Friday, October 23, 2015

It is not so far..................




How High is Space?


Look up, there’s space. Astronomically speaking, it’s right there, just outside a thin layer of atmosphere. But how far away is it? How high is space?

Space is defined by the point at which the Earth’s atmosphere ends, and the vacuum of space takes over.
As you can probably imagine, with such a subjective definition, people disagree on exactly where space begins.
The edge of space. Credit: NASA
The edge of space. Credit: NASA
The first official definition of space came from the National Advisory Committee for Aeronautics (the predecessor to NASA), who decided on the point where atmospheric pressure was less than one pound per square foot.
This was the altitude that airplane control surfaces could no longer be used, and corresponded to roughly 50 miles, or 81 kilometers.
X 15
X-15 Ship #1 on Lakebed
Any NASA test pilot or astronaut who crosses this altitude is awarded their astronaut wings.
Shortly after that definition, the aerospace engineer Theodore von Kármán calculated that above an altitude of 100 km, the atmosphere would be so thin that an aircraft would need to be traveling at orbital velocity to derive any lift.
This altitude was later adopted as the Karman Line by the World Air Sports Federation.

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