The elusive Green Flash is a wonderful short-lived sight very rarely observed above the setting (or rising) sun. I’ve been hoping to see the phenomenon every since I first heard about it decades ago. But when I did see it a couple of weeks ago, it caught me completely by surprize!
This observation set me down an internet rabbit hole. I now know that the effect is very well studied and understood, but it is complicated. At the September 8 2025 Astrocafé, I presented my understanding of how the Green Flash is formed, involving (1) Atmospheric Dispersion, (2) Rayleigh Scattering, (3) Inferior and Superior Mirages, and (4) Human Colour Perception. Take a look: https://www.youtube.com/watch?v=RFzGsBjA2Q8&t=2832s
The Green Flash