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However, the human body has both short-term and long-term adaptations to altitude that allow it to partially compensate for the lack of oxygen. There is a limit to the level of adaptation; mountaineers refer to the altitudes above 8,000 metres (26,000 ft) as the death zone, where it is generally believed that no human body can acclimatize.
The Armstrong limit or Armstrong's line is a measure of altitude above which atmospheric pressure is sufficiently low that water boils at the normal temperature of the human body. Exposure to pressure below this limit results in a rapid loss of consciousness, followed by a series of changes to cardiovascular and neurological functions, and ...
Humans are generally adapted to lowland environments where oxygen is abundant. [12] At altitudes above 2,500 meters (8,200 ft), such humans experience altitude sickness, which is a type of hypoxia, a clinical syndrome of severe lack of oxygen. Some humans develop the illness beginning at above 1,500 meters (5,000 ft). [13]
The human body has optimal endurance below 150 m (490 ft) elevation. [6] The concentration of oxygen (O 2) in air is 20.9% so the partial pressure of O 2 (PO 2) at sea level is about 21.2 kPa (6.3 inHg; 3.07 psi). In healthy individuals, this saturates hemoglobin, the oxygen-binding red pigment in red blood cells. [7]
The term "Kármán line" was invented by Andrew G. Haley in a 1959 paper, [20] based on the chart in von Kármán's 1956 paper, but Haley acknowledged that the 275,000 feet (52.08 mi; 83.82 km) limit was theoretical and would change as technology improved, as the minimum speed in von Kármán's calculations was based on the speed-to-weight ...
Human populations have developed agricultural production strategies to exploit varying characteristics of altitudinal zones. Elevation, climate, and soil fertility set upper limits on types of crops that can reside in each zone.
Furthermore, if the point is attached to the Earth (e.g., a mountain peak), then altitude (height above sea level) is called elevation. [2] In a two-dimensional Cartesian space, height is measured along the vertical axis (y) between a specific point and another that does not have the same y-value.
Height measurement using a stadiometer. Human height or stature is the distance from the bottom of the feet to the top of the head in a human body, standing erect.It is measured using a stadiometer, [1] in centimetres when using the metric system or SI system, [2] [3] or feet and inches when using United States customary units or the imperial system.