Where does Earth's atmosphere and outer space begin? A new paper says space is just 50 miles away from the planet's surface.
Astrophysicist Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics argues that scientists may have gotten the boundary of outer space all wrong.
In a new study scheduled for publication in the Acta Astronautica journal, McDowell says outer space begins at a 50-mile altitude, a whole 12 miles lower than the Kármán Line, which represents the prevalent theory since the 1960s that outer space begins 62 miles above the surface of the Earth.
What Is The Kármán Line
In 1963, aerodynamics researcher Theodore von Kármán suggested that the speed needed to lift an object into the atmosphere is the same as the speed needed to keep it in orbit around the Earth. Von Kármán said that the horizontal movement of the object on orbit would counteract the effects of gravity.
However, McDowell says the traditional view of the edge of space is based on decades of misinterpreted data about objects orbiting the Earth.
Since he was 13 years old, McDowell has been collecting data about every rocket launched into space, a hobby that often compelled him to identify which rockets actually went into outer space and which ones remained within the Earth's atmosphere.
Edge Of Space Closer Than Previously Thought
In his study, McDowell examined the orbital patterns of 43,000 satellites based on data he collected from the North American Aerospace Defense Command, which tracks aerospace in the United States and Canada.
An overwhelming majority of the satellites were located in orbit well above the Kármán Line, which means they are inarguably in outer space.
However, 50 satellites caught McDowell's attention. After completing their missions, the satellites made several revolutions around the planet at altitudes well below the traditional 62-mile limit.
The Soviet Elektron-4, for instance, went around the Earth 10 times at an altitude of 52 miles before entering the atmosphere and blowing itself up.
"Are you going to say [these satellites are] in space and then not in space every two hours?" says McDowell. "That doesn't seem very helpful."
McDowell went on to develop a mathematical model that identifies the point at which satellites got off their orbits and burned themselves up during their entry into the atmosphere. The model pinpoints it is mostly at an altitude of 50 miles, although it can happen anywhere from 41 to 55 miles.
Consistent With Existing Knowledge
The new findings are consistent with existing knowledge about the atmosphere. The mesopause, which is the coolest layer of the atmosphere, sits 52 to 62 miles above the surface of the Earth.
Here, temperatures drop drastically, and more charged particles are flowing freely about. In other words, the mesopause looks a lot more like space than the lower layers of the atmosphere.
Meteors that hit the Earth also disintegrate at 43 to 62 miles above the planet, which is where the air in the atmosphere compresses and quickly heats up the meteor up to 3,000 degrees Fahrenheit.