Hold on to your hats, or in this case, your helmets: Scientists have finally pinpointed the so-called edge of space — the boundary between Earth's atmosphere and outer space.
With data from a new instrument developed by scientists at the University of Calgary, scientists confirmed that space begins 118 kilometres above Earth's surface. A little further than originally assumed.
The boundary recognized by many in the space industry is also a somewhat arbitrary 100 kilometres. Scientist Theodore von Kármán long ago calculated that at this altitude the atmosphere is so thin that it's negligible, and conventional aircraft can no longer function because they can't go fast enough to get any kind of aerodynamic lift.
This 100km boundary is accepted by the Federation Aeronautique Internationale (FAI), which sets aeronautical standards.
The United States, however, has never officially adopted a set boundary standard because it would complicate the issue of overflight rights of satellites and other orbiting bodies, according to NASA.
NASA's mission control uses 122 kilometres as their re-entry altitude because that's where the shuttle switches from steering with thrusters to manoeuvring with air surfaces, NASA states.
Others point out that the "Now Entering Space" sign should be posted way out at 21 million kilometres because that's the boundary where Earth's gravity is no longer dominant.
Article by Andrea Thomspon, 9 April 2009. Copyright-Imaginova Corp. Thanks to Dave Reneke for passing this on.