Topics in the Philosophy of Relativity Theory and Quantum Mechanics

(3 Credit Hours) · Undergraduate

This course is designed for students with little prior familiarity with modern physics; formal mathematics will be kept to a minimum. The lectures start with an outline of Newton's laws of classical mechanics, and the problem Newton faced in distinguishing between absolute and relative motion of bodies. The question arises whether space and time are substances in their own right (Newton) or merely kinds of relations between bodies (Leibniz). The key concept that emerges is that of inertial frames of reference and how different such frames are related to each other. We discuss the fable of Albert Keinstein, who in 1705 anticipated part of Albert Einstein's discussion of this relation two hundred years later. This leads to a discussion of how Einstein came up with his theory of special relativity, which predicts the subtle phenomena of length contraction of "fast" moving rigid bodies and time dilation of "fast" moving clocks, as well as the relativity of simultaneity. Emphasis will be put on the debt Einstein owed to the so-called ether theorists of the 19th century, who were grappling with conceptual issues related to electromagnetism and in particular the behaviour of light. A philosophical debate has arisen in recent years as to how to understand the mentioned relativistic effects: are they the result of novel geometric properties of space-time, or special properties of the forces of cohesion that hold in rigid bodies and clocks? We will look at the arguments on both sides of the debate. Some simple physical arguments due to Einstein will then be examined which led him to his general theory of relativity of 1915: his revolutionary theory of gravity. An intuitive way of understanding the role "space-time curvature" plays in the theory will be discussed, as well as the way in which special relativity emerges from general relativity in the appropriate conditions. The final quarter of the course will concern the role of probability in quantum mechanics. Does this theory require us to change our notion of what probability means? A sketch of the different interpretations of quantum mechanics will be given, and the role of probability in each of them will be examined.