What separates planet Earth from the sky? As more countries and businesses turn to the stratosphere, the debate over how to define outer space is growing. Ask someone where outer space is, and they will likely point to the sky. It’s up, isn’t it? basic.
Except, no one really knows where “aerospace” ends and “outer space” begins. This may sound trivial, but setting those boundaries can be important for a number of reasons. Including, but not limited to, any high-flying humans will be classified as astronauts.
Now, with Virgin Galactic seemingly on the cusp of launching propelled travelers on suborbital paths, many people are wondering if these lucky tourists will ever earn astronaut wings. From now on, they will do so, according to US practice.
What separates planet Earth from the sky?
The answer is: Atmosphere
International treaties define “space” as free for exploration and use by all, but the same does not apply to sovereign airspace over nations. The laws that govern aerospace and outer space are different. Flying a satellite 55 miles over China is fine if space starts at 50 miles, but set the edge at 60 miles, and you might find your satellite treated as an act of military aggression.
“Where does a country’s airspace stop and space begin?” asks Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics. “Once you agree on the boundaries of space, you agree to the boundaries to which space law applies.” However, the United States and some other countries have resisted an international formal definition of space, stating that it is not necessary and that “no legal or practical problems have arisen in the absence of such a definition.”
Others argue that maintaining distinct boundaries will be crucial, given the increase in the number of national space programs and in private spaceflight endeavors increasing the volume of suborbital traffic. In general, most experts say that space begins at the point where orbital dynamic forces become more important than aerodynamic forces, or when the atmosphere alone is not sufficient to support a flying ship at suborbital speeds.
Earth is the only planet known to sustain life. Discover the origins of our home planet and some of the key ingredients that help make this blue spot in space a unique global ecosystem. Historically, it has been difficult to pinpoint this point at a particular altitude.
In the 20th century, Hungarian physicist Theodor von Karmann decided that the boundary would be about 50 miles, or roughly 80 kilometers, above sea level today. 62 miles, or roughly one hundred kilometers above sea level.
The International Federation of Aviation (FAI), which tracks standards and records in astronautics and aviation, defines space as starting at an altitude of one hundred kilometers. It is, after all, a beautiful round number. But the FAA, the US Air Force, NOAA, and NASA generally use the 50-mile (80-kilometre) boundary, with the Air Force awarding astronaut wings to travelers who exceed that mark.
Meanwhile, NASA’s mission controller puts the line at 76 miles (122 kilometers), because this is “the point where atmospheric drag becomes noticeable,” Bhavya Lal and Emily Nightingale of the Science and Technology Policy Institute wrote in a 2014 review.
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