Evening star., 1926-11-24
PICTURE OF MOON
GIVEN IN LECTURE
Dr.. Fred E. Wright Explains
Peculiar Conditions Exist
ing on Satellite.
If anybody-ever visits the moon he

IF anybody~ever visits the moon he
will f1nd himself in a queer place.
Conditions on the earth's satellite,
where there is no atmosphere detect
able and where the force of gravity
is only one sixth as great as on the
earth. are difficult to picture from
earthly standards, according to DR..
Fred f. Wright. petrologist of the
geogphysical laboratory of the Car
negie Institution, in a lecture at the
institution last night.
DR.. Wright has just been named
chairman of a committee Of geolog-
lists. mathematicians and astronomers
to conduct an intensive study Of the
moon, which still contains many ele-
ments OF mystery, although 1t phys
ical Features have been rather thor
oughly explored through the tele-
scope:
ProiectiIe Could Hit Earth.
In his lecture last night DR.. Wright
imagined the situation of an artil-
leryman on the moon. The ordinary
76-millimeter field gun, whose range
is about $4,000 yards on earth, would
send projectile ESQ miles across the
surface of the moon. The German
long-ra gun that bombarded Paris
from 20 miles away could be trained
on a target 3 400 miles away If fired
on the moon. A projectile fired with
a velocity of two kilometers sec
ond, impracticable but not entirely
impossible in future warfare, would
completely circle the moon and hit
the artilleryman on the back OF the
head.
Or such a projectile might leave the
Lite xIn ~ y or
some other planet. In order for q sim
liar projectile to be fired off the earth
that is out Of the attractive force of
the earth so that it would never re-
turn-it would have to leave the gun
at a muzzle velocity Of Is miles or
more second.
The surface Of the moon, the tele-
scope reveals. is pitted with great
holes-50 miles or more in diameter.
Two explanations have been given of
the origin Of these holes, DIR. Wright
explained. One school holds that they
are extinct volcanoes. although their
similarity to volcanoes on earth Is
difficult to see at first. On earth the
volcanic eruptions are acted upon by
powerful force of gravity. The
rocks and lava are thrown only a few
feet and fall near the crater, SO that
it. On the moon eruptions with no
greater force behind them would be
hurled entirely clear Of the area sur
rounding the crater, so that this would
remain a great hole in the ground.
Another theory is that these great
holes have been caused by meteors
pelting against the surface of the
moon. Very few meteors ever strike
the actual surface Of the earth. They
are burned up by friction in the 500
miles of atmosphere they must go
through before hitting the ground,
and the larger of them appear as
shooting stars. But on the moon
there is no atmosphere to burn them
up. They will strike the surface
with all their original mass and
speed.
Meteor Theory Tenable.
This theory also is tenable, DR..
Wright holds. The effect Of one of
these meteors striking the surface Of
the moon would be about the same
as a small volcano. One Of the few
places where q meteor Of considerable
size ever has struck the earth Is at
the famous meteor hole in Arizona.
Here the depression caused is very
similar to the appearance of the cra-
ters of the moon.
DR.. Wright also has been investi-
eating the force of gravity on earth
and is developing a new form of ap
paratus for measuring its intensity.
DR.. Wright discussed at some
length the various theories Of isostacy,
which holds that the crust of the
earth, about so miles thick. floats on
a surface of heavier rock. One theory
is that there is a perfect balance
everywhere in the weight of the
earth's crust, the mountains being of
considerably lighter material than the
land under the depths Of the sea. and
that they all float at the same depth.
Another theory Is that there are va
riations in weight and that the sea
bottoms have sunk deeper than the
mountains into the underlying rock.
Determination of the truth Of
isostasy, DR.. Wright explained. de-
pends largely upon extremely accurate
measurements of the force of grav-
ity at many points on the earth's
surface.