Synopsis

This course of four lectures offers an introduction to the philosophy of modern physics. This is a technical area, although an interdisciplinary one. Its closest cousin is the branch of physics called ‘foundations of physics’. Thus in both areas, we examine the mathematical structures of physical theories. This course will emphasise two specific theories: relativity and quantum theory. 

The first and second lectures will survey the philosophy of relativity theory. I will emphasise Einstein’s famous ‘hole argument’, as a lesson about the foundations of general relativity. Einstein devised this argument in late 1913, as an argument against general covariance: namely, that any generally covariant theory would be radically indeterministic. Late in 1915, after he had found the field equations of general relativity, which are generally covariant, he re-assessed the argument as showing only that we should not think of spacetime points as objects, on pain of a radical indeterminism. Broadly speaking, there the matter rested, until about twenty years ago, when the assessment of the argument became again a live topic, because of its connection with other issues in the interpretation of general relativity. The controversy continues today.

The third and fourth lectures are devoted to the measurement problem of quantum theory: in short, Schroedinger’s cat. There are many aspects, technical and philosophical (and even historical), one could discuss about this. I will in part be guided by the interests of the class. But here are two:

(i) The nature and role of decoherence. In short, decoherence gives a dynamical basis to the selection of a preferred quantity, but does nothing to ‘select’ an individual, definite measurement-outcome, or more generally a definite macroscopic reality.

(ii) The current prospects for the Everett interpretation (also known as: the relative-state, or many worlds, interpretation). In short, the interpretation is very strange, but its current prospects are surprisingly good!

BOOKS    NB: Most of the books cited will surely be in your College library.

All four Lectures: The Stanford Encyclopedia of Philosophy (SEP), and the Pittsburgh philosophy of science e-arXive, both available online, have many good philosophy of physics articles.

First and second Lectures:

Theoretical Concepts in Physics, Longair M, (2nd edn CUP 2003); Chapter 17.1-2.

SEP article on Einstein’s philosophy of science: http://www.seop.leeds.ac.uk/entries/einstein-philscience/

SEP article on Einstein’s Hole Argument

http://www.seop.leeds.ac.uk/entries/spacetime-holearg/

Third and fourth Lectures:

Speakable and Unspeakable in Quantum Mechanics, Bell J S (2nd edn CUP 2004); Chapters 20 and 23

Philosophical Concepts in Physics, Cushing J T (2nd edn CUP 1998); Chapters 20-22.

SEP article on Bell’s theorem:

http://www.seop.leeds.ac.uk/entries/bell-theorem/

SEP article on decoherence in quantum mechanics:

http://www.seop.leeds.ac.uk/entries/qm-decoherence/

Pittsburgh e-arXive articles on the Everett interpretation include the following two:

philsci-archive.pitt.edu/archive/00000208/

and

philsci-archive.pitt.edu/archive/00000681/