In the novel A Beast Cannot Feign, the last book of the Gaia's Wasp trilogy, a government official claimed our atmosphere shields us like a four-foot-thick sheet of stainless steel. Was he correct?
Let's consider one square centimeter of dirt, about half the size of a dime. That dirt supports a skinny column of air that reaches all the way up to space, roughly a hundred miles. How far would it reach (that is, how tall is the skinny column) if the air were replaced by the same weight of stainless steel?
How much does the skinny column weigh? Sea-level air pressure, which is just the weight of our atmosphere, is 14 lbs per square inch. This is 2.2lbs/cm2 = 1kg/cm2.
In other words, each square centimeter of Earth support a skinny column of air that weighs one kilogram. Suppose that column of air was replaced by a column of stainless steel with the same weight. How tall would it be?
Stainless steel has a density of 8g/cm3, so a one-kilogram stainless-steel column must contain 1,000 g / (8 g/cm3) = 125 cm3. If its cross-sectional area is 1 cm2, then its height must be 125 cm, or 49 inches.
In other words, we live under the gaseous equivalent of a four-foot-thick sheet of stainless steel.
Four feet of stainless steel is pretty impressive. No wonder it blocks cosmic rays. Would it protect us from the boxcar full of gold?