Three Scientific Revolutions: How They Transformed Our Conceptions of Reality
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But as his controversial discoveries continued and his disagreements with both the Aristotelians and the ecclesiastical authorities over the interpretation of natural phenomena increased, so did the hostility. For example, when the Aristotelians explained the amount of support water gave to floating objects as due to their shapes, in contrast to Archimedes’ principle of specific gravity, Galileo published a reply entitled (in translation), Discourse on Bodies on or in Water, supporting Archimedes. In 1612 he entered into a dispute with a Jesuit mathematician named Christopher Scheiner (who wrote under the pseudonym Apelles) over the nature of the recently cited dark spots circling the sun. Scheiner argued that they were tiny stars similar to the four stars circling Jupiter, while Galileo, based on their formation, maintained they were like clouds circling the earth. Again challenging the distinction between the celestial and terrestrial worlds, this proved quite contentious (today sun spots are explained as magnetic fields that emit massive bursts of energy that appear as dark areas on its surface).
Then in a famous “Letter to Castelli” written on December 21, 1613, he openly expressed his disdain for those ecclesiastical authorities who rejected his discoveries because they conflicted with traditional biblical beliefs. Conceding that regarding questions concerning salvation and faith there was no higher authority than Holy Scripture, he adds that
I should think it would be prudent if no one were permitted to oblige Scripture . . . to sustain as true some physical conclusions of which sense and demonstration and necessary reasons may show the contrary. . . . I do not think it is necessary to believe that the same God who has given us our senses, reason, and intelligence wished us to abandon their use, giving us by some other means the information that we could gain through them. . . . (p. 226)
Though a rationally sound objection, the clergy considered it not only as a rejection of the heavenly nature of the universe, but also as contesting the authority of scripture and the Church itself, a crucial turning point in his relation with the Church. The following year on December 21 a fiery young Dominican named Tommaso Caccini “denounced from the pulpit of Santa Maria Novella the Galileists, and all mathematicians along with them, as practitioners of diabolical arts and enemies of true religion” (p. 238). About the same time, the cardinals of the Inquisition started examining Galileo’s writings to see if they contained heretical material. Hoping to defend himself, he journeyed to Rome at the end of 1615 but with little success.
A commission of theologians was formed in February of 1616 that decided against the motions of the earth and the centrality of the sun, instructing Cardinal Bellarmine to inform Galileo of its decision, after which he was told to abandon those suppositions. Bellarmine met with Galileo on February 24 before a notary and a witnesses, leaving a notarized but unsigned record stating, in the words of Drake, that he “told Galileo of the official findings against the motion of the earth and stability of the sun,” while the commissary of the Inquisition “admonished Galileo in the name of the pope that he must not hold, defend, or teach in any way, orally or in writing, the said propositions on pain of imprisonment. Galileo Agreed” (p. 253). This is crucial in connection with his final trial and conviction in that Galileo did agree “not to hold, defend, or teach in any way, orally or in writing the motion of the earth and stability of the sun.” An edict was then dispensed proscribing all books purporting to reconcile Christianity with heliocentrism, though none of Galileo’s were included. Finally, in 1992, the Catholic Church acknowledged that Galileo was correct and it was wrong.
Then in the fall of 1618 the citing of three comets again evoked the question of the reality of the distinction between the celestial and terrestrial worlds depending on the location of the comets, the distinction that previously had been raised by Galileo’s lunar observations. Orazio Grassi (writing under the pseudonym of Lothario Sarsi of Siguenza), a well-known astronomer and critic of Galileo’s observations, argued that because there was no evidence of parallax (again no change in the position of the stars as one moved) nor of enlargement, they must be in the translunar world and thus should have caused no opposition on the part of Galileo. But because Grassi’s (or Sarsi’s) argument embraced Tycho Brahe’s modified geocentric view that the sun, encircled by the planets, revolved around the central Earth, Galileo dismissed it because of its asymmetry. In his rebuttal he not only ridiculed Tycho’s system, he also mocked the distinction between the two worlds so cherished by the Aristotelians and the Christians, declaring “[n]ever having given any place in my thoughts to the vain distinction (or rather contradiction) between the [terrestrial] elements and the heavens . . .”25 (brackets added).
His second reply to Grassi in the Il Saggiatore (or The Assayer) written in 1623, is extremely important because it contains a further crucial revision of the traditional worldview. Drawing a sharp distinction between the ordinary sensory world and the independent micro-mechanistic world whose particles, being devoid of sensory qualities, were defined in terms of measurable physical properties, such as mass, motion, shape, and size, this would greatly contribute to the transition to Newton’s corpuscular-mechanistic cosmology whose reality and exact nature posed the central problem of science and philosophy during the following three centuries.
I know of no previous or even later analysis to match Galileo’s meticulous justification of the distinction, in section xlviii of Il Saggiatore, by analyzing the nature and origin of sensory qualities. While we normally distinguish pains and tickling sensations as being obviously subjective, we think of colors, sound, tastes, hardness, and heat as residing in the objects surrounding us independently of their being perceived. But having learned more about how dependent these latter sensory experiences are on our sense organs, nervous system, and the brain, Galileo argued that they too should be considered as subjective. But as previously indicated, how neurophysiological processes in the brain create the perceptual world as we experience it is still one of the greatest (if not the greatest) mysteries confronting us.
Both scientists and philosophers talk as if the ordinary perceptual world, being dependent on our brains, exists in our brains.But does that really make much sense, any more than saying it exists in the pineal gland, as René Descartes held? Certainly the Apple® computer I am using in composing this does not simply exist in my brain, nor does the car I get into and drive, the apartment I live in, the wife I live with, or the body I have. If my body exists in my brain because it is perceived, then since my brain is part of my body it, too, must exist in the brain, which does not make sense. Does the pistol someone uses to commit suicide exist in their brain? Did the nuclear disasters in Hiroshima and Nagasaki merely exist in people’s brains?
Does it not make more sense to acknowledge that the world in which we exist, which includes colors, sounds, tastes, etc., is objectively real within the conditions in which we experience it, which seems to be true of the various dimensional contents of the universe as a whole? This does not preclude the necessity of revising our conception of this world, as in the Copernican revolution, but of recognizing the conditional status of all that is experienced and exists. This is the thesis I will be defending: that the universe consists of a seemingly endless series of objective contexts or conditions that is the destiny of scientists to explore and understand.
Galileo’s justification of the distinction between the independent external causes of these sensory experiences and their modifications or additions due to their interaction with the human organism is clearly described. Though he discusses each sensory quality individually, I think the clearest general statement of his position is the following:
I do not believe that for exciting in us tastes, odors, and sounds, there are required in external bodies anything but sizes, shapes, numbers, and slow or fast movements; and I think that if ears, tongues, and noses were taken away, shapes and numbers and motions would remain but not odors or tastes or sounds. These, I believe, are nothing but names, apart from the living animal—just as tickling
and titillation are nothing but names when armpits and the skin around the nose are absent.26
Since nothing was then known about the molecular, atomic, or subatomic structure of matter, he assigned the sizes, shapes, numbers, and movements to the “minute particles” or “corpuscles” that he believed constituted material objects. As examples, he says sounds “are created and are heard by us when . . . a rapid tremor of the air, ruffled into very minute waves, moves certain cartilages of a tympanum within our ear . . . that vision, the sense which is eminent above all others, is related to light . . . and that a multitude of minute particles having certain shapes and moving with certain velocities” striking the senses produce “the sensation which we call heat” (pp. 311–12).
These independent physical properties, later named “primary qualities,” versus the subjective “sensory qualities,” by John Locke in his Essay Concerning Human Understanding, became accepted scientific distinctions constituting Newton’s corpuscular-mechanistic worldview. But the attempt to discover the actual nature of these particles and corpuscles and their properties, along with how they produce the sensory effects they do has been a major challenge of scientific research ever since. Thus it is fair to say that Galileo helped set the agenda of the physicists, chemists, physiologists, and microbiologists of modern science, along with the epistemological problems of Descartes and Locke, as well as most twentiethcentury philosophers.
Galileo himself was aware of his enormous originality and influence, immodestly listing his various books and their contributions in a letter to Belisario Vinta, a close scientific friend, seeking a better position. As again quoted by Drake, they consist of
two books on the system and constitution of the universe—an immense conception full of philosophy, astronomy, and geometry; three books on local motion, an entirely new science, no one else, ancient or modern, having discovered some of the very many admirable properties that I demonstrate to exist in natural and forced motions, whence I may reasonably call this a new science discovered by me from its first principles: three books on mechanics . . . and though others have written on this same material, what has been written to date is not one-quarter of what I write, either in bulk or otherwise. (p. 160)
Though not mentioned, he also asserted the valid principles of the uniformity of nature and the conservation of momentum.
This brings us to his most famous book, the English title of which is Dialogue Concerning the Two Chief World Systems—Ptolemaic & Copernican, whose renown is based on two factors: (1) it’s astute arguments written in colloquial Italian and presented in dialogue form essentially showing the superiority of the heliocentric cosmology that made it the greatest scientific dialogue ever written; and (2) the scandalous conviction of Galileo of heresy by the Catholic Inquisition based on his alleged duplicity in writing the book, that has been called “the disgrace of the century.”
Having described in another work the contents of his book and the ensuing trial and conviction in greater detail, I shall focus mainly on the arguments he introduced to refute the objections to the movements of the earth. Taking place over four days, the dialogue is between three interlocutors, one of whom is Salviati, a Florentine aristocratic friend who has the role of an academician representing Galileo; another is Sagredo, a Venetian nobleman who acts as the moderator; and the third named Simplicius after a sixth-century scholastic who defends Aristotelianism and the connotations of whose name perhaps added to his selection as the opponent.
The first day’s dispute concerns the distinction between the sublunar and translunar worlds. Salviati argues that while the distinction may have been warranted in Aristotle’s day, new telescopic evidence such as Galileo’s observations showing the moon’s surface to be similar to the earth’s; the discovery of four stars circulating Jupiter; the rectilinear trajectory of meteors; the detection of sun spots, novas, and new stars; along with Kepler’s discovery of the elliptical shape of Mars’s orbit is strong evidence that the distinction is no longer valid.
The second day begins with Simplicius defending, as was commonly believed at the time, the complete authority of Aristotle’s writings: “There is no doubt that whoever has this skill will be able to draw from his books demonstrations of all that can be known; for every single thing is in them.”27 But previously Galileo had Sagredo express his firm belief in the limits, at the time, of knowledge: “there is not a single effect in nature, even the least that exists, such that the most ingenious theorists can arrive at a complete understanding of it” (p. 101).
But turning to the main dialogue of the day, as Galileo had argued, rather than accept the usual explanation that the apparent rising and setting of the sun was caused by the entire universe revolving from east to west in a single day, Salviati points out that the same appearance could be explained more simply and harmoniously by attributing a diurnal rotation to the much smaller earth from west to east. Not only was it incongruous to have the sphere of the fixed stars, at the farthest distance from the earth, complete their revolution in one day while the closer planets completed theirs in a much longer time, the westward revolution attributed to the fixed stars was contrary to the eastward revolution of the planets. Thus Salviati concludes that “by making the earth itself move, the contrariety of motions is removed, and the single motion from west to east accommodates all the observations and satisfies them all completely” (p. 117).
Salviati then addresses the counter argument that despite its simplicity, attributing the diurnal rotation to the earth cannot be true because then one would see clouds, birds, or other aerial objects displaced to the west as the earth revolved eastward. The example of dropping an object from the masthead of a ship is introduced, declaring that during the fall the object would descend at an angle inclined further from the masthead rather than parallel to it, even affirming that the experiment had been performed and shown the described result.
Salviati replies that this could not be true because when he had performed the experiment a solid object dropped from the masthead of a uniformly moving ship fell parallel to the masthead. He reinforces his argument by pointing out that in the cabin of a uniformly moving ship (as in an airplane today) everything happens as if the ship were stationary; objects dropped or thrown have the same trajectory as if the cabin were at rest. Since the objects partake of two motions, that of the uniformly moving container and the downward fall, the former cancels out leaving only the falling object as visible. Thus an object dropped from a tower falls parallel to the tower despite the rotation of the earth during the fall. As Salviati concludes:
With respect to the earth, the tower, and ourselves, all of which keep moving with the diurnal motion along with the stone, the diurnal movement is as if it did not exist; it remains insensible, imperceptible, and without any effect whatever. All that remains observable is the motion which we lack, and that is the grazing drop to the base of the tower. (p. 171)
While the second day’s dialogue addressed the opposition to the earth’s rotary motion, the third day deals with Simplicius’ dissent to the earth’s annual revolution around the sun based on the ordinary experience of seeing the sun circle the earth and the fact that as a terrestrial heavy body the earth naturally should be in the center of the cosmos. Salviati first responds by pointing out that Simplicius’ argument presupposes that the cosmos is a finite sphere, yet it has not been proven whether that is its shape or whether it is “infinite and unbounded.” But as indicated previously, because Giordano Bruno was burned at the stake by order of the Holy Office partially for advocating an infinite universe, this argument is not pursued further.
Instead, Salviati offers Kepler’s second two astronomical laws based on the sun’s gravitational force as evidence of its central position and Galileo’s telescopic evidence of Mars’s radical deviation from a circular orbit, as seen from the earth, as refuting the Aristotelian view that all the planetary orbits are circular. As Salviati states regarding several orbital trajectories:
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p; This approach and recession is of such moment that Mars when close looks sixty times as large as when it is most distant. Next, it is certain that Venus and Mercury must revolve around the sun, because of their never moving far away from it, and because of their being seen now beyond it and now on this side of it, as Venus’s changes of shape conclusively prove. (p. 322)
He next cites Galileo’s telescopic observations showing that the obits of Mercury and Venus are below Earth’s while those of Mars, Jupiter, and Saturn are above it. When Simplicius refers to the anomaly in the Copernican system of only the Moon revolving around Earth while all the other planets revolve around the Sun, Salviati replies that this anomaly has been mitigated by the discovery of the four satellites circling Jupiter. Sagredo then brings up two other objections, the observed retrograde, loop-like motion of the five planets as seen from the earth and the absence of parallax when observing the stars. As for the first, Sagredo refers to a diagram by Galileo showing that “these stoppings, retrograde motions, and advances,” are illusions produced by the annual revolution of the earth around the sun (p. 342).
Regarding the absence of parallax or displacement when viewing the stars from the different positions on the earth as it revolves around the sun, this can be explained by attributing a much greater distance to the stars than normally believed. The Aristotelian response was that for a star to be seen from such a great distance “it would have to be so immense in bulk as to exceed the earth’s orbit—a thing which is, as they say, entirely unbelievable” (p. 372). Lacking any evidential rebuttal, Salviati gives the sensible answer that without knowing how the stars transmit their light from such a great distance it is impossible to draw a definite conclusion.