by Carl Sagan
One science-fiction writer, L. Ron Hubbard, has founded a successful cult called Scientology-invented, according to one account, overnight on a bet that he could do as well as Freud, invent a religion and make money from it. Classic science-fiction ideas are now institutionalized in unidentified flying objects and ancient-astronaut belief systems-although I have difficulty not concluding that Stanley Weinbaum (in The Valley of Dreams) did it better, as well as earlier, than Erich von Däniken. R. De Witt Miller in Within the Pyramid manages to anticipate both von Däniken and Velikovsky, and to provide a more coherent hypothesis on the supposed extraterrestrial origin of pyramids than can be found in all the writings on ancient astronauts and pyramidology. In Wine of the Dreamers, by John D. MacDonald (a science-fiction author now transmogrified into one of the most interesting contemporary writers of detective fiction), we find the sentence “and there are traces, in Earth mythology… of great ships and chariots that crossed the sky.” The story Farewell to the Master, by Harry Bates, was converted into a motion picture, The Day the Earth Stood Still (which abandoned the essential plot element, that on the extraterrestrial spacecraft it was the robot and not the human who was in command). The movie, with its depiction of a flying saucer buzzing Washington, is thought by some sober investigators to have played a role in the 1952 Washington, D.C., UFO “flap” which followed closely the release of the motion picture. Many popular novels today of the espionage variety, in the shallowness of their characterizations and the gimmickry of their plots, are virtually indistinguishable from pulp science fiction of the ’30s and ’40s.
THE INTERWEAVING of science and science fiction sometimes produces curious results. It is not always clear whether life imitates art or vice versa. For example, Kurt Vonnegut, Jr., has written a superb epistemological novel, The Sirens of Titan, in which a not altogether inclement environment is postulated on Saturn’s largest moon. When in the last few years some planetary scientists, myself among them, presented evidence that Titan has a dense atmosphere and perhaps higher temperatures than expected, many people commented to me on the prescience of Kurt Vonnegut. But Vonnegut was a physics major at Cornell University and naturally knowledgeable about the latest findings in astronomy. (Many of the best science-fiction writers have science or engineering backgrounds; for example, Poul Anderson, Isaac Asimov, Arthur C. Clarke, Hal Clement and Robert Heinlein.) In 1944, an atmosphere of methane was discovered on Titan, the first satellite in the solar system known to have an atmosphere. In this, as in many similar cases, art imitates life.
The trouble has been that our understanding of the other planets has been changing faster than the science-fiction representations of them. A clement twilight zone on a synchronously rotating Mercury, a swamp-and-jungle Venus and a canal-infested Mars, while all classic science-fiction devices, are all based upon earlier misapprehensions by planetary astronomers. The erroneous ideas were faithfully transcribed into science-fiction stories, which were then read by many of the youngsters who were to become the next generation of planetary astronomers-thereby simultaneously capturing the interest of the youngsters and making it more difficult to correct the misapprehensions of the oldsters. But as our knowledge of the planets has changed, the environments in the corresponding science-fiction stories have also changed. It is quite rare to find a science-fiction story written today that involves algae farms on the surface of Venus. (Incidentally, the UFO-contact mythologizers are slower to change, and we can still find accounts of flying saucers from a Venus populated by beautiful human beings in long white robes inhabiting a kind of Cytherean Garden of Eden. The 900° Fahrenheit temperatures of Venus give us one way of checking such stories.) Likewise, the idea of a “space warp” is a hoary science-fiction standby but it did not arise in science fiction. It arose from Einstein’s General Theory of Relativity.
The connection between science-fiction depictions of Mars and the actual exploration of Mars is so close that, subsequent to the Mariner 9 mission to Mars, we were able to name a few Martian craters after deceased science-fiction personalities. (See Chapter 11.) Thus there are on Mars craters named after H. G. Wells, Edgar Rice Burroughs, Stanley Weinbaum and John W. Campbell, Jr. These names have been officially approved by the International Astronomical Union. No doubt other science-fiction personalities will be added soon after they die.
THE GREAT INTEREST of youngsters in science fiction is reflected in films, television programs, comic books and a demand for science-fiction courses in high schools and colleges. My experience is that such courses can be fine educational experiences or disasters, depending on how they are done. Courses in which the readings are selected by the students provide no opportunity for the students to read what they have not already read. Courses in which there is no attempt to extend the science-fiction plot line to encompass the appropriate science miss a great educational opportunity. But properly planned science-fiction courses, in which science or politics is an integral component, would seem to me to have a long and useful life in school curricula.
The greatest human significance of science fiction may be as experiments on the future, as explorations of alternative destinies, as attempts to minimize future shock. This is part of the reason that science fiction has so wide an appeal among young people: it is they who will live in the future. It is my firm view that no society on Earth today is well adapted to the Earth of one or two hundred years from now (if we are wise enough or lucky enough to survive that long). We desperately need an exploration of alternative futures, both experimental and conceptual. The novels and stories of Eric Frank Russell were very much to this point. In them, we were able to see conceivable alternative economic systems or the great efficiency of a unified passive resistance to an occupying power. In modern science fiction, useful suggestions can also be found for making a revolution in a computerized technological society, as in Heinlein’s The Moon Is a Harsh Mistress.
Such ideas, when encountered young, can influence adult behavior. Many scientists deeply involved in the exploration of the solar system (myself among them) were first turned in that direction by science fiction. And the fact that some of that science fiction was not of the highest quality is irrelevant. Ten-year-olds do not read the scientific literature.
I do not know if time travel into the past is possible. The causality problems it would imply make me very skeptical. But there are those who are thinking about it. What are called closed time-like lines-routes in space-time permitting unrestricted time travel-appear in some solutions to the general relativistic field equations. A recent claim, perhaps mistaken, is that closed timelike lines appear in the vicinity of a large, rapidly rotating cylinder. I wonder to what extent general-relativists working on such problems have been influenced by science fiction. Likewise, science-fiction encounters with alternative cultural features may play an important role in actualizing fundamental social change.
In all the history of the world there has never before been a time in which so many significant changes have occurred. Accommodation to change, the thoughtful pursuit of alternative futures are keys to the survival of civilization and perhaps of the human species. Ours is the first generation that has grown up with science-fiction ideas. I know many young people who will of course be interested but in no way astounded if we receive a message from an extraterrestrial civilization. They have already accommodated to that future. I think it is no exaggeration to say that if we survive, science fiction will have made a vital contribution to the continuation and evolution of our civilization.
PART III. OUR NEIGHBORHOOD IN SPACE
CHAPTER 10
THE SUN’S FAMILY
Like a shower of stars the worlds whirl, borne along by the winds of heaven, and are carried down through immensity; suns, earths, satellites, comets, shooting stars, humanities, cradles, graves, atoms of the infinite, seconds of eternity, perpetually transform beings and things.
CAMILLE FLAMMARION,
Popular Astronomy, translated by J. E. Gore
&
nbsp; (New York, D. Appleton & Company, 1894)
IMAGINE THE EARTH scrutinized by some very careful and extremely patient extraterrestrial observer: 4.6 billion years ago the planet is observed to complete its condensation out of interstellar gas and dust, the final planetesimals falling in to make the Earth produce enormous impact craters; the planet heats internally from the gravitational potential energy of accretion and from radioactive decay, differentiating the liquid iron core from the silicate mantle and crust; hydrogen-rich gases and condensible water are released from the interior of the planet to the surface; a rather humdrum cosmic organic chemistry yields complex molecules, which lead to extremely simple self-replicating molecular systems-the first terrestrial organisms; as the supply of impacting interplanetary boulders dwindles, running water, mountain building and other geological processes wipe out the scars attendant to the Earth’s origin; a vast planetary convection engine is established which carries mantle material up at the ocean floors and subducts it down at the continental margins, the collision of the moving plates producing the great folded mountain chains and the general configuration of land and ocean, glaciated and tropical terrain varies continuously. Meanwhile, natural selection extracts out from a wide range of alternatives those varieties of self-replicating molecular systems best suited to the changing environments; plants evolve that use visible light to break down water into hydrogen and oxygen, and the hydrogen escapes to space, changing the chemical composition of the atmosphere from reducing to oxidizing; organisms of fair complexity and middling intelligence eventually arise.
Yet in all the 4.6 billion years our hypothetical observer is struck by the isolation of the Earth. It receives sunlight and cosmic rays-both important for biology-and occasional impact of interplanetary debris. But nothing in all those eons of time leaves the planet. And then the planet suddenly begins to fire tiny dispersules throughout the inner solar system, first in orbit around the Earth, then to the planet’s blasted and lifeless natural satellite, the Moon. Six capsules-small, but larger than the rest-set down on the Moon, and from each, two tiny bipeds can be discerned, briefly exploring their surroundings and then hotfooting it back to the Earth, having extended tentatively a toe into the cosmic ocean. Eleven little spacecraft enter the atmosphere of Venus, a searing hellhole of a world, and six of them survive some tens of minutes on the surface before being fried. Eight spacecraft are sent to Mars. Three successfully orbit the planet for years; another flies past Venus to encounter Mercury, on a trajectory obviously chosen intentionally to pass by the innermost planet many times. Four others successfully traverse the asteroid belt, fly close to Jupiter and are there ejected by the gravity of the largest planet into interstellar space. It is clear that something interesting is happening lately on the planet Earth.
If the 4.6 billion years of the Earth history were compressed into a single year, this flurry of space exploration would have occupied the last tenth of a second, and the fundamental changes in attitude and knowledge responsible for this remarkable transformation would fill only the last few seconds. The seventeenth century saw the first widespread application of simple lenses and mirrors for astronomical purposes. With the first astronomical telescope Galileo was astounded and delighted to see Venus as a crescent, and the mountains and the craters of the Moon. Johannes Kepler thought that the craters were constructions of intelligent beings inhabiting that world. But the seventeenth-century Dutch physicist Christianus Huygens disagreed. He suggested that the effort involved in constructing the lunar craters would be unreasonably great, and also thought that he could see alternative explanations for these circular depressions.
Huygens exemplified the synthesis of advancing technology, experimental skills, a reasonable, hard-nosed and skeptical mind, and an openness to new ideas. He was the first to suggest that we are looking at atmosphere and clouds on Venus; the first to understand something of the true nature of the rings of Saturn (which had seemed to Galileo as two “ears” enveloping the planet); the first to draw a picture of a recognizable marking on the Martian surface (Syrtis Major); and the second, after Robert Hooke, to draw the Great Red Spot of Jupiter. These last two observations are still of scientific importance because they establish the permanence at least for three centuries of these features. Huygens was of course not a thoroughly modern astronomer. He could not entirely escape the fashions of belief of his time. For example, he presented a curious argument from which we could deduce the presence of hemp on Jupiter: Galileo had observed that Jupiter has four moons. Huygens asked a question few modern planetary astronomers would ask: Why does Jupiter have four moons? An insight into this question, he thought, could be garnered by asking the same question of the Earth’s single moon, whose function, apart from giving a little light at night and raising the tides, was to provide a navigational aid to mariners. If Jupiter has four moons, there must be many mariners on that planet. But mariners imply boats; boats imply sails; sails imply ropes; and, I suppose, ropes imply hemp. I wonder how many of our present highly prized scientific arguments will seem equally suspect from the vantage point of three centuries.
A useful index of our knowledge about a planet is the number of bits of information necessary to characterize our understanding of its surface. We can think of this as the number of black and white dots in the equivalent of a newspaper wirephoto which, held at arm’s length, would summarize all existing imagery. Back in Huygens’ day, about ten bits of information, all obtained by brief glimpses through telescopes, would have covered our knowledge of the surface of Mars. By the time of the close approach of Mars to Earth in the year 1877, this number had risen to perhaps a few thousand, if we exclude a large amount of erroneous information-for example, drawings of the “canals,” which we now know to be entirely illusory. With further visual observations and the development of ground-based astronomical photography, the amount of information grew slowly until a dramatic upturn in the curve occurred, corresponding to the advent of space-vehicle exploration of the planet.
The twenty photographs obtained in 1965 by the Mariner 4 fly-by comprised five million bits of information, roughly comparable to all previous photographic knowledge about the planet. The coverage was still only a tiny fraction of the planet. The dual fly-by mission, Mariner 6 and 7 in 1969, increased this number by a factor of 100, and the Mariner 9 orbiter in 1971 and 1972 increased it by another factor of 100. The Mariner 9 photographic results from Mars correspond roughly to 10,000 times the total previous photographic knowledge of Mars obtained over the history of mankind. Comparable improvements apply to the infrared and ultraviolet spectroscopic data obtained by Mariner 9, compared with the best previous ground-based data.
Going hand in hand with the improvement in the quantity of our information is the spectacular improvement in its quality. Prior to Mariner 4, the smallest feature reliably detected on the surface of Mars was several hundred kilometers across. After Mariner 9, several percent of the planet had been viewed at an effective resolution of 100 meters, an improvement in resolution of a factor of 1,000 in the last ten years, and a factor of 10,000 since Huygens’ time. Still further improvements were provided by Viking. It is only because of this improvement in resolution that we today know of vast volcanoes, polar laminae, sinuous tributaried channels, great rift valleys, dune fields, crater-associated dust streaks, and many other features, instructive and mysterious, of the Martian environment.
Both resolution and coverage are required to understand a newly explored planet. For example, even with their superior resolution, by an unlucky coincidence the Mariner 4, 6 and 7 spacecraft observed the old, cratered and relatively uninteresting part of Mars and gave no hint of the young and geologically active third of the planet revealed by Mariner 9.
LIFE ON EARTH is wholly undetectable by orbital photography until about 100-meter resolution is achieved, at which point the urban and agricultural geometrizing of our technological civilization becomes strikingly evident. Had there been a civilization on Mars of comparabl
e extent and level of development, it would not have been detected photographically until the Mariner 9 and Viking missions. There is no reason to expect such civilizations on the nearby planets, but the comparison strikingly illustrates that we are just beginning an adequate reconnaissance of neighboring worlds.
THERE IS NO question that astonishments and delights await us as both resolution and coverage are dramatically improved in photography, and comparable improvements are secured in spectroscopic and other methods.
The largest professional organization of planetary scientists in the world is the Division for Planetary Sciences of the American Astronomical Society. The vigor of this burgeoning science is apparent in the meetings of the society. In the 1975 annual meeting, for example, there were announcements of the discovery of water vapor in the atmosphere of Jupiter, ethane on Saturn, possible hydrocarbons on the asteroid Vesta, an atmospheric pressure approaching that of the Earth on the Saturnian moon Titan, decameter-wavelength radio bursts from Saturn, the radar detection of the Jovian moon Ganymede, the elaboration of the radio emission spectrum of the Jovian moon Callisto, to say nothing of the spectacular views of Mercury and Jupiter (and their magnetospheres) presented by the Mariner 10 and Pioneer 11 experiments. Comparable advances were reported in subsequent meetings.
In all the flurry and excitement of recent discoveries, no general view of the origin and evolution of the planets has yet emerged, but the subject is now very rich in provocative hints and clever surmises. It is becoming clear that the study of any planet illuminates our knowledge of the rest, and if we are to understand Earth thoroughly, we must have a comprehensive knowledge of the other planets. For example, one now fashionable suggestion, which I first proposed in 1960, is that the high temperatures on the surface of Venus are due to a runaway greenhouse effect in which water and carbon dioxide in a planetary atmosphere impede the emission of thermal infrared radiation from the surface to space; the surface temperature then rises to achieve equilibrium between the visible sunlight arriving at the surface and the infrared radiation leaving it; this higher surface temperature results in a higher vapor pressure of the greenhouse gases, carbon dioxide and water; and so on, until all the carbon dioxide and water vapor is in the vapor phase, producing a planet with high atmospheric pressure and high surface temperature.