The Karman Line is the boundary 62 miles (100 kilometers) above sea level that bounds the Earth’s atmosphere and the beginning of space. However, deciding exactly where to start a space can be somewhat tricky and depends on who you ask. This is because Earth’s atmosphere It does not end abruptly but instead becomes thinner and thinner at higher elevations, which means that there are no ultimate upper limits.
International law states that “outer space must be available for the exploration and use of all.” According to NOAA (Opens in a new tab). But because of the variety of definitions of where space actually begins and there is no definitive law that asserts true boundaries. The door to “Where Space Begins” was left wide open, calling for a range of different interpretations.
for NASA And the US Army, for example, outer space It begins at an altitude of 50 miles (about 80 kilometers), according to NOAA. However, for the international community, including international aviation association (Opens in a new tab) (FAI), space starts a little higher, at 62 miles (100 km), at the Karmann Line.
Related: Layers of the Earth: Exploring Our Planet Inside and Out
The theory behind the Karman line
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As the plane ascends to a higher and higher altitude, the density of the surrounding air decreases and decreases. This means cabin air needs to be compressed to enable people to breathe, but this also has an impact on the way an aircraft flies.
The plane is held aloft by an aerodynamic force called lift, which needs to balance the downward drag gravity. The lower the density of the air, the faster the aircraft moves so that its wings generate the necessary lift.
But there is a second way they can travel at high speed to counter gravity. discovered by Isaac Newton In the seventeenth century, long before the birth of aerodynamics. In fact, Newton completely ignored atmospheric influences and simply wondered what would happen if a cannonball was fired horizontally at an increasingly high speed.
The answer is that it travels more and more before falling back to a land. Finally, when you arriveorbital velocityThe cannonball travels all the way around the planet without ever hitting the ground.
Fast forward to the mid-20th century, when a Hungarian-American aeronautical engineer named Theodore von Karmann asked a simple question. At what altitude does the speed need to keep the aircraft elevated through aerodynamic lift to become so high that it exceeds orbital velocity?
Karman made the necessary calculations, then rounded the answer down to that memorable number of 100 kilometers (62 miles). This elevation is now known as the “Karman Line” in his honor.
Given the debate over whether it begins 50 miles (80 km) or 62 miles (100 km) away, some people question whether it is easier to define space as the absolute point at which Earth’s atmosphere ends. But this definition will complicate matters further.
Traveling outside the confines of the Earth’s atmosphere will take you about 6000 miles (10,000 km) above the Earth’s surface to top layer top (Opens in a new tab) Earth’s atmosphere – the outer shell. The exosphere represents the edge of the atmosphere, so why not also the beginning of space?
The International Space Station (ISS) orbits the Earth at an average altitude of 248 miles (400 km) and a low Earth orbit Satellites keep on heights Less than 620 miles (Opens in a new tab) (1,000 km). With the limits of space at this new altitude of 6,000 miles (10,000 km), most of our spacecraft orbiting the Earth would not be considered “spacecraft” and no visitor to the International Space Station would be called, say, astronauts.
This new definition will confuse the definition of space water even more than the two definitions we currently have of 50 miles (80 km) and 62 miles (100 km). So far, it’s our best option.
For more information on Theodor von Kärmann’s work and Kärmann’s line, see the biography of NASA (Opens in a new tab) On Major and ‘Theodor von Karmann, 1881-1963 (Opens in a new tab)Written by Sidney Goldstein.
NASA. (2019, October 2). Earth’s Atmosphere: A Layered Cake – Climate Change: The Planet’s Vital Signs. NASA. Retrieved on November 11, 2022 from https://climate.nasa.gov/news/2919/earths-atmosphere-a-multi-layered-cake/ (Opens in a new tab)
NASA. Earth’s atmosphere. NASA. Retrieved on November 11, 2022 from https://www.grc.nasa.gov/WWW/K-12/airplane/atmosphere.html (Opens in a new tab)
Orbital types. ESA. Retrieved on November 11, 2022 from https://www.esa.int/Enopped_Support/Space_Transportation/Types_of_orbits (Opens in a new tab)
Where is the space? NESDIS. Retrieved on November 11, 2022 from https://www.nesdis.noaa.gov/news/where-space (Opens in a new tab)
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