User:Stephen Poppitt/Books/Quantum Mechanics for Beginners


Quantum Mechanics for Beginners An Introductory Framework

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This book is intended as an introduction to the subject for the general reader.

As such, this is a largely non-mathematical treatment, avoiding algebra wherever possible. Where it can't be entirely avoided, it's limited to some examples. The intention is that anyone, regardless of their knowledge of physics or mathematics, will be able to follow the main text. The general approach is to present the subject in a logical order, starting from first principles, and, in general, dealing with the subject as history rather than as physics: it begins with the earliest discoveries, and proceeds to explain subsequent developments in the order in which they occured.

Books on this subject tend to be written on the assumption that the reader will have more knowledge than is reasonable to expect. I hope that I am not making that assumption. To understand the later chapters, it will definitely be an advantage to have first read chapter one, which sets out the main principles. In particular, the section Basic Concepts of Quantum Mechanics is essential reading for anyone coming to the subject for the first time.

It should be stressed that, despite some of the language used, and some of the exaggerated claims made for it, this branch of physics is still only a theory. It is not a law of physics, but only an incomplete attempt to explain certain strange results obtained from experiments and the odd behaviour of some of the particles in the sub-atomic world.

Albert Einstein famously believed that quantum theory was a lot of nonsense, even though it was he who had given birth to it. He spent much of his life arguing with those who took his original theory (conventionally known as the old quantum theory) in directions that he didn't want it to go. To the end of his days, he never accepted what became known as the Copenhagen interpretation of the theory.

His reasons are set down in the later chapters: so if you find yourself doubting the theory, you'll find yourself in good company.

The most important player in this game is Schrödinger, who, like Einstein, believed that much of quantum theory is basically nonsense. Hence Schrödinger's famous cat makes an appearance in chapter two, debunking the quantum theories of Einstein's opponents, the so-called Copenhagen school.

However, Schrödinger's most important contribution is not his cat. It is, rather, his invention of the equation which bears his name; an equation based on his rejection of the Copenhagen interpretation of quantum theory. It is one of the great ironies of modern physics that his detractors subsequently built their reputations and their quantum theories upon it.

Schrödinger's equation - which predicts the motion of sub-atomic, atomic, and even molecular particles, in the same sense that Keppler's laws of planetary motion predict the behaviour of planets - is touched upon in chapter one. However, no attempt is made there to explain it in mathematical terms. It's widely accepted as the basis of particle physics, because it successfully predicts the behaviour of all known particles. But it doesn't attempt to explain that behaviour: it doesn't offer a theory as to why particles behave as they do. It is not a model of the universe: it tells you what's happening, but not what's causing it.

Furthermore, Schrödinger's equation is not incompatible with Einstein's theory of relativity. Schrödinger specifically incorporates relativity in some of his mathematics: Einstein had formulated Special Relativity in 1905 and General Relativity in 1915, some years before Schrödinger produced his equation in 1926.

Quantum theory - or, more accurately, the various quantum theories - are attempts to explain why particles behave in the ways which Schrödinger's equation describes. The most widely accepted of the many theories is known as the Copenhagen interpretation. But it remains only one interpretation of Schrödinger's results: there are many other competing explanations.

An exploration of this subject logically begins with the historical background from which the earliest quantum theories arose...

As edited by Stephen Poppitt

Quantum Mechanics for Beginners

An Introductory Framework

1. Introductory Principles: History of Quantum Mechanics; Introduction to Quantum Mechanics; Basic Concepts of Quantum Mechanics
2. The Quantum Theories: Old Quantum Theory; Quantum Mechanics after 1925
3. The Interpretation of Quantum Mechanics: Interpretations of Quantum Mechanics; Copenhagen Interpretation
4. Einstein's Objections: Principle of Locality; EPR Paradox; Bell's Theorem
5. Schrödinger's Objections: Schrödinger's Cat
6. Measurement Problems: The Measurement Problem; Measurement in Quantum Mechanics
7. Related Concepts: Quantum Number; Quantum Information; Quantum Statistical Mechanics
8. Advanced Topics: Quantum Field Theory; String Theory; Quantum Gravity
Appendix A - Quantum: Quantum; Quantum State
Appendix B - Quantisation of Charge: The Elementary Charge; Quarks
Appendix C - Space: Euclidean Space

Physics Quantum Mechanics