The price of gaining an accurate theory has been the erosion of our common sense

Review of Richard Feynman’s QED: The strange theory of light and matter

The title of the post is a quote from Feynman’s book. Written by a Nobel laureate and one of the most beloved scientists, it is perhaps the best explainers of a theory that flips everything we know about physical phenomena on its head. It explains quantum electrodynamics (QED), a theory that explains 99% of all phenomena that involve photons and electrons.

But to be able to understand it one must, as Feynman puts it:”accept some very bizarre behaviour: a single beam of light reflecting from all parts of a mirror, light travelling in paths other than a straight line, photons going faster or slower than the speed of light, electrons going backwards in time, photons disintegrating into a positron-electron pair, and so on.”

This book is a series of four lectures that Feynman gave in 1983 at the University of California in Los Angeles. It is a short and entertaining, but intense read. Feynman goes into quite a lot of detail about how QED can be explained by the use of arrows drawn on a sheet of paper (!). But as Feynman claims, more than a few times in the book, what you get from the book is the spirit of the theory. To be able to use it accurately students regularly study it for several years. (Here’s an example of how I used QED to explain a new type of flat lens).

There is enough packed into the last few pages of the book as is in the remainder. In them Feynman, who says “Being a professor means having the habit of not being able to stop talking at the right time”, tries to explain the rest of physics apart from QED. His aim is to show that physicists’ search for elegance in nature through theories of physics is necessary, mostly because of the complexity of understanding how nature works. Perhaps we are being too naive, perhaps not. We won’t know till we make theories and test them. QED has stood 70 years of rigorous testing.

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