Shut up and let me think! Or why you should work on the foundations of quantum mechanics as much as you please

If you have a restless intellect, it is very likely that you have played at some point with the idea of investigating the meaning and conceptual foundations of quantum mechanics. It is also probable (albeit not certain) that your intentions have been stopped on their tracks by an encounter with some version of the “Shut up and calculate!” command. You may have heard that everything is already understood. That understanding is not your job. Or, if it is, it is either impossible or very difficult. Maybe somebody explained to you that physics is concerned with “hows” and not with “whys”; that whys are the business of “philosophy” —you know, that dirty word. That what you call “understanding” is just being Newtonian; which of course you cannot ask quantum mechanics to be. Perhaps they also complemented these useful advices with some norms: The important thing a theory must do is predict; a theory must only talk about measurable quantities. It may also be the case that you almost asked “OK, and why is that?”, but you finally bit your tongue. If you persisted in your intentions and the debate got a little heated up, it is even possible that it was suggested that you suffered of some type of moral or epistemic weakness that tend to disappear as you grow up. Maybe you received some job advice such as “Don’t work in that if you ever want to own a house”. I have certainly met all these objections in my short career, and I think that they are all just wrong. In this somewhat personal document, I try to defend that making sense of quantum mechanics is an exciting, challenging, important and open scientific endeavor. I do this by compulsively quoting Feynman (and others), and I provide some arguments that you might want to use the next time you confront the mentioned “opinions”. By analogy with the anti-rationalistic Copenhagen command, all the arguments are subsumed in a standard answer to it: “Shut up and let me think!” ∗ [email protected] — http://www.pabloecheniquerobba.com 1 ar X iv :1 30 8. 56 19 v3 [ qu an tph ] 2 9 Se p 20 13 1 On a personal note Science alone of all the subjects contains within itself the lesson of the danger of belief in the infallibility of the greatest teachers in the preceding generation. . . Learn from science that you must doubt the experts. As a matter of fact, I can also define science another way: Science is the belief in the ignorance of experts. — Feynman (1968) I have recently decided that I will spend some time and effort to try to come up with a consistent and satisfying account of how QM (quantum mechanics) works and what QM means. That is, consistent and satisfying to me. My decision is based on a fact and a conviction: The first is that I enjoy the topic immensely, the second is that I believe that a conceptual tidying up is an urgent necessity in the field. Both circumstances combined make my decision an easy bargain. Although many scientists and philosophers certainly agree with me on this, there is a strong and steady current of thought, and statements, that sees such a tidying-up enterprise as futile and entirely irrelevant. Everything is perfectly tidy for them. Their viewpoint (slightly caricaturized or not so much, depending on who we are talking about) is that nonrelativistic QM has been completely understood an unspecified number of decades ago, that the so-called “measurement problem” is no problem at all, and that all the discussions about the different “interpretations” of QM are a distraction at best, a waste of the time and effort of otherwise reasonable individuals at worst. What you need to do about QM, they say, is just learn it from some undergraduate-level textbook —which one, it doesn’t matter, since the topic has been carved in stone long ago and now it is just an exceedingly straightforward application of linear algebra. Then you apply it to whatever practical application gets you the most funding, money, h-index or just the fastest path to tenure if you haven’t got it yet, and you are done. If you do not care about money, stability or prestige, you can choose the topic to which you want to apply the finished theory known as QM on the basis of the common interest of your department, of the scientific community, of humankind, or of the whole biosphere, whichever group you consider to be the worthy beneficiary of your efforts. What is also remarkable is that the advocates of this position not only decline to work in such an irrelevant enterprise as the foundations of QM themselves (something that falls entirely within the bounds of their scientific and personal freedom), but they very frequently add (and they do that with vigor) that you shouldn’t waste your time in that either. . . or something to that effect. Maybe this intensity of purpose is what has caused the whole viewpoint to be sometimes dubbed “Shut up and calculate!”; a motto which has been attributed to Feynman but that seems to have been actually coined by Mermin (2004) (even if he is not sure about it). The proponents of the shut-up-and-calculate approach to the understanding of QM often perform this pastoral work (of trying to save as many lost souls as possible from the bleak fate of irrelevance) wearing the dignified robes of pragmatism, commitment to progress, clarity, and orthodoxy. Also, among their ranks, we can find celebrated scientists and deep thinkers that have achieved significant advances in so many fields, which makes their claims even more appealing. I don’t know what the experience of the reader has been, but I have met this friction, this headwind, this resistance, frequently in my (short) career. When you start studying, 1 In fact, although Feynman maybe didn’t say it, he was indeed close. When he is discussing the measurement rules for the double-slit experiment in his famous Lectures, he writes (Feynman, 1963a, p. 101): “So at the present time we must limit ourselves to computing probabilities.”