Evening star. [volume] (Washington, D.C.) 1854-1972, 1883-09-29

than three OF them since 1910.
1t is hardly necessary to say that If any reti-
blaze cannot fail to carry disaster and destruc-
ton to all life upon them. We can conceive that
! forms of life may be possible under almost any
| imaginable physical conditions, provided only
the course Of events by which they have been
| reached has been gradual enough to allow the
necessary adaptations. One would not dare to
deny the possibility Of life Of some kind on the
| airless moon, or even on the sun ITSELF But all
| we know makes it certain that no planetary lite
could survive the tremendous and catastrophe
change Of conditions involved in sudden thou
sand-fOld Increase OF the solar radiation.
STELLAR MAssEs-sHOOTING sTARs-THOUsANDs
OF MILLIONS OF THEM.
Thus far we have been considering only COLI
sions of stellar masses. But space is filled also
with minor particles, separated from each other
only by intervals of few hundred miles; and
| these, in the form of meteors and shooting stars
are rushing through space, dropping continu-
ally upon the larger worlds, increasing their
size and adding to their store of heat and en-
ergy. Every year the earth 4encounters nearly
three thousand millions Of them, according to
the estimate of Prof. Newton, ranging from the
merest particles to masses Of several hundred
weight. Very probably, also, the comets belong
to the same category, being really nothing but
perhaps even only puffs of meteoric dust. Nearly
| all the meteOrs which strike the earth are very
minute. Perhaps hundred or so reach the
ground each year as recognizable masses of
to some hundreds Of pounds, but all the
rest are disspated in the upper air, and
| never come down unless as impalpable
dust, not to be certainly identified.
The whole amount of matter falling daily upon
the earth from outer space is probably about 100
tons on the average ct is variously estimated
| from Is to 500. "A hundred tons is in itself a
very considerable quantity, but utterly insignif-
! cant as compared with the mass of the earth,
and entirely incapable ofappreciable effect upon
our temperature Assuming even the largest
estimate (5OO tons day), and also that the
| average velocity with which meteors enter our
| atmosphere is 10 miles second (probably con-
nually received from them by the earth is only
about So calories for each square meter of her
| surface-less than would be impaired by two
minutes perpendicular sunshine, and only about
| 100 600 of the heat actually received from the
sun in year. Retaining the same extravagant
estimate OF 500 tons day, it appears that the
earths diameter would grow an inch in about
100, 600 of years, and that her distance from
| the sun would be reduced abo ut 50 feet in
million years. In consequence OF the resistance
| experienced in moving through the meteoric
swarms.
It would not, however, be just to the general
reader to dismiss the subject without fair no.
views at variance with those above expressed
| The late Prof Pierce maintained to the end
that the heat Of the sun is chiefly due to the i'm
pact Of meteOrs, and also that the earth itself
sun, necessary result If the solar heat is really
so produced. OF course we have no space to
discuss the matter here, and must be content
| with merely saying that the quantity of matter
which falls upon the earth, If his idea is correct,
ought to be easily noticeable, amounting to
about fifty tons day on each square mile It
involves also serious dificultiesin the planetary
theory.
So far as human beings are concerned, the
| most important question connected with our
subject is whether anything is to be feared
from comets. as consequence either of COL
| lisions with the earth or of their fall into the
sun. 1t may be said, just as of the stars be-
fore. first, that cometary collisions, either with
sun or earth. must be very rare occurrences.
and, secondly. that they are practically certain
| to happen some time or other. Babinet COM
puted, on the one hand, that a comet would
strike the earth on the average about once in
10000 GOO years; on the other, we know at least
| three comets whose orbits cut the eartf's path
so closely that If they should ever reach the
crossing at the same time as the earth col
lision must occur. These comets are known
as Bela's, Temples, followed by the LeOnid
meteOrs in it's train, and the comet Of 1862.
which precedes the Perseids. One of the three,
however (Biela's), has probably ceased to exist
as comet, and it is quite possible that the
other two may vanish In the same way before
we meet them.
AS to cometarv encounters with the sun, no
comet has yet been known actually to strike
the sun, but several have grazed very near it. !
The great comet of last year brushed through
the corona, and came within SOC, 600 miles of
the photosphere and there is no assignable
reason why some other comet should not
actually pierce it.
CONSEQUENCES OF COMET HITTING THE EARTH !
As to the consequences of comets collision
with the earth, it is impossible to predict them
with scientific certainty; probably, however,
they would be Insignificant. We know abso- |
lutely that the whole quantity Of matter in .
small compared with that Of the earth; but just |
how small no one can say. 1t Is impossible to |
contradict authoritatively either the man who |
says he could carry comet home In his pocket |
comets nucleus is equivalent to an iron BAH |
one hundred miles in diameter. An attempt has |
been made to get at the density of the central |
nucleus on the assumption that it holds to itself
the enormous volume of the head and envelopes |
by It's gravitatiOnal attraction, as ii the sur |
rounding nebulOsity were an atmosphere in |
equilibrium around the nucleus but the as
sumption Is more than doubtful, and the derived |
conclusion, Of course, is of little value. It |
seems, on the whole, more probable that q |
comet is throughout only cloud Of dust and |
vapOr-a mere smoke wreath-than that there |
Is at the center any solid kernel Of preponder-
ant mass.
II comet really has at the center any great
mass Of stone or iron, or even q close-p packed |
swarm Of aerOltes weighing q ton or two |
apiece, collision with it would Of course be q
most serious matter, spreading devastation and
confagration possibly over half the globe at
once; not amounting, probably, to anything like
q destruction Of the world, but far more disas-
trous than any earthquake or volcanic eruption.
It is far more likely, however, that the encoun-
ter with comet would be entirely harmless
simply most magnificent and brilliant shower
OF shooting stars lasting for an hour or two-al
phenomenon which one might well desire to see
As for the effect Of q collision between q
comet and the sun. in respect to which there
has been much disquieting speculation Of late.
the probability IL that we on the earth should
never know It, unless We happened to be ex-
pressly watching the event. For few min
ufes inst tha nuClena Was niorcinn fha ,,ho.