Where does earth’s atmosphere end? Where does outer space begin? It’s a mystery that astronomers at the University of Calgary claim to have solved.
The inner edge of outer space is too high for balloons to get to and too low for satellites to cruise. But two years ago, Canadian astronomers sent a supra-thermal ion imager up in a NASA rocket. As the rocket reached 73 miles above the earth’s surface, the imager detected a sharp increase in the number of fast-moving charged ions that populate space (but not our atmosphere). That’s significantly higher than the 62-mile-high Kármán line — a rough guesstimate formulated in the 1950s. The final frontier turns out to have a rather precise border.
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