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 73 miles (118 kilometers) above Earth's
surface.
A lot
remains very fuzzy, however, as the boundary is surrounded by a host of
misconceptions and confusing, conflicting definitions.
For
starters, astronauts can say they've
been to space after only passing the 50-mile (80-kilometer) mark.
Meanwhile
the boundary recognized by many in the space industry is also a somewhat
arbitrary 62 miles (100 kilometers). 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 62-mile 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 76 miles (122 kilometers) as their re-entry altitude
because that's where the shuttle switches from steering with thrusters to
maneuvering with air surfaces, NASA states. Others point out that the "Now
Entering Space" sign should be posted way out at 13 million miles (21
million kilometers) because that's the boundary
where Earth's gravity is no longer dominant.
(While
astronauts experience weightlessness in space, this isn't because there's no
gravity there, it's due to the balance of forces acting on them as they
orbit.)
In the new
study, an instrument called the Supra-Thermal Ion Imager detected the boundary
by tracking the relatively gentle winds of Earth's
atmosphere and the more violent flows of charged particles in space, which
can reach speeds well over 600 mph (1,000 kph).
The ability
to gather data in that area is significant because it's very difficult to make
measurements in this region, which is too high for balloons and too low for
satellites.
"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," says project scientist
David Knudsen of the University of Calgary.
The
instrument was carried by the JOULE-II rocket on Jan. 19, 2007. It traveled to
an altitude of about 124 miles (200 kilometers) above sea level and collected
data for the five minutes it was moving through the "edge of space."
The
finding, detailed in the Journal of Geophysical Research on April 7,
could aid the study of space weather and its impacts
on Earth.
The data
"allows us to calculate energy flows into the Earth's atmosphere that
ultimately may be able to help us understand the interaction between space and
our environment," Knudsen said. "That could mean a greater
understanding of 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."
This article was update at 4:14 p.m. ET.
advertisement
