Although this book has been available for more than 25 years, I recently reread it and found it remarkably helpful. As always with Freeman Dyson, this book is a provocative exploration of a set of interesting and often unusual themes in nature, thoughtfully related to the larger issues of the day. In Infinite in All Directions Dyson searches for meaning on the diversity of the Earth’s ecosystem, the inner workings of the universe, and the place of humanity in our larger cosmological structure.
Presented originally as a set of lectures at Aberdeen, Scotland, in 1985, the chapters of this book have a familiarity and sensitivity to events of the time that one might expect. This is both a strength and weakness of this book. Dyson’s interest in the origins and evolution of life emerges clearly in this volume, and this discussion sparked in part by the debates over abortion and creationism is most welcome. His concern for Cold War issues, especially a lengthy discussion of the place of Austria, seems someone archaic more than twenty years later.
Somewhere in the middle is Dyson’s admittedly important perspective and provocative essay on “nuclear winter,” a theory advanced by Carl Sagan and others in the 1980s that suggested that a nuclear exchange between the superpowers would trigger a worldwide ice age. He questioned the theory with some excellent points drawn, as he said, from his background. Indeed, science may be autobiographical, Dyson writes, for Carl Sagan drew his analogies for “nuclear winter” from his studies of the cold, dry environment of Mars and the dust particles in its thin atmosphere.
This is one approach, Dyson concludes, but not the only one and he drew his analogies from the London fog. “We both use the same mathematics and both work with the same laws of physics. Why then do we reach different conclusions?” (p. 262). As he notes: “If the atmosphere after a nuclear war is filled with dry soot, the temperature on the ground will fall and the Earth will experience nuclear winter. If the atmosphere is filled with wet soot, the temperature on the ground will stay roughly constant as it used to do under a London fog. The severity of a nuclear winter depends on whether the soot-laden atmosphere is predominantly dry or predominantly wet” (p. 263).
Moreover, since we live on a water-dominated planet Dyson believes that such a nuclear exchange would not trigger the type of ice age that Sagan advanced. This does not mean that Dyson saw no threat to humanity in nuclear weapons. He certainly did. In fact, he spent considerable space ruminating on the choices that scientists must make in confronting such scientific questions. In all cases, the mode of science is to seek to disprove or at least modify any new theory. Doing so helps to self-correct the state of knowledge, and there is no higher calling in science. “Every new theory has to fight for its existence against intense and often bitter criticism,” Dyson comments (p. 258).
He then adds, “On the other hand, nuclear winter is not just a theory. It is also a political statement with profound moral implications” (p. 259). In such a situation scientists face a dilemma that cannot be minimized. They may take their normal approach as scientists and seek to disprove the theory, which Dyson believed in the case of nuclear winter would be successful, but doing so would provide the decision makers with cover for belligerent actions. As he wrote: “So my instinct as a scientist comes into sharp conflict with my instinct as a human being…What does a scientist do when science and humanity pull in opposite directions” (p. 259).
He offered three possible solutions, one ignoring humanity and seeking to disprove the theory, another embracing humanity and nuclear winter as a theory. A third option, one followed by most scientists in the “nuclear winter” debate, was to privately seek to disprove but publicly to support the theory. He offered this succinct statement of this third approach: “it will not do us any good in the long run to believe a wrong theory, but it will not do us any good in the short run to attack it publicly, so let us keep silent and reserve judgment until the facts become clear” (p. 260).
Dyson, like many others, chose that third option in the “nuclear winter” debate. Dyson’s discussion of “nuclear winter” is an especially useful object lesson in the nature and conundrums of scientific thought and practice. Those who hold the mistaken belief that scientific understanding is objective and linear will be well served in reading this case study.
Scientific understanding is infinitely more complex, convoluted, interesting, and significant than most believe. Apply this issue to the major scientific debates of the present, of which there are many, and it is apparent that there are few easy answers. As always, Freeman Dyson’s work is challenging and thoughtful. “Infinite in All Directions,” despite some essays that are a bit out of date, is a worthy contribution which all would profit by reading.