The New Physics and Its Evolution

Author's Preface

During the last ten years so many works have accumulated in the domain of Physics, and so many new theories have been propounded, that those who follow with interest the progress of science, and even some professed scholars, absorbed as they are in their own special studies, find themselves at sea in a confusion more apparent than real.

It has therefore occurred to me that it might be useful to write a book which, while avoiding too great insistence on purely technical details, should try to make known the general results at which physicists have lately arrived, and to indicate the direction and import which should be ascribed to those speculations on the constitution of matter, and the discussions on the nature of first principles, to which it has become, so to speak, the fashion of the present day to devote oneself.

I have endeavoured throughout to rely only on the experiments in which we can place the most confidence, and, above all, to show how the ideas prevailing at the present day have been formed, by tracing their evolution, and rapidly examining the successive transformations which have brought them to their present condition.

In order to understand the text, the reader will have no need to consult any treatise on physics, for I have throughout given the necessary definitions and set forth the fundamental facts. Moreover, while strictly employing exact expressions, I have avoided the use of mathematical language. Algebra is an admirable tongue, but there are many occasions where it can only be used with much discretion.

Nothing would be easier than to point out many great omissions from this little volume; but some, at all events, are not involuntary.

Certain questions which are still too confused have been put on one side, as have a few others which form an important collection for a special study to be possibly made later. Thus, as regards electrical phenomena, the relations between electricity and optics, as also the theories of ionization, the electronic hypothesis, etc., have been treated at some length; but it has not been thought necessary to dilate upon the modes of production and utilization of the current, upon the phenomena of magnetism, or upon all the applications which belong to the domain of Electrotechnics.

L. POINCARE.

The Evolution of Physics

Revolutionary change in modern Physics only apparent: evolution not revolution the rule in Physical Theory-- Revival of metaphysical speculation and influence of Descartes: all phenomena reduced to matter and movement-- Modern physicists challenge this: physical, unlike mechanical, phenomena seldom reversible--Two schools, one considering experimental laws imperative, the other merely studying relations of magnitudes: both teach something of truth--Third or eclectic school-- Is mechanics a branch of electrical science?

Sec. 5. The Measure of Temperature: Fundamental and derived units--Ordinary unit of temperature purely arbitrary--Absolute unit mass of H at pressure of 1 m. of Hg at 0 deg. C.--Divergence of thermometric and thermodynamic scales--Helium thermometer for low, thermo-electric couple for high, temperatures--Lummer and Pringsheim's improvements in thermometry.

Sec. 6. Derived Units and Measure of Energy: Importance of erg as unit--Calorimeter usual means of determination--Photometric units.

Sec. 7. Measure of Physical Constants: Constant of gravitation--Discoveries of Cavendish, Vernon Boys, Eoetvoes, Richarz and Krigar-Menzel--Michelson's improvements on Fizeau and Foucault's experiments-- Measure of speed of light.

Principles

Sec. 1. The Principles of Physics: The Principles of Mechanics affected by recent discoveries--Is mass indestructible?--Landolt and Heydweiller's experiments --Lavoisier's law only approximately true--Curie's principle of symmetry.

Sec. 2. The Principle of the Conservation of Energy: Its evolution: Bernoulli, Lavoisier and Laplace, Young, Rumford, Davy, Sadi Carnot, and Robert Mayer--Mayer's drawbacks--Error of those who would make mechanics part of energetics--Verdet's predictions--Rankine inventor of energetics--Usefulness of Work as standard form of energy--Physicists who think matter form of energy-- Objections to this--Philosophical value of conservation doctrine.

Sec. 3. The Principle of Carnot and Clausius: Originality of Carnot's principle that fall of temperature necessary for production of work by heat-- Clausius' postulate that heat cannot pass from cold to hot body without accessory phenomena--Entropy result of this--Definition of entropy--Entropy tends to increase incessantly--A magnitude which measures evolution of system--Clausius' and Kelvin's deduction that heat end of all energy in Universe--Objection to this-- Carnot's principle not necessarily referable to mechanics --Brownian movements--Lippmann's objection to kinetic hypothesis.

Sec. 4. Thermodynamics: Historical work of Massieu, Willard Gibbs, Helmholtz, and Duhem--Willard Gibbs founder of thermodynamic statics, Van t'Hoff its reviver--The Phase Law--Raveau explains it without thermodynamics.

Sec. 5. Atomism: Connection of subject with preceding Hannequin's essay on the atomic hypothesis--Molecular physics in disfavour--Surface-tension, etc., vanishes when molecule reached--Size of molecule--Kinetic theory of gases--Willard Gibbs and Boltzmann introduce into it law of probabilities--Mean free path of gaseous molecules--Application to optics--Final division of matter.

The Various States of Matter

Sec. 1. The Statics of Fluids: Researches of Andrews, Cailletet, and others on liquid and gaseous states-- Amagat's experiments--Van der Waals' equation--Discovery of corresponding states--Amagat's superposed diagrams--Exceptions to law--Statics of mixed fluids-- Kamerlingh Onnes' researches--Critical Constants-- Characteristic equation of fluid not yet ascertainable.

Sec. 2. The Liquefaction of Gases and Low Temperatures: Linde's, Siemens', and Claude's methods of liquefying gases--Apparatus of Claude described--Dewar's experiments--Modification of electrical properties of matter by extreme cold: of magnetic and chemical-- Vitality of bacteria unaltered--Ramsay's discovery of rare gases of atmosphere--Their distribution in nature--Liquid hydrogen--Helium.

Sec. 3. Solids and Liquids: Continuity of Solid and Liquid States--Viscosity common to both--Also Rigidity-- Spring's analogies of solids and liquids--Crystallization --Lehmann's liquid crystals--Their existence doubted --Tamman's view of discontinuity between crystalline and liquid states.

Sec. 4. The Deformation of Solids: Elasticity-- Hoocke's, Bach's, and Bouasse's researches--Voigt on the elasticity of crystals--Elastic and permanent deformations--Brillouin's states of unstable equilibria--Duhem and the thermodynamic postulates-- Experimental confirmation--Guillaume's researches on nickel steel--Alloys.

Sec. 2. Osmosis: History of phenomenon--Traube and biologists establish existence of semi-permeable walls--Villard's experiments with gases--Pfeffer shows osmotic pressure proportional to concentration-- Disagreement as to cause of phenomenon.

Sec. 3. Osmosis applied to Solution: Van t'Hoff's discoveries--Analogy between dissolved body and perfect gas--Faults in analogy.

Sec. 4. Electrolytic Dissociation: Van t'Hoff's and Arrhenius' researches--Ionic hypothesis of--Fierce opposition to at first--Arrhenius' ideas now triumphant --Advantages of Arrhenius' hypothesis--"The ions which react"--Ostwald's conclusions from this--Nernst's theory of Electrolysis--Electrolysis of gases makes electronic theory probable--Faraday's two laws--Valency-- Helmholtz's consequences from Faraday's laws.

The Ether

Sec. 1. The Luminiferous Ether: First idea of Ether due to Descartes--Ether must be imponderable--Fresnel shows light vibrations to be transverse--Transverse vibrations cannot exist in fluid--Ether must be discontinuous.

Sec. 2. Radiations: Wave-lengths and their measurements--Rubens' and Lenard's researches-- Stationary waves and colour-photography--Fresnel's hypothesis opposed by Neumann--Wiener's and Cotton's experiments.

Sec. 3. The Electromagnetic Ether: Ampere's advocacy of mathematical expression--Faraday first shows influence of medium in electricity--Maxwell's proof that light-waves electromagnetic--His unintelligibility--Required confirmation of theory by Hertz.

Sec. 4. Electrical Oscillations: Hertz's experiments-- Blondlot proves electromagnetic disturbance propagated with speed of light--Discovery of ether waves intermediate between Hertzian and visible ones--Rubens' and Nichols' experiments--Hertzian and light rays contrasted--Pressure of light.

Sec. 5. The X-Rays: Roentgen's discovery--Properties of X-rays--Not homogeneous--Rutherford and M'Clung's experiments on energy corresponding to--Barkla's experiments on polarisation of--Their speed that of light--Are they merely ultra-violet?--Stokes and Wiechert's theory of independent pulsations generally preferred--J.J. Thomson's idea of their formation-- Sutherland's and Le Bon's theories--The N-Rays-- Blondlot's discovery--Experiments cannot be repeated outside France--Gutton and Mascart's confirmation-- Negative experiments prove nothing--Supposed wave-length of N-rays.

Sec. 6. The Ether and Gravitation: Descartes' and Newton's ideas on gravitation--Its speed and other extraordinary characteristics--Lesage's hypothesis--Cremieux' experiments with drops of liquids--Hypothesis of ether insufficient.