The New Physics and Its Evolution | Page 6

provoked by Röntgen's sensational experiments has a very
remote origin, it has, at least, been singularly quickened by the
favourable conditions created by the interest aroused in its astonishing
applications to radiography.
A lucky chance has thus hastened an evolution already taking place,
and theories previously outlined have received a singular development.
Without wishing to yield too much to what may be considered a whim
of fashion, we cannot, if we are to note in this book the stage actually
reached in the continuous march of physics, refrain from giving a
clearly preponderant place to the questions suggested by the study of
the new radiations. At the present time it is these questions which move
us the most; they have shown us unknown horizons, and towards the

fields recently opened to scientific activity the daily increasing crowd
of searchers rushes in rather disorderly fashion.
One of the most interesting consequences of the recent discoveries has
been to rehabilitate in the eyes of scholars, speculations relating to the
constitution of matter, and, in a more general way, metaphysical
problems. Philosophy has, of course, never been completely separated
from science; but in times past many physicists dissociated themselves
from studies which they looked upon as unreal word-squabbles, and
sometimes not unreasonably abstained from joining in discussions
which seemed to them idle and of rather puerile subtlety. They had seen
the ruin of most of the systems built up a priori by daring philosophers,
and deemed it more prudent to listen to the advice given by Kirchhoff
and "to substitute the description of facts for a sham explanation of
nature."
It should however be remarked that these physicists somewhat deceived
themselves as to the value of their caution, and that the mistrust they
manifested towards philosophical speculations did not preclude their
admitting, unknown to themselves, certain axioms which they did not
discuss, but which are, properly speaking, metaphysical conceptions.
They were unconsciously speaking a language taught them by their
predecessors, of which they made no attempt to discover the origin. It
is thus that it was readily considered evident that physics must
necessarily some day re-enter the domain of mechanics, and thence it
was postulated that everything in nature is due to movement. We,
further, accepted the principles of the classical mechanics without
discussing their legitimacy.
This state of mind was, even of late years, that of the most illustrious
physicists. It is manifested, quite sincerely and without the slightest
reserve, in all the classical works devoted to physics. Thus Verdet, an
illustrious professor who has had the greatest and most happy influence
on the intellectual formation of a whole generation of scholars, and
whose works are even at the present day very often consulted, wrote:
"The true problem of the physicist is always to reduce all phenomena to
that which seems to us the simplest and clearest, that is to say, to

movement." In his celebrated course of lectures at l'École
Polytechnique, Jamin likewise said: "Physics will one day form a
chapter of general mechanics;" and in the preface to his excellent
course of lectures on physics, M. Violle, in 1884, thus expresses
himself: "The science of nature tends towards mechanics by a
necessary evolution, the physicist being able to establish solid theories
only on the laws of movement." The same idea is again met with in the
words of Cornu in 1896: "The general tendency should be to show how
the facts observed and the phenomena measured, though first brought
together by empirical laws, end, by the impulse of successive
progressions, in coming under the general laws of rational mechanics;"
and the same physicist showed clearly that in his mind this connexion
of phenomena with mechanics had a deep and philosophical reason,
when, in the fine discourse pronounced by him at the opening
ceremony of the Congrès de Physique in 1900, he exclaimed: "The
mind of Descartes soars over modern physics, or rather, I should say,
he is their luminary. The further we penetrate into the knowledge of
natural phenomena, the clearer and the more developed becomes the
bold Cartesian conception regarding the mechanism of the universe.
There is nothing in the physical world but matter and movement."
If we adopt this conception, we are led to construct mechanical
representations of the material world, and to imagine movements in the
different parts of bodies capable of reproducing all the manifestations
of nature. The kinematic knowledge of these movements, that is to say,
the determination of the position, speed, and acceleration at a given
moment of all the parts of the system, or, on the other hand, their
dynamical study, enabling us to know what is the action of these parts
on each other, would then be sufficient to enable us to foretell all that
can occur in the domain of nature.
This was