What is Kármán line?
[[File:1000px-Atmosphere layers-en.PNG|thumb|200px|The boundaries between the Earth's surface and outer space, at the Kármán line, {{Convert|100|km|mi|abbr=in}} and [[exosphere]] at {{Convert|690|km|mi|abbr=in}}. Not to scale.|alt=A dark blue shaded diagram subdivided by horizontal lines, with the names of the five atmospheric regions arranged along the left. From bottom to top, the troposphere section shows Mount Everest and an airplane icon, the stratosphere displays a weather balloon, the mesosphere shows meteors, and the thermosphere includes an aurora and the Space Shuttle. At the top, the exosphere shows only stars.]] The '''Kármán line''' is the [[altitude]] where [[Outer space|space]] begins. It is 100 km (about 62 miles) high. It commonly represents the [[border]] between the [[Earth's atmosphere]] and [[outer space]].<ref>{{cite web|url=http://www.fai.org/icare-records/100km-altitude-boundary-for-astronautics|title=The 100 km Boundary for Astronautics|author=S. Sanz Fernández de Córdoba|publisher=Fédération Aéronautique Internationale|date=2004-06-24|accessdate=2014-05-07|archive-date=2011-08-22|archive-url=https://www.webcitation.org/618QHms8h?url=http://www.fai.org/astronautics/100km.asp|url-status=dead}}</ref> This definition is accepted by the [[Fédération Aéronautique Internationale]] (FAI). The FAI is an international standard setting and record-keeping body for [[aeronautics]] and [[astronautics]]. The line is named after [https://en.m.wikipedia.org/wiki/Theodore_von_Kármán Theodore von Kármán] (1881–1963), a [[Hungarians|Hungarian]]-[[United States|American]] [[engineer]] and [[physicist]]. He was active in aeronautics and astronautics. He was the first to calculate that around this altitude, the [[Earth's atmosphere|atmosphere]] becomes too thin to support aeronautical [[flight]]. An [[aircraft]] at this altitude would have to travel faster than [[orbital speed|orbital velocity]] (velocity at which a body moves around another body.) to obtain enough [[Lift (force)|lift]] to support itself.<ref>