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A world shrouded in fog is quiet. The phenomenon makes you feel like you have to whisper, or it might drift away.
But have you ever really thought about what fog is and how it forms?
Here's everything you need to know about the science of fog, accompanied by breathtaking photos of it enshrouding different parts of the world.
Fog is like a cloud that touches the ground.
It forms when water vapor condenses to become liquid water droplets or ice crystals, suspended in the air.
Source: NASA/NOAA
It has to be very humid out for there to be enough water in the air to form fog — near 100%.
Sources: National Geographic, Farmer's Almanac
You can see fog because of the condensed water in the air. You can't see water vapor, on the other hand, because it's a gas.
Source: National Geographic
Fog condenses around dust particles in the air.
Source: National Geographic
If it's polluted, fog will condense around that, too.
Source: National Geographic
Sea fog condenses around the salt in the air from the ocean. The warm coastal air often collides with the colder water, forming fog.
Source: National Geographic, NASA/NOAA
Morning fog is technically called radiation fog. It forms overnight as the ground cools the air above it. When the sun heats the ground during the day, the fog goes away.
Source: National Weather Service
Freezing fog forms when supercooled water droplets freeze instantly, often in subzero temperatures.
Source: National Weather Service
Cooler mountain air drains down into valleys in the evening, causing fog there as the night progresses.
Source: NASA/NOAA
When there are wildfires, super fog can form when the water in the air condenses around ash and smoke. It's particularly thick, with visibility under 10 feet.
Source: NASA/NOAA
If the lighting's just right, you can see a rainbow in fog. Some call it a "fog bow."
Source: UK Met Office
The foggiest place in the US is Point Reyes, California, with over 200 fog days a year.
Source: Farmer's Almanac
Fog can dampen the contrast of your surroundings, so it may seem like you're driving slower than you are.
Source: UK Met Office
The foggiest place in the world is over the Atlantic Ocean off the coast of Newfoundland. It regularly sees 200 fog days a year, too.
Source: UK Met Office
If you condensed all the water in enough fog to fill an Olympic-sized swimming pool, you would only yield about a third of a gallon.
Source: UK Met Office