What Is Fog?

What is fog? Hi, welcome to Curious Kids Every Day. I'm Josh. How are you doing today? It's so good to hear from you. Hey, have you ever walked outside early in the morning and noticed that everything looked kind of hazy? And you couldn't see as far away because well, it almost seemed like the ground was covered in a cloud. Not always, but when this happens, it's normally in the morning. But then as quick as it shows up, it's gone. Do you know what we call that haze that you see in the morning sometimes? We call it fog. Have you ever wondered what causes fog? What fog even is? Well, I got a couple of emails about this from a couple of curious kids named John and Ada. They wondered what is fog. But let's figure it out together. Fog is made of tiny drops of water floating in the air very close to the ground. Did you know that there is water in the air around you all the time? Usually you can't see it because it's in the form of water vapor. And water vapor is water that has mixed into the air as an invisible gas. But fog happens when that invisible water vapor cools down and turns into tiny liquid water droplets. Those droplets are so small and light that they can float in the air instead of falling right away like rain. So in a way, fog is a lot like a cloud. The big difference is where it is. A cloud is up in the sky and fog is a cloud that forms at ground level. Now, we keep saying that fog is floating. And fog does look like it's floating. But in reality, those water droplets are actually falling very, very slowly. Each tiny drop of water is heavier than air. So gravity is doing its job by pulling it downward. But because the droplets are so small, the air pushes back and slows them down a lot. Those tiny movements in the air can sometimes even lift them a little. So instead of falling straight to the ground like rain, the droplets drift and hover and move in all directions on their ultimate path to the ground. That's why fog kind of seems like it's just floating there in the air. But why does fog only show up sometimes? Well, fog usually happens when the air near the ground gets cool enough that water vapor starts changing into tiny droplets. And fog doesn't form every morning because it needs just the right conditions. First, there has to be enough water vapor in the air, which means that the air has to be a little moist. But if the air is too dry or it doesn't cool down enough or if it's windy and the air keeps mixing, then those droplets don't form. What I'm trying to say is, conditions have to be just right for fog to fit. The air has to be moist, the temperature has to have dropped enough and the air needs to stay calm. But then, when the sun comes up and warms the ground in the air, those tiny droplets can turn back into invisible water vapor and the fog vanishes. Have you ever looked out a window early in the morning and seen the fog? And then you went back to playing and you forgot all about it until a little bit later and you said, "Oh right, there was fog outside. I want to go look at that again." But then it's all just gone. It's because the sun came out and it warmed up quick. Now, one of the main things about fog is that it makes it hard to see. And depending how thick the fog is, it can be hard to see even things that are really close up. I was on a drive a few mornings ago and I almost missed my turn because it was so foggy outside. I could only see things directly in front of me. When that happens, you have to start driving really slow. The reason you can't see things that are further away when you're in the fog is because all those tiny droplets, they scatter light. That means that they send the light in lots of different directions. So instead of light traveling straight from far away things, right into your eyes, the droplets keep getting in the way. They bounce the light in all different directions. It's the same thing that would happen if you were up in the clouds. You wouldn't be able to see things that were too far away from you. So yes, fog is basically just a cloud, but it's a cloud that's on the ground. And then once things warm up, the fog disappears. And fog disappears faster than clouds do because it's right next to the ground where temperatures can change quickly when the sun comes up. Clouds are higher in the sky where temperature changes happen much more slowly, so that's why they last longer over there. I'm always excited when I walk outside in the morning and see fog. It's like a special little treat. I like to pretend I'm up in the air walking through actual clouds in the sky because in a way, I am just down here on the ground. Alright, let's have a quick quiz. What is fog mostly made of? Tiny drops of liquid water. And what is the invisible form of water in the air called? It's called water vapor. And why is fog often more common in the morning? Because the ground and air often cool down overnight. Let's play true or false? True or false? Fog is usually made of smoke. That's false. Fog is made of tiny drops of water. True or false? Fog is basically a cloud very close to the ground. That is true. True or false? Fog can make it harder to see because tiny water droplets scatter light. That's true. The droplets send light in lots of directions. True or false? Fog always stays all day once it appears. That's false. It often disappears when the air warms up. Would you rather walk through a very foggy forest or a very foggy playground? I don't know that I've ever been on a foggy playground before. That could be fun. And also a little hazardous. I would love to walk through a foggy forest. I'm trying to remember if I've ever done that before. Well, anyway, I think that's what I would choose. A foggy forest. That sounds so cool. Alright, let's play a round of what am I? What am I? I am invisible most of the time. I am water mixed into the air as a gas. And when I cool down, I can help form fog. What am I? I am water vapor. So fog is just a bunch of tiny water droplets floating in the air near the ground. It happens when the ground and the air above the ground cool down, which can happen during the night time before the sun comes out. That's why sometimes if you wake up early, you look outside and you see fog. And that's also why once the sun comes up, that fog disappears. peers. Isn't it amazing to think that the air has some water in it? Sometimes, like when there's fog in the air, we can even see it. What kind of question do you think we'll ask tomorrow on curious kids every day? I can't wait to find out so until then, keep asking questions and stay curious kids. And we've got a few birthdays today. Today is Miguel's birthday. Miguel is from Maryland and Miguel is turning 5. Happy Birthday Miguel! Finley Alice is from California and Finley Alice is turning 4. Happy Birthday Finley Alice. Mateo is from Florida and Mateo is turning 6. Happy Birthday Mateo. Russell is from California and Russell is turning 8. Happy Birthday Russell! Sebastian is turning 7. Happy Birthday Sebastian! To all the grownups listening, if you're curious kid, once they're birthday mentioned on the show, please visit supportcuriouskids.com and join the Curious Kids Club. That's supportcuriouskids.com. See you tomorrow!