Myths and Marvels of Astronomy
and meteors are closely connected, every comet being probably (many
certainly) attended by flights of meteoric masses. The meteors which
produce the celebrated November showers of falling stars follow in the
track of a comet invisible to the naked eye. May we not reasonably
suppose, then, that those glorious comets which have not only been
visible but conspicuous, shining even in the day-time, and brandishing
round tails which, like that of the 'wonder in heaven, the great
dragon,' seemed to 'draw the third part of the stars of heaven,' are
followed by much denser flights of much more massive meteors? Now some
among these giant comets have paths which carry them very close to our
sun. Newton's comet, with its tail a hundred millions of miles in
length, all but grazed the sun's globe. The comet of 1843, whose tail,
says Sir J. Herschel, 'stretched half-way across the sky,' must actually
have grazed the sun, though but lightly, for its nucleus was within
80,000 miles of his surface, and its head was more than 160,000 miles in
diameter. And these are only two among the few comets whose paths are
known. At any time we might be visited by a comet mightier than either,
travelling on an orbit intersecting the sun's surface, followed by
flights of meteoric masses enormous in size and many in number, which,
falling on the sun's globe with the enormous velocity corresponding to
their vast orbital range and their near approach to the sun--a velocity
of some 360 miles per second--would, beyond all doubt, excite his whole
frame, and especially his surface regions, to a degree of heat far
exceeding what he now emits.
We have had evidence of the tremendous heat to which the sun's surface
would be excited by the downfall of a shower of large meteoric masses.
Carrington and Hodgson, on September 1, 1859, observed (independently)
the passage of two intensely bright bodies across a small part of the
sun's surface--the bodies first increasing in brightness, then
diminishing, then fading away. It is generally believed that these were
meteoric masses raised to fierce heat by frictional resistance. Now so
much brighter did they appear, or rather did that part of the sun's
surface appear through which they had rushed, that Carrington supposed
the dark glass screen used to protect the eye had broken, and Hodgson
described the brightness of this part of the sun as such that the part
shone like a brilliant star on the background of the glowing solar
surface. Mark, also, the consequences of the downfall of those two
bodies only. A magnetic disturbance affected the whole frame of the
earth at the very time when the sun had been thus disturbed. Vivid
auroras were seen not only in both hemispheres, but in latitudes where
auroras are very seldom witnessed. 'By degrees,' says Sir J. Herschel,
'accounts began to pour in of great auroras seen not only in these
latitudes, but at Rome, in the West Indies, in the tropics within
eighteen degrees of the equator (where they hardly ever appear); nay,
what is still more striking, in South America and in Australia--where,
at Melbourne, on the night of September 2, the greatest aurora ever seen
there made its appearance. These auroras were accompanied with unusually
great electro-magnetic disturbances in every part of the world. In many
places the telegraph wires struck work. They had too many private
messages of their own to convey. At Washington and Philadelphia, in
America, the electric signal-men received severe electric shocks. At a
station in Norway the telegraphic apparatus was set fire to; and at
Boston, in North America, a flame of fire followed the pen of Bain's
electric telegraph, which writes down the message upon chemically
prepared paper.' Seeing that where the two meteors fell the sun's
surface glowed thus intensely, and that the effect of this accession of
energy upon our earth was thus well marked, can it be doubted that a
comet, bearing in its train a flight of many millions of meteoric
masses, and falling directly upon the sun, would produce an accession of
light and heat whose consequences would be disastrous? When the earth
has passed through the richer portions (not the actual nuclei, be it
remembered) of meteor systems, the meteors visible from even a single
station have been counted by tens of thousands, and it has been computed
that millions must have fallen upon the whole earth. These were meteors
following in the train of very small comets. If a very large comet
followed by no denser a flight of meteors, but each meteoric mass much
larger, fell directly upon the sun, it would not be the outskirts but
the nucleus of the meteoric train which would impinge upon him. They
would number thousands of millions. The velocity of downfall of each
mass would be more than 360 miles per second. And they would continue to
pour in upon him for several days in succession, millions falling every
hour. It seems not improbable that, under this tremendous and
long-continued meteoric hail, his whole surface would be caused to glow
as intensely as that small part whose brilliancy was so surprising in
the observation made by Carrington and Hodgson. In that case, our sun,
seen from some remote star whence ordinarily he is invisible, would
shine out as a new sun, for a few days, while all things living on our
earth, and whatever other members of the solar system are the abode of
life, would inevitably be destroyed.
The reader must not suppose that this idea has been suggested merely in
the attempt to explain outbursts of stars. The following passage from a
paper of considerable scientific interest by Professor Kirkwood, of
Bloomington, Indiana, a well-known American astronomer, shows that the
idea had occurred to him for a very different reason. He speaks here of
a probable connection between the comet of 1843 and the great sun-spot
which appeared in June 1843. I am not sure, however, but that we may
regard the very meteors which seem to have fallen on the sun on
September 1, 1859, as bodies travelling in the track of the comet of
1843--just as the November meteors seen in 1867-8, 9, etc., until 1872,
were bodies certainly following in the track of the telescopic comet of
1866. 'The opinion has been expressed by more than one astronomer,' he
says, speaking of Carrington's observation, 'that this phenomenon was
produced by the fall of meteoric matter upon the sun's surface. Now, the
fact may be worthy of note that the comet of 1843 actually grazed the
sun's atmosphere about three months before the appearance of the great
sun-spot of the same year. Had it approached but little nearer, the
resistance of the atmosphere would probably have brought its entire mass
to the solar surface. Even at its actual distance it must have produced
considerable atmospheric disturbance. But the recent discovery that a
number of comets are associated with meteoric matter, travelling in
nearly the same orbits, suggests the inquiry whether an enormous
meteorite following in the comet's train, and having a somewhat less
perihelion distance, may not have been precipitated upon the sun, thus
producing the great disturbance observed so shortly after the comet's
perihelion passage.'
There are those, myself among the number, who consider the periodicity
of the solar spots, that tide of spots which flows to its maximum and
then ebbs to its minimum in a little more than eleven years, as only
explicable on the theory that a small comet having this period, and
followed by a meteor train, has a path intersecting the sun's surface.
In an article entitled 'The Sun a Bubble,' which appeared in the
'Cornhill Magazine' for October 1874, I remarked that from the observed
phenomena of sun-spots we might be led to suspect the existence of some
as yet undetected comet with a train of exceptionally large meteoric
masses, travelling in a period of about eleven years round the sun, and
having its place of nearest approach to that orb so close to the solar
surface that, when the main flight is passing, the stragglers fall upon
the sun's surface. In this case, we could readily understand that, as
this small comet unquestionably causes our sun to be variable to some
slight degree in brilliancy, in a period of about eleven years, so some
much larger comet circling around Mira, in a period of about 331 days,
may occasion those alternations of brightness which have been described
above. It may be noticed in passing, that it is by no means certain that
the time when the sun is most spotted is the time when he gives out
least light. Though at such times his surface is dark where the spots
are, yet elsewhere it is probably brighter than usual; at any rate, all
the evidence we have tends to show that when the sun is most spotted,
his energies are most active. It is then that the coloured flames leap
to their greatest height and show their greatest brilliancy, then also
that they show the most rapid and remarkable changes of shape.
Supposing there really is, I will not say danger, but a possibility,
that our sun may one day, through the arrival of some very large comet
travelling directly towards him, share the fate of the suns whose
outbursts I have described above, we might be destroyed unawares, or we
might be aware for several weeks of the approach of the destroying
comet. Suppose, for example, the comet, which might arrive from any part
of the heavens, came from out that part of the star-depths which is
occupied by the constellation Taurus--then, if the arrival were so timed
that the comet, which might reach the sun at any time, fell upon him in
May or June, we should know nothing of that comet's approach: for it
would approach in that part of the heavens which was occupied by the
sun, and his splendour would hide as with a veil the destroying enemy.
On the other hand, if the comet, arriving from the same region of the
heavens, so approached as to fall upon the sun in November or December,
we should see it for several weeks. For it would then approach from the
part of the heavens high above the southern horizon at midnight.
Astronomers would be able in a few days after it was discovered to
determine its path and predict its downfall upon the sun, precisely as
Newton calculated the path of _his_ comet and predicted its near
approach to the sun. It would be known for weeks then that the event
which Newton contemplated as likely to cause a tremendous outburst of
solar heat, competent to destroy all life upon the surface of our earth,
was about to take place; and, doubtless, the minds of many students of
science would be exercised during that interval in determining whether
Newton was right or wrong. For my own part, I have very little doubt
that, though the change in the sun's condition in consequence of the
direct downfall upon his surface of a very large comet would be but
temporary, and in that sense slight--for what are a few weeks in the
history of an orb which has already existed during thousands of millions
of years?--yet the effect upon the inhabitants of the earth would be by
no means slight. I do not think, however, that any students of science
would remain, after the catastrophe, to estimate or to record its
effects.
Fortunately, all that we have learned hitherto from the stars favours
the belief that, while a catastrophe of this sort may be possible, it is
exceedingly unlikely. We may estimate the probabilities precisely in the
same way that an insurance company estimates the chance of a railway
accident. Such a company considers the number of accidents which occur
among a given number of railway journeys, and from the smallness of the
number of accidents compared with the largeness of the number of
journeys estimates the safety of railway travelling. Our sun is one