Evening star., 1940-04-02
Of Stors, Men
And Atoms ~.
Notebook Of Science Progress
In Field, Laboratory
And Study
By Thomas r. Henri.

s"sS Ss~Sy
By Thomas r. Henry.
A black moon encircled in a band cf
pearly gold will sweep over the Southern
United States from Texas to Florida
next Sunday afternoon, providing one
Of the astronomical shows of the century.
Scientific instruments already are
being set up to observe this ring eclipse"
Of the sun. It will be attended by many
Of the spectacular features Of a total
eclipse and will be observable to some
degree over the whole continent except
Alaska. The light Of the sun will be
reduced to that Of cloudy, gray win
ter afternoon.
Such show occurs somewhere IN the
world nearly every year, but often over
the oceans or in some obscure spot where
1t is not feasible to send an expedition.
A joint expedition of the National Geo.
graphic Society and the United States
Bureau Of Standards is setting up sta
tion near San Antonio at which scien-
lists will play game Of bouncing radio
balls off the electric roof of the world.
This is the ionosphere, region of radio
rejecting layers which lie from so to
$50 miles above the earths surface.
Without these layers radio waves would
move in straight lines into space and
practically no reception would be posi-
BILE beyond the horizon.
These layers, experts of the two insti-
tutions explain in announcing the expe-
dition, consist Of concentrations of ions.
or wounded molecules of the gases that
make up the air. The gas molecules
are torn and therefore electrified from
collisions with the billions Of rays of SUM-
light that plough through on their way
to the earth. When night falls the
creation Of ions stops. Very quickly the
lowest of the layers practically disap-
pears. Gradually the higher layers be-
come less densely ionized but radio sig
mails reflected from them are stronger
because they do not have to pass twice
through the electrified region of the
lowest daytime level, losing energy on
the way.
TT is certain that marked changes in
some Of these layers can be noted, like
those that occur at night, at the moment
Of greatest darkness when a narrow ring
of the sun will be visible entirely sur
rounding the dark disk of the moon. A
trailer mounted equipment, operated by
storage batteries. will send upward radio
signals of steadily increasing frequency.
This frequency increase will take place
in one minute and will be repeated over
and over again during the progress of the
eclipse. The time required for the ecnos
to return from the rejecting layers st
different stages of darkness will be re-
ported photographically. These tracings
may throw light on the processes oc-
curing on the sun which determine the
ionization of the earth's atmosphere "
One of the most ambitious programs
Is that of the Mcdonald Observatory Of
the University Of Chicago, which is situ-
ated within so miles of the center of the
eclipse. Astronomers there under the d.
rection of DR.. Otto struve are seizing
the opportunity to observe conditions en-
the extreme edges of the disk of the sun.
The disk of the moon will eliminate
all the stronger radiation from the
center of the sun which, under normal
conditions, mingles with the radiation
eclipse this disk will cover SO per cent of
the suns diameter.
1t is we'll known. DR.. Struve points
out. that the sun seems much brighter
at the center than near the rim, but 1t is
only during such ring eclipse that the
surface brightness at the edge can be
measured. The measurements are ex-
pected to shed considerable light on the
actual composition of the sun. A special
television apparatus has been devised
to record the small additional amount
of light emitted by the corona. or pearly
outer edge of the atmosphere of the sun.
when seen against the normal blue sky
of daylight
With the aid of red Alter, DR.. Struve
said, amateur astronomers will be able
to observe prominences at the obscured
edge of the sun. The mountains at the
edge of the moon, which will appear as
tiny irregularities in the black disk, can
be photographed.
The path Of the most perfect phase Of
the eclipse will cross the Mexican border
at Big Bend, Tex, about 3:38 pm. It
will move eastward along a 150-mile-
wide path. At New Orleans it will last
~ minutes and 54 minutes in Talla-
hassee, Fla. The partial phases, which
will vary in different latitudes, can be
observed all over the United States and
most Of Canada. The ring aspect, how
ever, will be clearly visible only along
line through Southern Texas, Louisi-
ana, Mississippi, Alabama, Georgia and
Florida.