Nemesis by Isaac Asimov Page A

though you think it would be a lot worse than you make it sound. What’s so bad about Nemesis giving the Solar System a little extra quiver—if it all settles down again afterward?”
    “Well, will it settle down again in quite the same place? That’s the problem. If Earth’s equilibrium position is a little different—a little farther from the Sun, a little nearer, if its orbit is a little more eccentric or its axis a little more tilted, or less—how will that affect Earth’s climate? Even a small change might make it an uninhabitable world.”
    “Can’t you calculate it out in advance?”
    “No. Rotor isn’t a good place to calculate from. It quivers, too, and a great deal. It would take considerable time and considerable calculation to deduce from my observations here
exactly
what path Nemesis is taking—and we just won’t be sure till it gets considerably closer to the Solar System, long after I am dead.”
    “So you can’t tell exactly just how closely Nemesis will pass the Solar System.”
    “It is almost impossible to calculate. The gravitational field of every nearby star within a dozen light-years has to be taken into account. After all, the tiniest uncalculated effect may build up to such a deviation in over two light-years as to make a passage that is calculated as a near-hit come out, actually, to be a total miss. Or vice versa.”
    “Commissioner Pitt said everyone in the Solar System will be able to leave if they want to by the time Nemesis arrives. Is he right?”
    “He might be. But how can one tell what will happen in five thousand years? What historical twists will takeplace and how that will affect matters? We can
hope
everyone will get off safely.”
    “Even if they’re not warned,” said Marlene, feeling rather diffident at pointing out an astronomical truism to her mother, “they’ll find out for themselves. They’ve got to. Nemesis will come closer and closer and it will be unmistakable after a while and they can calculate its path much more accurately as it comes closer.”
    “But they will have that much less time to make their escape—if one is necessary.”
    Marlene stared at her toes. She said, “Mother, don’t be angry with me. It seems to me as though you’d be unhappy even if everyone got away from the Solar System safely. Something else is wrong. Please tell me.”
    Insigna said, “I don’t like the thought of everyone leaving Earth. Even if it is done in orderly fashion, with plenty of time and with no casualties to speak of, I still don’t like the thought. I don’t want Earth to be abandoned.”
    “Suppose it must be.”
    “Then it will be. I can bow to the inevitable, but I don’t have to like it.”
    “Are you sentimental about Earth? You studied there, didn’t you?”
    “I did my graduate work in astronomy there. I didn’t like Earth, but that doesn’t matter. It’s the place where human beings originated. Do you know what I mean, Marlene? Even if I didn’t think much of it when I was there, it’s still the world where life developed over the eons. To me it’s not only a world but an idea, an abstraction. I want it to exist for the sake of the past. I don’t know if I can make that clear.”
    Marlene said, “Father was an Earthman.”
    Insigna’s lips tightened a bit. “Yes, he was.”
    “And he went back to Earth.”
    “The records say he did. I suppose he did.”
    “I’m half an Earthperson, then. Isn’t that so?”
    Insigna frowned. “We’re all Earthpeople, Marlene. My great-great-grandparents lived on Earth all their lives. My great-grandmother was born on Earth. Everyone, without exception, is descended from Earthpeople. And not just human beings. Every speck of life on every Settlement,from a virus to a tree, is descended from Earth life.”
    Marlene said, “But only human beings know it. And some are closer than others. Do you think about Father, sometimes, even now?” Marlene looked up briefly at her mother’s face and