Washington standard. [volume] (Olympia, Wash. Territory) 1860-1921, 1882-09-15
That Threatening Comet.

The threatened destruction Of the earth,
by comet falling into the sun, some
fifteen years hence, was referred to edi
torially by the Tribune last Sunday. 1t
was then stated that the matter would
be referred to the Trtbusc astronomer.
The promise was made in y jocular way;
but so many readers have since expressed
desire to ''hear from him" On the SUBJ
ject that he has undertaken response
There is certainly some reason t. think.
or fear, that the comet referred to will
really fall into the sun. Tnc mere fact
that the comets of 1868. 1919 and 1880
were all travelling in nearly the same
path does not prove their identity. But
the fact that they (or it) nearly grazed
the surface of the sun at the nearest APP
proach does furnish good reason TO think
that the motion in the curve was thereby
retarded; and the necessary eonse-
quence of such retardation must be final
destruction of the orbit. The comet of
lS43 passed within about 80,Q00 miles u
what appears to us to be the SUMS nor
NAL surface. The observation of the solar
eclipse of 1869 satisfied the writer that
the sun hes an atmosphere which extends
at least 800, 900 miles above the apparent
surface. That is, it extends out ten times
as far as the least distance of the comet.
The solar atmosphercmust be exceeding
~ rare in that vicinity, but SO is the
earth's atmosphere at the height of 100
miles; and yet we know that the latter
retards the flight of meteors so much as
to warm them up to the luminous point
the motion being converted into heat.
tits easily shown that the passage through
q resisting medium destroys much more
of the tangential motion than it does of
that which results from the action of the
centripetal force. Hence the orbit bends
inward more rapidly than before. This
means that the comet returns sooner to
the aphelion point. shortening the major
axis of the orbit and the period of revolu-
ton. If the comet pass through the re-
sisting medium at each perihclion return,
the orbit is soon broken up by the fall of
the comet into the sun.
1t is easy to calculate, approximately,
the quantity of heat developed by such a
catastrophe. If take the suns radius
as the unit of measure. then the square
of the velocity on reaching his surface.
plus unity divided by the major axis of
the orbit, is a constant quantity-the
same for every member of the solar sys-
tenn, except small variation due to the
quantity of matter in the falling mass.
With this we may calculate that para
bolic orbit would give greatest velocity
OF 1924 miles per second; and if the axis
OF the orbit were shortened to equal that
of the earth's orbit the greatest velocity
would be about 1872 miles If, therefore,
the orbit of the comet should be short
ened down by two or three more peri
helion passages before the final collapse
we should still have u maximum velocity
of about $50 miles. This would be con-
verified into heat. Dividing this velocity
by 223 feet, and squaring the result, we
obtain. in round numbers, $4,000, 900
degrees of the Fahrenheit scale as the
rise of temperature of the falling mass.
A large part of this would be distributed
by conduction among the material COM
posing the sun.
The next important point is to know
the quantity of matter in the comet; and
,l;at we do not know. But we have sew
al iiIulltCt IcdSOuS IoT DellcNlnr tnlt
at no time has it been more than about
one part in 5000 of the earth's mass.
And it is probably now much less than
even that relatively small quantity. The
passage through the suns atmosphere
shears OFF the gaseous matter of the
comet and its attendant train of meteors,
both of which are left behind by the more
solid nucleus, as the latter rushes away
in its diminished orbit. Hence, though
the shortening of the period does not de-
tract very much from the perthelic We
locity, it does materially lessen the guam
tity of matter that is left to be heated up
by the last grand rush down into the
bowels of the sun.
Now. if we allow the very greatest
possible value for the mass of the comet
just before it loses its individuality, we
shall find the heat generated by the i'm
pact to be just about equal to that thrown
of by tho sun during one week. Allow
ing what seems to the writer 10 be the
ma1imum probable value, the resulting