Evening star. [volume] (Washington, D.C.) 1854-1972, 1935-02-23
STARS, MEN AND ATOMS
Notebook of Science Progress in Field,
Laboratory and Study.
BY THOMAS r. HENRY.

When men first looked at the moor
through telescopes they saw with
earth-bound eyes its lofty mountains
and great, fiat valleys.
These astronomers interpreted
what they saw in accordance with thu
familiar topography of the earth
They had every reason to believe
that the great satellite was another
world with much the same sort Of
| landscape. So when they drew maps
| they labeled the dark level spaces
mares" or seas. They supposed them
to be great expanses of water sur.
rounded by mountains, presenting
much the same picture to moon
jewellers as did the earth's oceans tc
themselves.
But when a developing physical
science attacked the problem of the
nature of the moons surface it be-
came obvious that these mares
could not be seas. 1t was physically
impossible for any appreciable amount
of water to exist on that airleSs chunk
of the earth's substance a quarter OF
million miles away. Just so it was
physically impossible for any moon
jewellers to live there.
What, then, we're the moon seas!
1t became customary to refer to them
as "craters," although the term
hardly could be synonymous with that
used to denote the hollowS in the
tops of earthly volcanoes. They were
far too extensive. The exact nature
of the mares" still remains some
what problematical.
Some Of the more notable of them
have been surveyed" by the Moon
Committee of the Carnegie Institution
of Washington, of which DR.. F. E
Wright of the geophysical laboratory
is chairman and which is making an
exhaustive study Of the satellites sur
face features. Approximately 100000
miles away from the object of their
survey, they have been able to make
fairly close calculations of distances
in miles and depths in feet by means
of several methods.
The method of determining heights
is described by Dr. Wright as "ascer-
tanning the length of the shadow
when near the limit of illumination
across the moons disk. We know
for any given time and for any point
on the moons surface the angle
which the suns rays make with the
vertical to the moons surface at that
point So it is simple to compute
from given angle and length of the
shadow the height of the feature
casting the shadow" The Carnegie
Institution scientists also have several
more complicated methods for their
moon surveying.
x 4 X y
One of the most remarkable of the
mares" they have surveyed is that
of Tycho, named for the great Danish
astronomer, Tycho Brach. They find
it to be approximately 1,700 feet deep
and 81 miles across. Nearby is the
great crater of Clavius, 1900 feet
deep and 142 miles across. Breaking
up its floors are several small craters,
the tiniest of which is larger than any
terrestrial volcanic crater. An mex
plicable feature at present is the
great wall" of the moon, apparently
a straight precipice about 10 miles
long and with a "down-throw" of
nearly 1000 feet on one side.
Some of the moons mountains, DR..
Wright and his associates find, reach
heights Of about $4,000 feet-almost
as high as the highest on earth. They
are extremely rough and precipitous
Even II there were plenty Of air and
water there and a reasonably equable
climate, the committee members con-
clude that they would be extremely
difficult to explore.
x X = X
Certainly some of the mares" they
conclude, must have been of volcanic
origin. 4
Now, ahterrestrial volcano Is q