Free Billions & Billions by Carl Sagan Page A

typical. This is key if we have any hopes of constructing a general theory of the origin of planetary systems: It now must encompass a diversity of planetary systems.
    Still more recently, a technique called astrometry has been used to detect two and possibly three Earth-like planets around a star very near to our Sun, Lalande 21185. Here the precise motion of the star is monitored over many years, and the recoil due to any planets in orbit about it is carefully watched. Departures from circular or elliptical orbits by Lalande 21185 permit us to detect the presence of planets. So here we have a familiar, or at least a somewhat familiar, planetary system to our own. There seem to be at least two and maybe more categories of planetary systems in adjacent interstellar space.
    As for life on these Jupiter-like worlds, it is no more likely than on our own Jupiter. But what is probable is that these other Jupiters have moons, like the 16 that circle our Jupiter. Because these moons, like the giant worlds they orbit, are close to the local star, their temperatures, especially for 70 Virginis, might be clement for life. At 35 to 40 light-years away, these worlds are close enough for us to begin to dream of one day sending very fast spacecraft to visit them, the data to be received by our descendants.
    Meanwhile, a range of other techniques are coming along. Besides pulsar timing glitches and Doppler measurements of theradial velocities of stars, interferometers on the ground or, better, in space; ground-based telescopes that cancel out the turbulence of the Earth’s atmosphere; ground-based observations using the gravitational lens effect of distant massive objects; and very accurate space-borne measurements of the dimming of a star when one of its planets passes in front of it all seem ready in the next few years to yield significant results. We are now on the verge of trolling through thousands of nearby stars, searching for their companions. To me it seems likely that in the coming decades we will have information on at least hundreds of other planetary systems close to us in the vast Milky Way Galaxy—and perhaps even a few small blue worlds graced with water oceans, oxygen atmospheres, and the telltale signs of wondrous life.

Part II

WHAT ARE
CONSERVATIVES
CONSERVING?

CHAPTER 7

THE WORLD THAT
CAME IN THE MAIL
    The world? Moonlit
Drops shaken
From the crane’s bill.
    DOGEN (1200–1253),
“Wake on Impermanence,” from Lucien Stryk and Takashi Ikemoto,
Zen Poems of Japan: The Crane’s Bill
(New York: Grove Press, 1973)
    T he world arrived in the mail. It was marked “Fragile.” A sticker depicting a cracked goblet was on the wrapping. I opened it carefully, dreading the tinkle of broken crystal, or the discovery of a shard of glass. But it was intact. With both hands, I lifted it out and held it up to the sunlight. It was a transparent sphere, about half filled with water. The number 4210 was inconspicuously taped to it. World number 4210: There must be many such worlds. Cautiously, I placed it on the accompanying Lucite stand and peered in.
    I could see life in there—a network of branches, some encrusted with green filamentous algae, and six or eight small animals, mostly pink, cavorting, so it seemed, among the branches. In addition, there were hundreds of other kinds of beings, as plentiful in these waters as fish in the oceans of Earth; but they were all microbes, much too small for me to see with the naked eye. Clearly, the pink animals were shrimp of some suitably unpretentious variety. They caught your attention immediately because they were so
busy
. A few had alighted on branches and were walking on 10 legs and waving lots of other appendages. One of them was devoting all its attention, and a considerable number of limbs, to dining on a filament of green. Among the branches, draped with algae much as trees in Georgia and north Florida are covered with Spanish moss, other shrimp could be seen moving as if