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Green Phenomena of Sunrise and Sunset

A few things you didn't know about the "green flash" .

Why you may want to explore the pages here on the "green flash" , more properly known as the green phenomena of Sunrise and Sunset.

You are watching the Sunrise as the Sun approaches a very low horizon .
Wham ! Bam !
Suddenly and unexpectedly , you see brilliant green light at the orient , the point on the horizon where the Sun rises .
It grows .
You are shocked .
You know immediately that this utterly startling , this fantastic , this glorious sight is something you will never forget .
Soon , the yellow light from the Sun forces you to look away .
You think : "I just saw the green flash. This was a truly remarkable display. I am so fortunate to see it."
Actually , although your observation is very accurate , you didn't see the green flash .

The "green flash" , if that term is ever determined to be a proper term , is dramatically brighter , flash-bulb bright , and dazzling .

The remarkable display you have seen is a green dot , or perhaps it should be called a green glow or a green spot or a green shift or a green patch .
Despite appearances , it is not actually something otherworldly .
At the risk of oversimplification , the green light from the Sun forms a green solar disk .
Using a term familiar to high school geometry students a century ago , an idealized Sunrise would display as a green _segment_ , the top portion of the green solar disk as it emerges above the horizontal line of the horizon .
You didn't think so at the time , but this green light is the Sun itself , or at least the green light from the Sun .
The Earth's atmosphere , acting as a prism , has split the light from the Sun into spectral colors .
The violet and blue suns rose first , but their light was scattered by that same atmosphere into insignificance .
When the green sun rose , you saw a segment of it until the yellow sun wiped it out .
When you realized this , your long-standing belief that the Sun can only appear as yellow , orange , red , or white was wiped out .

You see the green sun , sort of , on any ordinary day .
You just can't make it out because the prism effect is greatly reduced away from the horizon and because light of other colors mixes in .
There are thousands of reports of green dots .
Most of them are mistakenly labelled green rays or green flashes .
There are many of these reports because a green dot is actually pretty easy to see , _under the proper conditions_.
From a very desirable location , with very low horizons to the East and West and consistently very clear haze-free weather , using binoculars or a telephoto lens , it should be possible to see a few hundred green dots every year .
Flash and ray phenomena seem to be much rarer .

A full explanation of the green phenomena of Sunrise and Sunset is clearly quite complicated , involving a variety of concepts from astronomy , meteorology , physiology and optics , and may only be accomplished quite far off in the future .
The many explanations in the literature are nearly all miserably inadequate and quite misleading , often because of inadequate treatment of the essential roles of magnification , elevation above the horizon , and mirage .
It wasn't until Professor Andrew T. Young of San Diego State University began creating his website , ground-breaking and now extensive and available at
http://aty.sdsu.edu/
that hardly any progress was made beyond the book published by Professor Mulder in 1922 .

Professor Mulder recorded many early observations , rejected many inapplicable theories and , importantly , elucidated the multi-faceted nature of the phenomena .
His book is still highly relevant .

Professor Young and I initially made the same usual nomenclatural mistakes of other observers , so , while our websites stand out from the awful morass of the scientific literature on this subject because they reflect a more complete and accurate understanding , they still contain nomenclature we wouldn't use today .

Other than Mulder's book , the only sources I can recommend for explanation are the websites of Professor Young and myself , with the caveat that none of these are fully satisfactory , especially the nomenclature , especially the definite article "the" and the words flash and ray .

More high-quality data is urgently needed , especially images or videos of what might be called green flashes or rays .
There are many sources of images of green dots , but apparently _none yet_ of green flashes or rays .

Links to some green pages :
http://upforthecount.com/astro/greenlinks.html

Walter Nissen
posted :            2016-09-05
minor update :      2016-10-03