When you're at the beach with your sweetie watching the sunset, listen closely as the sun sets into the water. If you hear cheering, that means that there was a green flash (and that you were watching the sunset at the foot of IB, where the green flash crew watches it every night). According to Wikipedia:
"Green flashes and green rays are optical phenomena that sometimes occur right after sunset or right before sunrise. When the conditions are right, a green spot is visible above the upper rim of the disk of the sun. The green appearance usually lasts for no more than a second or two. Rarely, the green flash can resemble a green ray shooting up from the sunset (or sunrise) point. Green flashes occur because the atmosphere can cause the light from the sun to separate out into different colors. "
There are a few different types of green (and blue!) flash.
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