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World's 'Most Widely Accepted Boundary' May Be Wrong

Astrophysicist says Karman Line is 50 miles above Earth, not 62
By Arden Dier,  Newser Staff
Posted Jul 26, 2018 10:00 AM CDT
The invisible Karman Line falls somewhere here.   (Getty Images/sharply_done)

(Newser) – Astrophysicist Jonathan McDowell calls the Karman Line the world's "most widely accepted boundary." It's otherwise known as the point where space meets Earth's atmosphere, and since before the launch of Sputnik, it's thought to have hovered 62 miles above our heads. Until now. In a new study, McDowell argues the Karman Line is at least 20% closer, or 50 miles away, and presents some straightforward data to back that up, per Live Science. If the Karman Line really is 62 miles away, says McDowell, it should've been impossible for the Soviet Elektron-4 satellite to orbit Earth 10 times at a distance of 52 miles, as it did before disintegrating in 1997. And that's just one of 50 examples of satellites making multiple rotations of Earth at altitudes below 62 miles that McDowell uncovered while surveying the orbital paths of 43,000 satellites since 1957, reports ScienceAlert.

Plugging the data into a mathematical model, McDowell found satellites tend to break from orbit 41 to 55 miles above Earth, though a fiery descent is all but guaranteed at 50 miles. This is believed to be the outer edge of the mesosphere, which extends 53 miles above Earth, according to NASA. "Adding to the evidence that this is the region where the atmosphere becomes important" is the fact that meteors, traveling faster than satellites, disintegrate in the range of 43 to 62 miles, says McDowell. If his data is correct, "you may be a little bit closer to the heavens" than you thought, per Live Science. But McDowell is considering greater implications, including what the Karman Line's positioning might mean for countries' airspace: If a US satellite flies "at 52 miles over China, for example, that could be (justifiably) construed as an act of military aggression," he says. (Cue the Space Force.)

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