What Comes Around

By Carl Sagan and Ann Druyan
Random House; 389 pp.

By Nigel Calder
British Broadcasting Corporation; 160 pp.

This time around, there will be no hysteria: no mass panic over global poisoning from the comet’s tail, no trembling over calamities to come. The portent of doom has been reduced to a logo for commemorative coffee mugs and souvenir sweatshirts – merely another means to move merchandise. This time, for the first time, the physics of Halley’s comet promises to be more interesting than its sociology.

Once again, then, the new smudge in the sky is a sign of its times. When it made its appearance in 87 B.C., when Julius Caesar was 14, the comet was a sudden irregularity in an otherwise ordered cosmos: clearly a message of some kind from the gods.

In 1986, it provides an excuse to scoff at the delusions of previous generations, and an opportunity to parade the fresh certainties of astronomy before a population that prefers television to telescopes. It is an advertisement for the calm rationality of modern science.

There is considerable similarity, therefore, between the treatments accorded Halley’s comet by both Nigel Calder and by the husband-wife collaboration of Carl Sagan and Ann Druyan. In both The Comet is Coming! and Comet, the story is essentially the same: a tale of the triumph of empiricism over superstition, of theory over myth. Gone are the groundless astrological interpretations, the baseless fears, the vacuous predictions. Through the work of brilliant men – Isaac Newton, Edmond Halley, Fred Whipple – we are privileged to know the comet, not to be cowed by it.

True enough, but there is nonetheless something disturbing about a view of history that sets out, not to appreciate how the comet was understood in its previous apparitions, but to emphasize above all that it was misunderstood. The tendency – particularly pronounced in the Sagan/Druyan volume – is to scorn the misguided efforts of those who interpreted the comet in mythic or astrological (i.e. pre-scientific) terms, and to laud those who managed to anticipate the modern view.

The opening historical sections of Comet, as a result, are the book’s weakest moments. An entire chapter, for example, is devoted to the cosmological theories of Thomas Wright and Immanuel Kant, two mid-18th century thinkers who are congratulated for “discovering” that the galaxy is a disc-shaped cluster of stars.

The heroism of their efforts is won, however, at the expense of garbled history: in fact, Wright did not only not propose, but could not accept, the disc model ascribed to him; his cosmology was not the result of superior science, but was the product of his own idiosyncratic theology; Kant’s contribution, equally unfounded in observational data, rested on a creative misinterpretation of Wright’s ideas; and although Kant would go on to become one of philosophy’s towering figures, neither cosmology made much of an impact on contemporary astronomers. In their attempt to show how modern science got it right, Sagan/Druyan simply get it wrong.

Calder’s account is on firmer historical footing, but he is even more explicit about his aims: the book is intended to allay comet fever, not to contribute to it – which is to say, we are to remain calm, we are to understand the comet in purely scientific terms, we are not to buy or sell Halley’s comet crash helmets.

The question, however, is not whether the comet will once again inspire irrationalism – in this day and age, one resists the rule of science only at the risk of condemning oneself as a hapless boob – but whether science, having successfully silenced all other discourses, actually has anything interesting to say about Halley’s comet. The answer, happily, is that indeed it does, especially when the story is told as deftly and as handsomely as in Comet.

Carl Sagan, Cornell University astronomer, is possibly the West’s most prominent scientist, a reasoned activist and a gifted popularizer. Ann Druyan is herself a skilled journalist, and if the history of Comet is occasionally skewed, the physics more than compensates.

To understand Halley’s comet, the authors stress, one must first understand comets themselves. And to understand comets is to immerse oneself in a full-blown theory of the solar system – a marvelous edifice built on meticulous observation, painstaking calculation and flashes of devilishly clever speculation. As told by Sagan/Druyan, the story is highly informative and hugely entertaining.

Calder’s volume, although also abundantly illustrated, is slimmer and less pyrotechnic. It is actually the companion publication to a documentary aired by the BBC five years ago, reissued to coincide with the comet’s appearance. And while the book is competently executed, it is inferior to Comet in both content and attitude.

In content, Calder’s treatment suffers from being out of date. His book includes the debate over whether the extinction of the dinosaurs was triggered by a comet striking the earth, but lacks the more recent suggestions that such an effect might be duplicated by even a small nuclear exchange (the nuclear winter hypothesis).

More importantly, in his attitude, Calder is simply a curmudgeon. The Sagan/Druyan offering is a book to both delight and create enthusiasts; Calder, by comparison, seems opposed to enthusiasm in principle – Halley’s comet is just a chunk of ice and dust, disgorging various gases in its tail as the sun warms it, no more, no less. It is a triviality, a piece of cosmic debris, and in Calder’s eyes any agitation or exuberance over it, even on the part of professional astronomers, is unseemly. Perhaps he has a point, but then who wants the firmament explained by a killjoy?

So while Calder is perfectly adequate to the task of introducing comet science circa 1986, Comet is the book that better captures the modern moment. It is also an artifact that can be handed down to one’s grandchildren, so that in the year 2062, when the smudge sweeps round again, they too can chuckle over the naive certainties of the previous generation.eg

  • Montreal Gazette January 18, 1986