South Bend news-times. (South Bend, Ind.) 1913-1938, 1918-11-18
Comets and
ProjechleS
BY GARRETT p. sERVISs.

announce the reappearance Of
Wolfr's periodical comet. which
emerses like a silver tailed dolphin
from the black ocean Of space once
every seven years, flirts awhile in
sight OF a few Of the planetary ships
of our squadron, takes a turn
around their flagship. the sun, and
then buries itself once more in the
fathOmless ether.
Now. this comet in itself has no
popular interest. ii is not one OF the
big ones But its return, like the
returns Of all its fellows, is a dem
onstration Of human efficiency on a
higher plane than that of war or Of
business. Think Of il for a moment
new comet, misty speck in the
sky, is noticed by some lone watcher
or detected by it's image on some
phOtogra phic plate. 1t is many mill
lions of miles away from the earth;
il is almost as indefinite as a cloud;
1t is travelling under the impulse OF
the suns attraction, not the earth's;
its speed can be calculated If its dis
lance is known, but the distance can
only be known by means Of most
accurate observations followed by
mathematical calculations based on
rules that human genius has fOrmu-
lated; vet, in a few days after its
first appearance, the astronomer
knows how far away ii is, how fast
il is moving. in what direction 1t is
travelling. what the form of its orbit
is, where it will be In space when
it has disappeared how long it will
be gone, when it will be back and
in what part Of the sky to look for
il when il returns within range of
vision. Perhaps. and this has nap
pened many times, the observations
and calculations show that the
comet will never come back, or will
go so far away that before it can
get back not only will all existing
empires of man have disappeared
and been forgotten, but the whole
earth may have undergone a geo.
logical revolution. continents RISING
or sinking. shrinking or expanding,
with new climates and a new age
spreading over the globe
Mans nearest Imitation Of
comet is a projectile from a big gun.
a comet starts to follow a straight
line; so does the projectile. As soon
as the comet feels the attraction of
star itsSpath changes to AZ curve
called a comic: the instant the pro-
iectile gets out Of the bore of the
gun the attraction of the earth
makes its straight path comic. The
orbits Of the great majority of
comets that have not been changed
by the attraction Of the sun and
planets are approximately para
bolas te trajectories Of all projec-
tiles, if not deformed by the attrac-
ton Of the earth, would be para
bolas
When a new comet appears It is
customary. for the purpose Of in
vestigating its orbit, to assume that
it is a parabola, and afterward APP
Dlv such corrections as further OBJ
servations may indicate; in deter
mining the orbit. called trajectory,
of a projectile the basis Of the cal
culation is the same assumption
viz. that the curve is a parabola.
One great difference between the
dynamics Of a comet and that Of
projectile is that the projeCtile has
TO contend with the variable resist
ance of the atmosphere, while the
comet. moving in virtually empty
space beyond the atmospheres of the
planets, and. ordinarily. beyond that
/ OF the sun also, meets with no re-
sistance.
The only things that affect its mo-
/ ton are the attractions of the sun,
/ the planets and any other bodies
within whose gravitatiOnal realms
! il may intrude. While the problem OF
/ the origin. or. as il Is sometirr es
called, the birthplace of comets has
not been solved. vet the tendency
at present is TO regard them as hav-
/ ing always belonged 10 the solar
4 system. since it's formation out of a
! nebula. the immense relative dis
tances TO which many of them go
! from the sun. as compared with the
! distances of the planets, being eX-
planned by the assumption that they
were formed out of remote. outlying
iparts of the original nebula, whose
dense central portion was shaped in
/ 10 the sun anu tic HlAiit-o-
But they look so much like giant
lighted bombs as they rush through
space with their streaming tails that
they have sometimes been Magma
lively described as missiles sent from
explosive stars. The very remarkab BILE
comet Of 1882. which narrowly miss
ed the sun. passing. in all prObabil-
ity. through its corona, came almost
exactly from the direction Of the
great star Sirius, and then returned
nearly on it's course, and the ques-
ton was half seriously asked: us
Sirius shooting at us?"
The implication was that the
comet had been hurled forth by
some great explosion in the star. a
view based upon the known fact
that our own sun sometimes elects
matter with velocity sufficient 10
carry il beyond the sphere of his
gravitational control. For that an
Initial velocity OF at least 3s3 miles
lper second would be required. But
liz sirius did shoot that comet at his
neignbors. II was only one Of a
series OF shots tried by the Dog
star on the same target because il
has been found that the comets OF