Space is just up there: Earth's air is an apple-skin-thin shield

A Space Daily explainer shows that the 100-kilometre Kármán line is a regulatory boundary, not a physical cliff; if you drove straight up at highway speed you’d reach space in under an hour, illustrating how incredibly thin Earth's breathable air is. About 99% of the atmosphere’s mass sits in the lowest ~32 km, and by 100 km altitude the air is roughly one millionth as dense as at sea level. The atmosphere’s layered protection—troposphere for life-supporting gases and the ozone-rich stratosphere—makes surface habitability possible, underscoring how the “apple-skin” thickness of the air is truly remarkable.