Many undergraduate physics courses contain an element known as “modern physics.” What is usually meant by “modern physics” in this context is two different topics: relativity and quantum mechanics. These two theories are undoubtedly the twin pillars of modern physics, the foundations upon which our contemporary understanding of the Universe is built. And they feel modern, somehow, in that they deal with concepts that are quite unfamiliar to us in everyday life. Relativity, for example, tells us that our measure of time depends upon our position in a gravitational field; quantum mechanics forces us to give up the notion that an object simultaneously possesses a definite position and momentum. These concepts appear to be, in that horrible phrase, bleeding-edge concepts. Yet it is worth remembering that these “modern” ideas now have a long history, in contrast to many of the speculative ideas we will meet later in this book. The theory of special relativity is almost a century old; Einstein’s extension of those ideas, which forms the theory of general relativity, was published about nine decades ago; quantum mechanics was cast into its present form not long after that. So these “modern” ideas are neither untried nor untested; quite the contrary — they have met with spectacular success, which is why we teach them to our students.
KeywordsGlobal Position System Quantum Mechanic Global Position System Gravitational Field Uncertainty Principle
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