Outer space may have just gotten a bit closer

http://www.sciencemag.org/news/2018/07/outer-space-may-have-just-gotten-bit-closer

Source:  By Paul Voosen, Science Magazine.

Excerpt: ...A new study argues that the boundary between Earth’s atmosphere and outer space—known as the Kármán line—is 20 kilometers, or about 20%, closer than scientists thought. Though the new definition won’t make a difference for launching rockets and spacecraft, it could help clarify a legal debate that will set the rules for space policy—and commercial spaceflight—for years to come. Until now, most scientists have said that outer space is 100 kilometers away. At that point, it’s been thought, the speed needed to achieve lift in the superthin atmosphere is equal to the speed needed to simply orbit the planet; once there, a spacecraft’s horizontal pace would counteract the tug of Earth’s gravity. ...A close look shows that the traditional definition flies in the face of evidence, says Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. ...“I’ve been making lists of rockets since I was 13,” he says. He often has to decide which launches qualify as reaching outer space, and which do not. Given how low many orbiting satellites fly, the 100-kilometer limit never seemed right to McDowell. He preferred the mesopause, the coldest point in Earth’s atmosphere, located roughly 85 kilometers up. (Recent estimates have bumped it somewhat higher.) ...He found that the atmosphere’s tug turns negligible between 66 kilometers and 88 kilometers, he will report in an upcoming issue of Acta Astronautica.... 

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