Evening star. [volume] (Washington, D.C.) 1854-1972, 1958-08-17

W NC CEedIcu ny heavenly COl-
lision.
The Volcano Theory
The same negative reasoning
does not kill of the volcanic
theory, which rests on the idea
that once the moon was hot, with
lots of molten material inside and
that now it is cool and beyond
further volcanic action.
The vulcanites may have some
thing. Unlike the earth. whose
average density is something like
water equals -, the moon is
only about as dense as granite (33
times water. This would seem to
indicate the absence of a molten
core.
1t also accounts for the fact that
though the moon is comparable in
size to the earth it is almost in
significant in mass. 1t would take
8lH moons, piled high on one
cosmic balance to equal one earth.
AS might be expected, the
moons gravitational field is much
smaller than that of the earth,
which in turn is smaller than
the suns. In the earth-moon sys-
tenn, the earth's gravitational in
fiuence prevails for a radius of
about 10000 miles from the
earth's center. The moons in
fluence rules for about $4,000 miles
out from the lunar center. In the
40,000or $4,000 miles between the
planet and the satellite, neither
has enough influence to overcome
the gravitational field of the sun
itself.
A Magnetic Field?
One unanswered question about
fields" is whether the moon has
a magnetic field like the earth's.
Will a compass needle point north
or west-or what will it do on
the surface of the moon? Moon
shooters hope to get partial an
swer with magnetometer aboard
the first rocket. 1t won't actually
get to the moons surface, but it
will get close enough (they hope)
to give an indication about lunar
magnetism.
There need be no doubt, how
ever. about the effects of gravity
on the moons surface. Sir Isaac
Newton discovered the law that
governs there as here. The first
visitors to the moon will find
gravity there extremely weak
compared to the terrestrial gravity
they have lived with all their
lives.
The ratio of the earth's gravity
at its surface to the moons grav-
ity at its surface is calculated as
1:0l65. This is usually inter-
preted as meaning that a 200
pound man would weigh" only
80 pounds on the moon, or con-
.versely that a man who could
high-jump 6 feet on earth could
soar to about 80 feet on the moon.
The theory doesn't work out quite
that way, however. because it ig-
nores the heavy, constructing gear
the would-be high-junper would
have to wear on the airless moon.
Extremes in Temperature
Part of his gear, incidentally,
would have to be highly efficient
insulator because of temperature
extremes on the moon. Because
the moon radiates heat almost as
fast as it receives it, some scien-
fists believe the surface itself never
gets very hot. But an object
like a space-suited human-might
not radiate heat so rapidly, with
the result that unless properly
insulated, it could get as hot as
boiling water in the course of
the moons two-week day" BY
the same token. the temperature
would drop to about 200 degrees
below zero Fahrenheit during the
two-week night.
For all the hardships facing
him, the first moon visitor is GER
tain to get the thrill Of a lifetime
"a look at the earth rising high
in the dark vacuum Of the lunar
sky. With an albedo six times
that Of the moon and disk of Is
times the moons apparent area,
the earth will be q marvellous
sight.
Unfortunately for young lovers
strolling on the moon, earthlight
will not have the romantic quality
of moonlight on the earth; it viii
be more IFe the blaze of Times
Square, with a greenish- blue cast.