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To see the air.

  1. Jul 28, 2012 #1
    My apologies if this post hit the wrong topic.

    I was wondering if it's possible to "see" the wind by means of an spectrometer or a similar device. I'm aware that light passes through air and it does leave behind some portion of it's wavelength through absorption, and this is invisible to the human eye thus we can't see it.

    If it's impossible to perform such thing, how about other properties, maybe water molecules. Could these be seen? Please note that I'm referring to a small, micrometereologic scale, for winds inside a person's seeing range, and not from a macroscopic view.

    Thank you.
     
  2. jcsd
  3. Jul 28, 2012 #2
    Actually we can observe refracted light passing through different air densities (heating of the road or looking at the light passing through the air around a bunsen burner). I gotta think that it would be theoretically possible for some type of machine to magnify the effect of different air densities in wind so that the human eye could pick it up. Temp changing air densities would have a much larger effect, in fact wind can mess this up.

    Another route would be to put something into the air that allows you to see wind. dust, smoke...
    Only smaller that an eye or machine could detect the movement when air strikes it. Aerodynamic "smoke" for cars type thing... A candle that has burned out shows this nicely except that the heat plays a bit of a role in changing the air flow. I personally used to watch dust move about as light came through a window at just the right angle... and I actually saw a fly defecate (it was stationary) sitting on a window sill. I digress...
     
  4. Jul 28, 2012 #3

    ZapperZ

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    Is there a rational reason to go through all of this? Why would you want to "see" air? What is wrong with other means of detection?

    Zz.
     
  5. Jul 28, 2012 #4
    The reason is mainly curiosity, although a device that helps to see close wind current velocities and their temperatures would prove to be very useful to the aviation community in general. I'm particularly interested in this because of my hang-gliding avocation.

    Putting a certain particle in the air would be effective, as I know this approach is used in wind tunnels to determine wing foil aerodynamics, however, I am looking for a less contaminant alternative, and it's also of my interest to achieve visualization of temperatures. The main problem with this approach, though, is that the smoke or dust would be carried away by the wind rapidly, and unless it's invisible to the human eye, it can obstruct a pilots seeing range.

    I'm aware that the visualization of H2O has been attempted, although it seems that the project is abandoned. Maybe thermal vision devices could be calibrated to show the air currents. Or maybe another molecule present in the air can be detected?
     
  6. Jul 28, 2012 #5
    Interesting.

    A question...

    Do they have some sort of hand held device that can fire some sort of "smoke/dust" bomb that would allow a hang glider to see where down drafts and up drafts are? Kinda like if you got into a bit of trouble and needed to try to lose or gain altitude?

    As for your question, out of my league now.
     
  7. Jul 28, 2012 #6

    Danger

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    I've heard it postulated that birds can see air currents, as an aid to catching thermals and suchlike. Do any of you know whether or not there is a basis in fact?
     
  8. Jul 29, 2012 #7

    A.T.

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    In high tech sailing they use laser wind sensors:

    https://www.youtube.com/watch?v=OxIm6qqm5so

    It might be possible to combine this technology with augmented reality devices to visualize the air movement more directly.
     
  9. Jul 29, 2012 #8
    I don't think that concluding evidence of what birds see is possible, but if anything, birds can feel air currents, because of the fact that to fly is their nature, and they possess an organic interpretation of the environment's variables.

    That Racer’s Edge® LWS might be exactly what I'm after, although $149,500.00 might be a bit high, and the firing approach could prove to be inadequate for real-time mapping. Could this be conceived differently, like a radar, and within the possibilities, less expensively?

    A smoke-grenade sounds fun, although wind currents are invisible and could be hundreds of meters away from a pilot. This is certainly a clever approach, and could be some sort of technique for special situations (determining a certain rising current's borders, maybe), but it wouldn't be useful for mapping either.
     
  10. Jul 29, 2012 #9

    krd

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    The thing to remember about the visual spectrum, is the rest of the spectrum is still there, just we can't see it. And that's our visual spectrum - I'm pretty sure butterflies and some other things see different spectra.

    If birds could see infrared - and if they could get a depth perception - they might be able to see the thermal vents.

    I would say they probably don't see them, and can just feel them. You don't need a weather man, or infra-red vision, to tell which way the wind blows.
     
  11. Jul 29, 2012 #10

    Danger

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    I suspect that you're right about birds just feeling the air. It seemed to me that I did that as a pilot, although I might be wrong. The idea of birds actually seeing it was probably just romanticism on my part, since I think that they should have a better mastery of the sky than we do.
    As far as bugs go, it's an established fact that most of them can see into the UV band. I'm not sure about IR, but it's likely.
     
  12. Jul 29, 2012 #11

    A.T.

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    It's a portable device running on batteries. If energy consumption is not an issue, you could of course fire it continuously and scan a perimeter with it. This is nothing a hang glider could have on board. But it was tested on bigger planes:

    http://adsabs.harvard.edu/abs/1995SPIE.2464..109T

    http://www.docstoc.com/docs/51910688/The-Gunship-Ballistic-Winds-(GBW)-Remote-Wind-Sensor-was

    https://www.youtube.com/watch?v=lxlSZ-SB1XQ
     
    Last edited: Jul 29, 2012
  13. Jul 29, 2012 #12

    krd

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    An interesting thing about the visual spectra - and this probably applies for animals too - it has to be in the gaps of the absorption spectra of atmospheric gases - otherwise those gases would appear to us like fogs - and you can't have too much vision in the infrared because there's so much of it around you wouldn't be able to see anything clearly. Our visual spectra allows us just enough to see, but not enough to make our lives difficult.

    I was thinking before - you could have aliens on planet with different atmospheric gases. They could be walking around in what looks to us like a dense fog, but they wouldn't be able to see that fog, and everything would be clear.

    And the same aliens might come along to earth - and while they're orbiting to them, the earth wouldn't seem blue with a few wisps of cloud. It would look like a planet shrouded in a gaseous fog. Depending where their visual spectra is.
     
  14. Jul 29, 2012 #13

    Danger

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    Krd, that is one of the coolest things that I've read in years. That approach never crossed my mind. (That's rather embarrassing, since I was a hard SF writer.) I can "see" what you mean about the clouding effect just from experience with night vision apparatus. Targets usually show up, but there's definitely a lot of clutter.
     
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