Palimpsest Read Online Free PDF

One
    What has already happened:
    SLIDE 1.
    Our solar system, as an embryo. A vast disk of gas and infalling dust surrounds and obscures a newborn star, little more than a thickening knot of rapidly spinning matter that is rapidly sucking more mass down into its ever-steepening gravity well. The sun is glowing red-hot already with the heat liberated by its gravitational collapse, until …
    SLIDE 2.
    Ignition! The pressure and temperature at the core of the embryo star has risen so high that hydrogen nuclei floating in a degenerate soup of electrons are bumping close to one another. A complex reaction ensues, rapidly liberating gamma radiation and neutrinos, and the core begins to heat up. First deuterium, then the ordinary hydrogen nuclei begin to fuse. A flare of nuclear fire lashes through the inner layers of the star. It will take a million years for the gamma-ray pulse to work its way out through the choking, blanketing layers of degenerate hydrogen, but the neutrino pulse heralds the birth cry of a new star.
    SLIDE 3.
    A million years pass as the sun brightens, and the rotating cloud of gas and dust begins to partition. Out beyond the dew line, where ice particles can grow, a roiling knot of dirty ice is forming, and like the sun before it, it greedily sucks down dirt and gas and grows. As it plows through the cloud, it sprays dust outward. Meanwhile, at the balancing point between the star and the embryonic Jovian gravity well, other knots of dust are forming …
    SLIDE 4.
    A billion years have passed since the sun ignited, and the stellar nursery of gas and dust has been swept clean by a fleet of new-formed planets. There has been some bickering—in the late heavy bombardment triggered by the outward migration of Neptune, entire planetary surfaces were re-formed—but now the system has settled into long-term stability. The desert planet Mars is going through the first of its warm, wet interludes; Venus still has traces of water in its hot (but not yet red-hot) atmosphere. Earth is a chilly nitrogen-and-methane-shrouded enigma inhabited only by primitive purple bacteria, its vast oceans churned by hundred-meter tides dragged up every seven-hour day by a young moon that completes each orbit in little more than twenty-four hours.
    SLIDE 5.
    Another three billion years have passed. The solar system has completed almost sixteen orbits of the galactic core, and is now unimaginably distant from the stellar nursery which birthed it. Mars has dried, although occasional volcanic eruptions periodically blanket it in cloud. Venus is even hotter. But something strange is happening to Earth. Luna has drifted farther from its primary, the tides quieting; meanwhile, the atmosphere has acquired a strange bluish tinge, evident sign of contamination by a toxic haze of oxygen. The great landmass Rodina, which dominated the southern ocean beneath a cap of ice, has broken up and the shallow seas of the Panthalassic and Panafrican Oceans are hosting an astonishing proliferation of multicellular life.
    SLIDE 6.
    Six hundred and fifty million years later, the outlines of Earth’s new continents glow by night like a neon diadem against the darkness, shouting consciousness at the sky in a blare of radio-wavelength emissions as loud as a star.
    There have been five major epochs dominated by different families of land-based vertebrates in the time between slides 5 and 6. All the Earth’s coal and oil deposits were laid down in this time, different animal families developed flight at least four times, and the partial pressure of oxygen in the atmosphere rose from around 4 percent to well over 16 percent. At the very end, a strangely bipedal, tailless omnivore appeared on the plains of Africa—its brain turbocharged on a potent mixture of oxygen and readily available sugars—and erupted into sentience in a geological eyeblink.
    Here’s what isn’t going to happen:
    SLIDE 7.
    The continents of Earth, no longer lit by the afterglow of