When climbers climb Mount Everest, they routinely carry oxygen tanks, devices that allow them to breathe freely at high altitudes. This is necessary because the closer you get to the edge of Earth’s atmosphere, the less oxygen there is available compared to the abundant amounts at sea level.
This is just one example of how variable the Earth’s atmosphere is, showing the elemental composition of its layers, from the troposphere near sea level to the exosphere in its outermost regions. Four key characteristics define where each layer ends and begins National Weather Service: temperature change, chemical composition, density and the movement of the gases contained therein.
So, where does the earth’s atmosphere actually end? And where does space begin?
Each of the layers of the atmosphere plays a role in ensuring that our planet can support all types of life and make the most of it block carcinogenic cosmic rays to generate the pressure required for water productionaccording to NASA.
“The further you get Earththe atmosphere becomes less dense,” Katrina Bossert, a space physicist at Arizona State University, told Live Science in an email. “The composition is also changing and becoming lighter atoms and molecules begin to dominate, while heavy molecules stay closer to the surface.”
As you move up in the atmosphere, the pressure or weight of the atmosphere above you quickly weakens. Although commercial aircraft have pressurized cabins, rapid changes in altitude can affect air quality slender Eustachian tubes connects the ear to the nose and throat. “That’s why your ears can pop when you take off on an airplane,” said Matthew Igel, associate professor of atmospheric sciences at the University of California, Davis.
Eventually, the air becomes too thin for conventional airplanes to fly at all, due to the inability of such vehicles to generate enough lift. This is the area that scientists have determined marks the end of our atmosphere and the beginning of space.
It is known as the Kármán Line, named after Theodore von Kármán, a Hungarian-American physicist who first attempted to define the boundary between Earth and space in 1957 earth sky.
Because this line marks the boundary between Earth and space, not only does it indicate the limits of an airplane, but it is also crucial for scientists and engineers when trying to figure out how spacecraft and satellites successfully stay in Earth orbit be able. “The Kármán line is an approximate region denoting the altitude above which satellites can orbit the Earth without burning up or falling out of orbit before orbiting the Earth at least once,” Bossert said.
“Usually it’s 100 kilometers [62 miles] above ground,” added Igel. “It’s possible for something to orbit the Earth at altitudes below the Karman line, but it would require an extremely high orbital velocity that would be difficult to sustain due to friction. But nothing forbids it.
“That’s the sense you should have of the Kármán line: it’s an imaginary but practical threshold between aerospace and aerospace,” he said.
According to Bossert, various factors such as the size and shape of the satellite play a role in how much drag it experiences and consequently its ability to successfully orbit the Earth. Typically satellites in low Earth orbit – a classification usually given to satellites less than 621 miles (1,000 km) but sometimes as little as 99 miles (160 km) above the Earth, according to the European Space Agency — will fall out of orbit after a few years, Bossert said, because “drag from Earth’s upper atmosphere is gradually slowing the orbital velocity.”
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However, that doesn’t mean Earth’s atmosphere is undetectable beyond 621 miles.
“The atmosphere doesn’t just disappear once you get into the region where satellites are orbiting,” Bossert said. “It’s thousands and thousands of miles away before evidence of Earth’s atmosphere is gone. The outermost atoms of Earth’s atmosphere, the hydrogen atoms that make up its geocorona [the outermost region of the atmosphere]can even go beyond that the moon.”
So if someone reached the Kármán line, would they notice anything? Would they be aware that they were essentially bridging the line between earth and space? Not really. “Nothing really changes,” Bossert said.
Hedgehog agreed. “The line isn’t physical per se, and so you wouldn’t notice crossing it, nor does it have any thickness,” he said.
What would it be like to be able to survive on the Kármán Line, even for a short time? What if you were dropped there without a custom-made space suit or mountaineer-style oxygen tank? If you could reach it, could you breathe at that high altitude? And could birds ever reach such heights?
“A flight up to the Kármán line is basically still possible,” said Igel. “In practice, however, animals cannot survive at altitudes above the ‘Armstrong limit’, which is around 20 km [12 miles] above the surface where the pressure is so low that the liquid in the lungs boils.”
Originally published on Live Science.