## Sunday, January 25, 2009 ... /////

### Anti-quantum zeal

A few days ago, we talked about the lethal flaws of the Bohmian mechanics.

It was very far from the first time when I noticed that rational arguments don't play an important role in the debates about the interpretation of quantum mechanics because one side always ends up by saying that regardless of any arguments, canonical quantum mechanics makes no sense. They won't hear any answer until you tell them the answer they are waiting for, namely that the microscopic world behaves just like the world they know from their everyday lives.

You know, when I was 15 or so, I was also "disappointed" by the philosophical framework of quantum mechanics.

It looked weird and incomplete. What I wanted to see as a theory of everything was just a more complete version of Einstein's equations of general relativity. I spent quite some time by attempts to develop alternatives to quantum mechanics. However, because I cared about the experiments, they had to be explained. So I was stealing methods and tools from quantum mechanics, one by one, seeing that it was inevitable, and eventually I had to steal all of quantum mechanics, including its probabilistic interpretation.

There simply can't be an alternative. Everyone who thinks that there is one is deluded and misunderstands some very important things about modern physics.

You know, to describe the measured discrete quantum numbers of atoms (or the interference of particles), you need the wave function and the conditions of its single-valuedness. On the other hand, particles are observed at specific points. And unless you accept the probabilistic interpretation of the wave function, with no additional classical degrees of freedom or hidden variables, you will ruin not only quantum mechanics but also the other pillar of the modern physics, relativity, as you can see by a detailed analysis of the EPR experiments.

Unlike the previous essay, this one will attempt to be more sociological in character.

Evidence vs prejudices

All these conclusions above may be surprising but they indisputably follow from the scientific evidence. You know, whether or not an electron has a uniquely defined classical position or spin before it is measured, is just another scientific question that can only be answered by scientific tools. It is not a philosophical or religious question.

The situation is analogous to the question whether the Earth was orbiting the Sun or vice versa.

You know, that wasn't a question to be answered by the priests according to their interpretation of the Scripture, either. The priests often found the question to be far too important to allow science to decide it. But that's why they were priests, not scientists. Some people simply can't get used to the fact that science can interfere with their basic beliefs and prejudices and it is science, not the prejudices, that offers us the only quasi-systematic method to find the right answers to any of these questions, including the very important ones.

When we ask Nature through experiments - and their careful analyses - whether the particles always have unique, well-defined, classical positions, before they're measured, She tells us
• No
• Probably no
• No
• No
• No
Some people obviously don't care about any of these lessons. Their answer has to be
• Yes
• Yes
• Yes
• Yes
• Yes
and they will simply never give up. The scientific evidence is completely irrelevant for them. Yes, Mephisto, it is called bigotry.

This is about their basic beliefs how the world should work. If the phenomena don't have a (classical) "mechanism" that they can imagine, they simply won't buy it! The theory makes no sense, does it? Electrons must be just like little children who are located somewhere, who remember something in their little brains, and who must be taught what to do. If similar analogies with the macroscopic world can't be made, they won't accept the theory.

A few days ago, Christine Dantas linked to an 2001 interview with Carver Mead, a semi-famous computer scientist who is also an armchair physicist. At that time, he published a book about Collective Electrodynamics, claiming that the photons don't exist because they're just collective illusions of the electrons, and that quantum mechanics has to be abandoned, too. To do so, he updated Cramer's transactional interpretation of quantum mechanics (which is closer to a fairy-tale about time machines than to an interpretation of quantum mechanics). A classic crackpot book.

If you read the interview, you will see the deep contrast in the types of arguments used by both sides. Richard Feynman, whose opinions about the character of quantum mechanics matched mine, was quoted as saying:
Things on a very small scale behave like nothing you have direct experience about. They do not behave like waves. They do not behave like particles ... or like anything you have ever seen. Get used to it.
He also promoted the "shut up and calculate" approach to the interpretation of quantum mechanics, trying to stop his students from pursuing nonsensical philosophies. (But the specific quote, "shut up and calculate", comes from David Mermin.)

Well, what Feynman says is obviously true. There's a huge body of evidence that the microscopic world where quantum phenomena matter simply behaves nothing like the macroscopic world we are used to - i.e. the world that was studied by cutting-edge science a few centuries ago. It's not shocking that the laws needed to understand the microscopic world differ from the intuition of the people whose lives were dominated by macroscopic, nearly classical events. But some people simply can't get used to it.

Carver Mead is an example. He said:
Physics that does not make sense, that defies human intuition, is obscurantist: It balks thought and intellectual progress. It blocks the light of the age.
Well, these words sound like a prayer from a religious zealot rather than words from a rational person. You know, Nature doesn't give a damn about human intuition. If you have good intuition to understand Nature, good for you. If you don't, that's too bad. But not even the light of the age allows you to blame or re-educate Nature when your intuition appears to be non-existent. And your lack of intuition for the observed phenomena is surely not a good reason to promote you to a spokesman of science!

To make things worse, his book started by the following sentence:
It is my firm belief that the last seven decades of the twentieth will be characterized in history as the dark ages of theoretical physics.
Almost like a Peter Woit multiplied by two. ;-) What a complete denial of the scientific method and the most important results of this method achieved in the 20th century. You know, the whole career (computers etc.) of this guy was made possible by the quantum revolution in theoretical physics but he still describes these developments as the "dark ages".

Quantum mechanics courses and beliefs about interpretations

The champions of the Bohmian and other crazy interpretations of quantum mechanics argue that the interpretation of quantum mechanics is not given enough space in the curriculums. And you know what? I agree with it completely. The only "detail" I disagree with are the answers that should be taught.

Most active physicists don't care about the interpretations. They silently and operationally accept the probabilistic interpretation and most of them don't want to ask deeper questions about it because they have been taught that it doesn't lead anywhere. It has become popular for most people to say a negative thing or two about the Copenhagen interpretation but if you study what the active physicists actually think, they would agree with the guys in the Copenhagen school (the Copenhagen people would probably be more ready for debates than the people today!) and they would agree that virtually no progress occurred after them.

So the active physicists agree that almost no progress occurred in the non-probabilistic interpretations. But if you investigate what the physicists actually think about the ideal or expected future status of the matters, regardless of their shared interpretation of the history, you will see that their attitudes are diverse, indeed.

Because this stuff isn't frequently discussed in between the physicists, you will hear them adopting the jargon of the philosophers, mentioning that the entanglement experiments prove "nonlocality" of the laws of physics (even though in their papers, they correctly talk about "local quantum field theories"). Also, you will hear them suggesting that there could be a deterministic picture underneath the quantum clothes, one that they just don't want to look for right now, and so on.

For example, when I discussed these matters with a very good physicist and the author of famous books, before his second, equally excellent book was finalized, I learned that sharp answers about these things are surely not common even though the evidence is surely vast enough to give us sharp answers to virtually all related questions.

If you know what book I am talking about, it's great as a popular book. Most readers of popular books don't want to focus on the actual correct insights and theories - theories that can actually be pursued in meaningful research - too much. They want to read about everything that has ever been associated with physics because it's more fun for them (and sometimes even for us). All the human players must be there, regardless of the validity of their statements, and all questions must be permanently open. This is of course not how the actual scientists may approach competing hypotheses because they would never get anywhere but popular readers can afford it. And the book covers the possible opinions about quantum mechanics extremely well. It also explains the EPR phenomena with a perfect example.

But to actually believe that all these interpretations are "alive" is simply crazy. I am not talking about the Bohm interpretation only. There are many other, manifestly wrong approaches. For example, the Ghirardi-Rimini-Weber theory (paper) argues that the wave function for all particles is a real wave (in 3N dimensions) that spreads but its dependence on the position of each chosen particle spontaneously "collapses" every 100 million years (3e15 seconds) - which they believe to be a sufficient reason why no mixed Schrödinger's cats were ever observed.

You have to choose a very long timescale because this kind of a "collapse" - and a "kick" it would give to the surrounding matter - has never been seen. On the other hand, they want this unseen effect to be responsible for the classical character of the whole macroscopic world we observe. They don't see any tension in between the previous two sentences. Isn't it just weird?

The collapse can't possibly be made compatible with quantum field theory that doesn't use and cannot use the particle positions as fundamental degrees of freedom (e.g. because particles can be created and destroyed, too). The very long time scale can't have anything to do with the scales of particle physics: it can't be derived from anything (it is rather a measure of the people's prejudice that defines who deserves to be called a conscious macroscopic observer; the solipsist theory that it is only your brain that is allowed to "collapse" the wave functions has exactly the same scientific support as this one).

Also, if you detect your photons by 10^{15} atoms on a thin and tiny photographic plate, you should be able to observe doubled images of the particle for a second or so. All these new predictions of the theory are absurd and I don't really believe that anyone seriously believes them. They just don't want to look at them. Their real goal is not a theory that only generates correct predictions; their real goal is a philosophically pleasing ideology that can be taught even if it is known to be scientifically invalid.

You simply can't explain the phenomena that influence every mesoscopic and macroscopic process everywhere in the Universe by a bizarre hypothetical effect that should appear at accessible scales but is so weak that it can't be observed. Basic rational physical intuition should be enough to see this much. Still, the paper has 800+ citations (although the popular books about the interpretation of quantum mechanics are the most famous ones among them).

Why are the people so obsessed with similar, manifestly contrived and almost certainly wrong ideas? Well, they have already partly understood that the wave function is useful. But if it is useful, it must "exist", they think, and the classical type of "existence" is the only type of existence they are ready to admit.

So the wave function must be "just another classical wave", and because observables (like positions) are observed with sharp values, they must either "exist" independently, or the wave function must literally "collapse". Otherwise they can't "imagine it", so it can make "no sense".

Because they want physics to "make sense", the discipline should forever study the ideal rules how to make the wave functions materialistically "collapse" - a hypothetical effect that is supported exactly by zero empirical (or rational & theoretical) evidence. Some people are more obsessed with these things than people in the past who used to be obsessed with geocentrism, creationism, or luminiferous aether (whose only justification was metaphysical, too).

Well, their beliefs are surely holy, and one must almost be afraid that we may insult their religious feelings. Except that the correct picture - where the wave function is just a tool to predict probabilities of measurements and no other information about the state of the world "exists" besides the complex amplitudes with the probabilistic meaning - makes a perfect sense, respects all the symmetries it should respect, correctly predicts everything that has been observed, and is composed out of several theoretical pieces that are consistent with each other and often reinforce each other.

That's what genuine science requires.

Determinism has been linked to science for quite some time. But if you look at the reasons why so many people around physics believe in 2009 that quantum mechanics has to be fundamentally wrong, you must see that not much has changed since the era of the Inquisition and witch hunts. People still hold certain beliefs that can't be touched by science. Just like their religious predecessors (and contemporaries), they think that science may be a good slave but it is a bad master. And when science begins to question their basic beliefs, its methods must be abandoned and replaced by Mead's "light of the age". Heretics, beware!

And that's their memo.
(Concerning heretics, Jennifer Marohasy talks about Jon Jenkins, an Australian professor who was effectively fired for a skeptical newspaper article about the catastrophic climate change. Science hasn't changed anything about the strength of people's religious and quasi-religious beliefs and their ability to do really nasty things to defend them.)
Bonus: Obama inauguration doubles U.S. blacks' brain mass

Steve Sailer has noticed a very cute article in The New York Times. New massive, gigantic, and representative nation-wide tests of 84 blacks (and even more whites!) after the inauguration show that all the IQ differences between ethnic groups became statistically insignificant. Congratulations, it is now time for everyone to celebrate!

After four more years of the removal of fake myths and the white science in general, most U.S. blacks will become able to contribute an idea for a footnote of a new revolutionary paper about the curvature of constitutional space. ;-)

If you want to read a somewhat more serious essay about the "stereotype threat theory" than the jokes on this blog, Cosmic Variance, or in the New York Times, open Sailer's Occam's butterknife.

#### snail feedback (2) :

I have the same views as yours on these matters of probabilistic interpretation, religious zeal and so on.

What troubles me about QM is that it seems to be incomplete. There is a sharp distinction between unitary evolution and instantaneous measurements. It is not clear what exactly constitutes a measurement, especially since the measurement apparatus itself is made of particles obeying QM laws. Wigner's 1962 paper ("The problem of measurement") shows how unitarity (or more accurately linearity) cannot hold during measurement. So at which point does Schrodinger's equation stop being valid and measurement begins?

Going further, one may ask: Is measurement really instantaneous, or does it happen over a time interval? Does it have some dynamics? In other words, can we somehow watch the wave function collapse? These are questions that could be potentially answered by experiment, if one has a good idea for a setup. What I like about Ghirardi's idea is that, although contradicting experiment, it is at least a falsifiable idea that tries to reconcile unitarity (or linearity) with measurement.

When relativity comes into play, things become even murkier. Considering now local operators, and the wave functional, what happens when we make a (local) measurement and find a particle in our detector? Does the wave functional change over some spacelike surface? What determines this surface? I'm just guessing wildly here, because I really have no idea.

You know, in all the courses I took and all the books I read so far about relativistic QM (mostly, but not limited to, QFT), the issue of measurement was almost never discussed. In fact, there is only one instance I can recall where it came up -- in a book dedicated to quantum measurement. And the comments there were not enlightening, to say the least.

I would love to hear your thoughts on this matter.

Cheers,
Guy