If we had not this vision, if we had always so much light in the sky that we could not perceive the stars, our lives, so far as we can infer, would be very much as they are now; there would still be the same needs and desires, the same appliances for our safety and satisfaction; this little gaslit world below would scarcely miss the stars now, if they were blotted out for ever. But our science would be different in some respects had we never seen them. We should still have good reason, in Foucault's pendulum experiment, for supposing that the world rotated upon its axis, and that the sun was so far relatively fixed; but we should have no suspicion of the orbital revolution of the world. Instead we should ascribe the seasonal differences to a meridional movement of the sun. Our spectroscopic astronomy--so far as it refers to the composition of the sun and moon--would stand precisely where it does, but the bulk of our mathematical astronomy would not exist. Our calendar would still be in all essential respects as it is now; our year with the solstices and equinoxes as its cardinal points. The texture of our poetry might conceivably be the poorer without its star spangles; our philosophy, for the want of a nebular hypothesis. These would be the main differences. Yet, to those who indulge in speculative dreaming, how much smaller life would be with a sun and a moon and a blue beyond for the only visible, the only thinkable universe. And it is, we repeat, from the scientific standpoint a mere accident that the present--the daylight--world periodically opens, as it were, and gives us this inspiring glimpse of the remoteness of space.
One may imagine countless meteors and comets streaming through the solar system, unobserved by those who dwelt under such conditions as have just been suggested, or some huge dark body from the outer depths sweeping straight at that little visible universe, and all unsuspected by the inhabitants. One may imagine the scientific people of such a world, calm in their assurance of the permanence of things, incapable almost of conceiving any disturbing cause. One may imagine how an imaginative writer who doubted that permanence would be pooh-poohed. "Cannot we see to the uttermost limits of space?" they might argue, "and is it not altogether blue and void?" Then, as the unseen visitor draws near, begin the most extraordinary perturbations. The two known heavenly bodies suddenly fail from their accustomed routine. The moon, hitherto invariably full, changes towards its last quarter--and then, behold! for the first time the rays of the greater stars visibly pierce the blue canopy of the sky. How suddenly--painfully almost--the minds of thinking men would be enlarged when this rash of the stars appeared.