Green Flash – Fact or Fiction

Green Flash – Fact or Fiction

For years Don has been claiming there is no such thing as the magical “green flash”” he does admit that his dad boasted about seeing the green flash several times whilst at sea …...

For years we religiously watched for this enigma, sitting up in the cockpit, beer and cocktail in hand waiting for the green flash to reveal itself so we could become one of the “few” that could claim a sighting.

While we were in Providencia a couple on a boat explained the phenomenon of the green flash – I had not realised it happened seconds after the sun set but with that information at hand I have now sighted the green flash several times – much to Don's disbelief !!!

The Green Flash is not to be confused with the Fools Flash which is the greenish tinge burned into your retina by looking directly at the sun, the flash is not an optical illusion. The Green Flash was first recorded by Captain Back of HMS Terror during an Arctic expedition in 1836-1837. It has written about and documented in novels and articles including Jules Verne “Le Rayon Vert” (The Green Ray) which mentions an ancient legend “he who has been fortunate enough once to behold it is enabled to see closely into his own heart and to read the thoughts of others”

The Green Flash can be seen anywhere in the world with a flat horizon, it is not only seen at sunset but can also be seen at sunrise though not common. It is only visible for a second or two. The ocean is a good place but also large lakes because of their substantial heat and its affects on the atmosphere. Very occasionally, the amount of blue light is sufficient to be visible as a "blue flash"

The Green Flash can also be synonymous with the green ray when at sunset a brief ray or green glow suddenly shoots up into the sky. Others include the inferior mirage flash, the mock mirage flash; there is even a cloud-top flash that can be seen as the sun sinks into distant cumulus. Rarer still is the moon's green flash – not detected with the naked eye.

Most images that are observed are inferior mirage flashes – flashes of brilliant green occur as the sun dips below the horizon and pass through the lowest layer of the atmosphere. The white light of the sun that we usually see is broken up and separated by the atmosphere into different colours. Green light is refracted more strongly than red light so are the last residual rays you see after the red rays have been blocked by the curvature of the earth. A mirage (similar to the mirage seen above a hot road) is also necessary. The mirage magnifies the difference between the red and green that a normal atmosphere would not achieve, the red light disappears first and the green light remains, therefore a green flash occurs.

Green flashes occur frequently if you know what to look for and have the right conditions. The air needs to be free of dust and smog and you must be above your apparent horizon where the sky meets the earth – you could be on a hill or building looking out to sea or a flat horizon. Take care of your eyes - if your thumb, extended horizontally at arm's length can cover the sun while touching a sea horizon then the sun is low enough to look safely – if the sun is too bright do not look at it !!!