Edge Of Space Defined

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For decades, the altitude where atmosphere ends and space begins has been pegged at a largely theoretical 100 km., known as the Karman Line. Theodore von Karman picked that value as the point where any aircraft would have to be flying faster than orbital velocity to stay aloft, and it's become the generally accepted line. Well, a team of scientists from the University of Calgary say the theory isn't far from precise reality. The so-called edge of space is actually at 118 km.

The scientists traded their slide rules for something called a Supra-Thermal Ion Imager, which was carried on a NASA rocket on Jan. 19, 2007. As everyone knows, the atmosphere doesn't really have a precise endpoint. It just gets thinner the higher you go. Instead, the device was able to detect where the ionosphere, which is driven by flows in space, and the atmosphere meet. Now that the dividing line is known, it will have a bearing on factors that are affected by the interaction between space and the earth environment ranging from the impact of sunspots to the effects of space weather on satellites and communications.