system
Given the following post, respond as if you're commenting on Reddit:
human
What causes the "Green Flash" as the sun sets over the ocean?

My friend and I saw a video of the legendary green flash and were trying to figure it out. The best we could figure was that as the sun sets behind the water light travels through the blue ocean and the light appears green. Have any studies been done as to what the cause is?
gpt
The underlying physical phenomenon is atmospheric refraction which separates the colors of sunlight (similar to a prism).  The ocean has nothing to do with it and green flashes can occur over land.  However, because the key requirements are 1) clear air and 2) a long distance from observer to horizon, people mostly see them over the ocean.