Yorkville enquirer. [volume] (Yorkville, S.C.) 1855-2006, 1910-05-17
THE TAIL OF A COMET.
It Pays Dearly For Its Brilliant Case
ous DISPLAY.

It Pays Dearly For Its Brilliant Case
Gus Display.
Travelling as comets do in very elOn-
gated ellipses, with the sun in one Of
the foci, as the attracting point Is
called, most of their journey is spent
in slow uneventfulness far away from
the hearth Of the system-hearth Is
just what the word focus means. They
are then small glubular aggregations,
sluggish and dina little rOundisn
nebula in look. Such they appear
when first described in the telescope
coming in from space, for they are
tered within the orbit of Mars. Dis
tance in part, but still more their own
behavior till then, keeps them hid.
Within this nebulosity, known as the
head, appears as 1t nears us a bright
spot, tine nucleus. Suddenly there oc-
ours a complete change in the deport-
ment Of the body, one which renders
it the observed Of all observers, and in
less civilized times occasionally its be-
ing held the harbinger of distress, dis
ease and death.
AS soon as the comet gets near
enough the heat of the sun sets up
commotion within 1t. By Very's deter
mination Of the temperature of the
unblanketed sunward side of the moon
we are enabled to infer that this heat
is great at the earth's distance from
the sun in spite of the cold Of space.
This temperature Is 353 degrees F.
And as the comet approaches the
sun this heat must increase inversely
as the square Of the distance. At half
the radius of the earth's orbit 1t Is al
ready four times as great above abso-
lutte zero, at a quarter sixteen times,
and so on increasingly, the tempera-
ture rising into thousands Of degrees.
No wonder the comet acts as 1t does.
1t at once becomes uneasy, wakes in
light and, as the spectroscOpe reveals,
disruptive electric discharges start In
it which let out the imprisoned gases.
Then begins that spectacular career of
perihelion passage which makes the
comet so superb an object and for
which it pays so dear. The gases
which are thus thrust out from the
interior of the separate meteorites, to-
gether with such particles Of the iron
as are made gaseous by the heat, fall
prey to another force besides gravita-
ton. This force is the impact Of light
ITSELF the light emitted by the sun.
That so immaterial a thing as beam
of light can have power to move even
a pith ball Is a conception not easy to
grasp Yet there is no doubt of the
fact, theoretically calculated years ago
by Clerk Maxwell from his electro
magnetic theory of light, for the CASE
Gus particles process to be repelled by
the sun at enormous speed each be-
having exactly as it should by math-
ematical analysis If such were the oc-
casioning cause. Evidently the light
waves have a propellins power in the
direction of their own motion equal
to their own speed
Why, then, is it that the planets be-
tray no such effect in spite Of their
size? The answer is, because of that
very size. Gravity acts on the mass,
a matter of three dimensions: the light
force on the surface of the body,
matter of two. AS a body diminishes
in size, therefore, it's surface bears a
greater and greater ratio to its mass
until when small enough the second
force is the stronger of the two.
This relation is betrayed in the m
duct of the tail. The impris d
gases, heated to expulsion on the sun
ward side Of the comet, rise toward 1t
in a series of exquisite mantling en-
velopes, as if the comets head were
yelling itself from the too ardent gaze
of the sun. Then, after rising % a
certain height their initial impetus
overcome, they fall back, repelled by
the light waves, although still attract
ed by gravity, and are driven out to
form the tail of the comet, fresh en-
velopes taking their place.
Sometimes only a single tail is form
ed, but at others two or even three are
shot out, and when this happens one is
nearly straight, one curved and one
greatly bent Now, calculation shows
that the repelling force in the case of
the first is fourteen times that of grav-
ity, in the second two and two-tenths
times, or something less, and in the
third only about one-fifth Of gravity
But these are the very ratios when
particles of hydrogen gas. Of the hy-
drocarbons and of iron or sodium
would respectively show.
AS the comet approaches the sun the
display becomes more violent and
more spectacular. Finer and wilder
grows the pageant the hairy star
loosening its tresses, which had stood
sedately coiled about its head amid
the depths of space, to stream in
gorgeous CLEANS behind it as it pays
it's orbital obeisance to the ruler of its
course. 1t seemingly backs away in
keeping with the etiquette to royalty
turning it's face sunward as it retreats
whence it came.
But it pays dearly for its display
The matter going to form the tail can
never be recovered but is driven far
ther away. At each successive return
to the sun some of it's mass and bril-
lance is thus lost, and this is why the
periodic comets, those that have made
many visits, are such small and in
conspicuous objects. 1t is only the
comets of long ellipses and very dis
tant habit of which the perihelior
pageant is so fine.-Youth's Compan
ion.
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