### Question

What is the easiest way to calculate the earth's athmoshpere's weight?

You could use the average atmospheric pressure of 14.7 lb/square inch at the earth's surface to estimate the atmosphere's total weight. That pressure means a column of air above every square inch of the Earth's surface weighs 14.7 lbs. Multiplying that by the total number of square inches gives the total weight of air.

Since we're estimating, use 4000 miles for the Earth's radius, and calculate the area of its surface with the formula for the area of a sphere: 4 x x (radius)2.

4000 miles x 5280 ft/mile x 12 inches/ft is about 250 million inches for the Earth's radius, so the formula give:

4 x 3.14 x (250,000,000)2 or about 8 x 10E17 square inches. Multiplying each of those square inches by 15 pounds gives 1.2 x 1019 pounds. Dividing by 2000 lbs/ton converts that to 6 x 1015, or 6,000,000,000,000,000 (that's 6 quadrillion) tons for the total weight of the atmosphere.
Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor

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'The strength and weakness of physicists is that we believe in what we can measure. And if we can't measure it, then we say it probably doesn't exist. And that closes us off to an enormous amount of phenomena that we may not be able to measure because they only happened once. For example, the Big Bang. ... That's one reason why they scoffed at higher dimensions for so many years. Now we realize that there's no alternative... '

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