# “Measure for Measure”—a pop-sci video on QM

This post is about a video on QM for the layman. The title of the video is: “Measure for Measure: Quantum Physics and Reality” [^]. It is also available on YouTube, here [^].

I don’t recall precisely where on the ‘net I saw the video being mentioned. Anyway, even though its running time is 01:38:43 (i.e. 1 hour, 38 minutes, making it something like a full-length feature film), I still went ahead, downloaded it and watched it in full. (Yes, I am that interested in QM!)

The video was shot live at an event called “World Science Festival.” I didn’t know about it beforehand, but here is the Wiki on the festival [^], and here is the organizer’s site [^].

The event in the video is something like a panel discussion done on stage, in front of a live audience, by four professors of physics/philosophy. … Actually five, including the moderator.

Brian Greene of Columbia [^] is the moderator. (Apparently, he co-founded the World Science Festival.) The discussion panel itself consists of: (i) David Albert of Columbia [^]. He speaks like a philosopher but seems inclined towards a specific speculative theory of QM, viz. the GRW theory. (He has that peculiar, nasal, New York accent… Reminds you of Dr. Harry Binswanger—I mean, by the accent.) (ii) Sheldon Goldstein of Rutgers [^]. He is a Bohmian, out and out. (iii) Sean Carroll of CalTech [^]. At least in the branch of the infinity of the universes in which this video unfolds, he acts 100% deterministically as an Everettian. (iv) Ruediger Schack of Royal Holloway (the spelling is correct) [^]. I perceive him as a QBist; guess you would, too.

Though the video is something like a panel discussion, it does not begin right away with dudes sitting on chairs and talking to each other. Even before the panel itself assembles on the stage, there is a racy introduction to the quantum riddles, mainly on the wave-particle duality, presented by the moderator himself. (Prof. Greene would easily make for a competent TV evangelist.) This part runs for some 20 minutes or so. Then, even once the panel discussion is in progress, it is sometimes interwoven with a few short visualizations/animations that try to convey the essential ideas of each of the above viewpoints.

I of course don’t agree with any one of these approaches—but then, that is an entirely different story.

Coming back to the video, yes, I do want to recommend it to you. The individual presentations as well as the panel discussions (and comments) are done pretty well, in an engaging and informal way. I did enjoy watching it.

The parts which I perhaps appreciated the most were (i) the comment (near the end) by David Albert, between 01:24:19–01:28:02, esp. near 1:27:20 (“small potatoes”) and, (ii) soon later, another question by Brian Greene and another answer by David Albert, between 01:33:26–01:34:30.

In this second comment, David Albert notes that “the serious discussions of [the foundational issues of QM] … only got started 20 years ago,” even though the questions themselves do go back to about 100 years ago.

That is so true.

The video was recorded recently. About 20 years ago means: from about mid-1990s onwards. Thus, it is only from mid-1990s, Albert observes, that the research atmosphere concerning the foundational issues of QM has changed—he means for the better. I think that is true. Very true.

For instance, when I was in UAB (1990–93), the resistance to attempting even just a small variation to the entrenched mainstream view (which means, the Copenhagen interpretation (CI for short)) was so enormous and all pervading, I mean even in the US/Europe, that I was dead sure that a graduate student like me would never be able to get his nascent ideas on QM published, ever. It therefore came as a big (and a very joyous) surprise to me when my papers on QM actually got accepted (in 2005). … Yes, the attitudes of physicists have changed. Anyway, my point here is, the mainstream view used to be so entrenched back then—just about 20 years ago. The Copenhagen interpretation still was the ruling dogma, those days. Therefore, that remark by Prof. Albert does carry some definite truth.

Prof. Albert’s observation also prompts me to pose a question to you.

What could be the broad social, cultural, technological, economic, or philosophic reasons behind the fact that people (researchers, graduate students) these days don’t feel the same kind of pressure in pursuing new ideas in the field of Foundations of QM? Is the relatively greater ease of publishing papers in foundations of QM, in your opinion, an indication of some negative trends in the culture? Does it show a lowering of the editorial standards? Or is there something positive about this change? Why has it become easier to discuss foundations of QM? What do you think?

I do have my own guess about it, and I would sure like to share it with you. But before I do that, I would very much like to hear from you.

Any guesses? What could be the reason(s) why the serious discussions on foundations of QM might have begun to occur much more freely only after mid-1990s—even though the questions had been raised as early as in 1920s (or earlier)?

Over to you.

Greetings in advance for the Republic Day. I [^] am still jobless.

[E&OE]

## 4 thoughts on ““Measure for Measure”—a pop-sci video on QM”

1. Hi Ajit, How are you?

I know next to nothing about physics but what is this that a particle can be in two places at the same time? Maybe I am not asking the question in the right way, but perhaps you know what I mean.

I in fact am not doing too well—am jobless and that’s the reason behind it. But yes, some conceptual-level thinking on research, esp. QM, has been going on.

I once had thought (in 1991/92) that I had cracked the problem you mention, and later on had even published a paper on it (in 2005), though more recently (over the last couple of years or so), I have gradually come to change my viewpoint. I am not retracting my paper; I realize that its contents would still have some value, some role to play, in my revised view, too. However, this time around, I have decided to attack the problem in a more comprehensive and systematic way, and so, begin by presenting the overall framework of my thoughts, rather than rushing in with publishing individual papers that provide more detailed treatments of the individual small aspects. I mean, my published papers were only on photons, only for monochromatic radiation, only with a scalar wave equation, and only in 2D. I would now rather spell out at least the nature of the solution in full generality first, and then go for specific treatments or simulations. That’s why, this time round, it could be a smallish book, or a series of longer-length journal papers, directly.

In writing the above, I presumed that you knew about the wave-particle duality, as presented in the video.

In case you don’t know what the wave-particle duality problem itself is—which I would find very hard to believe because it has become so much a part of the popular culture by now—then please do see the video. The presentation of the problem itself, is done fairly well in there. For a free online write-up, guess Feynman’s presentation (in his Lectures) remains a pretty good source: http://www.feynmanlectures.caltech.edu/I_37.html. From the tons of specifically pop-sci level books, when I was still reading pop-sci accounts (until early 1991), I had found the discussions in the British books conceptually superior to any others; e.g, (a). Alastair I. M. Rae’s “Quantum physics: illusion or reality?” (1st edition—the treatment in the second edition has gone a bit down, IMO), and (b) John Gribbin: https://en.wikipedia.org/wiki/In_Search_of_Schr%C3%B6dinger's_Cat (again, this book is better, IMO, than its sequel: https://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_Kittens_and_the_Search_for_Reality).

In the more likely case that you already know what the wave-particle duality problem really is like, but are simply wondering aloud “how could it possibly be like that?,” then, well, … :). … That‘s what makes this physics problem so interesting, doesn’t it?

Please let me know whether you have read (at least the pop-sci) material like the above, and if necessary amplify your question(s), and then I will be happy to supply a more relevant description/explanation of what at least the problem itself is like, and/or to suggest other sources (textbook or pop-sci level).

Best,

–Ajit
[E&OE]

2. My best wishes for your finding a good job. Take care of yourself.

I have heard that physicists talk about wave function collapse on observation. I am interested in the philosophical aspect of this thing. Can you tell me in everyday language about it? I will not be able to understand the physics of this. By the way I have read three books of Schrodinger about philosophy and I like him very much.

Yes, according to the mainstream interpretation of QM, if your experimental apparatus is designed to measure the position of a quantum object, then the wavefunction representing it does collapse to a point during such an observation. Now, a wavefunction completely characterizes the state of a quantum system. Thus, during position measurement, a wave—which is continuously spread throughout space—is said, in the mainstream (Copenhagen) interpretation, to collapse to an infinitely sharp spike, of Dirac’s delta. But the spike (i.e. Dirac’s delta) is obviously defined in reference to a single distinguished point and no other points. This assertion—that there is such a collapse—is actually to be taken, in the mainstream (Copenhagen) interpretation as a postulate; it is known as the collapse postulate.

The above was a slightly more rigorous way of putting it. To put it in the everyday language, it would be something quite similar to what you yourself have said, so I didn’t pursue that.

IMO, the collapse postulate is the only remaining problem about foundations of QM.

You (and everyone else) is welcome to think about it. However, let me clarify and very emphatically and firmly state one very important point.

The problem of the collapse postulate is a problem from physics, not from philosophy.

If you wish to fully understand and address this specific problem of physics, then you have no choice but to learn physics: classical physics and quantum physics, at least up to the UG (Physics major) level. There is no other way about it.

Sorry, it does sound discouraging, but to the best of my knowledge, it is true. It is primarily a problem of physics, not of philosophy.

So, there.

I have not read Schrodinger’s writings on philosophy. I would have read them if I were to think that the problem was from philosophy. But it is not, and so, though I have books that in part deal with this aspect of Schrodinger’s, during my reading I skip those parts. (Just the way his alleged affairs or sex life has no relevance to understanding the process of how he might have come up with his equation, similarly, for his philosophy. And I skip both, when I read books that contain such materials.)

Over the years, I have come to realize that, contrary to my earlier expectations, studying the explicit philosophy (or the philosophic poutings) of a physicist provides more insight into the man rather than into the theory of physics he himself has put forth. For instance, consider Leibniz. I heard him being mentioned in Dr. Peikoff’s audio courses on history of philosophy/Objectivism. I did try to see how Leibniz’s philosophic ideas of those monads might have prompted him to formulate his ideas about the energetics program, about the least action principles, about the calculus of variations. In the end, I realized that it was not necessary to do so. The two sets of ideas are more separate than connected, at least when you try to pursue the connection in the direction: from philosophy to physics. Here, see my recent couple of posts on the calculus of variations: https://ajitjadhav.wordpress.com/2017/01/06/see-how-hard-i-am-trying-to-become-an-approved-full-professor-of-mechanical-engineering-in-sppu-4/ and the post just before that. Two points: (i) you can read these two posts without knowing anything about Liebniz’s monads (or Maupertuis’ worlds), even though at least a common-sense acceptance of such philosophic ideas as the existence of an objective reality, logic, primacy of physics over maths, are of course taken for granted, and (ii) my pursuit of the question of what the $\delta$ means was in fact not helped by my readings of Leibniz’s or others’ specific out-shoots of philosophy—not even one bit, looking at it in retrospect.

So, some general philosophy is required, and does help, but detailed philosophies, esp. of physicists, are not at all necessary.

As I once recently remarked on Prof. Scott Aaronson’s blog, if you must introduce consciousness into a theory of physics, you don’t have to invoke QM for that, even just the plain old simple classical physics would do. Ditto, for philosophizing about the collapse postulate now.

Whatever philosophic viewpoint you wish to talk about, you can always in principle pursue that viewpoint without having to talk about it in reference of the collapse postulate. But if you really wish to address the collapse problem itself, then what you have to study and talk about is physics.

Best,

–Ajit