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Blue Pool - colour change phenomenon

  1. Jul 27, 2009 #1
    On the weekend I visited Blue Pool in Dorset, England.

    This is an old abandoned clay mine that has filled with water to produce an attractive pool. Apparently the colour of the pool constantly changes colour....

    http://www.bluepooltearooms.co.uk/" [Broken]

    I didn't observe the colour changes myself, but I wasn't exactly making scientific observations, the changes didn't leap out at me, they are very subtle or very gradual if they exist at all.

    But why does the pool change colour at all? (Assuming that it actually does change colour.) Is the explanation of fine clay particles diffracting light a viable explanation? I can't help question that explanation because surely the clay particles would all be randomly oriented, surely you would require alignment and some kind of group behaviour to get this effect?

    Can anybody out there shed any light on this for me? Perhaps its a complex dynamical effect?

    Thanks
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jul 27, 2009 #2
    The braggs equation of diffraction
    n(lambda)=2dsin(angle)
    n is the order of diffraction, lambda is wavelength, d is the width of the grating element(distance between two particles of clay)
    If the distance is of the order of the wavelength of light, different colors are diffracted differently at the plane of the particles depending on all the above factors
    You see different spots at different colors, since the particles are not stationary, you see changing colors
     
    Last edited: Jul 27, 2009
  4. Jul 27, 2009 #3

    DaveC426913

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    Is it possible that the colour changes occur over longer times than is the assumption? It sounds like you assume seconds or minutes. Is it possible it's more like hours?
     
  5. Jul 27, 2009 #4
    I have a problem understanding why the pool as a whole changes colour. Unless, individual bits of the pool change colour and give the overall impression of a colour change? But then why don't those small individual changes just kind of balance each other out providing an overall stationary effect?

    In the leaflet I had it said the changes occured over a period of minutes. I haven't found any validation of that though, and nothing online.
     
  6. Jul 27, 2009 #5
    Did you understand the equation?
    The individual molecules in water do not change color
    It's diffraction, white light that comes out of the pool and hits your eyes is no more white light because its constituents split up differently according to their wavelengths only if the clay particles are close enough to satisfy the equation(of the order of 1000 AU)
    The poool would be looking colorful with different spots on the surface in different colors which change if the particles change distances or you change the line of sight.
    And yes, it gives a stationary effect at one spot if the wavelengths along the line of sight give VIBGYOR, but that is not quite possible
     
    Last edited: Jul 27, 2009
  7. Jul 27, 2009 #6

    DaveC426913

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    You are misunderstanding. No one thinks the molecules are changing colour. The mystery is why virtually the whole pool (it seems) is acting in-concert. i.e. why would the entire pool have the separation of its clay particles change simultaneously?


    I think one of the problems we're encountering in this thread is that we don't have an accurate account of what is actually observed. One critical question at least: How much of the pool changes colour? Small sections? All of it at once?

    Well, at that distance, they're unlikely to be orbiting the Sun, let alone affecting the Blue Pool! :biggrin:
     
  8. Jul 27, 2009 #7
    No it's Armstrong unit not astronomical unit
     
  9. Jul 27, 2009 #8
    Small sections, every point
     
  10. Jul 27, 2009 #9

    DaveC426913

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    What is an Armstrong unit?

    (And why would it have the same abbreviation as another distance unit?)
     
  11. Jul 27, 2009 #10

    DaveC426913

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    Do you know this? Have you personally seen it, or read an account of it?
     
  12. Jul 27, 2009 #11
    What do yoou mean? Even if they don't the pool appears colorful.Places where the particles change position change color
     
  13. Jul 27, 2009 #12

    DaveC426913

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    You are guessing. I am inquiring as to the actual observed experience.
     
  14. Jul 27, 2009 #13
    10^-10 meters it is written as an A with a small circle above
     
  15. Jul 27, 2009 #14

    DaveC426913

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    Yes, it is.

    So what does that have to do with AUs (Astronomical Units) or these Armstrong units you speak of?
     
  16. Jul 28, 2009 #15
    What happens when you see sunlight through a small gap between your fingers?It splits up That is exactly what happens here see the last part in this"[URL [Broken]
     
    Last edited by a moderator: May 4, 2017
  17. Jul 28, 2009 #16

    cristo

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    You mean Angstrom, not Armstrong!
     
  18. Jul 28, 2009 #17
    Oh sorry
     
  19. Jul 28, 2009 #18

    DaveC426913

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    You fun-wrecker... :devil:
     
  20. Jul 28, 2009 #19
    He really is?
     
  21. Jul 29, 2009 #20

    DaveC426913

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    Yes. He ruined my fun.

    I was teasing you about AUs and about Armstrong unit (apparently, 'Armstrong' is a common misspelling of Angstrom. Don't know why).
     
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