Syllabus

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Course Description

There was an explosion in our understanding of physics at the turn of the 20th century. Einstein imagined riding along with a light wave and realized as a consequence that parts of the foundation of our understanding of physics, e.g. our notion of time, need to be revised when we take into account objects moving near the speed of light. Thus began special relativity. Simultaneously, a collection of physicists realized together that some physical observables, like the energies of an electron orbiting the nucleus, are not well described by a continuum of values, but rather by discrete quantum jumps. Incorporating this discreteness into physical models also required an upheaval of the bedrock of physics, classical mechanics, and led to the invention of quantum mechanics.

In retrospect, one way to capture these two revolutions is to say that they each introduced a new fundamental physical scale, captured by a constant of nature. These are the speed of light, c, and Planck’s constant, ℏ. As you turn on these constants you move from classical mechanics to special relativity and quantum mechanics respectively, see the Figure. If you do an experiment where they are both relevant at once you move towards the upper right corner of the Figure and the end of the modern physics era, the discovery of quantum field theory.

A third revolution, which built more slowly but with inexorable strength, was statistical mechanics. Unlike relativity and quantum mechanics, which changed what we think of as making up the world, statistical mechanics was a change in how we approach the description and quantifica- tion of the world. We leave the detailed understanding of a few objects behind for a much broader understanding of a great many objects. The advent of these three theories opened up a vast array of applications to physics and we will touch on many of these. A major focus will be understanding classical and quantum waves, but there will also be overviews of particle physics, nuclear physics, optical and molecular physics, condensed matter physics, astronomy, and cosmology.