Today’s Wonder of the Day was inspired by Logan. Logan Wonders, “Why does mist float?” Thanks for WONDERing with us, Logan!

Picture it: You’re walking home with friends on a cool autumn night. You chat happily, walking along the sidewalk toward home. Looking up, you can barely make out the moon,  just visible through the mist. Or is it fog? Wait. What’s the difference between fog and mist, anyway?

Earth’s atmosphere contains all kinds of particles. Sometimes, those particles limit people’s ability to see. When moisture in the air limits visibility, it’s in the form of fog or mist.

Most of the time, people can’t see the water vapor in the air. But when the vapor cools quickly, it becomes visible. This often happens when warm air vapor comes in contact with cooler surfaces like land or the ocean. Then, fog or mist hangs in the air, making it harder for people to see objects farther away.

The difference between fog and mist comes down to how heavily this moisture limits sight. Fog is thicker. If you can’t see more than ⅝ of a mile (1 km) in front of you, then you’re dealing with fog. If you can see more than ⅝ of a mile but less than 7 miles (11 km), it’s mist.

Have you ever seen fog or mist? They’re more common in some places than in others. For example, Scotland is known for its frequent mists. San Francisco, California also experiences heavy summer fogs.

Of course, you can also make mist yourself! Don’t believe us? Just go outside on a cold day and breathe. That’s right! When you can see your breath on a cold day, it’s because the water droplets in your breath become visible when they meet the cold air. Just like mist!

Fog and mist aren’t the only things that hang in the air and decrease visibility. Haze is similar but is made up of dry particles instead of moisture. Smog is a type of air pollution. It looks a bit like mist, but it’s made of smoke, gases, and chemicals. Dust, sand, and volcanic ash in the air can even get into people’s eyes and cause damage.

Moisture suspended near bodies of water, mountains, or forests can be a beautiful sight. It even plays an important role in the ecosystem. For example, fog provides the California redwoods with much of their moisture.

Many people also think fog and mist are mysterious. In stories, movies, and TV shows, they often represent hidden truths, confusion, and even danger. Sometimes, fog and mist are used to indicate that a character is in a dream or experiencing something that isn’t real. Fog and mist certainly do seem spooky. But remember, they’re just moisture in the air! 


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