Donald Moffitt - Genesis 02

that size. It would have to have some sort of exoskeleton supporting its weight like a scaffolding, or an external shell, like the orthocone creatures on the Father World—and of course, then they couldn’t be very active.”
    Jorv’s boyish face had been working, and now he said, “Don’t take away my big dinosaurs, Ame! I’ve been running a different set of assumptions through the computer, and I can get bipeds up to twenty feet tall and quadrupeds twice that scale.”
    “Bone is bone, and histology is histology,” Ame said tolerantly, “but if you want to postulate more efficient absorptive surfaces than human beings have, and a food intake of a quarter ton a day, and radiators to get rid of body heat, you’re welcome to your big dinosaurs.”
    It was the usual sort of professional banter, but Bram could all but see Smeth’s suspicious mind working to make something more of it. Poor Smeth, he thought. The case was hopeless, but it wasn’t up to him to tell Smeth that!
    “So these … dinosaurs disappeared at the approximate time of the core explosion?” Jun Davd mused. “Hmmm … allowing time for some undefined process to spread to Earth’s latitude in the galaxy at the quite reasonable rate of about one and one-half percent of the speed of light?”
    “Not just the dinosaurs, Jun Davd,” Jorv said. “They disappeared completely—every last one of them—but many other land animals and most marine species disappeared at the same time. If the record that we’ve been given is correct.”
    “And about one hundred fifty-five million years before that mass extinction,” Ame put in, “there was another major extinction in which half of all animal families were wiped out. And one hundred and fifty-five million is almost an exact multiple of twenty-six million.”
    “What’s the significance of twenty-six million?” Jun Davd asked.
    Ame and Jorv fell over themselves to be the one to tell him. Ame won out. “The geological record we got from Original Man—and you must realize it’s only a summary, without the detail we’d like—shows that there seem to be major species die-offs at intervals that work out to an average of about twenty-six million years.”
    Jorv amended: “In two cases, there seems to have been a follow-up extinction of species at an interval somewhere between thirteen and fifteen million years.”
    “That’s what worries me,” Ame said. “There were two cycles of extinction that followed the dinosaur disappearances that don’t appear to have affected the precursors of Homo sapiens, but add another thirteen million years to that and you get a value pretty close to the time when Original Man’s Message was cut off.”
    “Jao,” Jun Davd said, turning around. “What sort of correlation can we get on that major date of one hundred and fifty-five million years prior to the last core explosion?”
    Jao’s fingers flew over his board. “It’s hard to say, Jun Davd. We got one scenario that could have put another core explosion about there. You know, the one where we factored in the expanding molecular ring at the center. But we don’t know enough yet.”
    Jun Davd turned back to Ame. “There’s not enough to go on,” he said. “We have one striking correlation of a core explosion with one of your two major extinctions and one more possible correspondence. But there’s been no more explosion since the dinosaurs disappeared and no periodic phenomenon that subdivides the major events into twenty-six-million-year cycles.”
    “How about this?” Jao said. “Imagine something that sweeps the galaxy like the spokes of a wheel. Imagine eight spokes. Four major spokes, like the arms of a cross. And in between, four minor spokes, also arranged roughly as a cross. As Man’s sun orbits the galactic center, it encounters a spoke approximately every twenty-six million years.”
    “Why eight spokes?” Jun Davd inquired.
    “You have to start somewhere. Eight has a nice symmetry. Besides, it works out in lots of ways. You’ll see in a minute.”
    “What do you mean?” Ame asked, leaning forward.
    “Look,” Jao said. He did something to his console, and the tremendous scene behind the holo wall vanished, to be replaced by the rough scrawls Jao was tracing on his touch pad with one meaty forefinger.
    “Hey, wait a minute!” Smeth protested.
    “The universe won’t go away,” Jao said. “I’ll bring it back in a minute. I want everyone to see this.”
    A bold