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.

And what then if our heavens were to open?  Very thin indeed is the curtain between us and the unknown.  There is a fear of the night that is begotten of ignorance and superstition, a nightmare fear, the fear of the impossible; and there is another fear of the night—­of the starlit night—­that comes with knowledge, when we see in its true proportion this little life of ours with all its phantasmal environment of cities and stores and arsenals, and the habits, prejudices, and promises of men.  Down there in the gaslit street such things are real and solid enough, the only real things, perhaps; but not up here, not under the midnight sky.  Here for a space, standing silently upon the dim, grey tower of the old observatory, we may clear our minds of instincts and illusions, and look out upon the real.