The Extraterrestrial Life Debate, 1750-1900

Michael J. Crowe

• Publisher: Dover Publications
• Year: 2012
• ISBN:
  9780486145013
• Topic: Storia
• Subtopic: Storia della scienza

`There isn't an uninteresting page in it. It is a masterly review of an intriguing subject, erudite and entertaining, clear and all-encompassing reading for anyone interested in 'one of the most wondrous and noble questions in nature' ― does extraterrestrial life exist?` ― New Scientist.

Are we alone in the universe? Are there other beings on other worlds who gaze into the night sky and try to imagine us, as we try to imagine them? Those questions have been debated since antiquity, but it was during the Enlightenment that they particularly began to engage the interest of prominent scientists and thinkers. In this fascinating volume, Professor Michael Crowe offers the first in-depth study in English of the international debate that developed between 1750 and 1900 concerning the existence of extraterrestrial life, a problem that engaged an extraordinary variety of Western thinkers across the spectrum of intellectual endeavor. Astronomers such as Herschel, Bode, Lalande, and Flammarion all weighed in, along with French philosophers Rousseau and Voltaire, American patriot Thomas Paine, Scots churchman Thomas Chalmers, and a host of others. Professor Crowe gives them all their say, as they address the question as a point of science, as a problem of philosophy, as well as a religious issue. The book ends with the `discovery` by Schiaparelli of the canals of Mars, the expansion of the canal theory by the American astronomer Percival Lowell, and the culmination of the canal controversy with the demonstration of its illusory nature.

`Crowe's book is lucid and rich in historical detail. His analysis is so fascinating and his comments on the contemporary debate so pertinent that The Extraterrestrial Life Debate can be recommended for the thoughtful reader without reservation. While a model of scholarly analysis, it has the unusual virtue of reading with the excitement of high adventure.` ― Sky & Telescope.

PART I

From 1750 to 1800

2

Astronomers and extraterrestrials

1. Wright, Kant, and Lambert: pioneer sidereal astronomers and proponents of a plurality of worlds

During the second half of the eighteenth century, the idea of a plurality of worlds won the attention of many if not most European astronomers. This chapter illustrates this point while developing three specific theses: (1) that the astronomical writings of the pioneers (Wright, Kant, and Lambert) of the most important astronomical advance of that half-century, the creation of sidereal astronomy, were permeated by pluralist concerns, (2) that the career of the premier astronomer of that period (Sir William Herschel) was deeply influenced by ideas of extraterrestrial life, and (3) that four of Herschel’s leading Continental contemporaries (Schröter, Bode, Laplace, and Lalande) were scarcely less involved in the pluralist quest than Herschel himself.

In 1750, two centuries after the commencement of the Copernican revolution, a second astronomical revolution began. Thomas Wright, Immanuel Kant, and Johann Lambert, in books published between 1750 and 1761, proposed daring new theories of the sidereal region, the realm of stars and nebulae. This second or sidereal revolution, which culminated only in the 1920s, encompassed three conclusions: (1) that the Milky Way is an optical effect arising from the scattering of millions of stars over a roughly planar area, (2) that these stars form a giant disk-shaped structure many light-years in diameter, and (3) that many of the nebulous patches seen in the heavens are galaxies comparable in magnitude to our own Milky Way galaxy. In discussing the writings of Wright, Kant, and Lambert it will be important to ask not only what contribution each made to this revolution but also how he came to make it. In doing this we shall see that this revolution was intimately related to the extraterrestrial life debate, a point too rarely recognized.

Thomas Wright of Durham, born in 1711, died in obscurity in 1786, despite having published a number of books, most notably his Original Theory of the Universe. The fluctuations in Wright’s reputation over the past two centuries furnish an instructive study of the difficulties in interpreting his astronomical writings.¹ Although the successes and reversals in the sidereal revolution influenced Wright’s standing, a central problem in his historiography was already evident in the efforts made in the 1830s by two Americans, C. S. Rafinesque and C. Wetherill, and in the 1840s by an Englishman, Augustus De Morgan, to rescue his reputation, for these authors championed quite different Wrights. De Morgan portrayed him as a “discoverer” who was “entitled to have his speculations considered, not as the accident of a mind which must give the rein to imagination . . . , but as the justifiable research and successful conclusion of thought founded on both knowledge and observation.”² On the other hand, Wetherill and Rafinesque praised him for “disdaining the narrow constructed algebraic Newtonian standard,” for possessing the “wisdom of an Ancient Sage,” and for promoting “the most expansive, sublime, and religious conception of the Universe or INFINITE CREATION.”³ Celestial scientist or religious sage? A century after De Morgan, F. A. Paneth repeatedly proclaimed Wright a pioneer of sidereal astronomy, even proposing the erection on Wright’s house of a marble plaque inscribed: “He was the first to explain the Milky Way.”⁴ Paneth’s position was shown to be unacceptable in the early 1970s, when Dr. Michael Hoskin, drawing on previously unpublished Wright manuscripts, revealed that Wright’s religious goals were paramount and that he had not one but three theories of the Milky Way, all wrong and increasingly so.⁵ It is Hoskin’s Wright that will concern us, although it will be suggested that Wright’s Original Theory as well as the pioneering books of Kant and Lambert can be properly understood only if they are read not least as tracts on extraterrestrials.

Although he lacked university training, Wright possessed a passion for learning so intense that in 1729, as he recorded in his journal, “Father, by ill advice, think him mad. Burn all the books he can get and endeavor to prevent Study.”⁶ As becomes clear from a Wright manuscript of 1734, this son of a carpenter had by then set for himself the colossal task not simply of constructing a new conception of the physical cosmos but also of integrating into it the domain of the spiritual. Heaven and hell, comets and the chaos, the stars and the “Sedes Beatorum,” planets and patriarchs, all these and “an infinite number of worlds” Wright sought to arrange and even to display on a giant chart (now lost) for which his manuscript was to provide the explanation. At the center of creation Wright placed the “Paradise of mortal spirits . . . surrounding the Sacred Throne of Omnipotence.” Beyond this was the “Region of Mortality, in which all sensible being such as y^c planetary bodies are imagined to circumvolve in all manner of direction round the Devine Presence. . . .” Finally, outside this shell of stars, he placed “the shades of Darkness & Dispare supposed to be the Desolate Regions of y^e Damn^d.”⁷ Although scarcely mentioning the Milky Way in this work, Wright later claimed that this sketch “prov’d afterwards the foundation of his Theory of y^e Univers a much more perfect work.” (p. 15) In fact, this manuscript reveals a speculative mind less in the tradition of Isaac Newton than in that of Tobias Swinden. Wright’s level of learning had advanced by 1742, when he published a magnificently illustrated text on the solar system entitled Clavis coelestis and enriched by references to the astronomical works of Bradley, Halley, Huygens, Newton, and Whiston. The expository character of the book makes pluralist references rare, but in his short section on stars he labels them “great Globes of Fire like the Sun [which] may very possibly be the Centers of other Systems of Planets. ”⁸

The title page of Wright’s An Original Theory or New Hypothesis of the Universe (1750) not only carries the promise of “Solving . . . the General Phenomena of the Visible Creation; and Particularly the Via Lactea” but also suggests its pluralist and religious orientation by quoting Edward Young’s lines:

One Sun by Day, by Night ten Thousand shine,
And light us deep into the Deity.⁹

His “Preface” conveys the same message by a quotation from Huygens’s Cosmotheoros on the value of speculation and one from Pope’s Essay on Man in support of a plurality of worlds. Wright’s universe consisted of a “vast Infinity of Worlds . . . crouded full of Beings, all tending through their various States to a final Perfection. . . .” (p. viii) Of the nine letters that make up Wright’s volume, the first is a sustained argument for the pluralist position, which Wright claims “has ever been the concurrent Notion of the Learned of all Nations . . .” (p. 3), and which he supports by quotations from such authors as Bruno, Milton, Huygens, Newton, Derham, Pope, and Young. His second letter is largely aimed at justifying analogical reasoning, so important to pluralists. Wright states: “All then that I pretend to argue for, is a Universality of rational Creatures to people Infinity, or rather such Parts of the Creation, as from the Analogy and Nature of Things, we judge to be habitable Seats for Beings, not unlike the mortal human.” (p. 12) His third letter supplies data on the planets, marshaled on behalf of “the Thing I have chiefly in this letter attempted to demonstrate [i.e.] that the planetary Bodies in general, are meer terrestrial, if not terraqueous Bodies, such as this we live on. . . .” (p. 26) His arguments for this claim are hardly impressive, consisting of little more than evidences that the planets shine by reflected light. The case he makes in his next letter for the stars being suns is stronger, but to surround them with planets he has recourse not to the telescope but to teleology: “If the Stars were ordained merely for the Use of Us, why so much Extravagance and Ostentation in their Number, Nature, and Make?” (p. 33) He concludes the letter by quoting Joseph Addison:

When I consider that infinite Host of Stars . . . with those innumerable Sets of Planets or Worlds, which were then moving round their respective Suns; when I still enlarge the Idea, and supposed another Heaven of Suns and Worlds rising still above this which we discovered; and these still enlightened by a superior Firmament of Luminaries, which are planted at so great a Distance, that they may appear to the Inhabitants of the former as the Stars do to us; in short, whilst I pursued this Thought, I could not but reflect on that little insignificant Figure which I myself bore amongst the Immensity of God’s Works. . . .¹⁰

This passage is noteworthy because of its suggestion that higher-order universes may exist, which may, however, be so distant that they appear to us as stars. Later in his book Wright advocates a similar idea.

Wright’s fifth and sixth letters deal primarily with the stars, attention being given to estimating their distances, to speculating on their motions, and in general to raising the question of their spatial arrangement. Researches of such astronomers as Huygens, Halley, and Bradley are capably used, as are some of Wright’s own observations. Nebulae are noted, and a crude calculation leads him to suggest that nearly four million stars are to be seen in the heavens. All of this is blended with much piety and pluralism, nothing catching the spirit of this better than his quoting of Young’s lines:

Devotion! Daughter of Astronomy!
An indevout Astronomer is mad.¹¹

In a broad sense, deism more than devotion may have been the daughter of post-Newtonian astronomy, but in any case the astronomy of Wright was enriched by the principle of plenitude and by pluralist notions only loosely connected with technicalities of the science. The appeal of this astronomy was such that it stimulated the Durham astronomer to exclaim after calculating the number of visible stars: “What! a vast Idea of endless Beings must this produce and generate in our Minds; and when we consider them all as flaming Suns, Progenitors, and Primum Mobiles of a still much greater Number of peopled Worlds, what less than an Infinity can circumscribe them, less than an Eternity comprehend them, or less than Omnipotence produce and support them . . . ?” (pp. 42–3) His enthusiasm for the notion of the plenitude of God’s action is evident in his statements:

Suns crowding upon Suns, to our weak Sense, indefinitely distant from each other; and Miriads of Miriads of Mansions, like our own, peopling Infinity, all subject to the same Creator’s Will; a Universe of Worlds, all deck’d with Mountains, Lakes, and Seas, Herbs, Animals, and Rivers, Rocks, Caves, and Trees; and all the Produce of indulgent Wisdom, to chear Infinity with endless Beings, to whom his Omnipotence may give a variegated eternal Life. (p. 46)

Wright’s expository skills are evident everywhere in his book, but his originality is apparent primarily in his seventh letter, where he expounds his theories of the Milky Way. Wright shows that if we were located in an extended planar array of stars, then we would see the stars as they appear in the Via Lactea (p. 62). Thus, Wright can be credited with recognizing the optical character of the Milky Way, but he does not propose that the stars form a disk; rather, he suggests two other theories. The first is that the stars of our system are located in the wall of a giant hollow sphere. On this model, the Milky Way is explained as the appearance seen when we look in a direction parallel to a plane tangent to the sphere in the region where we are located. Wright’s other theory places the sun in a flattened ring of stars comparable in shape to the ring of Saturn. Just as a denizen of the Saturnian ring system would see a higher density of ring particles when looking in any direction parallel rather than perpendicular to the plane of the ring, so also would we on this model see ourselves encircled by a diffuse glow. Ingenious though these two theories may be, Wright (as discussed later) eventually forsook them.

Wright’s religious concerns are in the forefront in his final two letters, as he places God at the center of creation, associated with a giant globe where “the Vertues of the meritorious are at last rewarded. . . .” (p. 81) Although showing some restraint in speculating about the forms of his extraterrestrials, he suggests: “Man may be of a very inferior Class; the second, third, or fourth perhaps, and scarce allowed to be a rational Creature.” (p. 81) His pious purposes also appear when his calculation that possibly 170 million inhabited globes exist within “our finite view” spurs him to reflect: “In this great Celestial creation, the Catastrophy of a World, such as ours, or even the total Dissolution of a System of Worlds, may possibly be no more to the great Author of Nature, than the most common Accident in Life with us. . . .” (p. 76) This deistic remark, made in a book containing no mention of Christ, stimulates Wright to comment: “This Idea has something so chearful [!] in it, that I own I can never look upon the Stars without wondering why the whole World does not become Astronomers. . . .” (p. 76) Wright’s blending of the spiritual and material is evident even in some of his elaborate diagrams; for example, in his Plate XXXII (based on his first model) he represents numerous shells of stars as each centered on the “Eye of Providence” (Figure 2.1). This diagram is historically significant because it shows pictorially what his ninth letter presents verbally: his belief in a plurality not only of worlds but of universes as well. These, in a passage of particular importance, he identifies as nebulae, that is, “the many cloudy Spots, just perceivable by us, as far without our starry Regions, in which tho’visibly luminous Spaces, no one Star ...