Welcome to Physics 314, "Introduction to Modern Physics." The material we will cover in this course spans the time period from 1887 to about 1930. That's at least seventy years ago. Why is it called Modern Physics if it's so old?
In the nineteenth century, the discipline of physics had reached a high point. Scientists could describe and predict many phenomena, both in the everyday world and in the far reaches of space, using only a few rules. The use of mathematics to explain the universe had several great triumphs:
You can read a bit more about the discovery of Neptune if you like.
By the turn of the century, electricity and magnetism had been harnessed to serve both the home (electric lights) and industry (motors); a large hydroelectric plant at Niagara Falls began operating in 1895, for example. New inventions were springing up all the time -- Marconi first demonstrated wireless radio communications in 1895, and the first trans-Atlantic message was sent (and received) in 1901.
In short, scientists were rightly proud of their understanding of the world.
However, during this period of great progress, there were some things which didn't quite fit into the successful theories. During the period that we will study in this course, experiments showed again and again that the existing laws failed in certain circumstances. We will look in detail at some of these experiments, so that you can see for yourself what puzzled the scientists at the turn of the twentieth century. Over the course of several decades, physics underwent a profound revolution, as researchers gradually realized that their fundamental rules weren't so fundamental after all. In fact, their basic notions of time, space, and existence had to be discarded in certain situations. The old rules weren't wrong, really; they just didn't apply when one examined things in new and out-of-the ordinary ways.
This revolution in the early twentieth century separates classical physics from the so-called modern physics. Let me write it again: the classical theories weren't "wrong;" after all, they did uncover Neptune, and they still do underlie most of our modern civilization's infrastructure: electricity, engineering and the internal combustion engine. They just weren't the whole story ....
Copyright © Michael Richmond. This work is licensed under a Creative Commons License.