The Mount Holly news. [volume] (Mount Holly, Burlington Co., N.J.) 1891-1942, 1911-01-24
THE TAIL OF A COMET
1t Pays Dearly For Its Brilliant
Gaseous Display.
FORMED BY LIGHT AND HEAT.
Far Away the Comet Is q GlobuIar
Mass, and as It Nears the Sun the
Action of That Body untwines the
Tail, Which Is Never Recovered.

Action of That Body UntWines the
Tail, Which Is Never Recovered.
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 globular aggregations,
sluggish and dina little roundish
nebula in look. Such they appear
when first deserted In the telescope
coming in from space, for they are
rarely seen at all until they have en-
tered within the orbit of Mars. Dis
lance In part, but still more their own
behavior till then, keeps them hid.
Within this nebulosity, known as the
head, appears as it nears US a bright
spot, the nucleus. Suddenly there oc-
ours complete change In the deport-
ment Of the body, one which renders
1t 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 it. By very's deter
mfnation 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.
rhfu earx, -, ~, &c QSo 1or~o,r N
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 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 it does.
1t at once becomes uneasy, wakes in
light and, as the spectroscope reveals,
disruptive electric discharges start in
1t 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
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 SUM-
That so immaterial a thing as a
beam Of light can have power to move
MIL ho1 Is x.1%
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
gaseous particles proceed to be repealed
by the sun at enormous speed, each
behaving exactly as 1t should by math-
ematical analysis If such were the oc-
sasioning cause. Evidently the light
waves have propelling 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
4OACC III lnC oul4dCC VI h4c DOQyt q
matter Of two. As body diminishes
In size. therefore. its surface bears
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 con-
duct Of the tail The imprisoned
gases, heated to expulsion on the sun
ward side Of the comet, rise toward it
In 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 to a
certain height, their initial impetus
overcome, they fall back, repealed 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 gray
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 which
particles of hydrogen gas, of the by
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
its orbital obeisance to the ruler of
its course. 1t seemingly backs away
in keeping with the etiquette to royal
ty, turning always its face sunward
as 1t 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
Their away. At each successive return
to the sun some Of its 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 perihelion
pageant is so fine.-Youth's Compan-
lon.