From Waiting for the Morning Train - An American Boyhood by Bruce Catton (about Halley's Comet)

This comet appears once every seventy-six years, swinging in from outer space, blazing briefly across our familiar sky, and then going off again on its mysterious round; once a thing to frighten gods and men, reduced now to the ticking of some inscrutable celestial timepiece, and perhaps none the less frightening for all that. It showed up on schedule in 1910, and one clear evening most of the town gathered on a knoll in the campus to have a look at it. I was out there along with everybody else, and I must say that I was disappointed. I had heard so much about this comet, and I expected something spectacular; all I could see - and I saw that only after much effort, asking annoying questions the while - was a dull thing like a smudged star, motionless, its fabulous tail something to be taken on faith. It hardly seemed worth looking at.

Still, I was impressed by the way people talked about it. Seventy-five years must pass before it would reappear. The grown-ups, of course, knew they would never see it again, but we youngsters were told that we might be around for the next visit, and we were invited to reflect on the wonders and marvels that would take place in the world before that day came.

Wonders and marvels there assuredly have been, and the day has not yet come. The point is that the last time we saw the comet we looked ahead with confidence. God was in His Heaven, and man at least was in his right mind. We could dream any dreams we liked and they were bound to be good ones. The one thing we could not possibly foresee was that the next time the comet came around we might be so appalled by the things that had happened since the last visit that we would be afraid to look ahead to the next one. We have learned much about the comet's homeland in outer space, and about the depths and forces that lurk there, and we have also learned a few things about the dark spaces and unspeakable powers in man himself, and none of this knowledge has been reassuring. The clock goes tick... tock, measured, inexorable, and it frightens the children. What if they lay hands on the pendulum and stop it? It is just possible that some day they may do it.