“QED: The Strange Theory of Light and Matter” by Richard Feynman


Having already read his autobiographies “Surely You’re Joking Mr Feynman” and “What Do You Care What Other People Think“, I was convinced that I could gain valuable insights into quantum electrodynamics (QED) from Feynman, who had a unique ability to explain the most complex concepts. “What one fool can understand, another can” (even though that one fool was a Nobel Laureate).

Feynman did not disappoint. He was not only a great physicist, but also a great teacher. He  explained QED so simply and plainly that I was reminded of a line from Sherlock Holmes, “Every problem is absurdly simple when it is explained to you”.

Feynman Diagram

The genius lies in the Feynman Diagrams. A simple diagram can capture the most fundamental interaction between a photon and an electron,  and complex diagrams build from combinations and variations of the simple diagram can be used to illustrate and illuminate the most complex problems in physics.

A Different Perspective

As far as I understand it, quantum electrodynamics differs from the classical wave-particle duality theory in that,  instead of building a model to explain and/0r predict the exact outcome of a particular event, it calculates the probability (amplitude) of the event. An amplitude is represented by a vector, the amplitudes of alternative events/paths are added and those of successive or simultaneous events are multiplied together to calculate the final amplitude, the square of which is the probability. For example, in the reflection of light by a surface of glass, it calculates accurately that 4% of the photons are reflected, though it can not predict whether or not a specific photon will be reflected.

On the large scale, quantum electrodynamics and classical physics agree, the latter being an approximation of the former. It is as if the complexities of quantum electrodynamics are encapsulated away and we are presented with a classical view of the universe that is simple and elegant.

For the philosophical minded people like me, it may well apply to the question of free will vs. inevitability. In the grand scheme of things, history or the fate of nations may be determined by laws, within which context, the life of an individual is very much free.



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