very longest rivers in the world.

    Cant find a good scientific definition of what constitutes a river complete with minimum measurable requirements. Not really sure what qualifies as a river. I live close to a vast flowing stream of water called the Niagara River which as I understand isn’t a river at all but a strait connecting two large bodies of water. Then there are rivers that are seasonal or dry at times. I’ve seen creeks wider than rivers and meandering streams that run for very long stretches.

    Where exactly do we measure the start of a river, or it’s end?
    Don't think that matters for this exercise. Sinuosity can just as easily be determined for a river 5 miles long as for one 500 miles long. Though presumably sinuosity increases with senility, I'd have thought. Most rivers are fairly well-defined, with a source determined to within a few hundred metres and an end either at the confluence with a larger one or whether they enter the sea. Though I suppose where the river stops and the estuary begins can sometimes be hard to define exactly.
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