It seems A J Richardson was an armchair scientist in his spare time. Or possibly an amateur astronomer. In any case, he sent a letter to the Rockhampton Morning Bulletin in 1896, in which he attempted to allay people’s fears of the imminent catastrophe of a comet striking the earth. Apparently the end of the world was nigh, even that long ago.
It may be that Archibald began thinking about comets after witnessing one during his voyage to Australia in 1861.
I’m not sure how well Archie’s theory about the head of a comet acting as a giant lens and creating the optical illusion of a tail (as opposed to possessing a real tail) would play with modern astronomers, but he had clearly done some research and some hard thinking on the subject.
(Archibald refers to a book by Ignatius Donnelly, a US congressman and doom-merchant, called Ragnarok: The Age of Fire and Gravel, which was published in 1883. See this page for more details.)
Here’s his letter:
Morning Bulletin, Rockhampton, Tuesday 3 March 1896
COMETS
TO THE EDITOR.
Sir,—Several letters were published in your columns a little while ago directing public attention to the prediction of a French scientist that a comet was about to strike the earth. Proctor, in his book Our Place among Infinities, arrives at the conclusion that meteors or shooting stars are fragments of comets, and says the earth passes each year through more than a hundred meteor systems, and yet suffers no injury; and that it appears evident the comet, and not our earth would suffer from a collision. Professor Young says “as regards the possibility of a collision with a comet, it is to be admitted that such an event is possible.
In fact if the earth lasts long enough, it is practically sure to happen. Such encounters will, however, be very rare. If we accept the estimate of Batinet, they will occur about once in every fifteen million years in the long run. The essential part of a comet is the coma or nebulosity, usually nearly spherical or oval in shape; next the nucleus, which may be single, double, or even multiple; and lastly the tail or train, which is a streamer of light. As the comet, he says, approaches the sun the tail follows it much as the smoke from a locomotive engine trails after it. But that the tail does not really consist of matter simply left behind in that way, is obvious from the fact that as the comet recedes from the sun, the tail precedes it instead of following.
Of the dimensions, as a general rule the head or coma of a telescopic comet is from 40,000 to 100,000 miles in diameter. The comet of 1680 had a head 600,000 miles across. The head of the comet of 1811 measured nearly 1,200,000 miles. That of Donali’s comet of 1858 was 250,000 miles in diameter. The head of the comet of 1882 (which many people here would remember) had a diameter of only 150,000 miles, but its tail was at one time one hundred million miles in length.
Regarding the nature of comets, he further says, “The density is probably much less than that of the best air pump vacuum, an estimate which is borne out by the fact that small stars can be seen through the head of a comet 100,000 miles in diameter. The spectrum of a comet is more or less faint and continuous, may be due to reflected sunlight, and almost beyond question indicates the presence of some gaseous hydrocarbon.” The author of Ragnarok seems to suppose that a comet and its tail are composed of vast quantities of gravel!
It occurred to me some years ago that the head of a comet, which, according to scientific authorities, is composed of a vast mass of gas, may possibly form one or more gigantic lenses, and that the tail consequently has no material existence, but is merely formed of concentrated sunbeams. Astronomers are satisfied that there are myriads of small bodies in interplanetary space, quite invisible to telescopic vision, circling round the sun, and it is probable these would be found in greater numbers towards that luminary, than towards the limits of the solar system.
A small lens or pocket microscope half an inch in diameter will concentrate the rays of the sun, and set fire to paper in a minute. Imagine then the power of a lens, infinitely more transparent than the clearest crystal, half a million miles in diameter. Would not such a lens enormously intensify the sun’s rays, instantly vaporise the multitudes of small bodies falling within its scope? The vapours or gases so formed would instantaneously condense when the sunbeam passed on. Many of the peculiarities of comets may be explained on this hypothesis, as, for instance, the spectrum, the direction of the tail, variations in brightness, and the extraordinary velocity of the tail at Perihelion.
Several comets at Perihelion travelled at the rate of 300 miles per second, the velocity of the extremity of the comet’s tail being then 40,000 miles per second. It is easy to understand that a beam of light could travel at this speed, but it is beyond credence that any material substance could attain such a great velocity. Assuming that these views are correct what consequences would ensue from a collision of earth and comet? The earth’s passage through the head of the comet would be performed in say forty minutes, during which time, if it happened in the night, we should perhaps see one shooting star more than usual. If the head really is gaseous the gas would be so highly attenuated that it could not affect us in the slightest. The results following our passage through the intense beam of light forming the tail would depend on our position with regard to the focus of the lens and had better be left to conjecture.
I may fairly ask you to publish this letter on the ground that it treats of a subject of great interest to many, and, although of a superficial nature, furnishes food for thought.
I am, &c.,
A. J. RICHARDSON
Rockhampton, 29th February, 1896