QED: The Strange Theory of Light and Matter
This book is about quantum electrodynamics, the theory which describes how light and matter interact on the smallest scales.
As can be expected from any book by Richard Feynman, this book is a joy to read. Feynman manages to explain in clear layman's terms why it seems that light travels by straight lines, how light reflects from surfaces, why it behaves wave-like and how light-particles interact with electrons. In the final part of the book he concludes with an appetizer on the so-called quantum chromodynamics (QCD), which is the theory of the (strong) interaction between even more exotic particles.
Feynman takes the reader by the hand starting with simple examples and step-by-step advance on those examples pointing out the strangeness of the theory when scales or distances get very, very small. It would not make sense to summarise here what is so perfectly described in his book, best is to read it yourself.
However I want to mention the main take-out for me, which is that the principle of least (or better stationary) action in fact is just a mere estimation of a more advanced approach, which is really mind blowing. That is that for a particle travelling from A to B, it is not enough to consider only shortest path taken by the particle, but one has to consider all possible paths between A and B. For each of those paths, one has to compute some complex-valued contribution, the so-called probability amplitude. Then one has to add all these amplitudes, Feynman’s little arrows, together resulting in an overall probability amplitude. And finally square the absolute value of this probability amplitude to obtain the probability that a particle shows up at B.
The mind-blowing part is that the particle seems to be not at one spot only, but "is there" all over the place. In case paths are very close and similar to each other they will reinforce each other, which leads as approximation to the principle of stationary action.
It looks complicated, it is complicated, but has some beautiful applications explaining the strange behaviour of both light and matter.
As I said, read it yourself. Jeroen Bos-mulder's Reviews > QED: The Strange Theory of Light and Matter
As can be expected from any book by Richard Feynman, this book is a joy to read. Feynman manages to explain in clear layman's terms why it seems that light travels by straight lines, how light reflects from surfaces, why it behaves wave-like and how light-particles interact with electrons. In the final part of the book he concludes with an appetizer on the so-called quantum chromodynamics (QCD), which is the theory of the (strong) interaction between even more exotic particles.
Feynman takes the reader by the hand starting with simple examples and step-by-step advance on those examples pointing out the strangeness of the theory when scales or distances get very, very small. It would not make sense to summarise here what is so perfectly described in his book, best is to read it yourself.
However I want to mention the main take-out for me, which is that the principle of least (or better stationary) action in fact is just a mere estimation of a more advanced approach, which is really mind blowing. That is that for a particle travelling from A to B, it is not enough to consider only shortest path taken by the particle, but one has to consider all possible paths between A and B. For each of those paths, one has to compute some complex-valued contribution, the so-called probability amplitude. Then one has to add all these amplitudes, Feynman’s little arrows, together resulting in an overall probability amplitude. And finally square the absolute value of this probability amplitude to obtain the probability that a particle shows up at B.
The mind-blowing part is that the particle seems to be not at one spot only, but "is there" all over the place. In case paths are very close and similar to each other they will reinforce each other, which leads as approximation to the principle of stationary action.
It looks complicated, it is complicated, but has some beautiful applications explaining the strange behaviour of both light and matter.
As I said, read it yourself. Jeroen Bos-mulder's Reviews > QED: The Strange Theory of Light and Matter
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