[Paleopsych] SW: On Physics and the Real World

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Theoretical Physics: On Physics and the Real World
http://scienceweek.com/2005/sw050916-6.htm

    The following points are made by George F.R. Ellis (Physics Today 2005
    July):
    1) Physics is the model of what a successful science should be. It
    provides the basis for the other physical sciences and biology because
    everything in our world, including ourselves, is made of the same
    fundamental particles, whose interactions are governed by the same
    fundamental forces. It's no surprise then, as Princeton University's
    Philip Anderson has noted, that physics represents the ultimate
    reductionist subject: Physicists reduce matter first to molecules,
    then to atoms, then to nuclei and electrons, and so on, the goal being
    always to reduce complexity to simplicity. The extraordinary success
    of that approach is based on the concept of an isolated system.
    Experiments carried out on systems isolated from external interference
    are designed to identify the essential causal elements underlying
    physical reality.
    2) The problem is that no real physical or biological system is truly
    isolated, physically or historically. Consequently, reductionism tends
    to ignore the kinds of interactions that can trigger the emergence of
    order, patterns, or properties that do not preexist in the underlying
    physical substratum. Biological complexity and consciousness -- as
    products of evolutionary adaptation -- are just two examples. Physics
    might provide the necessary conditions for such phenomena to exist,
    but not the sufficient conditions for specifying the behaviors that
    emerge at those higher levels of complexity. Indeed, the laws of
    behavior in complex systems emerge from, but are to a large degree
    independent of, the underlying low-level physics. That independence
    explains why biologists don't need to study quantum field theory or
    the standard model of particle physics to do their jobs.
    3) Moreover, causes at those higher levels in the hierarchy of
    complexity have real effects at lower levels, not just the reverse as
    often thought. Consequently, physics cannot predict much of what we
    see in the world around us. If it could predict all, then free will
    would be illusory, the inevitable outcome of the underlying physics.
    4) True complexity, with the emergence of higher levels of order and
    meaning, including life, occurs in modular, hierarchical
    structures.[1,2] Consider the precise ordering in large intricate
    networks -- microconnections in an integrated chip or human brain, for
    example. Such systems are complex not merely because they are
    complicated; order here implies organization, in contrast to
    randomness or disorder. They are hierarchical in that layers of order
    and complexity build upon each other, with physics underlying
    chemistry, chemistry underlying biochemistry, and so forth. Each level
    can be described in terms of concepts relevant to its own particular
    structure -- particle physics deals with behaviors of quarks and
    gluons, chemistry with atoms and molecules -- so a different
    descriptive language applies at each level. Thus we can talk of
    different levels of meaning embodied in the same complex structure.
    5) The phenomenon of emergent order refers to this kind of
    organization, with the higher levels displaying new properties not
    evident at the lower levels. Unique properties of organized matter
    arise from how the parts are arranged and interact, properties that
    cannot be fully explained by breaking that order down into its
    component parts.[3,4] You can't even describe the higher levels in
    terms of lower-level language.[5]
    References (abridged):
    1. G. F. R. Ellis, in The Re-Emergence of Emergence, P. Clayton, P. C.
    W. Davies, eds., Oxford U. Press, New York (in press); also available
    at http://www.mth.uct.ac.za/~ellis/emerge.doc
    2. G. Booch, Object Oriented Analysis and Design with Applications,
    2nd ed., Benjamin Cummings, Redwood City, CA (1994)
    3. N. A. Campbell, Biology, Benjamin Cummings, Menlo Park, CA (1996)
    4. R. B. Laughlin, A Different Universe: Reinventing Physics from the
    Bottom Down, Basic Books, New York (2005)
    5. S. Hartmann, Stud. Hist. Philos. Mod. Phys. 32, 267 (2001)
    Physics Today http://www.physicstoday.org
    --------------------------------
    Related Material:
    PARTICLE PHYSICS: AN EXCHANGE CONCERNING RELEVANCE
    Notes by ScienceWeek:
    In general, "reductionism" is the idea that macroscopic phenomena can
    be explained in terms of microscopic entities and/or events, but the
    specific meaning of the term depends upon context and the conceptual
    identification within a particular science of levels of understanding.
    In biology in general, for example, "reductionism" is the term applied
    to attempts to explain biological phenomena in the language of physics
    and chemistry. In neurobiology, the term "reductionism" may be applied
    to attempts to explain human cognitive behavior in terms of the
    behavior of nerve cells and their connections. In evolutionary
    biology, the term "reductionism" may be applied to attempts to explain
    the dynamics of evolution in terms of molecular genetics. In physics
    and chemistry, the term "reductionism" may be applied to attempts to
    explain the macroscopic behavior of physical or chemical systems in
    terms of events at the level of atomic phenomena. Also in physics, the
    term "reductionism" may be applied to attempts to explain both the
    macroscopic behavior of a physical system and/or the microscopic
    atomic behavior of the entities of the system in terms of events at
    the still more microscopic level of fundamental particles and
    fundamental forces.
    The various sciences are split by scientists (not by nature) into
    various levels of explanation, with researchers working at the various
    levels using various techniques and concepts. Ordinarily, in the
    practice of science, the working scientist does not spend much time
    cogitating about whether a general reductionist approach is useful or
    not useful, philosophically valid or not valid, or whatever. The
    attitude essentially is that here is a house, I choose to study in
    detail the nature of the bricks, you choose to study in detail the
    nature of the construction of the house, I enjoy what I'm doing, you
    enjoy what you're doing, and each of us is making some contribution to
    a general understanding of the nature of the entity "house". This
    division of labor has been quite fruitful in science, and there is
    never much of a problem concerning the existence of various levels of
    investigation until the person who studies bricks says that what he or
    she is doing is more important than what the person who studies the
    construction of the house does, or when the person studying the
    construction of the house says it is the study of the construction of
    the house that is more important than the study of bricks. From the
    standpoint of "nature", from the perspective of the giant star
    *Betelguese, for example, a relatively nearby stupendous and violent
    supergiant star apparently 400 to 500 times the diameter of our Sun,
    any serious bickering on the planet Earth about the relative merits of
    various levels of understanding in science begins to smack of farce.
    But science is a human enterprise, and occasionally the bickering
    about reductionism and levels of understanding does get serious and
    does occupy attention.
    In 1996, in a most prestigious physics journal (_Reviews of Modern
    Physics_), the physicist Robert Cahn stated that particle physics is
    essential to the understanding of our everyday world, that "particle
    physicists construct accelerators kilometers in circumference and
    detectors the size of basketball pavilions not ultimately to find the
    *t-quark or the *Higgs boson, but because that is the only way to
    learn why our everyday world is the way it is... Given the masses of
    the quarks and *leptons, and nine other closely related quantities,
    [the current theory of particle interaction] can account in principle
    for all the phenomena in our daily lives."
    In July 1998, in the journal _Physics Today_, Pablo Jensen, a
    condensed matter physicist, took issue with Cahn's views and suggested
    that Cahn's "reductionist vision seems to be shared by many other
    particle physicists." Stating that he wished to "reopen a debate in
    the physics community," Jensen made the following points: 1) The
    reductionist ideas of Cahn and other reductionist particle physicists
    are wrong: even if we knew all the "fundamental" laws, we could not
    say anything useful about our everyday world. Our everyday world is
    irremediably macroscopic, and macroscopic concepts are needed to
    understand it. 2) Contrary to the pretensions of particle physicists,
    science is organized in decoupled layers, each with its own elementary
    entities or concepts, which generally are not simply derived from
    those of the lower level but constructed in creative efforts...
    Particle physics is practically irrelevant to understanding our
    everyday world... "If we learned tomorrow that previous results and
    analysis had overlooked certain systematic errors, and that the
    t-quark mass is near 195 *GeV and not 175 GeV, it is particle physics
    that would have to adjust to remain in agreement with the rest of
    physics, and not vice versa." 3) Considering, for example, the
    property of *chirality of large molecules (e.g., a sugar or any
    biological molecule), for all practical purposes, such molecules do
    not show the symmetry expected from the fundamental laws -- in this
    case, quantum mechanics. 4) In the study of phase transitions, there
    are characteristics of such transitions that apparently depend on the
    collective behavior of the system and are not determined by the
    microscopic interactions. 5) Each level of complexity must be studied
    with its own instruments, and requires the invention of new concepts
    adapted to describe and understand its behavior... Intermediate
    concepts such as *entropy, *dissipative structures, cells, genes,
    etc., cannot be simply "deduced" from the fundamental laws: such
    concepts are said to be "emergent" because they arise at high levels
    of complexity and must be invented at those levels to deal with
    specific situations... These emergent concepts are as real and as
    fundamental as the concepts and particles introduced by particle
    physicists. The author concludes: "By all means let us each study our
    chosen "layer" of reality, whether it involves quarks or convective
    cells. But let us also remember that each layer is just one part of
    the greater whole. Accounting for all the phenomena in our daily lives
    *in principle* is entirely different from accounting for them in
    actuality."
    In the November 1998 issue of _Physics Today_, Robert Cahn presents a
    rebuttal to the critique of Pablo Jensen, the author making the
    following points: 1) The empirical parameters of the *Standard Model
    of particle physics shape the most familiar aspects of our physical
    surroundings... Given *these parameters, the Standard Model, which
    subsumes the Maxwell and Schroedinger equations, determines all the
    fundamental processes of *electroweak and strong interactions. Changes
    in the basic parameters would produce worlds quite different from our
    own. 2) The stuff of daily life is made just of electrons and the
    lightest quarks. However, we cannot understand these particles by
    themselves, because they are intimately connected to others accessible
    only in high energy collisions. 3) Concerning the supposed irrelevance
    of particle physics, constructs that embody the essential physical
    features of complex systems are indispensable, but their success is
    not a reason for abandoning the search for basic physical laws. 4)
    Nature is not neatly partitioned into autonomous layers, as Jensen
    suggests. On the contrary, the macroscopic makes manifest the
    microscopic... The gross properties of the materials around us, their
    color, conductivity, and strength, reflect the details of their
    quantum mechanical states. Likewise the structure of atoms reflects
    divisions in the subatomic world... "Only by willfully closing our
    eyes can we miss the connection between the fundamental interactions
    and their manifestations that surround us." The author concludes: "We
    particle physicists share with all physicists the goal of explaining
    the world. We differ by asking ever more basic questions. Like young
    children who relentlessly insist, Why?, particle physicists ask, Why
    is there light? Why are electrons light and protons heavy? Why are
    there electrons or protons, anyway? 'Just because' and 'Who cares?'
    will not satisfy the curious child, nor should they satisfy us."
    The same issue of the journal includes a number of letters on the
    subject from other physicists, and in one of these letters Paul Roman
    suggests that perhaps the motivation for the debate is that the
    physics research "grant pie is shrinking while the number of
    pie-hungry individuals is still increasing." Perhaps that is so, and
    perhaps that is also the motivation behind debates concerning the
    reductionist approach in other sciences. But perhaps such motivations
    are also part of science as a human enterprise. Meanwhile, the
    enormous furnace of Betelguese continues to roar.
    References (abridged):
    R.N. Cahn (Lawrence Berkeley Natl. Lab., US) (Rev. Mod. Phys. 1996
    68:951) QY: Robert N. Cahn, Lawrence Berkeley National Laboratory,
    Berkeley, CA US
    P. Jensen (Claude Bernard University, FR) Particle physics and our
    everyday world. (Physics Today July 1998) QY: Pablo Jensen, Claude
    Bernard University, Villeurbanne FR)
    R.N. Cahn (Lawrence Berkeley Natl. Lab., US) "Particle physics and our
    everyday world": A reply (Physics Today November 1998) QY: Robert N.
    Cahn, Lawrence Berkeley National Laboratory, Berkeley, CA US
    --------------------------------
    Notes by ScienceWeek:
    Betelguese: Also known as Alpha Orionis. It is the 10th brightest star
    in the sky, with a luminosity 5000 times that of the Sun, with an
    estimated distance of 400 light years. Some astronomers believe its
    distance is 1400 light years, which would make its luminosity 50,000
    times that of the Sun. The star is a variable, its size swelling and
    contracting with a period of several years.
    t-quark: (top-quark) A quark is a hypothetical fundamental particle,
    having charges whose magnitudes are one-third or two-thirds of the
    electron charge, and from which the elementary particles may in theory
    be constructed. A t-quark is one of the types of quarks and has an
    electrical charge of +2/3.
    Higgs boson: Higgs fields (named after Peter W. Higgs, University of
    Edinburgh, UK) constitute a set of fundamental theoretical fields that
    induce spontaneous symmetry breaking. In general, spontaneous symmetry
    breaking occurs in systems whose underlying symmetry state is
    unstable. A Higgs particle is associated with a Higgs field in the
    same way that a photon is associated with the electromagnetic field.
    Higgs bosons are massive mesons whose existence is predicted by
    certain theories. Mesons are apparently composed of quark and
    anti-quark pairs; they are produced by various high-energy
    interactions and decay into stable particles.
    leptons: Leptons are a class of point-like fundamental particles
    showing no internal structure and no involvement with the strong
    forces. There are 6 leptons: the electron, the muon, the massive tau
    lepton, and a specific neutrino associated with each of the former (3
    neutrino "flavors").
    GeV: (Gev) Also written as Bev, a billion electronvolts. An
    electronvolt is defined as the energy acquired by an electron falling
    freely through a potential difference of one volt, and is equal to
    1.6022 x 10^(-19) joule.
    chirality: In chemistry, chirality is a property of certain asymmetric
    molecules, the property being that the mirror images of the molecules
    cannot be superimposed one on the other while facing in the same
    direction.
    entropy: A measure of disorder in a system.
    dissipative structures: In general, a dissipative system is a system
    that loses energy by conversion of energy into heat.
    Standard Model: In particle physics, the *Standard Model is a
    theoretical framework whose basic idea is that all the visible matter
    in the universe can be described in terms of the elementary particles
    leptons and quarks and the forces acting between them.
    these parameters: The parameters referred to here are the masses of
    the quarks, the masses of the charged leptons, the strength of 3
    forces, 4 numbers that describe the weak transformations of one quark
    type into another, the mass of the *W boson, and the mass of the Higgs
    boson.
    W boson: Very massive charged particles (+ or -) that convey part of
    the weak force between leptons and *hadrons. Bose-Einstein statistics
    is the statistical mechanics of a system of indistinguishable
    particles for which there is no restriction on the number of particles
    that may simultaneously exist in the same quantum energy state. Bosons
    are particles that obey Bose-Einstein statistics, and they include
    photons, *pi mesons, all nuclei having an even number of particles,
    and all particles with integer *spin.
    pi mesons: (pions) Pi mesons are subatomic particles with masses
    approximately 270 times the mass of the electron.
    spin: In quantum mechanics, "spin" is the intrinsic angular momentum
    of a subatomic particle.
    hadrons: Hadrons are particles with internal structure, e.g., neutrons
    and protons.
    electroweak and strong interactions: The fundamental forces comprise
    the gravitational force, the electromagnetic force, the nuclear strong
    force, and the nuclear weak force. The electroweak interactions
    comprise the electromagnetic and nuclear weak interactions, the latter
    involved in radioactive decay processes.