Act III in Dyson’s drama was the symbiotic coming together of the metabolizers and the replicators. Dyson cited biologist Lynn Margulis’s work in explaining how some components within the modern cell, such as the mitochondria, began as separate self-sufficient organisms before being incorporated into other cells. Thereafter they thrived and worked to the mutual advantage of themselves and their hosts; likewise, RNA, beginning as an invader, then as a parasite, became a full and useful citizen of the cell.
The RNA might splinter off a version of itself that later turned into DNA. The cells would come to own a genome, a stock of genetic information that helped operate the cell on a more businesslike footing, especially the consistent production of proteins, just as early post-British America, consisting of a loose affiliation of states under the Articles of Confederation, was replaced by a more stable union under a federal constitution.
And what about that genome? Biologist Carl Woese holds that in those early days of life, cells did not hoard their genetic material, but rather shared it around freely. Dyson, adopting this view, extended his computer hardware-software metaphor. He refers to this early epoch of life as being typified by the exchange of “open-source software,” that is, the free exchange of genetic information among many types of cells. Woese argued that this epoch was characterized by a pre-Darwin type of evolution, one in which genetic material moved horizontally among cells rather than vertically down through a lineage of generations.
In laying out his scheme for the great experiment of life, Dyson the biologist called upon the talents of two of his intimate colleagues, Dyson the mathematician and Dyson the physicist. He drew upon statistical mechanics and upon his former work with the alignment of atoms in a magnet. It all had to be numerically rigorous. The Tarner Lectures at Cambridge (appearing later in book form as Origins of Life) represent the only time when, in a presentation aimed at the general public, Dyson used equations, lots of them. These formulas embodied the mathematical machinery whereby, in one of the most crucial chemical experiments of all time, un-alive molecules cycled through trillions of trials until they had assembled themselves into living cells.
Garden of Eden
Dyson illustrated the mystery of life with a graph. The horizontal axis corresponded to the increasing complexity of the chains of molecules. The vertical axis represented the effectiveness of the molecules’ enzyme action, depicting how well metabolism proceeded. The graph divided into three zones. The upper left Dyson called the “garden of Eden.” Here the combination of complexity and effectiveness was so great that the organisms never died. This was the realm of immortality. The lower right part of the graph was the absolute elsewhere, the dead zone. Here, through a combination of insufficient enzyme effectiveness or the wrong number of constituent molecules, the cells were not well adapted to their environment. They could not maintain homeostasis. And in the middle estate, between death and immortality, was life. Here the cells lived for a while, grew, reproduced, and then died.3
This was not the end of the story but the beginning. Only here, at the point where Dyson’s model had finished its job by establishing a semi-stable population of enzyme-based or protein-based confederations of molecules, could the nucleotides enter the picture. Only then, when the pinpoint-replicating molecules implanted themselves into the sloppy but established primitive metabolizing proto-cells, could the smart process of genetic inheritance take hold and the era of modern cells begin. Only after the wide-open period of open-access software sharing, in which RNA and then DNA codes were tried out in a variety of cell types, could the next big biological experiment begin.
To summarize Dyson’s toy model of life: as a starting point for life he favored homeostasis (a confederation of molecules roughly reproducing) over replication (exact duplication); the diversity of architecture over uniformity (which would come later); the flexibility of function (the ability of the proto-cells to do things) over the tyranny (or, as biologist Richard Dawkins insisted, the selfishness) of genes; and the ability of the whole organism to tolerate errors rather than insisting on the exact precision of components.4
What did biologists think of Dyson’s theory? Not very much, as he himself admits.5 The versatility of the RNA-first theory of the origin of life is just too tempting. Carl Woese, however, says that the metabolism-first idea is not necessarily wrong, and that Dyson has done a good service in drawing attention to the importance of homeostasis.6 He does, however, question Dyson’s use of the word “error” to characterize the less than perfect replication of life molecules. After all, what does “error” mean at this early point in biological history? If a bit of chemistry works, it works. That the organisms reproduced at all is more important than fidelity to a particular genetic plan.
Dyson has little to say about later pilgrimages of life from its home base, possibly in some relatively warm coastal shallow or near a deep-sea thermal vent, into the outer space of cold ocean water, or later still from water onto dry land or, billions of years along, the emigration of Homo sapiens out of Africa into the wilds of Eurasia.
HOMESTEADING
When Freeman Dyson feels strongly enough about something he plants his feet and declares himself. He writes a manifesto. He wrote one on the subject of nuclear-powered space exploration during his Orion days (1958). He wrote one on the subject of climate change during one summer at Oak Ridge (1974). His book Weapons and Hope (1984) set forth an expansive view of war and peace, and Origins of Life (1985) offered his hypothesis about the emergence of living things from the primordial kettle of nonliving chemicals. The advent of life—a crew of chemicals venturing forth in its membrane spacecraft—was a counterpoint between two tendencies, the selfish but exacting government imposed by replication molecules and the flexible homeostasis kept going by metabolizing molecules.7
Dyson’s grandest manifesto, the clearest summation of what he was up to in the 1980s—indeed the most compact statement of what he has been striving for in his writings ever since—appeared in his next book, Infinite in All Directions (1988). There he openly declared that he was preaching a sermon. It came to this:
My message is the unbounded prodigality of life and the consequent unboundedness of human destiny. As a working hypothesis to explain the riddle of our existence, I propose that our universe is the most interesting of all possible universes, and our fate as human beings to make it so.8
Dyson is aware that with his phrase “most interesting of all possible universes,” he risks sounding like the fictional character Dr. Pangloss in Voltaire’s comic novel, Candide. Pangloss’s slogan, “this is the best of all possible worlds,” is supposed to ameliorate our bewilderment over a life often filled with catastrophes. Dyson, having lived through world war and cold war, doesn’t pretend this is a benign universe, only that it is interesting. What he means by interesting we shall see in due course.
The first part of Dyson’s message, about the prodigality of life, refers to the millions of species inhabiting our planet. Following the early open-source, or pre-Darwin era of development, when biological architecture was freely adapted by organisms, a proprietary era set in, a time when some groups of cells—the first species—began to hoard their genes; to be exact we can say that certain genes were applicable only for select species of organisms. This, according to Carl Woese, marked the advent of the Darwin interlude.
Billions of years later, with the emergence of humans and their vast overlay of technological artifacts, including the ability to alter climate and radically influence other species and ecosystems on a worldwide basis, humans have entered a post-Darwin phase of evolution. This boisterous percolation of human culture, says Dyson, operates a thousand times faster than ordinary biological evolution. Dyson largely skips the Darwinian phase, the mainstay of evolutionary biology, in order to concentrate on events in the post-Darwin era. This is where his interest lies. This is where human destiny unfolds.
Humans in Space
The second panel in Dyson’s triptych of
messages, the unboundedness of human destiny, refers to the vast history of emigration, starting with our species moving from its apparent roots in Africa, out into Asia and Europe, followed thousands of years later by a flow by foot across the Bering land bridge into the Americas and later still the Polynesian dispersal by canoe into the Pacific archipelagos. Finally came the European sailings across the Atlantic and Indian oceans, a process that for good and bad reconnected all the races of the world.
This odyssey was just the beginning. The cultures and nations are far from reaching equilibrium and there remain ample opportunities for Panglossian catastrophe through starvation, nuclear war, and climate radicalization. But the next step in the cosmic human destiny is to explore and then inhabit selected outlying precincts of our solar system. Reckoned in terms of past human explorations and emigrations, the off-Earth enterprise is still at an early stage. Apollo technology brought men to the Moon. Since then we have backtracked, doing no more than dispatching a few astronauts at a time to a station held in fixed Earth orbit.
What comes after that? Dyson’s friend, Princeton physicist Gerard O’Neill, suggested building cylindrical space stations, big enough to accommodate cities and agriculture, and gently rotating so as to provide a sense of gravity to those positioned around the edge, a situation not unlike the crew compartment on 2001: A Space Odyssey. For Dyson the O’Neill cylinders were too big and too small at the same time. Parked in the inner solar system, they weren’t ambitious enough. On the other hand, they would be too expensive for what they did, acting as a mere suburb to Earth. Dyson wanted something cheaper, like a spacefaring equivalent of the Mayflower, something that could appeal to the intrepid outdoorsmen like George Dyson and his Vancouver friends.9
For the time being humans will have to stay put. We could meanwhile proceed with a personless search for life that’s already out there. Much scientific information can be gained relatively cheaply. One of the biggest goals of these missions—indeed one of the most stirring aims in all of science—would be the identification of extraterrestrial life. For many years now Dyson has enthusiastically written about how and where to look for off-Earth life.
Canterbury Tales
Some places seem more likely than others to harbor life. Jupiter’s moon Europa, for example, probably has a deepwater ocean, insulated from above by an icy crust and warmed from below by a tidal force operating between planet and moon. It would be difficult to land a craft on Europa and bore down through thick icepack. A better chance for seeing Europan fish, Dyson argues, is to imagine that a meteorite strike might temporarily break the ice and splash some aquatic creatures into space, much as strikes on Mars have sprung rocks into space, some of which have found their way to Earth. Dyson says that we should look for such freeze-dried fish in the diaphanous ring of material that surrounds Jupiter.10
Some prospecting for life can be done with telescopes on Earth or with visiting probes for a close-up inspection. Previously such visits to the various neighborhoods of the solar system—Magellan at Venus, Rover and Viking on Mars, Galileo at Jupiter, Cassini at Saturn, and the Voyagers and Pioneers in the outer portions and beyond—have radioed back much information about the local environment, but so far no evidence for life has presented itself. Finding life out there isn’t going to be easy. The pilgrimage bringing ourselves or other life forms to the outer solar system will require even more time.
Geoffrey Chaucer’s medieval poem depicted a guide leading a party of pilgrims toward the saint’s shrine. Along the way they entertained themselves with stories. Well, Dyson is the Chaucer of interplanetary space. While we immigrate into space in slow motion, as it were, he tells stories. His stories take the form of thought experiments. Favoring a cheap-quick-small approach to exploration rather than using expensive-slow-large space missions, he asked why, instead of 1-ton spacecraft, we couldn’t have 1-kilogram craft? Instead of heavy rocket propellant and a bulky engine, why not use something light—a skimpy but sturdy broadly deployed sail for catching the thrust of the sun’s light. A kilogram-sized craft would need only a 30-meter-square sail in order to achieve speeds for reaching Uranus in a few years.
You can get to Uranus the old way or you can get there the new way. The old way was to use chemical rockets to boost the 1-ton Voyager 2 craft and a nine-year travel time for a one-flyby view. Dyson considered Voyager to have been a good mission and it had just passed Uranus at the time of his writing about it. Contrast now what a follow-up mission could be. His 1-kg craft would not merely fly by but would linger. It would have the leisure to scrutinize the planet and its trove of moons.
Dyson never insists that his vision of the future will be accurate. He always attaches a disclaimer: This is one of many things that could happen. Don’t complain if it doesn’t happen this particular way. With my scientific knowledge of the world, I am saying that certain things are possible, things involving fast ships, and observations. I make these predictions as an entertainment, as an exercise in creative scientific thinking, in the spirit of Project Orion.
Astrochicken
Dyson’s signature proposal came at a 1988 lecture at the University of Washington. He called his kilogram craft “Astrochicken,” since it is about the size of a chicken. It would not be built but grown.11 It would be organized biologically and its blueprints would be written in the digital language understood by DNA. It employs a symbiosis of plant and animal and electronic components. The plant part provides a basic life-support system using photosynthesis for producing energy. The animal part provides sensors and nerves and muscles for observing, orienting, and navigating. Finally, the electronic part is there to receive instructions from Earth and to transmit back to Earth what it learns.12 What would happen when Astrochicken got to Uranus? It would keep up its energy level by grazing on ice and organic materials available in Uranus’s rings.
Inspect the planets and moons, sure, but a more likely place to find life, Dyson argues, is on asteroids and comets, for the simple reason that these small denizens of deep space account for more total surface area than the planets. Dyson is so sure of himself that he offered a $100 bet that the first extraterrestrial life discovered will reside not on a planet but on an asteroid or comet.13 But what kind of organism could live on a comet? One that must tolerate vacuum, low temperatures, and low gravity. It won’t be easy, but it is conceivable.14
Indeed, the movement of life on Europa from a subsurface aqueous environment into a vacuum environment above the crust might be less arduous than the movement of terrestrial life onto dry land after 3 billion years in the sea, Dyson argues.15 He illustrates his point by examples from an 1895 science fiction novel, Dreams of Earth and Sky, by Konstantin Tsiolkovsky. In this story creatures live in airless space. They accomplish this by being part plant and part animal—with airtight skin and winglike limbs that act as solar collectors.
Dyson not only proposes the style of the organism but also the manner of its detection. He believes we could find such peeping, light-gathering organisms through “pit lamping,” a name deriving from a form of nocturnal stalking in which human hunters spot their prey by the use of head-mounted lamps worn by miners; the light reflects from the victim’s eyes in a focused return beam. This eye light shows up as bright spots against a dark background. Dyson suggests that we go pit lamping for life in the outer solar system.16 The sun shines into the distance, and we look for a telltale deer-in-the-headlight fixed stare back.
Dyson Trees
In the cold parts of the solar system it helps if creatures are warm-blooded. After all, Dyson says, polar bears survive in Arctic regions devoid of plants. They keep their blood warm by eating seals. On a comet, warm-blooded plants would have to eat sunlight by evolving advanced solar collection arrays, including lenslike structures for focusing meager sunlight onto efficient receiver-like tissue. Comets might be cold but they are water-rich. If the plants put down sufficient roots nutrients could be mined from below. With gravity so low, the plants might grow as t
all as they liked, perhaps reaching a scale as large as the comet itself. Maybe bigger. Dyson foresees 100-mile-long trees sprouting from ten-mile-wide comets. In low gravity there is no reason why trees can’t attain mega-Sequoia proportions. These hypothetical horticultural wonders, sometimes referred to now as “Dyson trees,” have figured in several novels.17
But who needs novelists when Dyson’s own writing is so vivid in evoking the trek of women and men out to the abode of comets. For all his talk about the remote detection of life or the dispatch of spacecraft to check on habitats in the far corners of the solar system, Dyson continues to harbor hopes, or at least dreams, of Homo sapiens boldly going forth to these places to look and perchance to live. Dyson trees could furnish both fuel and shelter for human settlers. “When humans come to live on the comets, they will find themselves returning to the arboreal existence of their ancestors.”18
Oort Archipelago
Like a person daydreaming of buying land in a beautiful but forlorn location in order to put up a holiday hideaway, Dyson has his eye on the Kuiper Belt, the girdle of comets and small bodies that ply mostly outside the orbit of Pluto. Indeed, having been demoted from planetary status, Pluto is itself now considered a Kuiper object. Dyson is also intrigued by the still further out Oort Cloud, a swath of small parcels, billions of them, with a large collective surface area.19
Dyson sees the Kuiper and Oort assemblies as something like the Alaska-Canada Inside Passage, a vast archipelago where homesteaders from Earth might make a go of it.20 The reasons for such a risky migration might be biological or political—such as escaping devastation or overcrowding on Earth, or mining minerals, or for seeking sheer adventure. Again, whenever Dyson discusses such fond ideas he is careful to say that he is not making a specific prediction. He is only speculating that certain kinds of living could happen. The laws of physics and biology do not forbid them. Like the first proto-cells on Earth who hung on to existence by agglomerating useful molecules while luxuriating in nutrient-rich tide pools or at the margins of warm mid-ocean vents, twenty-second-century Kuiper Belt city-states might grow by accretion of celestial objects tethered together, much as Indonesia grew by stitching together islands.21
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