If you just spent a half hour on the packed, humid subway train, full of people with coffee breath who smell faintly like wet dog, then this video is just what you need to restart your morning. Photographer Simon Christen spent over two years filming the fog rolling over San Francisco at dawn, and calls his completed work a “love letter” to his favorite natural  phenomenon. It’s pretty beautiful, guys.
So how did Christen get this incredible footage, aside from obsessively checking weather conditions and various webcams at ungodly hours of the morning? Through science! Well, okay, technically through nature, but we can explain it through science.
Fog is made up of tiny water droplets forming as vapor in the air. The cooler the air gets, the less water vapor it can hold. At a certain point (the “dew” point), the air is saturated with water vapor. Once the air gets any cooler, the water vapor condenses on the particles constantly floating through the air — kind of like dust. The more water vapor in the air, the higher the temperature at which this all occurs.
So now that you understand this particular curiosity, watch the video:
(via Vimeo, HowStuff Works)
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