Lesson: Chapter - 19

Modern Physics

Almost everything we’ve covered in the previous 15 chapters was known by the year 1900. Taken as a whole, these 15 chapters present a comprehensive view of physics. The principles we’ve examined, with a few elaborations, are remarkably accurate in their predictions and explanations for the behavior of pretty much every element of our experience, from a bouncy ball to a radio wave to a thunderstorm. No surprise, then, that the physicist Albert Michelson should have claimed in 1894 that all that remained for physics was the filling in of the sixth decimal place for certain constants.

But as it turns out, the discoveries of the past 100 years show us that most of our assumptions about the fundamental nature of time, space, matter, and energy are mistaken. The “modern” physics of the past century focuses on phenomena so far beyond the scope of ordinary experience that Newton and friends can hardly be blamed for failing to notice them. Modern physics looks at the fastest-moving things in the universe, and at the smallest things in the universe. One of the remarkable facts about the technological advances of the past century is that they have brought these outer limits of nature in touch with palpable experience in very real ways, from the microchip to the atomic bomb.

One of the tricky things about modern physics questions on
Physics is that your common sense won’t be of very much use: one of the defining characteristics of modern physics is that it goes against all common intuition. There are a few formulas you are likely to be tested on—E = hf in particular—but the modern physics questions generally test concepts rather than math. Doing well on this part of the test requires quite simply that you know a lot of facts and vocabulary.

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