The Starship and the Canoe. Kenneth Brower
son of a British physicist than the bastard of a French-Indian trapper.
But under the beard, the long hair, and the tan, George bears strong resemblance to his father. He has the same long face. His cranium, on the outside at least, is identical. He has the big nose. Both Freeman Dyson and George Dyson have broken their noses, but George’s break is more spectacular. His nose takes several turns before finishing. He is homelyhandsome. His features are strong, but they lack the nice symmetry and proportion that break young girls’ hearts.
His eyes are his extraordinary feature. They are so dominated by the irises that the pupils seem pinpricks. His eyes are large, green, and steady, and he holds them wide open.
3
Comets
“First I have to clear away a few popular misconceptions about space as a habitat,” said Freeman Dyson, lecturing in London in 1972. “It is generally considered that planets are important. Except for Earth, they are not. Mars is waterless, and the others are for various reasons basically inhospitable to man. It is generally considered that beyond the sun’s family of planets there is absolute emptiness extending for light-years until you come to another star. In fact, it is likely that the space around the solar system is populated by huge numbers of comets, small worlds a few miles in diameter, rich in water and the other chemicals essential to life. We see one of these comets only when it happens to suffer a random perturbation of its orbit which sends it plunging close to the sun. It seems that roughly one comet per year is captured into the region near the sun, where it eventually evaporates and disintegrates. If we assume that the supply of distant comets is sufficient to sustain this process over the thousands of millions of years that the solar system has existed, then the total population of comets loosely attached to the sun must be numbered in the thousands of millions. The combined surface area of these comets is then a thousand or ten thousand times that of Earth. I conclude from these facts that comets, not planets, are the major potential habitat of life in space. If it were true that other stars have as many comets as the sun, it then would follow that comets pervade our entire galaxy. We have no evidence either supporting or contradicting this hypothesis. If true, it implies that our galaxy is a much friendlier place for interstellar travelers than it is popularly supposed to be. The average distance between habitable oases in the desert of space is not measured in light-years, but is of the order of a light-day or less.
“I propose to you then an optimistic view of the galaxy as an abode of life. Countless millions of comets are out there, amply supplied with water, carbon, and nitrogen, the basic constituents of living cells. We see when they fall close to the sun that they contain all the common elements necessary to our existence. They lack only two essential requirements for human settlement, namely warmth and air. And now, biological engineering will come to our rescue. We shall learn to grow trees on comets.
“To make a tree grow in airless space by the light of a distant sun is basically a problem of redesigning the skin of its leaves. In every organism the skin is the crucial part which must be most delicately tailored to the demands of the environment. The skin of a leaf in space must satisfy four requirements. It must be opaque to far-ultraviolet radiation to protect the vital tissues from radiation damage. It must be impervious to water. It must transmit visible light to the organs of photosynthesis. It must have extremely low emissivity for far-infrared radiation, so that it can limit loss of heat and keep itself from freezing. A tree whose leaves possess such a skin should be able to take root and flourish upon any comet as near to the sun as the orbits of Jupiter and Saturn. Farther out than Saturn the sunlight is too feeble to keep a simple leaf warm, but trees can grow at far greater distances if they provide themselves with compound leaves. A compound leaf would consist of a photosynthetic part, which is able to keep itself warm, together with a convex mirror part, which itself remains cold but focuses concentrated sunlight upon the photosynthetic part. It should be possible to program the genetic instructions of a tree to produce such leaves and orient them correctly toward the sun. Many existing plants possess structures more complicated than this.
“Once leaves can be made to function in space, the remaining parts of a tree—trunk, branches, and roots—do not present any great problems. The branches must not freeze, and therefore the bark must be a superior heat insulator. The roots will penetrate and gradually melt the frozen interior of the comet, and the tree will build its substance from the materials which the roots find there. The oxygen which the leaves manufacture must not be exhaled into space; instead it will be transported down to the roots and released into the regions where men will live and take their ease among the tree trunks. One question still remains. How high can a tree on a comet grow? The answer is surprising. On any celestial body whose diameter is of the order of ten miles or less, the force of gravity is so weak that a tree can grow out for hundreds of miles, collecting the energy of sunlight from an area thousands of times as large as the area of the comet itself. Seen from far away, the comet will look like a small potato sprouting an immense growth of stems and foliage. When man comes to live on the comets, he will find himself returning to the arboreal existence of his ancestors.”
4
Flying Squirrels
George Dyson lives ninety-five feet above the ground in a Douglas fir in British Columbia. His tree stands on land leased by friends from the provincial government. It is the last tree before the water, and the front window of his tree house looks down into Indian Arm of the Strait of Georgia. The tree is the biggest around, and its foliage is dense. Through his seaward windows George can look out unseen at the traffic on the strait. Through his landward windows he can study anyone approaching from that direction. At night the city of Vancouver glows on the horizon.
George built his house in 1972, the year his father lectured on comets and the hospitality of interstellar space.
George’s stairs are the tree’s branches. They make a spiral staircase, leading him round and round the trunk as he ascends. The first branches begin some distance above the ground, so at the foot of the tree George has nailed a ladder. Climbing from the top rung to the first branch is difficult, and George intended it that way. He likes his privacy. The hands of any visitor are covered with pitch by the time he reaches George’s door, but George knows where to put his own hands, and they stay clean. For visitors, even those young and nimble, the first few climbs up to the tree house are scary, but George runs up as if his Douglas fir lay horizontal on the ground. He has climbed it drunk and he has climbed it in winter storms. He could climb it in his sleep. All the motions—swinging around this branch, reaching for that one, pulling up—have been burned by repetition into his autonomic nervous system. He hauls up his firewood by rope. When he wants to descend he rappels.
The house is lashed to the tree, not nailed, for the treetop sways in the wind and the attachment must be flexible to endure. George has confidence in the lashings. In 1975 the worst storm in many years hit British Columbia, and George, who at the time had been living elsewhere, moved back into his tree to see how a big storm felt. The storm did its best; the tree whipped wildly about; George fell asleep.
The house is shingled, inside and out, with red-cedar shakes. The outside shakes have weathered as dark as the tree trunk, fine camouflage. The inside shakes, protected from the weather, look fresh split, retaining the warm red-blond of the heart of the log they came from. The house has a single tiny room. The ship-tight, red-blond interior is free-form, for George built to include fourteen branches as structural members. His ingenuity does not call attention to itself, and the number of incorporated branches is a surprise when you total it up. The door’s hinges are screwed into the main trunk. Above the hinges, the biggest of the inner limbs forks from the trunk, thick as a man’s thigh, passes over George’s bed and exits through the wall. In the morning, George’s eyes open wide and green on living bark, and he can pull himself out of bed on the limb’s solidness.
The bed is Procrustean. George is six feet tall, and the house is two or three inches narrower than that, so he must sleep slightly bent. The bed’s hard planks are softened somewhat by a mattress of two blankets, thin and nondescript, which are covered by a Persian rug, thick and beautiful. At the head is a handmade leather cushion that George uses as a pillow. Like most of the things he has owned for a while, the cushion has begun to have