When climbers climb Mount Everest, they regularly carry oxygen cylinders, 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 will be available compared to the abundant oxygen found on the ocean floor.
This is just one example of how variable Earth’s atmosphere is and reflects the elemental makeup of its layers, from the troposphere, near the ocean floor, to the exosphere, in its outermost regions. Where each layer ends and begins is defined by four major characteristics National Weather Service (opens in new tab)Temperature change, chemical composition, density and movement of gases within it.
So, with that in mind, where exactly does Earth’s atmosphere end? And where does space begin?
Each layer of the atmosphere plays a role in ensuring that our planet can host all kinds of life, doing everything Blocking cancer-causing cosmic radiation (opens in new tab) To Creating the pressure required to produce water (opens in new tab)According to NASA.
“As you walk away EarthThe atmosphere becomes less dense,” Katrina Bossert, a space physicist at Arizona State University, told Live Science in an email. “The composition also changes, and the lighter atoms And the molecules tend to dominate, while the heavier molecules tend to stay closer to the Earth’s surface.”
As you move up in the atmosphere, the pressure or weight of the atmosphere above you rapidly weakens. Even though commercial aircraft have pressurized cabins, rapid changes in altitude can affect slim eustachian tube (opens in new tab) Connecting the ear to the nose and throat. “This is why your ears can explode during takeoff in an airplane,” said Matthew Igel, an assistant professor of atmospheric science at the University of California, Davis.
Eventually, as the air becomes too thin for conventional aircraft to fly, such craft are not able to generate enough lift. This is the region where scientists mark the end of our atmosphere and the beginning of space.
This is known as the Karmann line, named after the Hungarian American physicist Theodor von Karmann, who in 1957 became the first person to attempt to define the boundary between Earth and outer space. earth sky (opens in new tab),
This line, given that it marks the boundary between Earth and space, not only shows where an aircraft’s boundaries are, but is also important to scientists and engineers when figuring out which spacecraft And how to get satellites to orbit the earth successfully. “The Carman line is an approximate region that denotes the altitude above which satellites will be able to orbit the Earth at least once before without burning up or falling out of orbit,” Bossert said.
“It is usually defined as 100 km. [62 miles] Above Earth,” Igel said. “It is possible that something orbits Earth at altitudes below the Karmann line, but this would require extremely high orbital velocity, which would be difficult to maintain due to friction. But nothing forbids.
“It has to make sense for the Karman line: it’s a hypothetical but practical boundary between air travel and space travel,” he said.
Various factors, such as the size and shape of a satellite, play a role in determining how much air resistance it will experience and, consequently, its ability to successfully orbit Earth, according to Bossert. Typically, satellites that are in low Earth orbit – a classification given to satellites at altitudes of less than 621 miles (1,000 km), but sometimes as low as 99 miles (160 km) from Earth , According to the European Space Agency (opens in new tab) — will drop out of orbit after a few years, Bossert said, “is slowly slowing orbital speed due to drag from Earth’s upper atmosphere.”
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However, this does not mean that the Earth’s atmosphere cannot be known beyond 621 miles.
“Once you get to the region where the satellites are in orbit the atmosphere doesn’t disappear,” Bossert said. “It’s thousands and thousands of kilometers away before the evidence for Earth’s atmosphere runs out. The very outermost atom from Earth’s atmosphere, the hydrogen atoms that make up its geocorona [the outermost region of the atmosphere]can go further Moon,
So, if someone were to reach the Karman Line, would they notice anything? Would they be aware that they were essentially expanding the boundary between Earth and space? Not necessary. “Nothing really changes,” Bossert said.
Igel agreed. “The line is not physical, and therefore no one will notice crossing it, nor does it have any thickness,” he said.
What about being able to survive on the Karman line, even for a short period of time? What if you were dropped there without an unconditional spacesuit or mountaineering-style oxygen tank? If you could achieve this, would you be able to breathe at such a height? And can birds ever reach such heights?
“In theory, flying all the way up to the Kármán line is still possible,” Igel said. “In practice, however, the animals cannot survive at altitudes above the ‘Armstrong limit’, which is about 20 km. [12 miles] above the surface, where the pressure is so low that the liquid Lungs boils.”
Originally published on Live Science.