Philosophy of physics

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The philosophy of physics can be understood as a branch of the philosophy of science or of natural philosophy and thus of ontology and deals with philosophical problems raised by theories of modern physics as well as with the conceptual foundations of these theories.

Problems of interpretation of physical theories

The subject areas of the philosophy of physics include the interpretation of physical theories with regard to their ontological presuppositions or implications: If a certain physical theory describes our world well, it follows, at least for epistemological realists , that these theories provide information about the structure of reality. The interpretation and rational reconstruction of classical ( Newtonian ) particle mechanics already raises problems. The problems in the interpretation of statistical physics, quantum mechanics and relativity are even more complicated .

thermodynamics

For example, several attempts have been made to attribute the directionality of time to the directionality of physical processes. This is because not all physical phenomena are time reversal invariant (i.e. the equations governing them allow the process in the opposite direction, as can be modeled simply by reversing the sign of the time parameter). Thermodynamics, for example, requires entropy to remain the same or increase over time. However, since the thermodynamic processes are ultimately realized by the smallest particles, for which the time-reversal invariant laws of classical particle mechanics actually apply, the relationship between the two theories requires explanation. Even Boltzmann has tried to find a solution to this problem in the 19th century. Today's theorists usually agree that his explanation is flawed, but sometimes diagnose this error differently.

theory of relativity

The special theory of relativity also poses problems for the philosophy of the time . Because the relativity of simultaneity that it demands is in contradiction to certain metaphysical theories about the nature of causality and modality (for example, to a modally logical, dynamic universe with splitting off unrealized possibilities, as suggested by Storrs McCall, Michael Tooley and other metaphysicists).

Quantum mechanics

In the case of quantum mechanics , a main problem of the attempts at interpretation is how the time development of the state values ​​relates to the measurement process. The former is deterministic, but the results of the latter can only be predicted stochastically. Usually it is said that (in most cases) the actual system state is a so-called superposition state, which is reduced to a unique state during the measurement, with a probability that can be specified by Born's rule . The scientific realist must now explain what in reality corresponds to such a superimposed state. A wide variety of suggested answers exist for this. Alternatively, different anti-realistic interpretations were offered. It is also controversial how exactly what constitutes a measurement process can be characterized in physical or ontological language (see the brief overview in the main article quantum mechanics , the more detailed description in interpretations of quantum mechanics and the discussion in related articles such as Wigner's friend ).

Furthermore, several realistic possible interpretations, which were discussed in particular in the debate about the EPR effect , do not seem to be compatible with classical views of the (local causal) nature of causality .

Metaphysical problems

Since the general theory of relativity in particular is the basis for modern cosmological models, the philosophy of space-time or relativity is in some areas strongly related to cosmology .

These interpretation problems are mostly closely related to the interest in metaphysical questions regarding the nature of space , time and causality as well as the constituents of reality. For the latter topic, the fundamental controversy is whether theoretical terms, i.e. the vocabulary that are central to the formulation of a theory, such as “atom”, per se go hand in hand with the assumption that something corresponds to them in reality. Many epistemological realists demand this, anti-realists, including in particular classical operationalism (as developed by Percy Williams Bridgman ) deny it. The modern epistemological realist then seems to have to include not only atoms in his ontology, but also quanta and fields; he also has to explain (apparent) transformations from “matter” to “energy” and vice versa.

Epistemological Problems

Like quantum mechanics, especially in some anti-realistic interpretations, special relativity also raises epistemological questions.

General epistemological problems

determinism

Relatively independently of the problems of interpretation of the physical theories, questions about the general nature of physical laws also fall into the philosophy of physics . Since modern physics can only make statistical statements in some areas, the regional or general validity of determinism is particularly controversial. Sometimes some philosophers try to combine this discussion with questions about free will (sometimes also about divine foreknowledge). In many cases, attempts to rescue the free will are viewed critically by the theorists of science.

See also

literature

General presentations and manuals

as well as the manuals on the philosophy of science , which mostly also contain chapters on spacetime and quantum physics, as well as more recent representations of natural philosophy

Interpretations of physical theories

Philosophy of spacetime or relativity
Philosophy of quantum mechanics
  • David Z. Albert: Quantum mechanics and experience . Harvard University Press, Cambridge, MA 1992, ISBN 0-674-74112-9 The most accessible presentation on the subject, maximum simplification of the theoretical apparatus.
  • Cord Friebe, Meinard Kuhlmann, Holger Lyre, Paul Näger, Oliver Passon, Manfred Stöckler: Philosophy of Quantum Physics. Introduction and discussion of the central concepts and problems of quantum theory for physicists and philosophers. Springer Spectrum 2015, ISBN 978-3-642-37789-1 Comprehensive presentation of the current state of discussion.
  • RIG Hughes: The Structure and Interpretation of Quantum Mechanics Less simplified than Albert, but manageable with school physics; largely an accessible introduction to physical theory - philosophical discussions take up little space.
  • Michael Redhead: Incompleteness, nonlocality, and realism . The Clarendon Press Oxford University Press, New York 1990, ISBN 0-19-824238-7
  • various articles in the Stanford Encyclopedia of Philosophy on quantum mechanics and quantum theory
Quantum field theory
  • MLG Redhead: Quantum field theory for philosophers , in: PSA: Proceedings of the Biennial Meeting of the Philosophy of Science Association 1982, 57-99
  • Paul Teller: An interpretive introduction to quantum field theory , Princeton University Press 1995
Statistical Physics / Thermodynamics
Chaos theory
  • Peter Smith: Explaining Chaos , Cambridge: Cambridge University Press 1994.

Web links

Individual evidence

  1. See u. a. the discussion at Huw Price, Time's Arrow; Albert, Time and Chance; Mellor, Real Time; Horwich, Arrow of Time and the SEP articles cited
  2. See Francisco Flores:  The Equivalence of Mass and Energy. In: Edward N. Zalta (Ed.): Stanford Encyclopedia of Philosophy . and the alternative positions and references discussed there.