The New Physics and Its Evolution by Lucien Poincare

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The International Scientific Series

THE NEW PHYSICS AND ITS EVOLUTION

by

LUCIEN POINCARE
Inspecteur-General de l'Instruction Publique

Being the Authorized Translation of _LA PHYSIQUE MODERNE, SON EVOLUTION_

New York
D. Appleton and Company

1909

Prefatory Note

M. Lucien Poincare is one of the distinguished family of
mathematicians which has during the last few years given a
Minister of Finance to the Republic and a President to the
Academie des Sciences. He is also one of the nineteen
Inspectors-General of Public Instruction who are charged with the
duty of visiting the different universities and _lycees_ in
France and of reporting upon the state of the studies there
pursued. Hence he is in an excellent position to appreciate at
its proper value the extraordinary change which has lately
revolutionized physical science, while his official position has
kept him aloof from the controversies aroused by the discovery of
radium and by recent speculations on the constitution of matter.

M. Poincare's object and method in writing the book are
sufficiently explained in the preface which follows; but it may
be remarked that the best of methods has its defects, and the
excessive condensation which has alone made it possible to
include the last decade's discoveries in physical science within
a compass of some 300 pages has, perhaps, made the facts here
noted assimilable with difficulty by the untrained reader. To
remedy this as far as possible, I have prefixed to the present
translation a table of contents so extended as to form a fairly
complete digest of the book, while full indexes of authors and
subjects have also been added. The few notes necessary either for
better elucidation of the terms employed, or for giving account
of discoveries made while these pages were passing through the
press, may be distinguished from the author's own by the
signature "ED."

THE EDITOR.

ROYAL INSTITUTION OF GREAT BRITAIN,
April 1907.

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.

Contents

EDITOR'S PREFATORY NOTE

AUTHOR'S PREFACE

TABLE OF CONTENTS

CHAPTER I

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?

CHAPTER II

MEASUREMENTS

Sec. 1. Metrology: Lord Kelvin's view of its necessity--
Its definition

Sec. 2. The Measure of Length: Necessity for unit--
Absolute length--History of Standard--Description of
Standard Metre--Unit of wave-lengths preferable--The
International Metre

Sec. 3. The Measure of Mass: Distinction between
mass and weight--Objections to legal kilogramme
and its precision--Possible improvement

Sec. 4. The Measure of Time: Unit of time the
second--Alternative units proposed--Improvements in
chronometry and invar

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.

CHAPTER III

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.

CHAPTER IV

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.

CHAPTER V

SOLUTIONS AND ELECTROLYTIC DISSOCIATION

Sec. 1. Solution: Kirchhoff's, Gibb's, Duhem's and Van
t'Hoff's researches.

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.

CHAPTER VI

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.

CHAPTER VII

WIRELESS TELEGRAPHY

Sec. 1. Histories of wireless telegraphy already written,
and difficulties of the subject.

Sec. 2. Two systems: that which uses the material media (earth,
air, or water), and that which employs ether only.

Sec. 3. Use of earth as return wire by Steinheil
--Morse's experiments with water of canal--Seine used as
return wire during siege of Paris--Johnson and Melhuish's
Indian experiments--Preece's telegraph over Bristol
Channel--He welcomes Marconi.

Sec. 4. Early attempts at transmission of messages through
ether--Experiments of Rathenau and others.

Sec. 5. Forerunners of ether telegraphy: Clerk Maxwell
and Hertz--Dolbear, Hughes, and Graham Bell.

Sec. 6. Telegraphy by Hertzian waves first suggested
by Threlfall--Crookes', Tesla's, Lodge's,
Rutherford's, and Popoff's contributions--Marconi
first makes it practicable.

Sec. 7. The receiver in wireless telegraphy--Varley's,
Calzecchi--Onesti's, and Branly's researches--
Explanation of coherer still obscure.

Sec. 8. Wireless telegraphy enters the commercial stage--
Defect of Marconi's system--Braun's, Armstrong's, Lee de
Forest's, and Fessenden's systems make use of earth--
Hertz and Marconi entitled to foremost place among
discoverers.

CHAPTER VIII

THE CONDUCTIVITY OF GASES AND THE IONS

Sec. 1. The Conductivity of Gases: Relations of matter to
ether cardinal problem--Conductivity of gases at first
misapprehended--Erman's forgotten researches--Giese
first notices phenomenon--Experiment with X-rays--
J.J. Thomson's interpretation--Ionized gas not obedient
to Ohm's law--Discharge of charged conductors by
ionized gas.

Sec. 2. The Condensation of water-vapour by Ions:
Vapour will not condense without nucleus--Wilson's
experiments on electrical condensation--Wilson and
Thomson's counting experiment--Twenty million ions
per c.cm. of gas--Estimate of charge borne by ion--
Speed of charges--Zeleny's and Langevin's
experiments--Negative ions 1/1000 of size of
atoms--Natural unit of electricity or electrons.

Sec. 3. How Ions are Produced: Various causes
of ionization--Moreau's experiments with alkaline
salts--Barus and Bloch on ionization by phosphorus
vapours--Ionization always result of shock.

Sec. 4. Electrons in Metals: Movement of
electrons in metals foreshadowed by Weber--Giese's,
Riecke's, Drude's, and J.J. Thomson's researches--Path
of ions in metals and conduction of heat--Theory of
Lorentz--Hesehus' explanation of electrification by
contact--Emission of electrons by charged body--
Thomson's measurement of positive ions.

CHAPTER IX

CATHODE RAYS AND RADIOACTIVE BODIES

Sec. 1. The Cathode Rays: History of discovery--Crookes'
theory--Lenard rays--Perrin's proof of negative
charge--Cathode rays give rise to X-rays--The canal
rays--Villard's researches and magneto-cathode rays--
Ionoplasty--Thomson's measurements of speed of rays--
All atoms can be dissociated.

Sec. 2. Radioactive Substances: Uranic rays of Niepce
de St Victor and Becquerel--General radioactivity of
matter--Le Bon's and Rutherford's comparison of uranic
with X rays--Pierre and Mme. Curie's discovery of
polonium and radium--Their characteristics--Debierne
discovers actinium.

Sec. 3. Radiations and Emanations of Radioactive
Bodies: Giesel's, Becquerel's, and Rutherford's
Researches--Alpha, beta, and gamma rays--Sagnac's
secondary rays--Crookes' spinthariscope--The emanation
--Ramsay and Soddy's researches upon it--Transformations
of radioactive bodies--Their order.

Sec. 4. Disaggregation of Matter and Atomic Energy:
Actual transformations of matter in radioactive bodies
--Helium or lead final product--Ultimate disappearance
of radium from earth--Energy liberated by radium:
its amount and source--Suggested models of radioactive
atoms--Generalization from radioactive phenomena
-Le Bon's theories--Ballistic hypothesis generally
admitted--Does energy come from without--Sagnac's
experiments--Elster and Geitel's _contra_.

CHAPTER X

THE ETHER AND MATTER

Sec. 1. The Relations between the Ether and Matter:
Attempts to reduce all matter to forms of ether--Emission
and absorption phenomena show reciprocal action--
Laws of radiation--Radiation of gases--Production of
spectrum--Differences between light and sound variations
show difference of media--Cauchy's, Briot's, Carvallo's
and Boussinesq's researches--Helmholtz's and
Poincare's electromagnetic theories of dispersion.

Sec. 2. The Theory of Lorentz:--Mechanics fails
to explain relations between ether and matter--Lorentz
predicts action of magnet on spectrum--Zeeman's experiment
--Later researches upon Zeeman effect--
Multiplicity of electrons--Lorentz's explanation of
thermoelectric phenomena by electrons--Maxwell's and
Lorentz's theories do not agree--Lorentz's probably more
correct--Earth's movement in relation to ether.

Sec. 3. The Mass of Electrons: Thomson's and
Max Abraham's view that inertia of charged body due
to charge--Longitudinal and transversal mass--Speed
of electrons cannot exceed that of light--Ratio of
charge to mass and its variation--Electron simple
electric charge--Phenomena produced by its acceleration.

Sec. 4. New Views on Ether and Matter:
Insufficiency of Larmor's view--Ether definable
by electric and magnetic fields--Is matter all electrons?
Atom probably positive centre surrounded by
negative electrons--Ignorance concerning positive
particles--Successive transformations of matter probable
--Gravitation still unaccounted for.

CHAPTER XI

THE FUTURE OF PHYSICS

Persistence of ambition to discover supreme principle
in physics--Supremacy of electron theory at present
time--Doubtless destined to disappear like others--
Constant progress of science predicted--Immense field
open before it.

INDEX OF NAMES

INDEX OF SUBJECTS

CHAPTER I

THE EVOLUTION OF PHYSICS

The now numerous public which tries with some success to keep abreast
of the movement in science, from seeing its mental habits every day
upset, and from occasionally witnessing unexpected discoveries that
produce a more lively sensation from their reaction on social life, is
led to suppose that we live in a really exceptional epoch, scored by
profound crises and illustrated by extraordinary discoveries, whose
singularity surpasses everything known in the past. Thus we often hear
it said that physics, in particular, has of late years undergone a
veritable revolution; that all its principles have been made new, that
all the edifices constructed by our fathers have been overthrown, and
that on the field thus cleared has sprung up the most abundant harvest
that has ever enriched the domain of science.

It is in fact true that the crop becomes richer and more fruitful,
thanks to the development of our laboratories, and that the quantity
of seekers has considerably increased in all countries, while their
quality has not diminished. We should be sustaining an absolute
paradox, and at the same time committing a crying injustice, were we
to contest the high importance of recent progress, and to seek to
diminish the glory of contemporary physicists. Yet it may be as well
not to give way to exaggerations, however pardonable, and to guard
against facile illusions. On closer examination it will be seen that
our predecessors might at several periods in history have conceived,
as legitimately as ourselves, similar sentiments of scientific pride,
and have felt that the world was about to appear to them transformed
and under an aspect until then absolutely unknown.

Let us take an example which is salient enough; for, however arbitrary
the conventional division of time may appear to a physicist's eyes, it
is natural, when instituting a comparison between two epochs, to
choose those which extend over a space of half a score of years, and
are separated from each other by the gap of a century. Let us, then,
go back a hundred years and examine what would have been the state of
mind of an erudite amateur who had read and understood the chief
publications on physical research between 1800 and 1810.

Let us suppose that this intelligent and attentive spectator witnessed
in 1800 the discovery of the galvanic battery by Volta. He might from
that moment have felt a presentiment that a prodigious transformation
was about to occur in our mode of regarding electrical phenomena.
Brought up in the ideas of Coulomb and Franklin, he might till then
have imagined that electricity had unveiled nearly all its mysteries,
when an entirely original apparatus suddenly gave birth to
applications of the highest interest, and excited the blossoming of
theories of immense philosophical extent.

In the treatises on physics published a little later, we find traces
of the astonishment produced by this sudden revelation of a new world.
"Electricity," wrote the Abbe Hauey, "enriched by the labour of so many
distinguished physicists, seemed to have reached the term when a
science has no further important steps before it, and only leaves to
those who cultivate it the hope of confirming the discoveries of their
predecessors, and of casting a brighter light on the truths revealed.
One would have thought that all researches for diversifying the
results of experiment were exhausted, and that theory itself could
only be augmented by the addition of a greater degree of precision to
the applications of principles already known. While science thus
appeared to be making for repose, the phenomena of the convulsive
movements observed by Galvani in the muscles of a frog when connected
by metal were brought to the attention and astonishment of
physicists.... Volta, in that Italy which had been the cradle of the
new knowledge, discovered the principle of its true theory in a fact
which reduces the explanation of all the phenomena in question to the
simple contact of two substances of different nature. This fact became
in his hands the germ of the admirable apparatus to which its manner
of being and its fecundity assign one of the chief places among those
with which the genius of mankind has enriched physics."

Shortly afterwards, our amateur would learn that Carlisle and
Nicholson had decomposed water by the aid of a battery; then, that
Davy, in 1803, had produced, by the help of the same battery, a quite
unexpected phenomenon, and had succeeded in preparing metals endowed
with marvellous properties, beginning with substances of an earthy
appearance which had been known for a long time, but whose real nature
had not been discovered.

In another order of ideas, surprises as prodigious would wait for our
amateur. Commencing with 1802, he might have read the admirable series
of memoirs which Young then published, and might thereby have learned
how the study of the phenomena of diffraction led to the belief that
the undulation theory, which, since the works of Newton seemed
irretrievably condemned, was, on the contrary, beginning quite a new
life. A little later--in 1808--he might have witnessed the discovery
made by Malus of polarization by reflexion, and would have been able
to note, no doubt with stupefaction, that under certain conditions a
ray of light loses the property of being reflected.

He might also have heard of one Rumford, who was then promulgating
very singular ideas on the nature of heat, who thought that the then
classical notions might be false, that caloric does not exist as a
fluid, and who, in 1804, even demonstrated that heat is created by
friction. A few years later he would learn that Charles had enunciated
a capital law on the dilatation of gases; that Pierre Prevost, in
1809, was making a study, full of original ideas, on radiant heat. In
the meantime he would not have failed to read volumes iii. and iv. of
the _Mecanique celeste_ of Laplace, published in 1804 and 1805, and he
might, no doubt, have thought that before long mathematics would
enable physical science to develop with unforeseen safety.

All these results may doubtless be compared in importance with the
present discoveries. When strange metals like potassium and sodium
were isolated by an entirely new method, the astonishment must have
been on a par with that caused in our time by the magnificent
discovery of radium. The polarization of light is a phenomenon as
undoubtedly singular as the existence of the X rays; and the upheaval
produced in natural philosophy by the theories of the disintegration
of matter and the ideas concerning electrons is probably not more
considerable than that produced in the theories of light and heat by
the works of Young and Rumford.

If we now disentangle ourselves from contingencies, it will be
understood that in reality physical science progresses by evolution
rather than by revolution. Its march is continuous. The facts which
our theories enable us to discover, subsist and are linked together
long after these theories have disappeared. Out of the materials of
former edifices overthrown, new dwellings are constantly being
reconstructed.

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