Evening star., 1951-10-03
Earth Wears Night Robe
Of Transparent Light
Naval Research Stoff Reports
On Shimmering Air Glow
By Thomas R. Henry

The earth wears night robe OF shin1-
mering, transparent light.
Existence of this "air glow"-a faint,
constant lumineScence that Is spread
more or less uniformly around the whole
planet-has been little known except to
astronomers; but group of Navy re-
search workers, working under an Office
of Naval Research contract at the Yerkes
Observatory, Williams Bay. Wis, has
largely solved it's mystery.
This has just been reported by DIR.
Alden B. Meinel. Yerkes astronomer, who
directed the work.
It long has been suspected that the
air glow was due to chemical reactions
in the upper atmosphere. The ultra
violet light in sunshine breaks up certain
molecules into their constituent atoms.
These air molecules reform at night In
this reformation minute amounts of light
are emitted. This makes the night
robe"
Reconciliation of Molecules.
Most of the light is in the red or in
frared parts of the light spectrum. The
latter is invisible but can be studied with
special instruments used by DR.. Meinel
and his associates. They showed for the
first time that this light was due to the
recombination of molecules containing
one atom Of hydrogen and one of oxygen.
This molecule, in turn might come from
the breaking up of water vapor, but
there is extremely little water in the
region of the atmosphere where air glow
takes place-approximat at an alti-
tude of as miles. The final conclusion
was that the combination was taking
place between atoms of ozone, an exc
tremely active form of oxygen, and
hydrogen atoms.
The project started as a study of the
aurora borealiS, the cause of which still
is not entirely clear. The Yerkes
astronomers studied the spectrum of
the soft yellow-green and red light
which constitutes the dancing and
naming fingers" in the northern
heavens.
1t formerly was believed that this
light was due to electrons elected from
the surface of the sun which caused
the air to shine when they struck the
earth's atmosphere. The difficulty vas
that such electrons would not have
been able to penetrate to levels where
the aurora appears.
Some years ago Norwegian scientist,
Lars Vegard, noted occasional light lines,
such as would be emitted by hydrogen
atoms; and it was concluded that the
lights were due to these particles, far
more massive than electrons shot from
the surface of the sun. The suns outer
atmosphere consists largely of hydrogen.
Studies by Speed Camera.
AS in the case of the air glow, the
Yerkes scientists studied both the
aurora's visible light and the invisible
infrared. The latter was almost unex-
plored because of the great technical
difficulty of observations Work was
made possible through the development
by DR.. Meinel of a camera so fast and
delicate that it can photograph in 60
seconds stars $4,000 times fainter than
the eye can see. There were also great
technical Improvements in the spectra-
scope and in the speeds Of infrared
sensitive emulsions.
The general effect of the work was
to confirm the hydrogen atom hypo-
thesis, but there were some curious
discrepancies. One of these vas the
shifting of one hydrogen light line far
towards the violet end of the spectrum.
Calculations showed that this could
happen only if the hydrogen atoms were
moving with enormous velocities. 1t was
determined that the necessary speed
was 100000 miles an hour-about the
greatest speed yet measured in the uni
verse except for light itself.
Another important result of the OBJ
servations was the Identification of a
new light band system of nitrogen. This
confirmed that some nitrogen in the
upper atmosphere exists in form which
scientists had predicted from theoretical
calculations. but had been unable to
produce in the laboratory.