Physics II: Modern Physics
What are relativity and quantum mechanics, and why were they viewed as revolutionary when they were formulated in the early 1900s? How and why does relativity and quantum mechanics compel us to discard commonsense ideas about the nature of the physical world that are part of classical mechanics? Why is there not agreement on how to interpret quantum mechanics, and why does quantum mechanics even need interpretation? This version of Physics II covers Einstein's theory of special relativity and selected topics in quantum mechanics, and is designed to introduce students to some of the formalism and central results of relativity and quantum mechanics, so that they can formulate scientifically grounded answers to the above questions. Throughout the course we will start with first principles and carefully build toward key results, allowing students to see how relativity and quantum mechanics—two of the pillars of modern physics—were constructed and how they cohere as mathematically consistent and experimentally verified theories. The first half of the course will cover relativity topics including the principle of relativity, spacetime intervals and proper time, coordinate transformations, time dilation and Lorentz contraction, and relativistic energy and momentum. The second half of the course will turn toward the foundations of quantum mechanics, including: spin-1/2 particles, wave-particle duality, and Bell's inequalities and the Einstein-Podolsky-Rosen paradox. If time permits, we may cover additional topics such as blackbody radiation, the photoelectric effect, Bohr's model of the hydrogen atom, and quantum cryptography. To gain a sense of the scientific, social, and material context in which the theories of relativity and quantum mechanics were developed, we will read a number of papers and book chapters by historians and philosophers of science. This course is designed to appeal to a wide range of students—both those whose interests lie outside of science as well as those who are drawn toward the sciences or mathematics. Students who take this course should be comfortable working with mathematical abstraction. Evaluation is based on weekly problem sets, participation in weekly discussion sections, and several short reflection assignments.