Notes on Revolutions in Physics in the Twentieth Century

Abstract

Often, the presentation in teaching paths of what is known in physics resembles a description of a series of incremental steps, giving the false impression of sequential progress in which historical and philosophical contexts play no role. In this essay, we collect a series of notes on the revolutions in physics in the twentieth century to show that things are quite different. From these remarks and observations, the role of a complex and lively cultural intermingling with philosophy and mathematics, as well as some specific features of the various developments, emerge clearly; moreover, the essential role of some specific individuals becomes evident. It is argued that it would be interesting to make a systematic comparison between the way the revolutions in fundamental physics took place in the last century and the way this discipline is organized today.

Appendices

Appendix A: On Stances Toward Research in Fundamental Physics

As mentioned at the outset, in this short essay we focus mainly on fundamental physics topics.

However, although there is some consensus on what is meant by this term, the concept of “fundamental” is not self-defined and can cause some confusion. For instance, it may obscure the role of the link between the various disciplines for progress, it may lead to overlooking the more complex passages in the history of science, and it may present a distorted picture of knowledge, exaggerating the importance of the state achieved in a certain moment, etc.

An amusing recent episode, which sheds light on these considerations, offering food for thought on modern procedures and ways of attaching importance to certain scientific topics and not to others, is provided in an article by White (2007), where the words “fundamentalist” occurred in the title shows its polemical nature.

This work was intended to oppose the strong pressure from other scientific communities to convey mainly or exclusively the resources of astronomers on a single research topic, Dark Energy, allegedly more fundamental than others.

Appendix B: The Photon, an Elusive Concept

It is interesting to report the opinion of Feynman on the meaning of the same point, expounded to a wide public (Feynman 1968). To fully appreciate his words, let us briefly recall the context. These remarks are from the above-mentioned speech, where Feynman repeatedly states that he owes a great and welcome debt to his father, who guided him in the development of a rich and original vision of science. As soon as he grew and concluded his scientific education, his father turns to him, begging for clarification on a question he has never been able to answer. Here is the exchange between father and son, as reported by Feynman (Feynman 1968).

(...) It was a wonderful world my father told me about.

You might wonder what he got out of it all. I went to MIT. I went to Princeton. I came home, and he said, “Now you’ve got a science education. I have always wanted to know something that I have never understood, and so, my son, I want you to explain it to me.” I said yes.

He said, “I understand that they say that light is emitted from an atom when it goes from one state to another, from an excited state to a state of lower energy.” I said, “That’s right.”

“And light is a kind of particle, a photon, I think they call it.” “Yes.”

“So if the photon comes out of the atom when it goes from the excited to the lower state, the photon must have been in the atom in the excited state.” I said, “Well, no.”

He said, “Well, how do you look at it so you can think of a particle photon coming out without it having been in there in the excited state?” I thought a few minutes, and I said, “I’m sorry; I don’t know. I can’t explain it to you.”

He was very disappointed after all these years and years of trying to teach me something, that it came out with such poor results (…)

Let us forget for a moment his eccentric attitudes and let us put aside the role homo novus that he—an American—happened to cover, among the many theoretical physicists from the old continent. Behind the brilliant prose to which we are accustomed, it is apparent that Feynman is very interested in philosophical questions, even though he professes the opposite in various circumstances; what he stigmatizes, apparently, is a certain type of thinking, which instead of addressing the problems and dilemmas posed by our attempt to reconcile our experience and our image of the world, is content with itself. We are therefore led to the conclusion that, also in this respect, Feynman is in full and perfect continuity with many of his predecessors who accomplished the scientific revolutions of ‘900. In fact, we can find no valid reason not to consider him among the main protagonists of physics in the latter part of the twentieth century.

We conclude with a sentence from a famous letter of Einstein to Michele Besso (12 Dec. 1951):

All those 50 years of careful pondering have not brought me closer to the answer to the question: ‘What are light quanta?’ Today any old scamp believes he knows, but he’s deluding himself.