Thanks for your response. I agree with your score card. Your photos was way better! Certainly the best I have seen. I have yet to hear a clear scientific explanation. The Wiki site was particularly garbled I thought. I am not sure I can do any better but here for the fun of it is my best shot: The reason that the sky is blue during the day is because the very short wavelength part of the spectrum (blue light) is reflected off the water particles in the outer atmosphere and diffused throughout the lower atmosphere. The reason that sun sets are red is that the light from the sun has far more atmosphere to pass through as it nears the horizon than it does when it is high in the sky. (A simple drawing would demonstrate this.) More water particles ( and pollution) equal more refraction and thus only the very long wavelength (red light) reaches our eyes. The visible light spectrum is comprised of blue red and green light. Our eyes are less sensitive to green light than they are to either red or blue light, however the green light is of course still present in the white light emitted by the sun. It is perhaps unfortunate that we usually cant see it. Other creatures probably do see it. However, now and again, when the red light is particularly visible ( as it has been for the last few days) a small portion of the green light becomes visible to the human eye. (don't ask me why I don't know!)
The point I was trying to make in my previous posting was, however, a separate, though related one. Here it is in detail: The reason some people see the flash and others, (perhaps even sitting at the same table) do not must surely be physiological? I.e. to do with the colour receptors in the eye and the brain of the individual. At other times the very same person who didn't see the green flash yesterday may see it tomorrow. The camera, in this case, even if it is digital, cannot lie. Why? Because it is constructed to record colour the way we see it. This "machine vision" is calibrated to replicate the total spectrum of light which the human eye can perceive. As such what the camera "sees" is not subject to physiological variation. It therefore follows that our experience of the green flash may be defined as a "subjective" experience.
The green flash is therefore a perfect example in favour of Kant's argument that we can never fully know the world as such and that what we see out there is always a product of our perceptual processes.
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