Q: What keeps our air from drifting into space and how does this happen?

A: Thanks to Earth’s gravity, the atmosphere doesn’t escape into space.

Gravity pushes down on Earth’s atmosphere, keeping its air from drifting away, according to the National Oceanic and Atmospheric Administration’s SciJinks online earth science education website.

Gravity is a force in the universe that pulls objects toward each other, according to NOAA. On Earth, gravity tugs everything down, toward the center of the planet.

About 14.7 pounds of air per square-inch press down on our bodies on the planet, though we can’t feel the pressure because we’re adapted to it, according to SciJinks.

Earth’s atmosphere includes five layers of gases, or air, that extend to about 6,200 miles above the planet, according to NOAA. The first layer, the Troposphere, extends about seven miles into the sky and contains the air we breathe and most of our weather and clouds.

It’s such a thin layer, according to SciJinks, that if the planet were scaled down to the size of a beach ball, the breathable atmosphere would be paper-thin.

In addition to holding air, the atmosphere protects Earth from the hazards of space, such as meteors and ultraviolet radiation from the sun, according to NOAA.

— Chris Aadland

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