Bonners Ferry herald. [volume] (Bonners Ferry, Idaho) 1904-current, 1910-06-04
THE TAIL OF A COMET
1t Pays Dearly For Its Brilliant
Gaseous Display.
FORMED BY LIGHT AND HEAT.

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 1t 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
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 1853 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 orbit it is al
ready four times as great above abso-
lutte zero. al 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,
dtsruptive 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 1t 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 tmmaterial a thing as a
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
electromagnetic theory of light, for 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
size2 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 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 II
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 to 6
1 -te,tx. At.rt,A fI.4 tx,ff foI t,,nr or
overcome, they fall back, repealed by
the light waves, although still attract
ed by gravity, and are driven out Il
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 ar
shot out, and when this happens on
is nearly straight, one curved and on
greatly bent. Now, calculation show
that the repelling force in the case o
the first is fourteen times that OF gray
, ity, in the second two and two-tenth
times, or something less. and In tn
third only about one-fifth of gravity
But these are the very ratios whic
particles of hydrogen gas, OF the by
! drocarbons and of iron or sodful
would respectively show.
AS the comet approaches the sun tn
display becomes more violent an
more spectacular. Finer and wilde
grows the pageant, the hairy star
loosening its tresses. which had stoo
sedately cotled about its head ami
the depths of space, to stream
gorgeous CLEANS behind 1t as it pay
its orbital obeisance to the ruler
its course. 1t seemingly backs ava
In keeping with the etiquette TO roya
. ty, turning always its face sunwar
as it retreats whence IL came.
But it pays dearly for its displa,
The matter going to form the tail ca
never be recovered, but is driven ia
Their away. At each successive retur
to the sun some of its mass and bri