Virginia citizen. (Irvington, Va.) 1891-1921, 1910-04-01
THE TAIL OF ACOMET
1t Pays Dearly For Its Brilliant
Gaseous Display.
FORMED BY LIGHT AID HEAT.
Far Away the Comet Is Giobular
Mass, and as II Nears the Sun the
Action of That Body untwines the
Tail. Which Is Never Recovered.

NCtion OF tnst ooor OntwtneS the
Tail. Which Is Never Recovered.
Travelling us comets do I'm very elon-
gated ellipSes. with the sun in Que of
the foci. as the attracting point is
called. most of their Journey is spent
I'm slow uneventfulneSs far away from
the hearth of the system-heartb Is
just what the word focus means They
are then small globular aggregations.
sluggish aud 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
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 bright
spot. the nucleus. Suddenly there oc-
ours complete change In the deport-
ment of the body. one which renders
Ii 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 II. BY Very's deter
minaion 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 1853 degrees Il.
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 It is al
ready four times as great above abso-
lutte zero. ut u quarter sixteen times,
and so on Increasingly. the tempera.
ture rising into thousands of degrees.
No wonder the comet acts as 1t does.
1t ut once becomes uneasy. wakes in
light and. as the spectroscope reveals.
descriptive 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 au object and for
which IL pays so dear The gases
which are thus thrust out from the
interior of the separate meteoritcs. to-
gcther with such PARTICLES of the iron
rs are made gaseous by the heat. fall
prey 10 another force besides gravita-
ton. This force is the impact OF light
itself. the light emitted Ivy the sun
That SO iminatcrial thing us a
beam Of light can have power TO move
even n pith ball is conception not
easy to grasp. Yet there is no doubt
OF the fact. theoretically calculated
nv Clort- In
electromagnetic theory of light. for the
gaseous particles proceed TO he repealed
by the sun at enormous speed. each
behaving exactly MS IL should by math
ematical analysis II such were the &C.
SEASONING cause. Evidently the light
waves have propclling power in the
direction of their own motion equal
to their own speed.
Why. then. is IL 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, a
matter Of two. AS q body diminishes
In size. therefore. Its surface bears q
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 1t
In series OF exquisite mantling en-
velopes. as II the comets head were
yelling itself from the too ardent gaze
or 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 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 frst is fourteen times that of gray
lily. In the second two and two-tenths
times. or something less. and In the
third only about one-fifth of gravity.
Hut these are the very ratios which
particles OF hydrogen gas. OF the n.y.
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 II pays |
Its orbital obeisance to the ruler or |
Its course. 1t seemingly backs away |
In keeping with the etiquette to royal |
~, turning always its face sunward |
as 1t retreats whence 1t 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 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 perihelIon
pageant is so ine.-Youth's Compan
ion.
What Aecountaney Means.