# Q & A: Weighing the Atmosphere

Q:
how heavy is the atmosphere
- erika (age 10)
emmerdale high school, london
A:
Erika -

Well, I don't know this off the top of my head, but we can figure it out... According to my science book, the air pressure at sea level is 14.7 psi. This means that if you took a column of air one square inch wide that went all the way up through the atmosphere, it would weigh 14.7 pounds. So in order to figure out how much the whole atmosphere weighs, all we need to do is figure out how many square inches make up the surface of the earth.

We can do this using the earth's radius, 3965 miles. This is the same as roughly 2.512*10^8 inches (or 251,200,000 inches). Since the earth is a sphere, we can use the equation for the surface area of a sphere, 4*pi*radius^2 (or 4*3.14*radius*radius). This gives us 7.93*10^17 square inches on the earth. Multiplying this by 14.7 pounds per square inch says that the atmosphere weighs about 1.17*10^19 pounds (or about 11,700,000,000,000,000,000 pounds)! That's a lot of air!

-Tamara

(published on 10/22/2007)