[Paleopsych] SW: Einstein on Physics and Progress

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History of Science: Einstein on Physics and Progress

    The following points are made by Albert Einstein (Physics Today 2005
    1) If philosophy is interpreted as a quest for the most general and
    comprehensive knowledge, it obviously becomes the mother of all
    scientific inquiry. But it is just as true that the various branches
    of science have, in their turn, exercised a strong influence on the
    scientists concerned and, beyond that, have affected the philosophical
    thinking of each generation. Let us glance, from this point of view,
    at the development of physics and its influence on the conceptual
    framework of the other natural sciences during the last hundred years.
    2) Since the Renaissance, physics has endeavored to find the general
    laws governing the behavior of material objects in space and time. To
    consider the existence of these objects as a problem was left to
    philosophy. To the scientist, the celestial bodies, the objects on
    Earth, and their chemical peculiarities, simply existed as real
    objects in space and time, and his task consisted solely in
    abstracting these laws from experience by way of hypothetical
    3) The laws were supposed to hold without exceptions. A law was
    considered invalidated if, in a single case, any one of its properly
    deduced conclusions was disproved by experience. In addition, the laws
    of the external world were also considered to be complete, in the
    following sense: If the state of the objects is completely given at a
    certain time, then their state at any other time is completely
    determined by the laws of nature. This is just what we mean when we
    speak of "causality." Such was approximately the framework of the
    physical thinking a hundred years ago.
    4) As a matter of fact, the framework was even more restrictive than
    it has been sketched. The objects of the external world were
    considered to consist of immutable mass points, acting upon each other
    with well-defined forces eternally attached to them and, under the
    influence of these forces, carrying out incessant motions to which, in
    the last analysis, all observable processes could be reduced.
    5) From a philosophical point of view, the conception of the world, as
    it appears to those physicists, is closely related to naive realism,
    since they looked upon the objects in space as directly given by our
    sense perceptions. The introduction of immutable mass points, however,
    represented a step in the direction of a more sophisticated realism.
    For it was obvious from the beginning that the introduction of these
    atomistic elements was not induced by direct observation.
    6) With the Faraday-Maxwell theory of the electromagnetic field, a
    further refinement of the realistic conception was unavoidable. It
    became necessary to ascribe the same irreducible reality to the
    electromagnetic field, continually distributed in space, as formerly
    to ponderable matter. But sense experiences certainly do not lead
    inevitably to the field concept. There was even a trend to represent
    physical reality entirely by the continuous field, without introducing
    mass points as independent entities into the theory.
    7) Summing up, we may characterize the framework of physical thinking
    up to a quarter of a century ago as follows: There exists a physical
    reality independent of substantiation and perception. It can be
    completely comprehended by a theoretical construction which describes
    phenomena in space and time -- a construction whose justification,
    however, lies in its empirical confirmation. The laws of nature are
    mathematical laws connecting the mathematically describable elements
    of this construction. They imply complete reality in the sense
    mentioned before.
    8) Under the pressure of overwhelming experimental evidence concerning
    atomistic phenomena, almost all of today's physicists are now
    convinced that this conceptual framework --notwithstanding its
    apparently wide scope -- cannot be retained. What appears untenable to
    physicists of our times is not only the requirement of complete
    causality but also the postulate of a reality which is independent of
    any measurement or observation.
    Physics Today http://www.physicstoday.org
    Related Material:
    The following points are made by Giorgio Parisi (Nature 2005 433:221):
    1) On 30 April 1905, Einstein completed his doctoral thesis on osmotic
    pressure, in which he developed a statistical theory of liquid
    behavior based on the existence of molecules. This work, together with
    his subsequent paper on "brownian motion", constitutes one of the most
    important, but often overlooked, contributions that Einstein made to
    2) In the closing decades of the 19th century, theoretical physics was
    in a state of turmoil. The big outstanding questions of that time have
    been much discussed. Such questions culminated in relativity and
    quantum mechanics -- theoretical developments in which Einstein's key
    role is being justly celebrated this year. But it should not be
    forgotten that the seemingly innocuous observations of Robert Brown
    (1773-1858) of the irregular motions of a suspension of pollen grains
    in water -- now known as brownian motion -- also heralded a revolution
    in physical thought.
    3) Although the concepts of atoms and molecules are now universally
    accepted, this was not the case at the turn of the 20th century. The
    statistical interpretation by Ludwig Boltzmann ((1844-1906) of the
    laws of thermodynamics -- a body of work deeply rooted in the ensemble
    dynamical motion of material atoms -- had many adherents. But there
    were also many heavyweight dissenters (for a time including Max Planck
    (1858-1947)), who did not accept that thermodynamics had its origins
    in the reversible motion of invisible hypothetical particles. And many
    distinguished physicists of the time (among them Wilhelm Roentgen
    (1845-1923)) suspected that brownian motion indicated a clear failure
    of Boltzmann's formulation of the second law of thermodynamics.
    4) It was in this context that Einstein's explanation for brownian
    motion made an initial impression. In particular, Einstein showed that
    the irregular motion of the suspended particles could be understood as
    arising from the random thermal agitation of the molecules in the
    surrounding liquid: these smaller entities act both as the driving
    force for the brownian fluctuations (through the impact of the liquid
    molecules on the larger particles), and as a means of damping these
    motions (through the viscosity experienced by the larger particles).
    This connection between displacement and the viscosity can be
    quantitatively expressed in one dimension as a relationship between
    displacement, viscosity, the universal gas constant, Avogadro's
    number, the Boltzmann constant, the temperature, and the radius of the
    suspended particles. This finding went beyond simply confirming the
    existence of atoms and molecules, and provided a new way of
    determining Avogadro's number. As Einstein himself remarked, the
    consequence of this relation is that one can see, directly through a
    microscope, a fraction of the thermal energy manifest as mechanical
    energy. By proving that a statistical mechanics description could
    explain quantitatively brownian motion, all doubts concerning
    Boltzmann's statistical interpretation of the thermodynamic laws
    suddenly faded.(1-3)
    References (abridged):
    1. Pais, A. Subtle is the Lord... (Oxford Univ. Press, 1982)
    2. Kuhn, T. S. Black Body Theory and the Quantum Discontinuity
    1894-1911 (Oxford Univ. Press, 1978)
    3. Mezard, M., Parisi, G. & Virasoro, M. A. Spin Glass Theory and
    Beyond (World Scientific, Singapore, 1987)
    Nature http://www.nature.com/nature
    Related Material:
    The following points are made by Daniel Kleppner (Physics Today 2005
    1) Albert Einstein had a genius for extracting revolutionary theory
    from simple considerations: From the postulate of a universal velocity
    he created special relativity; from the equivalence principle he
    created general relativity; from elementary arguments based on
    statistics he discovered energy quanta. His 1905 paper on quantization
    of the radiation field (often referred to, inaccurately, as the
    photoelectric-effect paper) was built on simple statistical arguments,
    and in subsequent years he returned repeatedly to questions centered
    on statistics and thermal fluctuations.
    2) In 1909, Einstein showed that statistical fluctuations in thermal
    radiation fields display both particle-like and wave-like behavior.
    His was the first demonstration of what would later become the
    principle of complementarity. In 1916, when he turned to the interplay
    of matter and radiation to create a quantum theory of radiation, he
    once again based his arguments on statistics and fluctuations.
    3) Einstein's theory of radiation is a treasure trove of physics, for
    in it one can discern the seeds of quantum electrodynamics and quantum
    optics, the invention of masers and lasers, and later developments
    such as atom-cooling, Bose-Einstein condensation, and cavity quantum
    electrodynamics. Our understanding of the Cosmos comes almost entirely
    from images brought to us by radiation across the electromagnetic
    spectrum. Einstein's theory of radiation describes the fundamental
    processes by which those images are created.
    4) Einstein's 1905 paper on quantization endowed Max Planck's quantum
    hypothesis with physical reality. The oscillators for which Planck
    proposed energy quantization were fictitious, and his theory for
    blackbody radiation lacked obvious physical consequences. But the
    radiation field for which Einstein proposed energy quantization was
    real, and his theory had immediate physical consequences. His paper,
    published in March 1905, was the first of his wonder year. In rapid
    succession he published papers on Brownian motion, special relativity,
    and his quantum theory of the specific heat of solids.
    5) In 1907, his interest shifted to gravity, and he took the first
    tentative steps toward the theory of general relativity. His struggle
    with gravitational theory became all-consuming until November 1915,
    when he finally obtained satisfactory gravitational field equations.
    During those years of struggle, however, Einstein apparently had a
    simmering discontent with his understanding of thermal radiation, for
    in July 1916, he turned to the problem of how matter and radiation can
    achieve thermal equilibrium. One could argue that 1916 was too soon to
    deal with that problem because there were serious conceptual obstacles
    to the creation of a consistent theory. Einstein, in his Olympian
    fashion, simply ignored them. In the next eight months, he wrote three
    papers on the subject, publishing the third, and best known, in
    References (abridged):
    1. A. Einstein, Phys. Z. 18, 121 (1917); English translation On the
    Quantum Theory of Radiation, by D. ter Haar, The Old Quantum Theory,
    Pergamon Press, New York (1967), p. 167
    2. A. Pais, Rev. Mod. Phys. 49, 925 (1977)
    Physics Today http://www.physicstoday.org

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