For, after all, our Earth too is a heavenly body, in spite of man’s doing his best to make it the reverse. It has some right to astronomic regard, even if it is our own mother. At the same time it is quite puerile to consider the universe as bounded by our terrestrial backyard. If man took himself a thought less importantly, he might perceive the humor of so circumscribed a view. Like children we play at being alone in the universe, and then go them one better by believing it too.
I shall, of course, not touch on any matters purely geologic, for fear of committing the very excesses I deplore; mentioning only such points as astronomy has information on, and which, by the sidelights it throws, may help to illuminate the subject.
Thus it certainly is interesting and may to many be a new point of view, that the changes introduced when paleologic times passed into neologic ones were in their fundamental aspects essentially astronomic; which shows how truly astronomic causes are woven into the whole fabric of the Earth. For it was then only, terrestrially speaking, that the year began. The orbital period had existed, of course, from the time the Earth first made the circuit of the Sun. But the year was more a succès d’estime on the Sun’s part than one of popular appreciation. As the Sun could not be seen and worked no striking effects upon the Earth, the annual round had no recognizable parts, and one revolution lapsed into the next without demarcation. Only with the clearing of the sky did the seasons come in: to register time by stamping its record on the trees. Before that, summer and winter, spring and autumn, were unknown.
Climate, too, made then its first appearance; climate, named after the sunward obliquity of the Earth, and seeming at times to live down to that characterization. Weather there had been before; pejoratively speaking, nothing but weather. For the downpours in paleologic times must have been exceeded in numbers only by their force. One dull perpetual round of rain was the programme for the day, with absolutely no hope of a happy clearance to-morrow. It was the golden age only for weather prophets whose prognostications could hardly go wrong. With climate, however, it was a very different matter. With polyp corals building reefs almost to the pole (81° 50′),[22] as far north nearly as man has yet by his utmost efforts succeeded in getting, while their fellows were busy at the like industry in the tropics, it is clear that latitude was laughed at and climate even lacked a name.
Another astronomic feature, then for the first time disclosed, was the full significance of the day and the revelation of its cause. While the Earth brooded under perpetual cloud, there could have been but imperfect recognition of day and night. Or perhaps we may put it better by saying that the standard of both was greatly depressed, dull days alternating with nights black as pitch. But the moment the Sun was let in, all this changed, though not in a twinkling. The change came on most gradually. We can see in our mind’s eye the first openings in the great welkin permitting the Earth its initial peeps of the world beyond, and how quickly and tantalously they shut in again like a mid-storm morning which dreams of clearing only to find how drowsy it still is. But eventually the clouds parted afresh and farther, and the Earth began to open its eyes to the universe without.
The cause of the clearing, of course, was the falling temperature of the seas. Evaporation went on much less fast as the heat of the water lessened. The whole round of aquatic travel from ocean to air, and back to ocean again, proceeded at an ever slackening pace. And here, if it so please geologists, may be found a reconciling of their demands for time to the relative pittance astronomy has been willing to dole them out, a paltry 50 or 100 millions of years, which like all framers of budgets they have declared utterly insufficient. For in early times the forces at work were greater, and by magnifying the means you quicken the process and contract the Earth’s earlier eras to reasonable limits.
Upon these various astronomic novelties, the Earth on thus awakening looked for the first time. Such regard altered for good its own internal relations. The wider outlook made impossible the life of the narrower that preceded it. A totally changed set of animals and plants arose, to whom the cosmos bore a different aspect. The Earth ceased to be the self-centred spot it seemed before. As long ago as this had the idea that our globe was the centre of the universe been cosmically exploded. The Earth knew it if man did not.
Tracks of Sauropus primævus (× ½). I. Lea.—Dana,
“Manual of Geology.”