Always a pleasure talking with you.
1) thank you for your kind comment. Im glad to see that Keith's scientific explanation, though far clearer than my attempt was not so very different.
2) Indeed the power of suggestion is astounding: here is a very strange tale: Long before the radio telescope was invented, the existence of the far distant planet Uranus and it's orbit was accurately predicted. The details of it's orbit were calculated mathematically. Once a powerful enough telescope was available : bingo! There it was, exactly as predicted. The strange thing is that a number of years later a researcher went back and checked the maths. They were completely wrong.
3) Green screen. When I quoted that the camera never lies I was being absolutely literal. The statement is limited to the image received by the camera's led sensors(or emulsion)it does not include image manipulation techniques like, for example green screen. Here, as you have suggested, a green object is only green because it reflects the green portion of the visible light spectrum. Remove green light from the source of illumination and any green objects will appear to be black. A different image can then be inserted into these black areas. This is generically known as masking. Your point is well taken. Exactly! If there is no green light getting through our atmosphere at sunset then we will not see any green light. But should some green light manage to get through, then our eyes and our cameras will see it.
However i suspect that the issue is, complicated by the way our eyes function. If overloaded with red and blue they will tend to produce after images in the complimentary colour, ie Green. Now a green flash of this sort is physiologically produced and will not be recorded by a camera. "Machine vision" Unlike the camera human eyes get tired!
So my thesis is that there are actually two different types of green flashes. Only one of them is visible to the camera (machine vision) but both are visible to the human eye. Usually the two types will tend to overlap. This may well suggest why two people sitting together may not see the same thing. The physiological version will tend to be diffused, as after images usually are (a green flash) whist the light from the sun will tend to be more focused (A green dot or patch) In a situation such as this, human vision is thankfully fallible. A bit like this theory!
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