The edge of Earth's upper atmosphere and space now detected

More precisely pinpointed than ever before. Turns out it's 118 km or 73
miles.

Yousuf Khan

FOXNews.com - Scientists Find the Edge of Space - Science News | Science
& Technology | Technology News
http://www.foxnews.com/story/0,2933,513837,00.html

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."

BradGuth wrote:
118 km sounds about right, except for what our geomagnetic force and
subsequent magnetosphere protects at times more than half way to our
Selene/moon.

118 km is within the ballpark of figures that have already been bandied
about.

Regarding the magnetic field, it's not part of the atmosphere, even
though it's used in protecting the atmosphere.

Our upper 10% mass of atmosphere is also getting extensively thinned
out by hydrogen and especially via helium, and in case you haven't
otherwise noticed, Eden/Earth has been losing a great deal of mass/
year.


No, I haven't noticed. What with the last I heard, Earth gaining many
millions of tons of mass per year in meteorite captures. Regarding the
hydrogen loss, it's being replenished by capturing the protons streaming
from the solar winds. Regarding helium loss, I mourn for our birthday
party industry. :-)

Yousuf Khan

On Apr 10, 12:15*pm, Yousuf Khan wrote:
BradGuth wrote:
118 km sounds about right, except for what our geomagnetic force and
subsequent magnetosphere protects at times more than half way to our
Selene/moon.

118 km is within the ballpark of figures that have already been bandied
about.

Regarding the magnetic field, it's not part of the atmosphere, even
though it's used in protecting the atmosphere.

Our upper 10% mass of atmosphere is also getting extensively thinned
out by hydrogen and especially via helium, and in case you haven't
otherwise noticed, Eden/Earth has been losing a great deal of mass/
year.

No, I haven't noticed. What with the last I heard, Earth gaining many
millions of tons of mass per year in meteorite captures. Regarding the
hydrogen loss, it's being replenished by capturing the protons streaming
from the solar winds. Regarding helium loss, I mourn for our birthday
party industry. :-)

* * * * Yousuf Khan

You heard wrong. What part of duh-101 did you miss while you were in
school?

A great deal of hydrogen influx and even some terrestrial outgassing
doesn't manage to recombine, and otherwise Eden/Earth has been losing
a great deal of mass/year, mostly of helium because He simply doesn't
recombine with anything.

~ BG