For decades, different groups have defined the edge of space--meaning, the barrier between Earth's atmosphere and outer space--differently. Now scientists have confirmed that the edge of space begins 73 miles (118 kilometers) above Earth's surface, by using data from a new instrument developed at the University of Calgary, according to Space.com.

The backstory is kind of complicated. When man first attained orbit in the late 1950s, a definition of 50 miles above the surface was used. Today, many in the space industry--including the Federation Aeronautique Internationale (FAI), which sets aeronautical standards--defines the limit as 62 miles. For example, that's what the Ansari X-Prize used for its $10 million reusable spacecraft competition. Meanwhile, NASA sets 76 miles as the re-entry point where the shuttle shifts from steering with thrusters to air surfaces.


So why 73 miles? In the new study, an instrument called the Supra-Thermal Ion Imager discovered the boundary by comparing the relatively gentle winds of our atmosphere, and the intense, 600 mile-per-hour charged particles in space, the report said.

"It's only the second time that direct measurements of charged particle flows have been made in this region, and the first time all the ingredients - such as the upper atmospheric winds - have been included," said project scientist David Knudsen, of the University of Calgary, in the article.

Knudsen added that the finding could aid in determining the link between sunspots and the warming and cooling of the Earth's climate, as well as "how space weather impacts satellites, communications, navigation, and power systems." (Image credit: Reuters/European Space Agency hand-out)