Calculating God Read Free Page B

he alternated whole words between his two speaking slits, and sometimes just syllables.
    “How so?”
    “How did you arrive at the dates for the extinctions?” he asked, ignoring my question.
    “We assume that all uranium on Earth formed at the same time the planet did, then we measure the ratios of uranium-238 to its end decay product, lead-206, and of uranium-235 to its end decay product, lead-207. That tells us that our planet is 4.5 billion years old. We then—”
    “Good,” said one mouth. And “good” confirmed the other. “Your dates should be accurate.” He paused. “You have not yet asked me where I am from.”
    I felt like an idiot. He was right, of course; that probably should have been my first question. “Sorry. Where are you from?”
    “From the third planet of the star you call Beta Hydri.”
    I’d taken a couple of astronomy courses while doing my undergraduate geology degree, and I’d studied both Latin and Greek—handy tools for a paleontologist. “Hydri” was the genitive of Hydrus, the small water snake, a faint constellation close to the south celestial pole. And beta, of course, was the second letter of the Greek alphabet, meaning that Beta Hydri would be the second-brightest star in that constellation as seen from Earth. “And how far away is that?” I asked.
    “Twenty-four of your light-years,” said Hollus. “But we did not come here directly. We have been traveling for some time now and visited seven other star systems before we came here. Our total journey so far has been 103 light-years.”
    I nodded, still stunned, and then, realizing that I was doing what I’d done before, I said, “When I move my head up and down like this it means I agree, or go on, or okay.”
    “I know that,” said Hollus. He clicked his two eyes together again. “This gesture means the same thing.” A brief silence. “Although I now have been to nine star systems, including this one and my home one, yours is only the third world on which we have found extant intelligent life. The first, of course, was my own, and the next was the second planet of Delta Pavonis, a star about twenty light-years from here but just 9.3 from my world.”
    Delta Pavonis would be the fourth-brightest star in the constellation of Pavo, the peacock. Like Hydrus, I seemed to recall that it was only visible in the Southern Hemisphere. “Okay,” I said.
    “There have also been five major mass extinctions in the history of my planet,” said Hollus. “Our year is longer than yours, but if you express the dates in Earth years, they occurred at roughly 440 million, 365 million, 225 million, 210 million, and 65 million years ago.”
    I felt my jaw drop.
    “And,” continued Hollus, “Delta Pavonis II has also experienced five mass extinctions. Their year is a little shorter than yours, but if you express the dates of the extinctions in Earth years, they also occurred at approximately 440, 365, 225, 210, and 65 million years ago.”
    My head was swimming. I was hard enough talking to an alien, but an alien who was spouting nonsense was too much to take. “That can’t be right,” I said. “We know that the extinctions here were related to local phenomena. The end-of-the-Permian one was likely caused by a pole-to-pole glaciation, and the end-of-the-Cretaceous one seemed to be related to an impact of an asteroid from this solar system’s own asteroid belt.”
    “We thought there were local explanations for the extinctions on our planet, too, and the Wreeds—our name for the sentient race of Delta Pavonis II—had explanations that seemed unique to their local circumstances, as well. It was a shock to discover that the dates of mass extinctions on our two worlds were the same. One or two of the five being similar could have been a coincidence, but all of them happening at the same time seemed impossible unless, of course, our earlier explanations for their causes were inaccurate or incomplete.”
    “And so you came