27-Feb Green Flash – A Converted Green Flash Atheist

27-Feb Green Flash – A Converted Green Flash Atheist

I was rubbishing Lindsay after dinner tonight about the so-called green flash that can sometimes ‘supposedly’ appear right on sunset. I informed Lindsay that during my many years at sea, I had watched countless sunsets from the bar but have never ever seen one. I sided with John our voyage leader as ‘The Green Flash Skeptics Society’ and we ganged up against Lindsay.

Only a short while later I was photographing the sunset from out of my porthole. I had no sooner taken some photos and put my camera down. Then, blow me days, saw my first evergreen flash developing, a slow green glow around the last edge of the sun as it dipped below the horizon. Wow, I thought, I have seen the light. I picked up my camera to check if I might have accidentally caught the start of it, and sure enough I had. I immediately resigned for the ‘The Green Flash Skeptics Society’ but even with this proof I still couldn’t convince the voyage leader, so hence there was only one converted that night not two.

Investigating further – green flashes are a rare optical phenomena that can occur at the very last moment of sunset or first moment of sunrise where a green ray shoots out from sunset/sunrise point. It typically occurs on unobstructed horizons but can be observed over mountain such as observed above. It is to do with the speed of refracted light traveling through layers of different density air, light moving more slowly though denser air than thinner air above. Light rays also curve slightly, following the curvature of the earth. When light is refracted in the atmosphere, the higher frequency green/blue light curves more than the red/orange rays. Thus right at the last moment of sunset, the green/blue refracted rays are seen by the observer after the red/orange rays have already dipped below the horizon.
Although the photo above does not show it too clearly, it should be noted that the photograph was taken just as the flash was starting and the photo has been optically zoomed in.