The Washington times., 1922-08-23
BY Garrett p. Serviss
'minent Astronomer and Authority
on Subjects Of Scientific
Interest.

Ou SuUJCCtS VI oClChthiC
o Interest.
V How can scient SITS be so
o positive that life does not ex-
n list on the planets because Of
extremely low temperatures and
other reasons? The law Of
gravitation must exist there to
some extent or there would be
no mass formations. II gravi-
3 tation exists, would not that
n cause interior heat sufficient to
Y overcome extreme low temper
8 atures on the surface, as Is so
! evident on our own globef
Again, would not this heat
tend to draw sufficient mois-
ture to sustain life? read
every article you write.-M. J.
c.. New York"
@ DO not .h;r' y" sci"r-
lists are positive that life
AZ does not exist on the plan
sets. Some are agnostic or non
committal on the subject, and
bonle .u4hk na- M,. -. .''s.s.-y
Is life on some OF the planets,
particularly Venus and Mars.
Is IL hHASAJ
absent from other planets such
sas Jupiter and Saturn. In speak
ling of life in this sense II Is nee
cessary to draw line somewhere,
ytf we would have any ground
Whatever for reasoning and argu'
ment. We must start with def
initions and terms of compari-
son, for to say broadly that be.
cause the Creator has infinite
bower there must be life on
revery planet, no matter how un'
like the earth that planet may
sbe, is a non-sequitur, that Is the
I Fconclusion does not follow from
the premises. This is, perhaps,
the most common Of all forms
( of fallacy in logic. ,
III Now, as TO gravitation and heat.
I The law of gravitation exists not
merely to some extent but to full
Fextent on every planet. You may
find II a bit of curious and inter-
esting information to know what
The force of gravity Is on the sur
face of each Of the eight planets,
/ Including the earth, that revolve
around the star, called the sun.
Here Immediately we have to IN
produce a term Of comparison in
order to have a standard by which
To reckon the amount OF the
force. For this term we take
The surface gravity on the earth.
II we call that unity, or LOO
then we find that on Mercury,
the smallest planet and the one
nearest the sun, the force Is
IN. az: on Venus, 0.S2, or perhaps
io.s5; on Mars. OBS; on Jupiter
PCS; on Saturn, 1.18; on Uranus
lo.90; on Neptune, 0.S9.
This shows that only two or
the planets have q greater force
OF surface gravity than the earth
has, viz, Jupiter and Saturn, both
OF which are enormously large
ieompared with the earth. Now,
here appears a very curious rela-
Stion, in which greater size coun'
Tteracts the effect of a greater class
with regard to gravity. The ap-
Ssolute gravitational force OF Jupi-
ter (measured by its mass Is
about S18 times that OF the earth'
and yet on its surface the force
Is only 2-6S. or a'little less than
1.-TWO and two-thirds times as great
rs on the earth. Why Is this? 1t
as because owing to its. greater
Esize Jupiter's surface Is about
eleven times as far from its CEN
Ter Of gravity as is the surface OF
the earth, and the law Of gravtta-
tion tells us that while the force
varies directly. as the mass, at the
same time It varies inversely, as
The square Of the distance. So We
ksquare IL and get 121; then we di-
oyide 818 by 121, and the quotient.
(which is about 2.63, represents the
force of gravity on Jupiter's sur
face as compared with its force
on the earth's surface.
Similar calculations applied to
khe other planets will explain why
MERCURY, which has less than one
twentieth as great a gravitational
Nkorce as the earth, nevertheless
has almost half as much surface
igravity, while Saturn, with a
seravitational force ninety.five times
Fhe earth's, has surface gravity
only Is per cent greater than that
on the earth.
III You are right in supposing that
the force of gravity on a planet
plays an important part with ref
kerenca 70 its habitability or slIita-