About the Work
Theory of Vortices by Henri Poincaré is a scientific treatise that examines the historical and theoretical attempts to explain the phenomenon of gravitation. The work is structured as a survey of gravitation theories, beginning with a statement of the problem and proceeding through a chronological review of proposals from the late seventeenth century through the early twentieth century. The book is presented in three major parts, each continuing the historical narrative and critical analysis of various physical models. Poincaré’s text engages with the work of numerous scientists and philosophers, including Isaac Newton, Leonhard Euler, James Clerk Maxwell’s contemporaries, and many lesser-known theorists. The book addresses fundamental questions in physics about the nature of force, the properties of the ether, and the relationship between gravitation and other physical phenomena such as light, electricity, and heat.
Context
The book emerges from a period of intense scientific debate about the nature of physical forces and the medium through which they propagate. By the time Poincaré wrote this work, the wave theory of light had gained widespread acceptance, and the concept of the ether as an all-pervading medium was central to physical theory. However, the mechanism of gravitation remained deeply problematic. Newton’s law of universal gravitation described how bodies attract each other with a force proportional to their masses and inversely proportional to the square of the distance between them, but it did not explain how this force was transmitted. The action-at-a-distance interpretation troubled many physicists, who sought a mechanical explanation involving some intervening medium.
The book situates itself within this ongoing search for a mechanical explanation of gravity. Poincaré reviews theories that attempted to explain gravitation through pressure differences in a fluid medium, through the impact of corpuscles, through vibrations of the ether, and through various other mechanisms. The text also reflects the growing tension between classical mechanics and newer discoveries in physics, particularly the relationship between gravitation and electromagnetism. The author notes that newer physics discoveries have a double bearing, offering outlines of reconstruction while simultaneously making phenomena more mysterious. The work engages with the conservation of energy principle as a constraint on any viable theory of gravitation, and it grapples with the philosophical implications of reducing matter to energy and tracing the universe to a homogeneous primal ether.
Structure of the Book
The book is organized into three parts, each continuing the historical survey of gravitation theories. The first part opens with a discussion of the unique properties of gravitation and establishes the criteria that any successful theory must satisfy. It then begins the historical review with early theories from the late seventeenth and eighteenth centuries. The second part continues this historical survey through the nineteenth century, examining theories proposed by various scientists and identifying their fundamental defects. The third part completes the survey with late nineteenth and early twentieth century speculations, then turns to a broader philosophical consideration of the ether, the nature of force, and the limits of scientific explanation. The structure is chronological, moving from Newton’s era through successive generations of theorists, with each theory presented and then subjected to critical evaluation.
Detailed Section-by-Section Summary
The first part of the book begins by acknowledging gravitation as the most incomprehensible of all forces. The author discusses how gravitation is included in the law of conservation of energy, noting that a body poised on a table’s edge possesses potential energy, which converts to kinetic energy when falling. He acknowledges that this reasoning might be questioned but sets that aside to focus on the unique properties of gravity. Gravitation is distinguished from all other forces because no body has been found opaque to it. Unlike light, which can be blocked by steel, or electricity, which can be blocked by glass, gravitation passes through all substances—metal sheets, glass, or any material—without appreciable effect. This presents what the author calls an “insoluble mystery.”
The text then turns to Newton’s own speculation on the cause of gravity. Years before his great generalization, Newton wrote a letter to Boyle in January 1678 proposing an etherial medium composed of various etherial spirits, with parts differing in subtlety. Newton supposed that ether grows finer from the air’s top to the earth’s center. A suspended body’s upper pores contain grosser ether, which endeavors to escape upward, forcing the body to descend. This early speculation by Newton himself is presented as the starting point for the long history of attempts to explain gravitation mechanically.
The first part then establishes six characteristics that any gravity theory must explain. First, gravitation has a radical, rectilinear direction that cannot be deflected. Second, its quantity is proportional to the acting mass. Third, its intensity is diminished by the square of the distance. Fourth, it acts instantaneously. Fifth, its quality is invariable and unaffected by screens. Sixth, its energy remains unchangeable over time. These six criteria serve as the standard against which subsequent theories are measured.
The historical survey begins with Arago’s Popular Astronomy, which claimed that gravitation travels fifty million times the velocity of light. Philippe Villemot, writing in 1707, proposed that pressure differences in the solar vortex explain gravitation. Bernoulli of Switzerland suggested “the central torrent” impelling bodies toward vortex centers. Lesage, in 1750, advanced the corpuscular theory with “ultra-mundane corpuscles” and mutual screening. Leonard Euler, in 1760, discussed gravity diminishing toward Earth’s center. Herapath, in 1816, published on gases, proposing one cause for heat, light, gravitation, electricity, cohesion, and aerial repulsion.
The second part continues the historical review, noting fundamental defects in an unnamed earlier theory, including the dissimilarity of stellar composition and the fallacy that pressure-differences result from temperature-differences. In 1861, Guyot published “A Sympathetic Glance at the Form and Forces of Matter.” He maintained that all properties of bodies derive from vibratory movements, with equilibrium existing under constant pressure of the ether upon matter. He argued that atomic vibration causes rarefaction of the imponderable fluid in the space between atoms, reducing its pressure there. This compels the admission that attraction is a mechanical force, consisting of ether rarefaction between molecules and bodies, and the reaction from the exterior pressure of the ether.
In 1844, Faraday issued a speculation on matter’s nature, followed in 1850 by a memoir on gravity’s relation to electricity, where he believed a connection existed but could not prove it. Later, in “The Conservation of Force,” he stated gravity is a simple attractive force varying inversely with the square of the distance. He inclined toward a cause of gravity not resident merely in particles but constantly in them and all space, preferring lines of force or an all-pervading ether over dispensing with conservation of force. The author notes that Faraday’s ideas were vague on this subject.
Seguin submitted speculations to the French Academy of Sciences in 1848 and 1858. Earlier he held a crude kinetic theory. In 1858, in Cosmos, he seemed to abandon this, holding that matter is inert and speaking of the “great principle of infinite conservation of motion.” However, he considered attraction a first cause emanating from Divine Will, though it might be a consequence of a more general law. He deemed further inquiry metaphysical and wiser to consider attraction an essential property of matter.
M. de Boucheporn read a memoir to the French Academy on July 30, 1849, explaining gravitation via external impulsion or a universal fluid. He posited that impulse intensity follows the inverse square law, ether resistance is negligible, quantity of motion equals volume times velocity squared, and pressure would make mean density three times surface density. Attraction results from a body A displacing ether, creating aspiration toward it; body B receives these waves, loses pressure on its nearer hemisphere, and the unbalanced half-pressure on the opposite hemisphere impels B toward A.
Gabriel Lamé, in 1852, attacked the problem, insisting on an all-pervading ether, contending its intervention explains heat, electricity, magnetism, attraction, cohesion, and chemical affinities. In 1858, J. J. Waterston of Edinburgh published “On the Integral of Gravitation,” contending that a force-generating faculty exists in space, directed centripetally, developing force in bodies inversely proportional to their mass. His theory is indefinite, making gravitation a function of space.
Professor James Challis, in 1859, published papers on attractive forces, “Force,” and “Gravitation.” Finding elasticity, cohesion, attraction, and repulsion insufficient, he was forced back upon the ether, though he questioned ascribing occult properties to it, conceiving another form of ether. In 1876, he returned to the problem, describing gravity as the residual effect of vibration, due to a “gravity-molecule” of a higher order, whose waves suffer no sensible retardation.
In 1861, Mr. J. S. Glennie published papers in The Philosophical Magazine, conceiving matter as elastic molecules of different orders, not an elastic ether and inelastic atoms. He postulated universal repulsion instead of attraction, but his theory fails to convince. Keller in 1863, Tait in 1864, and Saigey in 1866 offered speculations; Saigey said bodies owe gravity to pressure of the medium, though why pressure varies is unstated. In 1867, Mr. James Croll revived Faraday’s difficulties, first concluding there must be destruction and creation of force, but, finding this contradicted conservation of energy, attacked the problem from that law’s viewpoint, pointing out that if gravity is correlated to other energy forms, it faces certain difficulties.
The third part continues with Mr. Croll’s discussion. Admitting gravity can perform mechanical work convertible into other energy forms, he noted the difficulty that a body does work without losing its force of gravity, appearing to violate conservation. After discussion, he concluded gravity is probably of the nature of an impact or pressure, but unable to account for it via corpuscular impact or pressure differences in a space-filling substance, he settled on it being a “pure force.”
In 1869, P. Leray published “A New Theory of Gravitation,” postulating an ether, equal currents crossing in all directions at every point, and that these currents are retarded in bodies proportionally to thickness and mean density. That same year, Boisbaudran published “A Note on the Theory of Weight,” concluding weight is caused by longitudinal vibrations of the ether. Guthrie in 1870 published “On Approach Caused by Vibration,” making gravitation a function of temperature, contrary to observation. Sir William Crookes in 1873 offered speculations on light-wave energy but had no positive theory. Lord Kelvin in 1901, in “On Ether and Gravitational Matter Through Infinite Space,” vaguely stated that potential energy of gravitation may be the ultimate antecedent of all motion, heat, and light. Speculations by the Cambridge school, Sir Oliver Lodge, and Dr. Gustav Le Bon mostly recounted difficulties.
The text then notes that newer physics discoveries have a double bearing, offering outlines of reconstruction yet making phenomena more mysterious. Gravity has no appreciable action on electricity, yet resembles it. Dr. Le Bon, in Evolution of Forces, suggested weight is due to ether-matter relations via lines of force, possibly involving gyratory atomic movements communicated to the ether. Gravitation is not arrested by any obstacle, is small for available masses but great for large ones, with tides raising seas one meter, a thousand kilogrammes per surface-meter. Professor Vernon Boys showed gravitation defies abandoning action at a distance. Laplace estimated its propagation speed immensely higher than light. Henri Poincaré considered it of the order of light vibration. Boys imagined gravitic waves analogous to light waves due to the inverse square law.
Mr. William B. Taylor, in 1876, regarded the corpuscular theory as conclusively disproved and undulations as impossible. Professor Challis’s mathematical efforts were vitiated by unwarranted assumptions of ether qualities analogous to gases. Experiments of Guyot and Guthrie showed gaseous vibrations cannot represent gravitation’s facts. The origin of undulation remains inscrutable. “Innate tendency” is an occult quality. Matter has been resolved into energy, tracing the universe to a homogeneous primal ether at rest, receiving an initial impulse, and returning to ether. Science attributes this impulse to “forces unknown to us,” possibly a human or divine Will. Even granting a prime mover, the question remains how the impulse is converted into vibration. What resisting power deflects motion from rectilinear direction? Is the universe a perpetual motion machine? There is no reason to believe the ether is a source of energy; it is never self-luminous.
Dr. A. Rabagliati, in his introduction to the author’s Vitality, Fasting and Nutrition, criticized scientists for defining ether as a solid without density or weight, or with density and no weight, calling such definitions purely metaphysical despite being derived from experiments, and suggesting such a body is “nothing.” The passage concludes that ether and gravitation remain unsolved, closely related mysteries, perhaps awaiting a “metaphysical Newton.”
Main Arguments
The central argument of the book is that gravitation presents a unique and unresolved problem in physics. The author establishes early that gravitation differs fundamentally from all other known forces because no substance has been found that can screen or block it. This property, combined with its instantaneous action and its proportionality to mass, makes it resistant to the mechanical explanations that had been proposed for other phenomena.
The book argues that the historical attempts to explain gravitation through mechanical means have all failed. The corpuscular theory, which posited ultra-mundane corpuscles impacting bodies, was regarded by many as conclusively disproved. The undulatory or vibrational theories, which sought to explain gravity through ether vibrations, were shown by experiments to be inadequate, as gaseous vibrations cannot represent gravitation’s facts. Theories based on pressure differences in a fluid medium failed to explain why pressure varies in the required manner.
A persistent difficulty identified throughout the book is the conservation of energy. If gravity can perform mechanical work convertible into other energy forms, then a body doing work should lose some of its gravitational force. But observation shows that a body does not lose its gravity by falling or by doing work. This apparent violation of conservation of energy defeated several theories and led some theorists to conclude that gravity must be a “pure force” not amenable to mechanical explanation.
The book also argues that the concept of the ether, which was central to nineteenth-century physics, is deeply problematic. The ether is defined in contradictory ways, as a solid without density or weight, or with density and no weight. Such definitions are characterized as purely metaphysical despite being derived from experiments. The author suggests that such a body is “nothing.” The ether is never self-luminous, and there is no reason to believe it is a source of energy.
The author concludes that the origin of undulation remains inscrutable and that “innate tendency” is an occult quality. Matter has been resolved into energy, tracing the universe to a homogeneous primal ether at rest, receiving an initial impulse, and returning to ether. Science attributes this impulse to “forces unknown to us,” possibly a human or divine Will. But even granting a prime mover, the question remains how the impulse is converted into vibration and what resisting power deflects motion from rectilinear direction.
Key Concepts
The book engages with several key concepts in the history of physics. The conservation of energy is a central principle that constrains all theories of gravitation. The author discusses how potential energy converts to kinetic energy and how any viable theory must account for the fact that a body does work without losing its gravitational force.
The concept of the ether is examined extensively. Various theorists proposed different forms of ether, from Newton’s etherial medium composed of various spirits with parts differing in subtlety, to Lamé’s all-pervading ether that explains heat, electricity, magnetism, attraction, cohesion, and chemical affinities, to Challis’s “gravity-molecule” of a higher order. The ether is consistently invoked as the medium through which gravitational effects are transmitted, but its properties remain contradictory and mysterious.
The inverse square law is a fundamental criterion that any theory must satisfy. The book lists this as one of the six characteristics that any gravity theory must explain, and it appears throughout the historical survey as a constraint on proposed mechanisms.
Action at a distance is another key concept. The book notes that Professor Vernon Boys showed gravitation defies abandoning action at a distance, and Laplace estimated its propagation speed immensely higher than light. The instantaneous action of gravity is listed as one of the six characteristics that must be explained.
The corpuscular theory of gravitation, associated with Lesage, proposed that ultra-mundane corpuscles impact bodies and produce attraction through mutual screening. This theory is discussed and ultimately regarded as conclusively disproved by some later theorists.
The relationship between gravitation and other forces is a recurring theme. The book notes that gravity has no appreciable action on electricity, yet resembles it. Various theorists proposed unified explanations for heat, light, gravitation, electricity, cohesion, and other phenomena, but these attempts are presented as unsuccessful.
Themes
A prominent theme in the book is the limits of mechanical explanation. The author traces the repeated failure of attempts to explain gravitation through mechanical means, whether through corpuscles, pressure differences, or vibrations. Each theory is presented and then shown to have fundamental defects. The book suggests that gravitation may ultimately resist mechanical explanation, pointing toward a “metaphysical Newton” who might resolve the mystery.
Another theme is the relationship between science and metaphysics. The book notes that several theorists, including Seguin, considered attraction a first cause emanating from Divine Will, and deemed further inquiry metaphysical. The author also discusses how science attributes the initial impulse of the universe to “forces unknown to us,” possibly a human or divine Will. The criticism of ether definitions as purely metaphysical despite being derived from experiments reinforces this theme.
The unity of physical forces is a recurring theme. Many theorists proposed that a single mechanism explains heat, light, gravitation, electricity, magnetism, cohesion, and chemical affinities. Herapath proposed one cause for all these phenomena, and Lamé contended that the ether’s intervention explains them all. These unified theories are presented as ambitious but ultimately unsuccessful.
The mystery of the universe’s origin and operation is another theme. The book raises questions about how an initial impulse is converted into vibration, what resisting power deflects motion from rectilinear direction, and whether the universe is a perpetual motion machine. These questions point beyond physics to deeper philosophical concerns.
The theme of the ether as a problematic concept runs throughout the book. The ether is invoked by nearly every theorist but defined in contradictory ways. The criticism that defining ether as a solid without density or weight makes it “nothing” highlights the conceptual difficulties of the ether hypothesis.
The Author’s Conclusions
The book concludes that ether and gravitation remain unsolved, closely related mysteries. After surveying the entire history of attempts to explain gravitation mechanically, the author finds that no theory has succeeded in accounting for all the observed phenomena. The corpuscular theory has been disproved, undulatory theories are impossible, and pressure-difference theories fail to explain why pressure varies in the required manner.
The author suggests that the origin of undulation remains inscrutable and that “innate tendency” is an occult quality. Matter has been resolved into energy, tracing the universe to a homogeneous primal ether at rest, receiving an initial impulse, and returning to ether. Science attributes this impulse to “forces unknown to us,” possibly a human or divine Will. But even granting a prime mover, the question remains how the impulse is converted into vibration and what resisting power deflects motion from rectilinear direction.
The book questions whether the universe is a perpetual motion machine and finds no reason to believe the ether is a source of energy, noting that it is never self-luminous. The author engages with the criticism that ether definitions are purely metaphysical and that such a body is “nothing.” The conclusion points toward the possibility that a “metaphysical Newton” might be needed to resolve the mystery of gravitation, suggesting that the problem may require a conceptual breakthrough beyond the mechanical frameworks that had been attempted.
Significance
The book is significant as a comprehensive historical survey of theories of gravitation, documenting the attempts of numerous scientists and philosophers to explain this fundamental force. It preserves and critically evaluates theories that might otherwise be forgotten, from Newton’s early speculation about etherial spirits to the speculations of late nineteenth and early twentieth century physicists.
The work is also significant for its identification of the criteria that any theory of gravitation must satisfy. By listing the six characteristics of gravitation, the author provides a framework for evaluating proposed explanations and demonstrates why so many theories have failed.
The book captures a transitional moment in the history of physics, when the ether hypothesis was being questioned and newer discoveries in electricity and magnetism were complicating the picture. The author notes that newer physics discoveries have a double bearing, offering outlines of reconstruction yet making phenomena more mysterious. This observation anticipates the conceptual revolution that would come with relativity theory, which would fundamentally change the understanding of gravitation.
The book’s engagement with the philosophical implications of physics, including the nature of force, the limits of mechanical explanation, and the relationship between science and metaphysics, gives it enduring value. The questions it raises about the origin of the universe’s motion, the conversion of impulse into vibration, and the possibility of a perpetual motion machine remain relevant to contemporary physics and cosmology.
The work also documents the persistent problem of the ether, a concept that dominated nineteenth-century physics and was ultimately abandoned. The criticism of ether definitions as contradictory and metaphysical foreshadows the rejection of the ether concept in twentieth-century physics. The book thus serves as both a historical record and a critical analysis of a central problem in physical theory.
