Tyndall, in his famous reply to the critics of his Belfast address, in speaking of the origin of life, referred to the Nebular Theory as follows: "According to it our sun and planets were once diffused through space as an impalpable haze out of which by condensation came the solar system. What caused it to condense? Loss of heat. What rounded the sun and planets? That which rounds a tear, molecular force." In these terse and graphic expressions we are made to understand the universality of law. So far as we have sounded the depths of the stellar universe we see the same obedience to gravitational laws, the same flashing lines in the spectrum. We encounter no phenomena that cannot be explained, or at least inferred, by the knowledge we have obtained from our little mote of the Cosmos.
Mr. See thinks it remarkable that "previous investigators have almost invariably approached the problem of cosmogony from the point of view of the planets and satellites, and that no considerable attempt has been made to inquire into the development of the great number of systems observed among the fixed stars." It is true our planetary system has been used as a standard of measurement for the universe, and a very comprehensive standard it has proved to be. The law of universal gravitation was based on terrestrial and lunar observations, spectroscopic analysis was determined in a terrestrial laboratory. As George Iles says, a coal of fire may be raked from a grate and broken up to illustrate the rapid cooling of smaller masses. Even a child's spinning top may be used in an astronomical lecture. The study of our Sun led to the study of the fixed stars, and so our little system has thus far furnished us with examples and illustrations by which we interpret the universe.
In our solar system we have a fair sample of the Cosmos in miniature, though our Sun is so modest in size, compared with the great orbs that appeal to us by their number and brilliancy. So far as our telescopes have sounded the heavens we find nebulous clouds in their structure showing inchoate masses, orbital and spiral arrangements, condensations in their centres. We have the binaries with their extraordinary properties, we have variables with their dark bodies revolving around their primaries. In our little system we also have dark bodies revolving around a luminous primary, from one of which we endeavor to interpret the mysteries of the universe; we have loose masses, as in comets with enormously elongated orbits; we have spheres of insignificant size, with small bodies revolving around them, and these epitomes revolving around a central sun; we have one of these bodies with meteoric rings; and, in the case of our own globe, a satellite of such size that except in the form of its orbit it might well represent a binary in embryo;—and, finally, a host of bodies big enough to reflect the rays of the sun, pursuing their various orbital paths. We are told that the stars are as distant from each other as we are from them. We may regard these systems of nebulæ, variables, doubles, etc., as different kinds or species of heavenly bodies; and to assert that our system is the only individual of the species in the universe seems contrary to all celestial analogy, for do we not have hundreds of binaries, thousands of variables, millions of suns, revealing the same fiery energy and consuming the same elemental fuel?
Professor Newcomb in his "Reminiscences" describes his first sweeping the heavens, at random, with the then new twenty-six inch refractor at the Naval Observatory and discovering a little cluster of stars so small and faint that the individual stars eluded even the great power of this instrument. He says: "I could not help the vain longing which one must sometimes feel under such circumstances, to know what beings might live on planets belonging to what, from an earthly point of view, seemed to be on the border of creation itself." One would suppose that this expression of a longing to ascertain the character of the beings inhabiting planets circling these distant suns would induce one to study a planet analogous to our Earth, and so near in comparison to these unimaginable distances as to be within a hand's grasp, so to speak. The little interest Professor Newcomb has taken in the subject is well expressed in his late book "Astronomy for Everybody." In his chapter on Mars, in which Everybody is certainly interested, he says: "The reader will excuse me for saying anything in this chapter about the possible inhabitants of Mars. He knows just as much of the subject as I do, and that is nothing at all." He might at least have given the various pronouncements of Schiaparelli, Lowell, and others as to the probable character of these remarkable markings on Mars, and their supposed significance.
While Professor Newcomb's attitude on the question of the plurality of worlds has been somewhat conservative in the past he has lately, however, expressed himself on the question in no uncertain terms. In a recent article in "Harper's Magazine," entitled "Probability of Life in Other Worlds," he has lent his sanction to the rational idea that other worlds may be the abode of intelligent creatures. His recognition of the principle will do much to offset the influence if it ever had any, of a recent book published in England by Alfred Russel Wallace, in which the distinguished author attempts to show that this world stands alone as the abode of intelligent life. Despite his epoch-making work with Darwin, nearly fifty years ago, which must forever merit our gratitude, and the charm of his various essays on protective coloring, mimicry, theory of birds' nests, etc., he has since those lucid days expressed convictions of such a nature that if a future DeMorgan should write on human paradoxes he would classify Mr. Wallace as chief among them. A profound believer in evolution, he exempts man from the inexorable logic of the principle with about as much reason as if, confessing his belief in the nebular hypothesis, he should insist that the Earth was an exception.
But to return to Professor Newcomb's recent utterances. In the above-mentioned article he says: "Not only does life, but intelligence, flourish on this globe under great variety of conditions as regards temperature and surroundings, and no sound reason can be shown why, under certain conditions which are frequent in the universe, intelligent beings should not acquire the highest development." Again he says: "Life, not wholly unlike that on the Earth, may therefore exist upon Mars, for anything we know to the contrary. More than this we cannot say." In his final summing up Professor Newcomb says: "It is therefore perfectly reasonable to suppose that beings not only animated but endowed with reason inhabit countless worlds in space."
It would seem as if a mind capable of entertaining an idea of our uniqueness in the universe betrays the survival of a mental condition which, centuries ago, regarded the stars as bits of luminous material expressly designed to illuminate this little earth, around which they all pursued their daily paths.