Air facts for kids
Air is the Earth's atmosphere. It is a mixture of many gases and tiny dust particles. Air is the clear gas that living things need to breathe. It does not have a set shape or volume.
Air has mass and weight because it is matter. The weight of air creates atmospheric pressure. There is no air in outer space.
Air is mostly made of about 78% nitrogen and 21% oxygen. It also has 0.9% argon and 0.04% carbon dioxide. Very small amounts of other gases are present too. On average, about 1% of the air is water vapor.
Humans and animals need to breathe oxygen from the air. When we breathe, our lungs take oxygen into our blood. They then send carbon dioxide back into the air. Plants need carbon dioxide from the air to live. They release the oxygen that we breathe. Without oxygen, we cannot survive. This shows how plants and humans have a symbiotic relationship.
Wind is simply air that is moving. Moving air helps create our weather.
Air can become polluted by certain gases. These include carbon monoxide, hydrocarbons, and nitrogen oxides. Smoke and ash can also pollute the air. This air pollution causes problems like smog, acid rain, and global warming. It can harm people's health and the environment.
For a long time, people have used air to create technology. Ships used sails to move with the wind. Windmills used the power of moving air to do work. Aircraft use propellers to push air over their wings, which helps them fly. Pneumatics use air pressure to move things. Since the late 1900s, air power has also been used to make electricity.
Air is invisible, meaning you cannot see it with your eyes. However, you might see a shimmering effect in very hot air.
In ancient Greece, air was one of the four classical elements. These were earth, water, air, and fire. Air was thought to be a key force in the creation of the cosmos.
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How Earth's Air Changed Over Time
Scientists are still learning about the Earth's air from billions of years ago. They make educated guesses based on what they discover.
Our current air is sometimes called Earth's "third atmosphere." This helps us tell it apart from two earlier types of air. Some scientists think the very first air was mostly helium and hydrogen.
About 3.5 billion years ago, Earth's surface cooled down. A crust formed, but there were still many volcanoes. These volcanoes released steam, carbon dioxide, and ammonia. This created the "second atmosphere." It was mainly carbon dioxide and water vapor, with some nitrogen. There was almost no oxygen. This second atmosphere had about 100 times more gas than our air today. Scientists believe the greenhouse effect from all the carbon dioxide kept Earth from freezing.
Over the next few billion years, water vapor cooled and formed rain. This rain filled the oceans. The oceans then began to soak up carbon dioxide. About half of the carbon dioxide was absorbed into the oceans. One of the first types of bacteria was called cyanobacteria.
Fossils show these bacteria existed about 3.3 billion years ago. They were the first living things to make oxygen. They changed Earth's air from having no oxygen to having oxygen. They did this through a process called oxygenic photosynthesis. This process turned carbon dioxide into oxygen.
Later, photosynthesizing plants evolved. They converted even more carbon dioxide into oxygen. Over time, extra carbon became trapped in fossil fuels, sedimentary rocks (like limestone), and animal shells.
As oxygen was released, it reacted with ammonia to create nitrogen. Also, bacteria helped turn ammonia into nitrogen.
As more plants grew, oxygen levels went up, and carbon dioxide levels dropped. At first, oxygen combined with other elements like iron. But eventually, oxygen built up in the air. This led to mass extinctions and more evolution.
When an ozone layer formed, life forms were better protected. Ozone is a special form of oxygen. It protects from harmful ultraviolet radiation from the sun. This oxygen-nitrogen air is what we call the "third atmosphere."
Interesting Facts About Air
- The average person breathes about two gallons of air every minute.
- Air acts like an insulator in the atmosphere. This means it helps keep things warm or cool.
- Most of the oxygen we breathe comes from ocean algae, not just land plants.
- Air can hold tiny water droplets. This is called humidity.
- When your ears pop as you drive up a hill, it's because there is less air pressure at higher elevations.
- Bioaerosols are tiny living things like microbes that can travel through the air.
- The fastest gust of wind ever recorded on Earth was 253 miles per hour.
Related pages
Images for kids
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Blue light is scattered more than other wavelengths by the gases in the atmosphere, surrounding Earth in a visibly blue layer when seen from space on board the ISS at an altitude of 335 km (208 mi).
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Mean atmospheric water vapor
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Space Shuttle Endeavour orbiting in the thermosphere. Because of the angle of the photo, it appears to straddle the stratosphere and mesosphere that actually lie more than 250 km (160 mi) below. The orange layer is the troposphere, which gives way to the whitish stratosphere and then the blue mesosphere.
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Temperature trends in two thick layers of the atmosphere as measured between January 1979 and December 2005 by microwave sounding units and advanced microwave sounding units on NOAA weather satellites. The instruments record microwaves emitted from oxygen molecules in the atmosphere. Source:
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Temperature and mass density against altitude from the NRLMSISE-00 standard atmosphere model (the eight dotted lines in each "decade" are at the eight cubes 8, 27, 64, ..., 729)
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Distortive effect of atmospheric refraction upon the shape of the sun at the horizon.
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An idealised view of three pairs of large circulation cells.
See also
In Spanish: Atmósfera terrestre para niños
