[Paleopsych] Science Week: Einstein, Lorentz, and the Ether

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History of Science: Einstein, Lorentz, and the Ether

    The following points are made by John Stachel (Nature 2005 433:215):
    1) During the 19th century, the mechanistic world-view -- based on
    Isaac Newton's formulation in the Principia (1687) of the kinematics
    and dynamics of corpuscles of matter, and crowned by his stunningly
    successful theory of gravitation -- was challenged first by the
    optics, then by the electrodynamics of moving bodies. By the mid 1800s
    Newton's corpuscular theory of light was no longer tenable. To explain
    Snell's law of refraction, this theory assumed that light corpuscles
    speed up on encountering a medium of higher refractive index. But in
    1849, Leon Foucault (1819-1868) and Hippolyte Fizeau (1819-1896)
    showed that, in fact, light slowed down, as predicted by the rival
    wave theory espoused by Newton's contemporary Christiaan Huygens
    (1629-1695). The problem now was to fit the wave theory of light into
    the newtonian picture of the world.
    2) Indeed, the ether -- the medium through which light waves were
    assumed to propagate in the absence of ordinary, ponderable matter --
    seemed to provide a physical embodiment of Newton's absolute space.
    But elucidating the relation between ether and ponderable matter
    presented grave problems: did moving matter drag the ether with it --
    either totally or partially -- or did the ether remain immobile? It
    proved impossible to reconcile the consequences of any of these
    hypotheses with all the experimental results on the optics of moving
    bodies. By the last third of the nineteenth century, many physicists
    were acutely aware of this problem.
    3) By 1865, James Clerk Maxwell (1831-1879) had demonstrated that
    light could be interpreted as wave-like oscillations of the electric
    and magnetic fields, obeying what we now call the Maxwell equations
    for these fields. It was realized that the optical problems were only
    a special case of similar problems in reconciling the electrodynamics
    of moving bodies with newtonian kinematics and dynamics. Towards the
    end of the century, however, Hendrik Antoon Lorentz (1853-1928) seemed
    to overcome all these problems through his interpretation of Maxwell's
    equations. Lorentz assumed that the electromagnetic ether is entirely
    immobile, in which case there would be no dragging of the ether.
    4) Although in newtonian mechanics it is impossible to distinguish any
    preferred inertial frame (this result is often referred to as the
    galileian principle of relativity), at first the situation seemed
    different for electrodynamics and optics. The rest frame of the ether
    provided a preferred inertial frame, and motion through it should have
    been detectable. Yet all attempts to detect the translational motion
    of the Earth through the ether by means of optical, electrical or
    magnetic effects consistently failed. Lorentz succeeded in explaining
    why: according to his theory, no such effect should be detectable by
    any experiment sensitive to first order in (v/c), where v is the speed
    of the moving object through the ether and c is the speed of light in
    that medium. Until the 1880s, no experiment with greater sensitivity
    had been performed, and Lorentz's explanation of the failure of all
    previous experiments was a crowning achievement of his theory.
    5) Newton's mechanics now seemed to have successfully met the
    challenge of optics and electrodynamics. But the seeds of its downfall
    had already been planted. Lorentz's explanation led him to introduce a
    transformation from newtonian absolute time to a new time variable in
    each inertial frame moving through the ether. As the relation between
    absolute time and this time varied from place to place in each
    inertial frame, Lorentz called this new variable the "local time" of
    that frame, regarding the local time as a purely formal expression.
    But Henri Poincare (1854-1912), the great mathematician who concerned
    himself extensively with problems of physics, was able to give a
    physical interpretation of this time variable within the context of
    newtonian kinematics: it is the time that clocks at rest in a frame
    moving through the ether would read if they were synchronized using
    light signals, without taking into account the motion of that frame.
    This was an important hint that the problems of the electrodynamics
    and optics of moving bodies were connected with the concept of time.
    But it was Einstein who made the final break with the concept of
    absolute time by asserting that the local time of any inertial frame
    is as physically meaningful as that of any other, because there is no
    absolute time with which they can be compared.[1-5]
    References (abridged):
    1. Einstein, A. Ann. Phys. (Leipz.) 17, 132-148 (1905)
    2. Einstein, A. Ann. Phys. (Leipz.) 17, 549-560 (1905)
    3. Einstein, A. Ann. Phys. (Leipz.) 17, 891-921 (1905)
    4. Einstein, A. Ann. Phys. (Leipz.) 18, 639-641 (1905)
    5. Einstein, A. Ann. Phys. (Leipz.) 19, 289-306 (1906)
    Nature http://www.nature.com/nature
    Related Material:
    The following points are made by A. Einstein and L. Infeld (citation
    1) What are the general conclusions which can be drawn from the
    development of physics? Science is not just a collection of laws, a
    catalogue of unrelated facts. It is a creation of the human mind, with
    its freely invented ideas and concepts. Physical theories try to form
    a picture of reality and to establish its connection with the wide
    world of sense impressions. Thus the only justification for our mental
    structures is whether and in what way our theories form such a link.
    2) We have seen new realities created by the advance of physics. But
    this chain of creation can be traced back far beyond the starting
    point of physics. One of the most primitive concepts is that of an
    object. The concepts of a tree, a horse, any material body, are
    creations gained on the basis of experience, though the impressions
    from which they arise are primitive in comparison with the world of
    physical phenomena. A cat teasing a mouse also creates, by thought,
    its own primitive reality. The fact that the cat reacts in a similar
    way toward any mouse it meets shows that it forms concepts and
    theories which are its guide through its own world of sense
    3) "Three trees" is something different from "two trees." Again "two
    trees" is different from "two stones." The concepts of the pure
    numbers 2, 3, 4..., freed from the objects from which they arose, are
    creations of the thinking mind which describe the reality of our
    4) The psychological subjective feeling of time enables us to order
    our impressions, to state that one event precedes another. But to
    connect every instant of time with a number, by the use of a clock, to
    regard time as a one-dimensional continuum, is already an invention.
    So also are the concepts of Euclidean and non-Euclidean geometry, and
    our space understood as a three-dimensional continuum.
    5) Physics really began with the invention of mass, force, and an
    inertial system. These concepts are all free inventions. They led to
    the formulation of the mechanical point of view. For the physicist of
    the early 19th century, the reality of our outer world consisted of
    particles with simple forces acting between them and depending only on
    the distance. He tried to retain as long as possible his belief that
    he would succeed in explaining all events in nature by these
    fundamental concepts of reality. The difficulties connected with the
    deflection of the magnetic needle, the difficulties connected with the
    structure of the ether, induced us to create a more subtle reality.
    The important invention of the electromagnetic field appears. A
    courageous scientific imagination was needed to realize fully that not
    the behavior of bodies, but the behavior of something between them.
    that is, the field, may be essential for ordering and understanding
    6) Later developments both destroyed old concepts and created new
    ones. Absolute time and the inertial coordinate system were abandoned
    by the relativity theory. The background for all events was no longer
    the one-dimensional time and the three-dimensional space continuum,
    but the four-dimensional time-space continuum, another free invention,
    with new transformation properties. The inertial coordinate system was
    no longer needed. Every coordinate system is equally suited for the
    description of events in nature.
    7) The quantum theory again created new and essential features of our
    reality. Discontinuity replaced continuity. Instead of laws governing
    individuals, probability laws appeared.
    8) The reality created by modern physics is, indeed, far removed from
    the reality of the early days. But the aim of every physical theory
    still remains the same. With the help of physical theories we try to
    find our way through the maze of observed facts, to order and
    understand the world of our sense impressions. We want the observed
    facts to follow logically from our concept of reality. Without the
    belief that it is possible to grasp the reality with our theoretical
    constructions, without the belief in the inner harmony of our world,
    there could be no science. This belief is and always will remain the
    fundamental motive for all scientific creation. Throughout all our
    efforts, in every dramatic struggle between old and new views, we
    recognize the eternal longing for understanding, the ever-firm belief
    in the harmony of our world, continually strengthened by the
    increasing obstacles to comprehension.
    Adapted from: The Evolution of Physics: From Early Concepts to
    Relativity and Quanta. A. Einstein and L. Infeld. Simon and Schuster
    1938, p.254.
    Related Material:
    The following points are made by Arthur I. Miller (citation below):
    1) By the spring of 1905, the 26-year-old Einstein had decided that
    physicists were "out of their depth". From calculations based on
    Planck's radiation law, Einstein drew the astounding "general
    conclusion" that light can be a particle and a wave, and in fact both
    at once, a wave/particle duality. Therefore the electromagnetic
    world-picture could not succeed, because Lorentz's theory could
    represent radiation, or light, only as a wave, and so could never
    provide a way to explain how the electron's mass is generated by its
    own radiation.
    2) Whereas Planck had discovered certain peculiarities about the
    energy of radiation, Einstein set out to explore the structure of
    radiation itself. Einstein's particles of light differed fundamentally
    from Newton's in ways that even he did not yet fully realize. Around
    the third week of May 1905, Einstein sent his friend Habicht what are
    surely some of the greatest understatements in the history of science.
    He wrote that he had only some "inconsequential babble" for his
    friend, whom he lambasted for neither writing nor visiting him during
    "So what are you up to, you frozen whale, you smoked, dried, canned
    piece of soul... I promise you four papers."
    3) The first paper is the light quantum paper that Einstein referred
    to as "very revolutionary". The second suggested a means to measure
    the size of atoms using diffusion and viscosity of liquids. The third
    paper explored Brownian motion using methods of the molecular theory
    of heat. Einstein wrote: "The fourth paper is only a draft at this
    point, and is an electrodynamics of moving bodies which employs a
    modification of the theory of space and time; the purely kinematic
    part of this paper will surely interest you."
    4) What is so incredible about this outburst of creativity is that by
    late May two papers were completed and the third was in draft form."
    [Editor's note: The fourth paper, the so-called relativity paper, was
    completed a few weeks later in June 1905.]
    Adapted from: Arthur I. Miller: Einstein, Picasso: Space, Time, and
    the Beauty That Causes Havoc. Basic Books, New York 2001, p.189.

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