Rock Island Argus. (Rock Island, Ill.) 1893-1920, 1910-04-01
THE TAIL OF A COMET
1t Pays Dearly for It's Brilliant Gaseous Display
Formed by Light and Heat.

| ready four times as great above abso-
lutte zero, at 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 speetroscope 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 a
beam Of light can have power to move
even 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 bis
electromagnetic theory of light, Tor the
gaseous particles proceed to be repealed
by the sun at enormous speed, each
behaving exactly as it should by math-
ematical analysis If such were the oc-
sasioning cause. Evidently the light
waves have a 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
force on the surface OF the body,
matter of two. AS body diminishes
in size, therefore. its 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 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overcome, they fall back, repealed by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-
veIopes taking their place.
Sometimes only single tan 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 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 1t as 1t pays
fits orbital obeisance to the ruler OF
in keeping with the etiquette to royal
ty, turning always its face sunward
as it retreats whence IL 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 It is only the
coraets OF long eiiipses and very dis
TAM habit Of which the perihe,ion |
pageant is 30 fne.-Youth's Compan-
Ion.