Tag Archives: Richard Feynman

“What is the feeling” between the two magnets?

Richard Feynman explains “why” questions in general are asking for an explanation in terms of the familiar.



Nic Astaire

In case you missed the layman’s answer:

When you push your hand against a chair, contrary to how it seems to you, the atoms of your hand DO NOT come in contact with the atoms of the chair. The electrical forces repel the atoms WITHOUT ANY CONTACT (although the distance is so small you’d need a microscope to see the spaces between the atoms).

With magnets its the same, except that the distance is large enough to be seen without a microscope due to alignments of the contributing forces.

form Quora


Feynman’s Question

One might ask why is it possible for Donald Trump to stay reasonably happy when woefully ignorant of the science of the world he lives in?

“I say, and I think you must all know from experience, that people– I mean the average person, the great majority of people, the enormous majority of people– are woefully, pitifully, absolutely ignorant of the science of the world that they live in, and they can stay that way. I don’t mean to say the heck with them, what I mean is that they are able to stay that way without it worrying them at all– only mildly– so from time to time when they see CP* mentioned in the newspaper they ask what it is. And an interesting question of the relation of science to modern society is just that– why is it possible for people to stay so woefully ignorant and yet reasonably happy in modern society when so much knowledge is unavailable to them?”
Richard Feynman, in The Pleasure of Finding Things Out, 1999

*From Wikipedia: CP-symmetry, often called just CP, is the product of two symmetries: C for charge conjugation, which transforms a particle into its antiparticle, and P for parity, which creates the mirror image of a physical system. The strong interaction and electromagnetic interaction seem to be invariant under the combined CP transformation operation, but this symmetry is slightly violated during certain types of weak decay. Historically, CP-symmetry was proposed to restore order after the discovery of parity violation in the 1950s.

Einstein lecturing at the College de France, Paris 1922


Pacem in Terris and the Meaning of It All

In a Review of Richard Feynman’s The Meaning of it all, Timothy Ferris calls it to our attention that  Feynman views the 1963 Encyclical of Pope John XXIII, “Pacem in Terris,”  as one of the most remarkable statements of our time. Ferris is no less impressed than I that the Pope, God’s representative on Earth, and Richard Feynman, one of man’s principal spokespersons for a Godless Earth and Cosmos, are of the same opinion regarding the “meaning of it all,” regarding what’s important, regarding what’s really important in respect to how we should fashion our lives together, regarding the moral or ethical underpinings of our lives.


Here is what Feynman says about the Encyclical at the very end of the Meaning of it All, the end of This Unscientific Age, the third of the John Danz lectures:

I consider the Encyclical of Pope John XXIII, which I have read, to be one of the most remarkable occurrences of our time and a great step to the future. I can find no better expression of my beliefs of morality, of the duties and responsibilities of mankind, people to other people, than is in that encyclical. I do not agree with some of the machinery which supports some of the ideas, that they spring from God, perhaps, I don’t personally believe, or that some of these ideas are the natural consequence of ideas of earlier popes, in a natural and perfectly sensible way. I don’t agree, and I will not ridicule it, and I won’t argue it. I agree with the responsibilities and with the duties that the Pope represents as the responsibilities and the duties of people. And I recognize this encyclical as the beginning, possibly, of a new future where we forget, perhaps, about the theories of why we believe things as long as we ultimately in the end, as far as action is concerned, believe the same thing.

Now this is not what most often happens, a Pope and a Nobel Prize winning physicist being of one mind. Feynman’s bonding with the Pope’s words in this instance is certainly remarkable, but probably no less so than the Pope’s own words regarding peace on earth, Pacem in Terris.

What does the Pope have to say in the Encyclical? But first what is an Encyclical? An Encyclical is a papal document in the form of a circulating letter concerning Catholic doctrine usually addressed to patriarchs, primates, archbishops, and bishops of the church, this one some 40 pages and 16,000 words long, much too long for me to include in this Blog post. I’ve read it myself (it’s readily available online if you follow this link, Pacem in Terris). I agree with Feynman that it is a truly remarkable document.

Now in my eighties this is my very first real contact with an Encyclical. Pacem In Terris  was the last one of a total of eight Encyclicals from Pope John. Pope Francis, the present Pope, has two to his name so far. The greatest number of Encyclicals, 85, were from Pope Leo XIII, between 1878 and 1903. The very first document to be given the name Encyclical is a letter, “Ubi Primum,” written in 1740 by Pope Benedict XIV.

No summary of the Pope ‘s 40 pages and 16,000 words is possible, but the following selections from Pacem in Terris should give you a good idea of what impressed Feynman. There are 172 paragraphs in the original document. I’ve selected a few of these that seem particularly relevant to us today, in the throes of a very painful and unsatisfactory presidential election cycle. Would that our politicians of all stripes stop whatever it is they are presently doing and read though this Encyclical of John XXIII.

To Our Venerable Brethren the Patriarchs, Primates, Archbishops, Bishops, …


1. Peace on Earth—which man throughout the ages has so longed for and sought after—can never be established, never guaranteed, except by the diligent observance of the divinely established order.
2. That a marvelous order predominates in the world of living beings and in the forces of nature, is the plain lesson which the progress of modern research and the discoveries of technology teach us. And it is part of the greatness of man that he can appreciate that order, and devise the means for harnessing those forces for his own benefit….
4. And yet there is a disunity among individuals and among nations which is in striking contrast to this perfect order in the universe. One would think that the relationships that bind men together could only be governed by force….
9. Any well-regulated and productive association of men in society demands the acceptance of one fundamental principle: that each individual man is truly a person. His is a nature, that is, endowed with intelligence and free will. As such he has rights and duties, which together flow as a direct consequence from his nature. These rights and duties are universal and inviolable, and therefore altogether inalienable…
11. We must speak of man’s rights. Man has the right to live. He has the right to bodily integrity and to the means necessary for the proper development of life, particularly food, clothing, shelter, medical care, rest, and, finally, the necessary social services. In consequence, he has the right to be looked after in the event of illhealth; disability stemming from his work; widowhood; old age; enforced unemployment; or whenever through no fault of his own he is deprived of the means of livelihood.
12. Moreover, man has a natural right to be respected. He has a right to his good name. He has a right to freedom in investigating the truth, and—within the limits of the moral order and the common good—to freedom of speech and publication, and to freedom to pursue whatever profession he may choose. He has the right, also, to be accurately informed about public events.
13. He has the natural right to share in the benefits of culture, and hence to receive a good general education, and a technical or professional training consistent with the degree of educational development in his own country…
16. The family, founded upon marriage freely contracted, one and indissoluble, must be regarded as the natural, primary cell of human society. The interests of the family, therefore, must be taken very specially into consideration in social and economic affairs, as well as in the spheres of faith and morals. For all of these have to do with strengthening the family and assisting it in the fulfilment of its mission.
17. Of course, the support and education of children is a right which belongs primarily to the parents.
18. In the economic sphere, it is evident that a man has the inherent right not only to be given the opportunity to work, but also to be allowed the exercise of personal initiative in the work he does.
19. The conditions in which a man works form a necessary corollary to these rights. They must not be such as to weaken his physical or moral fibre, or militate against the proper development of adolescents to manhood. Women must be accorded such conditions of work as are consistent with their needs and responsibilities as wives and mothers.
20. A further consequence of man’s personal dignity is his right to engage in economic activities suited to his degree of responsibility. The worker is likewise entitled to a wage that is determined in accordance with the precepts of justice. This needs stressing. The amount a worker receives must be sufficient, in proportion to available funds, to allow him and his family a standard of living consistent with human dignity…
21. As a further consequence of man’s nature, he has the right to the private ownership of property, including that of productive goods. This, as We have said elsewhere, is “a right which constitutes so efficacious a means of asserting one’s personality and exercising responsibility in every field, and an element of solidity and security for family life, and of greater peace and prosperity in the State.”
22. Finally, it is opportune to point out that the right to own private property entails a social obligation as well.
23. Men are by nature social, and consequently they have the right to meet together and to form associations with their fellows. They have the right to confer on such associations the type of organization which they consider best calculated to achieve their objectives…
25. Again, every human being has the right to freedom of movement and of residence within the confines of his own State. When there are just reasons in favor of it, he must be permitted to emigrate to other countries and take up residence there. The fact that he is a citizen of a particular State does not deprive him of membership in the human family, nor of citizenship in that universal society, the common, world-wide fellowship of men…
28. The natural rights of which We have so far been speaking are inextricably bound up with as many duties, all applying to one and the same person. These rights and duties derive their origin, their sustenance, and their indestructibility from the natural law, which in conferring the one imposes the other…
30. Once this is admitted, it follows that in human society one man’s natural right gives rise to a corresponding duty in other men; the duty, that is, of recognizing and respecting that right. Every basic human right draws its authoritative force from the natural law, which confers it and attaches to it its respective duty. Hence, to claim one’s rights and ignore one’s duties, or only half fulfill them, is like building a house with one hand and tearing it down with the other.

What has been the most difficult concept for you to grasp?

There are those who think that given the proper surroundings you can grasp any concept. Salmon Khan, someone whose Khan Academy I greatly admire, says that the only thing you have to know is “that you can learn anything.”

He qualifies that somewhat when he adds:
Most people are held back not by their innate ability, but by their mindset. They think intelligence is fixed, but it isn’t. Your brain is like a muscle. The more you use it and struggle, the more it grows. New research shows we can take control of our ability to learn. We can all become better learners. We just need to build our brains in the right way.

Now, “that you can learn anything” has not been my own personal experience. There have been an endless number of things that I have not been able to learn (I’m still struggling with elements of pre-calculus, not to mention power series and intervals of convergence from my Cal 2 text). But let me be quick to say that that’s not the same thing as saying you can’t try, and profitably, to learn anything. And I think that’s probably what Sal means.

Now even those who seem to be the brightest of the brightest, such as, for example, the STEM graduates of Cal Tech, MIT, Stanford, Harvard and Princeton probably find some concepts too difficult for them. And if they don’t while in school they keep at it until they do (although that’s probably not the reason they keep at it).
All this is to say that intelligence and other gifts are not equally shared or distributed. From experience we learn early on that they are not. But this is something that we talk about very little, because it’s politically incorrect to say so in a country such as the United States where we are not all, somehow, “equal.” Nor is it to say that everyone’s intelligence doesn’t have limits, even that of Richard Feynman. It does.
Anyway I stumbled on these ideas while thinking about a Quora question that came in my email this morning, What is the most difficult concept to grasp in physics? and then about Alejandro Jenkins’ fascinating answer that I repeat here:

A famous Harvard physics professor (Ed Purcell maybe?), said that undergraduate physics students come in expecting that the hardest thing they’ll have to learn will be either relativity or quantum mechanics.  Actually, those are the most novel topics (i.e., the ones involving notions that are the most surprising from our ordinary, common-sense perspective).  But the hardest thing that an undergraduate physics students must learn is the classical dynamics of spinning tops (also called, in this context “rigid bodies”).Having taught classical mechanics to advanced undergraduates in physics, I find this to be true.  The following figure, which I’ve taken from chapter VI, sec. 37 of the Mechanics by Landau andLifshitz, shows possible values of the angular momentum vector, in the non-inertial body frame, for a free, asymmetric top.  The ellipsoid is a surface of constant energy, and the closed curves are given by the intersection of that ellipsoid with spheres of various radii, corresponding to different values of the total magnitude of the angular momentum:

This leads to an interesting result about the free asymmetric top, which some people call the “tennis racket theorem“: the top can spin stably about the principal axes with the least (x_1) or the greatest moments of inertia (x_3), but not around the intermediate axis (x_2).  You can demonstrate this by spinning a tennis racket or a ping-pong paddle in the air, as shown here:

If you still don’t believe me that tops can really be such a headache, I suggest looking up the “Poinsot construction”, which even inspired a humorous poemby Prof. David N. Williams, of the U. of Michigan.  Or check out the explicit solutions to the motion of the free asymmetric top in terms of Jacobi elliptic functions (and this is for a free top, mind you, with no net torque acting on it).

The great theoretical physicist James Clerk Maxwell (1831-1879), discoverer of the laws of electrodynamics, wrote that

“To those who study the progress of exact science, the common spinning-top is a symbol of the labours and the perplexities of men.”

Actually, tops can be such a tricky subject to teach that many lecturers tend to gloss over them, especially now that we’re in a rush to get to quantum physics.
Still, even though the classical mechanics of spinning tops can be hard to grasp, it’s perfectly well defined.  The mathematics of (non-relativistic) quantum mechanics is fairly straightforward by comparison, but the interpretation of what the rules of quantum mechanics mean, especially insofar as they concerns the process of measurement, remains quite obscure.  Most physicists are content to compute observable quantities, leaving the interpretation to the philosophers, an attitude captured in a famous dictum, often wrongly attributed to Richard Feynman, to “shut up and calculate”; see N. D. Mermin, “Could Feynman have said this?“, Physics Today 57, 10 (2004).

Things do get pretty hairy when you need a description that’s both quantum and relativistic, which is the regime of high-energy physics.  This requires what’s known as quantum field theory, which is a subject that still presents many conceptual difficulties, despite its great predictive successes.  But quantum field theory is not usually studied at the undergraduate level.

Alejandro Jenkins  Caltech PhD ’06 (physics), Harvard ’01 (Physics and Math)