1. Mick West

    Mick West Administrator Staff Member

    I've noticed that the cheaper the camera nowadays, the brighter the colors. The more expensive digital SLRs now produce much flatter, but more accurate colors, but small pocket cameras often have a "vivid" setting more as a default. It simply makes your vacation photos look better.

    Comparison - look especially at the blue of the base.
    [​IMG]
     
    Last edited: May 18, 2014
    • Like Like x 1
    • Agree Agree x 1
  2. Leifer

    Leifer Senior Member

  3. KAT

    KAT Active Member

    Hate to rain on the parade here but....

    I have it on "good authority" that the sky is blue NOT because of of our memories or because of Manganese di-Bromo di-Fluoro-Benzidine (salts).

    It is blue from OZONE.

    this particular one from http://www.drkalidas.com/pathways/oxidative.html
    but this concept is widely promulgated on sites advertising its benefits, the bit I changed to red. Might be worth a debunk of its own, that idea.
     
  4. jonnyH

    jonnyH Active Member

    Are these the "remarkable medical properties" to which the good Dr refers?
     
  5. KAT

    KAT Active Member

    NOPE. It is only harmful if breathed. If taken in water or by injection it is about 30 different kinds of good for you. Fancy (and not cheap) clinics take a pint of your blood, add ozone while you watch then transfuse it back. It is tangentially related to the hydrogen hyperoxide cure. I'll do a thread on it when I get more time, or you're welcome to if you like.
     
  6. Mick West

    Mick West Administrator Staff Member

    It's not clear if you were joking, but the sky is not blue due to ozone, it's blue due to Rayleigh scattering from the nitrogen and oxygen. Nothing to do with ozone.
    http://en.wikipedia.org/wiki/Diffuse_sky_radiation

    Ozone health stuff is off-topic.
     
    • Like Like x 1
  7. WeedWhacker

    WeedWhacker Senior Member

    Yeah, that occurred to me too.....since Rover pics from Mars (a planet with a VERY thin atmosphere in comparison to Earth's) show a blue sky as well. And, AFAIK Mars does not have an ozone layer similar to Earth's.

    I will say, though, that Human visual perception is key, in this discussion. (And possible flawed memory). But, would certainly be interesting (to say the least) to be able to view the Martian sky with the unaided, naked eye. Ah well.....one can dream....
     
  8. KAT

    KAT Active Member

    I said I had it on "good authority" in quotes, and then mentioned it is widely promoted for health benefits as well. I thought the varied fonts and colours would help too....and you thought I was serious? maybe we need a joke icon.
     
  9. WeedWhacker

    WeedWhacker Senior Member

    LOL! (That, at least...though dated, is obvious). Much relief was had by all...........
     
  10. Mick West

    Mick West Administrator Staff Member

    I said it was not clear if you were joking, i.e. not clear to everyone who might read this. We don't want to promote misconceptions by repeating them ironically.
     
  11. deirdre

    deirdre Moderator Staff Member

    we do have a joke icon.
     
  12. Mick West

    Mick West Administrator Staff Member

    • Like Like x 1
  13. skephu

    skephu Senior Member

    The sky may not be less blue today than it used to be when the sky is clear, but we have clear blue skies less often because of the increase in cirrus coverage over North America and Europe. And invisible cirrus haze (which has become more common) does make the sky less blue. In that sense, I believe there is truth to the statement.
     
  14. Mick West

    Mick West Administrator Staff Member

    Citation needed! How much, and how often?
     
  15. skephu

    skephu Senior Member

    You know that there are a lot of papers about cirrus trends in recent years. See e.g. Minnis P: "Contrails, cirrus trends, and climate" from 2004, followed up by a truckload of papers on the same topic.
    In the 2004 paper, Minnis calculated the frequency of clear skies, and found that in the USA it decreases by 1.3% per decade. But that's the absolute change, not the relative change. Given that clear-sky coverage is about 40%, the relative decrease is about 3.2% per decade. That means that in the last 50 years, clear skies may have decreased by about 15% over the US. This is mostly caused by the increase in cirrus which is mostly due to contrails.
     
  16. Graham2001

    Graham2001 Active Member

    Found this circa 1940s (Believed to be of the 1944 Eruption of Mount Augustine, slide film used not specified) slide on the Alaska Volano observatory website, I'll admit I've no idea if they've digitally tweaked the image, but it also looked to my eyes as if it had been take more recently.
    [​IMG]
     
  17. skephu

    skephu Senior Member

    I would expect that the blueness of the sky is correlated with the known global dimming/global brightening processes:
    [​IMG]

    This paper from 1981 demonstrates a significant reduction in the number of clear days and an increase in the number of cloudy/hazy days per year starting from 1901:
    Stanley A. Changnon, 1981: Midwestern Cloud, Sunshine and Temperature Trends since 1901: Possible Evidence of Jet Contrail Effects. J. Appl. Meteor., 20, 496–508.

    The paper implicates contrails in the decrease of clear days in areas of heavy air traffic:
    Of course, industrial pollution, smog, etc. also contributed to the increase in cloudiness/haziness, and probably a less blue sky, or a decrease in the number of clear days when the sky is as blue as it used to be.

    Global brightening in the last 20 years may have reversed this globally, but probably not everywhere locally.
     
    Last edited: Mar 20, 2015
    • Like Like x 1
  18. Trailblazer

    Trailblazer Moderator Staff Member

    • Like Like x 1
  19. Trailspotter

    Trailspotter Senior Member

    However, there is ONE picture of the deep blue sky:rolleyes:

    This suggests that the colours in this set of old photos are probably real and not fainted over the time.
     
    Last edited: May 1, 2015
    • Like Like x 1
  20. Whitebeard

    Whitebeard Senior Member

    Nice pic of a Trident 3 as well
     
  21. Balance

    Balance Senior Member

    I would just like to throw it out there, that I was fortunate to know a man that knew some men that maintained the flight simlators at Heathrow. I was informed for the cost of a bottle of whisky on any weekend, I could play the slot machines for an afternoon. Turned out our slot machine was the Trident 3.

    Aside from the fact my sister crashed (tipped the wings on landing thinking it could be steered by the steering wheel as it went off course on the tarmac) and I ploughed through the runway barrier and halted on the perimeter road because I didn't know where the brakes were - we had a great time! I can boast, after the learning experience I successfully landed at Kai Tak first attempt, though the engineer glanced at the graph and uttered "...bit of a fighter approach but you got it down" :cool:
     
    • Like Like x 2
    • Funny Funny x 1
  22. Trailspotter

    Trailspotter Senior Member

    I wouldn't know. To me it is just another trijet, similar to one that I flew by regularly at the time.
    [​IMG]
    This picture was taken in 1980, the year of Moscow Olympics. As one can see, the sky over my old country was bluer too :cool:
     
    Last edited: May 1, 2015
  23. Spectrar Ghost

    Spectrar Ghost Senior Member

    You flew Tupolevs?
     
  24. Trailspotter

    Trailspotter Senior Member

    No, Tupolevs flew me:)
     
    • Funny Funny x 6
  25. Spectrar Ghost

    Spectrar Ghost Senior Member

    Well played.
     
  26. Donnn

    Donnn New Member

    Just want to add: When the human eye grows older, it often looses some of it's capabilities. This can be associated with particular forms of illness, but even without major illness there is a degradation happening.
    This is not limited to the tissue of eye itself, but can also be a form of age dependent neuro-degeneration.
     
  27. M Bornong

    M Bornong Senior Member

    http://www.thisiscolossal.com/2014/...d-tool-for-measuring-the-blueness-of-the-sky/

    [​IMG]

    It seems to me they were seeing the same hues, we do, more than 200 years, ago.
     
    Last edited: Mar 2, 2016
    • Like Like x 4
    • Winner Winner x 1
    • Informative Informative x 1
    • Useful Useful x 1
  28. Rocky Milano

    Rocky Milano New Member

    Its not that the sky is a different color blue, its that there aren't any blue sky days anymore. Just a dull thin layer of contrails spreading in the form of grid pattern days. Right Mick?
     
    • Funny Funny x 2
  29. deirdre

    deirdre Moderator Staff Member

    what do you mean? There are tons of blue sky days still.
    blue.PNG
    P1010363.JPG
     
    • Agree Agree x 2
  30. Spectrar Ghost

    Spectrar Ghost Senior Member

    Just today we had a clear sky, with just a few clouds off to the south and east. Particularly noteworthy was the fact that what persistent contrails there were occurred only in very close proximity to the existing clouds, where the high RH would naturally be. Each appeared to end fairly abruptly at a consistent distance from the cloud proper, too.
     
  31. Trailblazer

    Trailblazer Moderator Staff Member

    There are still plenty of blue sky days. When the air is dry, you won't see persistent contrails and the sky will be just as blue as in the past.

    What may well be true is that days where conditions are suitable for cirrus formation will be somewhat cloudier nowadays than they would have been in the days before widespread air travel, especially in areas (like where I live) that see lots of overflights.

    When the sky is clear, though, it's probably a lot clearer than it was 100 years ago, especially in cities, thanks to the reduction in smoke pollution from sources on the ground.
     
  32. NoParty

    NoParty Senior Member

    As much as I LOVE bright blue days...we've had far, far too many of them the last few years...
    such that my incomparable, gorgeous state of California is in a dire drought condition.


    That said, I love the Cyanometer...and since Amazon doesn't appear to be selling 'em,
    I may just print this one on nice, durable card stock for those stunning Yellowstone skies...
     
  33. skephu

    skephu Senior Member

    NOAA's Chuck Long's research shows the sky is whitening:
    Evidence of clear-sky daylight whitening: Are we already conducting geoengineering?

    Direct shortwave radiation from the Sun shows no trend (red curve) but diffuse radiation (blue curve) is increasing:

    upload_2016-4-27_18-1-35.


    The red-to-blue ratio of the color of the sky is increasing:

    upload_2016-4-27_18-3-46.

    indicating that there is a whitening trend. So, OP is debunked.

    Chuck Long hypothesizes that the culprit for the whitening may be increased "ice haze" from increased jet air traffic.
     
  34. NoParty

    NoParty Senior Member

    • Funny Funny x 1
  35. Trailblazer

    Trailblazer Moderator Staff Member

  36. skephu

    skephu Senior Member

    I have tried to illustrate the change in the sky's color according to Chuck Long's research. His research shows that the red-to-blue ratio, red measured at 870 nm and blue at either 415 or 500 nm, has increased by ~10% in 16 years. Unfortunately, 870 nm is infrared, which cannot be represented as an RGB color. So for simplicity, I just assumed that the R/B ratio in the sky color just increased by 10%. Also, his research shows a 4.5 W/m2 increase per decade in diffuse radiation, so in 16 years that is about 7 W/m2. Since the total radiation is about 1 kW/m2, this means a 0.7% increase. So I assumed that R+G+B would increase by 0.7%. This gave the following comparison:

    upload_2016-5-1_14-11-1.
    Left half of the image is "sky blue", corresponding to RGB components (135,206,250). Right half is (145,206,244). This corresponds to a 10% increase in the red/blue ratio and a 0.7% increase in overall brightness.

    Would you notice the difference? And if it occurred slowly over 16 years?
     
    • Informative Informative x 4
    • Useful Useful x 1
  37. M Bornong

    M Bornong Senior Member

    Was Charles Long talking all days in general, or only days when contrails are forming,is there a day to day hold over of the ice crystals? Shouldn't the ice crystals fully sublimate on the days of low humidity at flight level?
     
  38. skephu

    skephu Senior Member

    It's a yearly average over days classified as clear-sky conditions (no visible contrails). There can be a sub-visible cirrus haze that is still classified as clear sky.
     
  39. M Bornong

    M Bornong Senior Member

    thanks, that would still be days that are borderline or approaching conditions for contrail formation, wouldn't it? If it's too dry up there we are not going to see the cirrus haze, it really means we are seeing more days with haze, is that correct?
     
  40. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    There is a thing called the Angstrom exponent https://en.wikipedia.org/wiki/Angstrom_exponent which gives a measure of aerosol size. This relates to attenuation of the sun (AOT) as a function of wavelength. Scattering is sort of the opposite, but since nothing (up there) is smaller is smaller than a molecule, any aerosol, or sub-visual cirrus, is going to make the sky whiter/less blue than the case with pure Rayleigh scattering.