Thursday, June 06, 2019

Quantum transitions take time. This is not news.

A number of people have asked me to weigh in on this story in Quanta Magazine (based on this paper [PDF version] and also reported in this press release from Yale, and several other popular outlets.)

Here's how Quanta breathlessly reported the result:
When quantum mechanics was first developed a century ago as a theory for understanding the atomic-scale world, one of its key concepts was so radical, bold and counter-intuitive that it passed into popular language: the “quantum leap.” Purists might object that the common habit of applying this term to a big change misses the point that jumps between two quantum states are typically tiny, which is precisely why they weren’t noticed sooner. But the real point is that they’re sudden. So sudden, in fact, that many of the pioneers of quantum mechanics assumed they were instantaneous. 
A new experiment shows that they aren’t.
This is mostly hype.  While it is true that in the very early days of quantum mechanics some researchers (notably Niels Bohr) thought that quantum transitions were instantaneous, the fact that they aren't has been known for decades.  What is new here is that this is the first time that this fact has been demonstrated experimentally.  I don't want to detract from the technical accomplishment here in any way, it's a truly impressive experiment.  But it's not the kind of conceptual breakthrough that the Quanta story implies.  It's a totally expected result.

It is natural to conclude from the fact that energy states are quantized that the transition between them must happen instantaneously.  Consider a system that transitions from energy state 0 to an adjacent energy state 1 (in some suitable units). It can't do it via a smooth transition between intermediate energy levels because these are physically impossible (that the whole point of quantum mechanics).  So if a system is going to transition from 0 to 1 without occupying any energy state in between, the transition must be instantaneous, right?

Wrong.  There is a different kind of "smooth" transition that a system can make between the 0 and 1 states, and that is via a superposition of the two states.  Just as a particle can be in two different locations at the same time, it can be in two different energy states at the same time.  To go smoothly from 0 to 1, the system transitions through a series of superpositions of both states, i.e. it starts out entirely in state 0, and then transitions smoothly to being mostly in state 0 and a little bit in state 1, to being half in each state, to being mostly in 1 and a little bit in 0, to being entirely in 1.  This has been known for decades, and is predicted by the math.  You can even predict how fast the transition happens.  For most common physical processes, like an atom absorbing or emitting a photon, the transition is really fast.  But it's not instantaneous.

The tricky part is not figuring out that quantum transitions take time (well, OK, figuring it out is tricky too, but it's easy once you know how) but designing an experiment that demonstrates that the theory is correct.  This is because any straightforward measurement of the energy of the system will always produce a result that shows the system is in one state or the other.  The existence of superpositions can only be demonstrated indirectly, usually through interference effects.  So to demonstrate the non-instantaneous nature of a quantum transition you have to do two things: first, you need to actually catch a system during a (typically very fast) transition and second, you need to come up with a way of getting the system to interfere with itself (or producing some other indirect effect that would not occur but for the existence of a superposition).  That's what Minev et al. did.

The way they did it is really cool, but the advance here is an experimental one, not a theoretical one.  They used a superconductor to produce a macroscopic quantum system that behaved like an atom in that it had a small number of discrete energy levels that it could transition between.  Then they "tickled" this "atom" with microwaves and observed that the resulting response exhibited the kind of interference effects that would be expected if if were transitioning through superposition states.  It's very cool, and a very impressive technical achievement, but it is in no way unexpected or surprising.

62 comments:

Unknown said...

Same could be said about virtually every story I see these days regarding quantum this or that. But hey, the gotta sell papers somehow.

Peter Donis said...

Good post! This one sentence sums up how to correct the misconception generated by the hype machine:

It's a totally expected result.

Exactly.

PonderSeekDiscover said...

Your blog is impossible to comment on! Third times a charm - hopefully!

But they really didn't prove anything about the quantum! Certainly they didn't prove anything about superposition! Superposition is in the math because Quantum Mechanics - not necessarily the quantum world, is linear!

Answer me the riddle posed by the Pre-stimulus response experiments. Never heard of them? How interesting! These are a number of experiments, there are two meta-analyses, one from 2012 and the other form 2017, which demonstrate that the human heart and brain become aware of an emotionally stimulating event 4.5 to 18 seconds prior to that event happening in spacetime. These empirical results have been published in top-notch peer-reviewed journals such as Frontiers of Psychology and SSRN (neuroscience) and are currently hosted by the U. S. National Institutes of Health; I'll link to them below. My question is, under the supposition that superposition is ontological and not simply an artifact of the math, how does one explain how the human heart and brain could receive meaningful information about an event which has yet to decohere!?! Here are the links:

Electrophysiological evidence of intuition: part 1. The surprising role of the heart.;

Electrophysiological evidence of intuition: Part 2. A system-wide process?;

Predictive Physiological Anticipation Preceding Seemingly Unpredictable Stimuli: A Meta-Analysis;

Opinion Article We Did See This Coming:Response to, “We Should Have Seen This Coming,” by D. Sam Schwarzkopf;

Electrophysiology of Intuition: Pre-stimulus Responses in Group and Individual Participants Using a Roulette Paradigm;

Predictive Physiological Anticipation Preceding Seemingly Unpredictable Stimuli: An Update of Mossbridge's et al. Meta-Analysis.

Nice reeftank, by the way; way back in 1998 through 2001, I had a very nice experimental tank. It was a reef tank with one fish, a yellow acanthus tang which I got for a steal because he was very pale yellow in color; I bought him for $12! My prime corals were an open-brain, an elegance, and a frog spawn, but I had all kinds - stonies, mushrooms, I even had a little tiny nudibranch - all white and about 1/4" in length, which came in with a coral! I had a massive ball of caulerpa floating on the top of the tank which I had to prune weekly to keep sufficient light on the corals. I love reef tanks and diving too! I'm homeless now, though. I live under a bridge crossing the L A River here in Los Angeles. I have a patent for a surge generator which doesn't use pumps; you would probably find it inte

Ron said...

> Nice reeftank

Huh???

Publius said...

I would state it as infinite gradients aren't allowed in nature, so the transitions must occur in a finite amount of time.

My guess: 10^-43 seconds.

Luke said...

> A number of people have asked me to weigh in on this story in Quanta Magazine …

Oh good, I wasn't the only one. :-) Thanks for posting this!

> What is new here is that this is the first time that this fact has been demonstrated experimentally.

Wait a second, then it wasn't really "known" until just now. After all, surely there are cases where theory said that X must exist/happen and then it was found out that this was false? Just because there are a bunch of other well-supported aspects of the theory doesn't mean that X is "known" before an experiment is done. Put another way, some of us are rather more empirical than others and for such people, this experiment is a bigger deal than you make it out to be. :-)

An analogous situation is femtochemistry. Back in the day, chemists postulated intermediate states of chemical reactions they could not observe. IIRC it was a long-held dogma. Then came along Ahmed Hassan Zewail and he used ultra-short laser flashes to image those intermediate states—finding that they did in fact exist. As a result, he got the 1999 Nobel Prize in Chemistry. Now, a difference between this and the physics situation, I think, is that chemistry theory wasn't quite as sure that such intermediates exist as physics was sure that quantum transitions take time. But I still think it's worth recognizing that experimentally demonstrating something can be a really, really big deal. That is, not everyone restricts themselves to this schema quite as well as you do, Ron:

> But it's not the kind of conceptual breakthrough that the Quanta story implies. It's a totally expected result.

I'm not at all disagreeing with this. I just propose that you believed the theory so thoroughly that the experimental corroboration was almost uninteresting. Others, I suspect, don't place nearly as much confidence in untested aspects of theory. Perhaps it's important that the enterprise of science has both types of people working in it?

> There is a different kind of "smooth" transition that a system can make between the 0 and 1 states, and that is via a superposition of the two states. Just as a particle can be in two different locations at the same time, it can be in two different energy states at the same time.

What's the difference between "it's actually in two different places at the same time" vs. "it's at one of the two different places and we can only bound this with probabilities"? After all, can't you only ever observe eigenvalues? (WP: Measurement in quantum mechanics § Measurable quantities ("observables") as operators: 3.) I'm interested in how precise that reasoning is from the discrete things observed, to the conclusion that a given atom exists simultaneously in two different locations. To-date, in my own (admittedly limited) explorations, I can't tell the difference between the two propositions in quotes in my first sentence.

Ron said...

> it wasn't really "known" until just now

It still isn't "known". There are all kinds of other possibly explanations of these results. It might have been experimental error. The experimental technique is indirect, it's possible that the underlying phenomenon that produced the result is totally different from what theory says. It's possible that the whole thing was a fraud, like cold fusion. Nothing in science is ever known with 100% certainty.

This result was "known" in the same sense that it was "known" >what the image of a black hole would look like before we actually saw it. In fact, the fact that we knew what the image would look like was a serious problem because creating that image required a great deal of interpolation of sparse data. Insuring that the result would not simply be a reflection of our preconceived notions was a major challenge.

> surely there are cases where theory said that X must exist/happen and then it was found out that this was false?

Yes, of course, but those events are exceedingly rare, and becoming rarer all the time. When they happen they *are* major news because results like that point the way forward. The people who make such discoveries win Nobel prizes. The last time it happened in physics was in 1998 when so-called "dark energy" was discovered.

> Others, I suspect, don't place nearly as much confidence in untested aspects of theory.

But this is not an "untested aspect of the theory". The fact that quantum transitions take time is simply a manifestation of the uncertainty principle, which is the single most well established part of QM. If any experiment were ever to demonstrate a violation of the uncertainty principle all of QM would crumble. It would be the biggest news in the history of physics.

> What's the difference between "it's actually in two different places at the same time" vs. "it's at one of the two different places and we can only bound this with probabilities"?

That is an excellent question! And in fact I started working on a follow-up post about that very topic yesterday. It's not a trivial thing to explain. Stay tuned! (But if you want a sneak preview, read up on pure vs mixed states, and proper vs improper mixed states.)

Ron said...

@Publius:

> My guess: 10^-43 seconds.

Nope.

Publius said...

1.6 nS? That's really slow!

A MOSFET can switch states in about a picosecond.

Luke said...

> It still isn't "known".

Okay. I still say that "'known' only by theory" and "'known by theory and experiment" is a crucial distinction.

> This result was "known" in the same sense that it was "known" what the image of a black hole would look like before we actually saw it. In fact, the fact that we knew what the image would look like was a serious problem because creating that image required a great deal of interpolation of sparse data. Insuring that the result would not simply be a reflection of our preconceived notions was a major challenge.

Did you watch the announcement of the five-σ confidence of discovery of the Higgs boson? They talked about doing the same thing. Another example is Avoiding the pitfalls of single particle cryo-electron microscopy: Einstein from noise.

P.S. This discussion has been extraordinarily helpful in helping me understand how you do EE&R. As best I can tell, you value R much more highly than I do, in contrast to EE. I see reality as much more susceptible to being rather different than we thought than you do—that is, I suspect that we could have a post-quantum revolution somewhat like the classical → quantum revolution. Some scientists were exceedingly confident that classical would solve the aether problem and the ultraviolet catastrophe. This whole matter could get rather more interesting if and when I get around talking about the EE I've done with regard to Christianity, and how I use R with regard to that EE. :-)

> > surely there are cases where theory said that X must exist/happen and then it was found out that this was false?

> Yes, of course, but those events are exceedingly rare, and becoming rarer all the time.

Did we see the same trajectory with the development of classical physics?

> The fact that quantum transitions take time is simply a manifestation of the uncertainty principle, which is the single most well established part of QM.

Is Heisenberg's unsharpness relation (a better translation from the German) epistemological or also ontological? I thought that de Broglie–Bohm theory forces it to be merely epistemological. Is this provably wrong?

> If any experiment were ever to demonstrate a violation of the uncertainty principle all of QM would crumble. It would be the biggest news in the history of physics.

But QM was the biggest news in the history of physics at the time it was discovered. Right? Well, there was also relativity, but hopefully you get my point.

> That is an excellent question!

Well thanks, I do occasionally come up with those amidst all the less-than-excellent questions. I look forward to reading the blog post!

Ron said...

> I still say that "'known' only by theory" and "'known by theory and experiment" is a crucial distinction.

That's because you still don't understand how scientific theories actually work.

> you value R much more highly than I do, in contrast to EE.

That's kind of like me saying that you value the Son more than the Father or the Holy Spirit. Or that a car enthusiast values spark plugs more than tires.

> Is Heisenberg's unsharpness relation (a better translation from the German) epistemological or also ontological?

It's ontological.

> I thought that de Broglie–Bohm theory forces it to be merely epistemological. Is this provably wrong?

Yes. There's no getting around Bell's theorem. The "catch" in Bohmian mechanics is that although particles have "real" locations (whatever that might possibly mean in light of what follows), you can never know what they are.

Here's how David Z. Albert puts it in "Quantum Mechanics and Experience" (which you really should read):

"[Bohmian mechanics] is the kind of theory whereby you can tell an absolutely low-brow story about the world, the kind of story (that is) that’s about the motions of material bodies, the kind of story that contains nothing cryptic and nothing metaphysically novel and nothing ambiguous and nothing inexplicit and nothing evasive and nothing unintelligible and nothing inexact and nothing subtle and in which no questions ever fail to make sense and in which no questions ever fail to have answers and in which no two physical properties of anything are ever “incompatible” with one another and in which the whole universe always evolves deterministically and which recounts the unfolding of a perverse and gigantic conspiracy to make the world appear to be quantum-mechanical."

Bohmian mechanics is just one step removed from the Cosmic Turing Machine, which also can't be ruled out on the basis of any experiment.

> QM was the biggest news in the history of physics at the time it was discovered. Right?

The history of QM is messy. It was discovered in bits and pieces, starting with Planck's work on black-body radiation and the ultraviolet catastrophe, then Einstein's work on the photoelectric effect, and then Bohr and then Schroedinger and Heisenberg and von Neumann and Bell. The whole thing unfolded over a period of many decades. It's not like there was one big "aha" moment like there was with relativity. It was kind of a big mess, and part of that mess still reverberates in the popular literature today.

Luke said...

@Ron (1/2)

> > I still say that "'known' only by theory" and "'known by theory and experiment" is a crucial distinction.

> That's because you still don't understand how scientific theories actually work.

Well, I don't understand your understanding of "how scientific theories actually work". And I have reason to think that your understanding is not a particularly helpful understanding for actually doing science. A tenured faculty member of one of the world's leading research institutions is a friend of mine and I once asked him this question: "What is the difference between good and great scientists?" His answer: "Good scientists remember the theory; great scientists also remember the original data." That seemed like a very good distinction to me. It matches with Underdetermination of Scientific Theory. Furthermore, it seems that many scientific discoveries are made once the signal just barely rises out of the noise; have you ever seen Hubble's original data?

Perhaps you could point to either peer-reviewed literature which supports your understanding of "how scientific theories actually work", or empirical evidence that those scientists who self-reflectively work with your understanding end up doing better science? If you can't, then I'm not sure why I should take it as anything other than "your understanding". Care to enlighten me?

> > you value R much more highly than I do, in contrast to EE.

> That's kind of like me saying that you value the Son more than the Father or the Holy Spirit. Or that a car enthusiast values spark plugs more than tires.

Some people are more willing to extrapolate further than others. I don't see how this is anything like your description. Although, there is plenty of talk in theology of overemphasizing one or two of the three persons of God, so the analogy might be better than I think. But you seem to assume that one cannot actually do this thing, making it a worse analogy in your head. :-)

Luke said...

@Ron (2/2)

> The "catch" in Bohmian mechanics is that although particles have "real" locations (whatever that might possibly mean in light of what follows), you can never know what they are.

You seem well-described by Robert Laughlin: "But physics maintains a time-honored tradition of making no distinction between unobservable things and nonexistent ones." (A Different Universe: Reinventing Physics from the Bottom Down, 55)

> Here's how David Z. Albert puts it in "Quantum Mechanics and Experience" (which you really should read):

I've requested the book from my interlibrary loan system, per our recent email exchange. As to the actual excerpt, I think I prefer this more mundane bit from Bohm:

>>     The assumption that any particular kind of fluctuations are arbitrary and lawless relative to all possible contexts, like the similar assumption that there exists an absolute and final determinate law, is therefore evidently not capable of being based on any experimental or theoretical developments arising out of specific scientific problems, but it is instead a purely philosophical assumption. (Causality and Chance in Modern Physics, 44)

Whether de Broglie–Bohm theory is a helpful instance of this is another question; Bernard d'Espagnat argues in On Physics and Philosophy that it doesn't help nearly as much as one might think after relativistic corrections. N.B. d'Espagnat does make a huge deal out of Bell's theorem in that book.

> The history of QM is messy. It was discovered in bits and pieces, starting with Planck's work on black-body radiation and the ultraviolet catastrophe, then Einstein's work on the photoelectric effect, and then Bohr and then Schroedinger and Heisenberg and von Neumann and Bell. The whole thing unfolded over a period of many decades. It's not like there was one big "aha" moment like there was with relativity. It was kind of a big mess, and part of that mess still reverberates in the popular literature today.

Fine. Do you believe this cannot possibly happen to the current theory of QM/​QFT?

Publius said...

Bully For Pilot Waves!

@Luke:
> I thought that de Broglie–Bohm theory forces it to be merely epistemological. Is this provably wrong?

@Ron:
Yes. There's no getting around Bell's theorem.

Bell on Bell's Theorem:

There was, however, one physicist who wrote on this subject with even greater clarity and insight than Wigner himself: the very J. S. Bell whom Wigner praises for demonstrating the impossibility of a deterministic completion of quantum theory such as Bohmian mechanics. Here’s how Bell himself reacted to Bohm’s discovery:

But in 1952 I saw the impossible done. It was in papers by David Bohm. Bohm showed explicitly how parameters could indeed be introduced, into nonrelativistic wave mechanics, with the help of which the indeterministic description could be transformed into a deterministic one. More importantly, in my opinion, the subjectivity of the orthodox version, the necessary reference to the “observer”, could be eliminated. …

But why then had Born not told me of this “pilot wave”? If only to point out what was wrong with it? Why did von Neumann not consider it? More extraordinarily, why did people go on producing “impossibility” proofs, after 1952, and as recently as 1978? … Why is the pilot wave picture ignored in text books? Should it not be taught, not as the only way, but as an antidote to the prevailing complacency? To show us that vagueness, subjectivity, and indeterminism, are not forced on us by experimental facts, but by deliberate theoretical choice? (Bell 1982, reprinted in 1987c: 160)

Wigner to the contrary notwithstanding, Bell did not establish the impossibility of a deterministic reformulation of quantum theory, nor did he ever claim to have done so. On the contrary, until his untimely death in 1990, Bell was the prime proponent, and for much of this period almost the sole proponent, of the very theory, Bohmian mechanics, that he supposedly demolished.


Lecture 7: Not even wrong. Why does nobody like pilot-wave theory?

Resources on pilot wave theory:
De Broglie-Bohm pilot-wave theory and the foundations of quantum mechanics

Quanta: New Support for Alternative Quantum View

PDF: On a Common Misconception Regarding the de Broglie-Bohm Theory

The pilot-wave dynamics of walking droplets

Ron said...

> Perhaps you could point to either peer-reviewed literature which supports your understanding of "how scientific theories actually work"

https://plato.stanford.edu/entries/popper/

> Good scientists remember the theory; great scientists also remember the original data.

Yep. I'm totally on board with that sentiment.

> physics maintains a time-honored tradition of making no distinction between unobservable things and nonexistent ones

What other reasonable definition of non-existence could there possibly be? How could you possibly distinguish between an unobservable thing and a non-existent one?

> Causality and Chance in Modern Physics

That book was published in 1971, after Bell but before Freedman and Clauser, so it was still an open question at that point. But it isn't any more.

> Do you believe this cannot possibly happen to the current theory of QM/​QFT?

What is "this"? It already *has* happened. The current theory is the result of this messy process (obviously).

Do I believe that the current theory can't undergo further revision? No, of course not. But there are some pretty hard constraints on what could possibly replace it. (We've been through this a zillion times.)

Ron said...

@Publius:

And how do any of the things you cited contradict what I said?

PonderSeekDiscover said...

Well, I looked at both contributors webpages and the one maintains reeftanks, which is cool, and you made a movie about homeless people, which is cool. At one time I maintained a really badass reeftank and I've been homeless for the last decade plus, so I thought I would mention both!

Unobservable does not necessarily mean non-existent and George Ellis has a very pragmatic definition of existence which covers unobservables:

"[...] Causation: The nature of causation is highly contested territory, and I will take a pragmatic view:

Definition 1: Causal Effect If making a change in a quantity X results in a reliable demonstrable change in a quantity Y in a given context, then X has a causal effect on Y.

Example: I press the key labelled “A” on my computer keyboard; the letter “A” appears on my
computer screen.

Now there are of course a myriad of causal influences on any specific event: a network of causation is always in action. What we usually do is to have some specific context in mind where we keep almost all parameters and variables fixed, allowing just one or two remaining ones to vary; if they reliably cause some change in the dependent variable in that context, we then label them as “the cause”.

[...]

Existence: Given this understanding of causation, it implies a view on ontology (existence) as
follows: I assume that physical matter (comprised of electrons, protons, etc.) exists. Then the
following criterion for existence makes sense:

Definition 2: Existence If Y is a physical entity made up of ordinary matter, and X is some kind of entity that has a demonstrable causal effect on Y as per Definition 1, then we must acknowledge that X also exists (even if it is not made up of such matter).

This is clearly a sensible and testable criterion; in the example above, it leads to the conclusion that both the data and the relevant software exist. If we do not adopt this definition, we will have instances of uncaused changes in the world; I presume we wish to avoid that situation."

[end quote]

At one point in time, electromagnetic radiation outside the visible spectrum was unobservable, but we take its existence for granted now. The neuroscientist, David Eagleman, has a nice blog post on this subject, The Umwelt.

PonderSeekDiscover said...

The problem here is, those pre-stimulus response experiments are in direct conflict with the accepted hypothesis that superposition is ontological; if you can use any of the current interpretations of QT to explain that empirical data, then please do! And they cannot be explained using holography either!

I have to ask, have you read Lee Smolin's latest, Einstein's Unfinished Revolution?

The only theory I am aware of, which consistently accounts for all empirical data to date, including those pre-stimulus experiments, is William Tiller's Psychoenergetic Science; see, for instance:

Why the Last Century’s Quantum Mechanics (QM) is Irrelevant in a Duplex, Reciprocal Subspace, Reference Frame for Our Cognitive World, an introduction;

Psychoenergetics applied to the mind/body concept;

What is Human Consciousness and How Do We Significantly Increase Its
Magnitude in Our World?
.

Tiller utilizes a bi-conformal reference frame, our distance/time dependent spacetime and a reciprocal frequency domain; in other words, particles and waves live in separate spaces and they interact via a postulated "deltron" moiety which can interact with both subluminal and superluminal entities. The de Broglie pilot wave is known to have superluminal components but orthodox science gets rid of these by hypothesizing that they propagate in a dispersive media; Tiller, and those pre-stimulus experiments back him up, suggests this is an erroneous hypostheis.

Here's some additional data in support of Tiller's theory, both represent inexplicable thermodynamic phenomena:

Neurocognitive and Somatic Components of Temperature Increases during g-Tummo Meditation: Legend and Reality;

Vice Documentary: Inside the Superhuman World of The Iceman

Ron said...

@PSD:

> one maintains reeftanks

Ah. Don is an infrequent contributor. And I didn't actually know that he keeps reeftanks. Now it makes sense.

> At one point in time, electromagnetic radiation outside the visible spectrum was unobservable

Sure, but that was a *technological* limitation. The positions of Bohm's particles are not knowable even in principle. This is what keep's Bohm's theory compatible with standard QM -- the "randomness" is hidden in the particle positions.

> I have to ask, have you read Lee Smolin's latest, Einstein's Unfinished Revolution?

Nope.

> The only theory I am aware of, which consistently accounts for all empirical data to date, including those pre-stimulus experiments

Well, here's another theory that accounts for the data: the pre-stimulus results are wrong.

Ron said...

@Luke:

> What's the difference between "it's actually in two different places at the same time" vs. "it's at one of the two different places and we can only bound this with probabilities"?

Upon re-reading this question I realize that I misread it. The answer to the question as posed is very simple: the difference is that if it's actually in two different places then those two instances can be brought back together and can interfere with one another. If it's actually in one place or the other then it can't produce interference.

PonderSeekDiscover said...

"The positions of Bohm's particles are not knowable even in principle."

Well, that's why you probably should read Smolin's latest book, it specifically addresses the incomplete nature of QT. And the definition of George Ellis is relevant to this discussion regardless; of course, I was unaware that you refuse to acknowledge empirical data, had I known that, then I wouldn't have bothered commenting in the first place. I swear, Hacker News is in serious decline . . .

"Well, here's another theory that accounts for the data: the pre-stimulus results are wrong."

If those pre-stimulus response experiments were wrong, then I highly doubt they would be published in the journals they were/are published in, nor would USNIH host them.

I mean, this is the problem with science, right? We supposedly have this crisis in theoretical physics right now, but it's no wonder why! We have theorists with the same mindset you indulge trying to build a "theory of everything" on QFT, knowing full well that QFT is about as jacked up as can be! And the reason it's jacked is primarily due to mindsets like yours refusing to acknowledge perfectly legitimate datasets, datasets whose rejection is highly irrational!

You probably haven't read, nor will you read, the paper by Bianchi and Rovelli either: Why all these prejudices against a constant??

Well, anyway . . . I see you work in crypto!?! That's probably why you reject the pre-stim results: you're A$$-deep in the Quantum Computation myth! Here's one for you. About a year ago I invented a new elementary, provably recursive arithmetic which extends the standard model - something which was supposedly impossible. Turns out, there exists a countable subsumption hierarchy of elementary recursive arithmetics bounded above by the Church/Kleene ordinal (as an ordered universe). I establish set-theoretic foundations with Aczel's AFA (maximal bisimulation) but you can think of my novel arithmetic as the structure (N^2, <, +, *, (1, 0), (0, 0)) with lexicographic order, coordinate-wise addition, and multiplication defined by:

(a, b) * (c, d) = (a * c, b * c + a * d + b * d).

This, then, naturally leads to the countable hierarchy with exponents conforming to the geometric sequence {2^n}:

0) (N, <, + *, 1, 0);

1) (N^2, <, +, *, (1, 0), (0, 0));

2) (N^3, <, +, *, (1, 0, 0, 0), (0, 0, 0, 0));

and etc.

This, of course, should have implication for crypto (actually it certainly does but you probably won't accept those implications) as well as for generalizations of probabilistic measures . . .

PonderSeekDiscover said...

That three exponent is a typo; it should be four, but you get the idea . . .

Don Geddis said...

@PonderSeekDiscover: "how does one explain how the human heart and brain could receive meaningful information about an event which has yet to decohere!?!"

There seem to be two possible explanations:

1. There exists some new physics, not at all compatible with everything we believe we know about physics, that will upend the entire field. This is much like the failure to find the ether medium for light. Einstein's solution to that one minor technical problem in a tiny corner of physics, required destroying and rebuilding all of space and time for all of physics. Perhaps such a major revolution will happen again.

or

2. The data is wrong, or its consequences are being misinterpreted.

I would bet heavily on #2. So heavily, that it isn't even worth (at this point) following and studying your links. They're at the level of "evidence" for paranormal activity.

"Nice reeftank, by the way"

Thanks. Alas, it is no longer active.

@Luke: "What's the difference between "it's actually in two different places at the same time" vs. "it's at one of the two different places and we can only bound this with probabilities"?"

Go back and study the original double-slit experiment again. Interference effects, with a single photon at a time, cannot be explained solely by our ignorance of "which" slit the photon passed through (but somehow it is "actually" only going through one). A single photon must instead pass through both slits.

Luke said...

@Don Geddis:

> Go back and study the original double-slit experiment again. Interference effects, with a single photon at a time, cannot be explained solely by our ignorance of "which" slit the photon passed through (but somehow it is "actually" only going through one). A single photon must instead pass through both slits.

As far as I understand it, this is not required in de Broglie–Bohm mechanics. Am I wrong?

Don Geddis said...

@Luke: "What's the difference between "it's actually in two different places at the same time" vs. "it's at one of the two different places and we can only bound this with probabilities"? ... [photon must pass both slits] ... As far as I understand it, this is not required in de Broglie–Bohm mechanics. Am I wrong?"

The pilot wave must explicitly explore the paths through both slits, and use those multiple paths to influence the final detection of "the photon".

It's a mere matter of language definition whether you choose not to include the critical "pilot wave" as part of what "is" a "photon". But the important part is that this doesn't recover the sense of your original question: "it's at one of the two different places and we can only bound this with probabilities." Because something needs to be in both slits at the same time. In de Broglie-Bohm, that "something" is "the pilot wave".

Yes, if you really want, I'll agree with you that technically de Broglie-Bohm have a concept called a "photon", and their photon is only at one of the slits. But every quantum theory needs "influence" coming through both slits. It's not possible to have a quantum theory where everything is local, and the uncertainty is only in the observer's knowledge. There must be non-local influence. In de Broglie-Bohm, they call that non-local influence the "pilot wave". Everybody else just calls it part of the photon itself.

Luke said...

@Ron: (1/2)

> > Perhaps you could point to either peer-reviewed literature which supports your understanding of "how scientific theories actually work"

> https://plato.stanford.edu/entries/popper/

IIRC, you haven't looked at academia's peer-review of Popper's work and the subsequent literature—aside from perhaps Deutsch. (Not sure if Deutsch has ever published in peer-review journals when it comes to philosophy of science.) When I pressed you to show scientists working according to your understanding, you provided results from an extremely narrow slice of all science done. Surely you will agree that "some ⇒ all" reasoning is not valid. I also have never seen you answer this question:

> Luke: What I am not aware of is a single shred of empirical evidence that the closer scientists get to articulating decision procedures—up to the actual formalism of a decision procedure—the better the resulting science.

What really weirds me out is that you seem to think you have answers when (to my knowledge) you haven't actually exposed those answers to being tested by reality and peer review. This seems utterly antithetical to the spirit of EE&R. Furthermore, how are you—from your own point of view—not sitting on a pile of pure gold which could immensely help scientists do better science and thus improve humanity far more than it currently is being improved?

Luke said...

@Ron: (2/2)

> Luke: I still say that "'known' only by theory" and "'known by theory and experiment" is a crucial distinction.

> Ron: That's because you still don't understand how scientific theories actually work.

> Luke: … "Good scientists remember the theory; great scientists also remember the original data." …

> Ron: Yep. I'm totally on board with that sentiment.

Then why did you say what you did about that "crucial distinction"?

> > physics maintains a time-honored tradition of making no distinction between unobservable things and nonexistent ones

> What other reasonable definition of non-existence could there possibly be? How could you possibly distinguish between an unobservable thing and a non-existent one?

Quarks are not observable. Nor were atoms when Brownian motion was first observed. Hidden Markov models are all about working with unobservables. The trouble with de Broglie–Bohm mechanics, unlike quarks and atoms-back-in-the-day, is that the unobservable ontology has yet to help predict more than the alternatives.

> That book was published in 1971, after Bell but before Freedman and Clauser, so it was still an open question at that point. But it isn't any more.

Did Freedman and Clauser test for non-local hidden variables?

> Luke: Others, I suspect, don't place nearly as much confidence in untested aspects of theory.

> Ron: But this is not an "untested aspect of the theory". The fact that quantum transitions take time is simply a manifestation of the uncertainty principle, which is the single most well established part of QM. If any experiment were ever to demonstrate a violation of the uncertainty principle all of QM would crumble. It would be the biggest news in the history of physics.



> Ron: Do I believe that the current theory can't undergo further revision? No, of course not. But there are some pretty hard constraints on what could possibly replace it. (We've been through this a zillion times.)

I agree with your "pretty hard constraints", while still standing by my "nearly as much confidence".

Luke said...

@Don Geddis:

> It's a mere matter of language definition whether you choose not to include the critical "pilot wave" as part of what "is" a "photon".

Pilot waves propagate faster-than-light and represent nonlocal state, so it doesn't seem reasonable to consider them "part of the photon". There seem to be two rather different ontologies at play, here. Randomness is not the same as determinism!

> It's not possible to have a quantum theory where everything is local, and the uncertainty is only in the observer's knowledge.

Aside from superdeterminism, yes I agree. But I don't see what the huge problem is with nonlocal state. It rips up some of our intuitions, but so much the worse for those intuitions. According to Tim Maudlin, this matter is what so irritated Einstein:

>> For example, it has been repeated ad nauseum that Einstein's main objection to quantum theory was its lack of determinism: Einstein could not abide a God who plays dice. But what annoyed Einstein was not lack of determinism, it was the apparent failure of locality in the theory on account of entanglement. Einstein recognized that, given the predictions of quantum theory, only a deterministic theory could eliminate this non-locality, and so he realized that local theory must be deterministic. But it was the locality that mattered to him, not the determinism. We now understand, due to the work of Bell, that Einstein's quest for a local theory was bound to fail. (Quantum Non-Locality & Relativity, xiii)

Oh well. Aside from superdeterminism, the desire for billiard-ball physics—mechanical philosophy—is dead. Obnoxiously, little philosophy seems to have truly grappled with nonlocality, making it hard to think through those now-falsified intuitions. An exception to this rule is Bernard d'Espagnat, who takes Bell's theorem and the experimental results quite seriously in On Physics and Philosophy (mathematics available in Veiled Reality).

Ron said...

@Luke:

> you haven't looked at academia's peer-review of Popper's work

I really don't understand why you have such a bee in your bonnet about peer review. Peer review is just a kind of evidence, not fundamentally different from any other evidence.

I also don't understand why you think that plato.stanford.edu doesn't qualify as academic peer review. Stanford University is a highly regarded academic institution. (But I also don't really care, so please don't explain it to me.)

> What really weirds me out is that you seem to think you have answers when (to my knowledge) you haven't actually exposed those answers to being tested by reality and peer review.

But I have. This blog is a submission of my ideas for review by anyone who wishes to review them. Anyone in the world with an internet connection can read what I post here and post comments in response, or write their own blog post, which Don has done, and which I've invited you to do on multiple occasions, and which you have declined to do. (That is also evidence, BTW.)

The reason I have confidence that I have the correct answers, at least about quantum mechanics, is that I've been doing this for thirty years now and for the last 10 or so I have seen no serious challenge to my worldview.

If you are asking why I haven't written up my ideas in a paper and submitted it to an academic journal, the answer is: I have done that as well. The paper was rejected on the grounds that nothing I said in it was new, a conclusion which I have come to believe was (and mostly still is) correct.

Also, I'm lazy.

> This seems utterly antithetical to the spirit of EE&R.

Yes, that's because you don't understand EE&R (c.f. your excessive focus on formal peer review).

> Then why did you say what you did about that "crucial distinction"?

Um, because it's true? I really don't understand this question. You said there's a "crucial distinction" between "'known' only by theory" and "'known by theory and experiment" and there isn't. The fact that there is no such crucial distinction is not challenged by reciting a slogan about good scientists.

The Higgs boson was known "only by theory" before the LHC. Now it is "know by theory and experiment." But this is not a "crucial distinction." The LHC confirming the Higgs was entirely expected, as are *all* of the other results it has produced. The LHC has not really advanced our knowledge much at all.

> Quarks are not observable. Nor were atoms when Brownian motion was first observed.

The crucial distinction being that quarks are *fundamentally* unobservable in isolation, as predicted by the theory. It's not just a technological limitation, as was the case with atoms (but is no longer the case).

> Did Freedman and Clauser test for non-local hidden variables?

No, Again, as I've said a zillion times, no experiment can rule out the Cosmic Turing Machine.

Luke said...

@Ron:

> I really don't understand why you have such a bee in your bonnet about peer review. Peer review is just a kind of evidence, not fundamentally different from any other evidence.

Peer review is where the people most able to critique a thing get a chance to critique that thing. I like to see things critiqued, to see how well they withstand the heat. In my experience, your average plato.stanford.edu article about a person generally won't contain much peer review of the person's positions (the point instead is to explain the positions). There is but a small bit of critique at SEP: Karl Popper § Critical Evaluation. And I'm not sure I've ever seen you reference anything in that section.

> But I have. This blog is a submission of my ideas for review by anyone who wishes to review them.

That is nothing like scientiifc/academic "peer review"—submitting your ideas to the people in the world best able to find problems, due to their training and knowledge of the literature.

> … or write their own blog post, which Don has done, and which I've invited you to do on multiple occasions, and which you have declined to do. (That is also evidence, BTW.)

I have in fact done a bunch of work on a guest blog post; I am not yet happy. Must I stop all commenting on your blog to avoid the kind of snide remark you have made, here? (What makes it snide is you didn't say what precisely it is evidence of.)

> The reason I have confidence that I have the correct answers, at least about quantum mechanics, is that I've been doing this for thirty years now and for the last 10 or so I have seen no serious challenge to my worldview.

This is entirely predicated upon the quality and knowledge and expertise of those who have investigated those "answers".

> Yes, that's because you don't understand EE&R (c.f. your excessive focus on formal peer review).

Does this constitute "excessive focus on formal peer review":

> Don Geddis: On the contrary, they have a lot to do with empirical reality. Most scientists continue to exhibit this bad thinking. That is why the culture and practice of science so rewards selfish others for tearing down the ideas proposed by any scientist. No scientist can be trusted to avoid bad thinking. It is the scientific method which allows the whole field to make progress, even if individual human brains are rarely able to on their own.

?

> No, Again, as I've said a zillion times, no experiment can rule out the Cosmic Turing Machine.

Why is your "Cosmic Turing Machine" the only logical possibility for nonlocal hidden variables which is consistent with the empirical evidence gathered by humanity to-date? (Note that I said the empirical evidence, not the theories built upon that empirical evidence.)

Ron said...

@LUke:

> Peer review is where the people most able to critique a thing get a chance to critique that thing.

No. Peer review is where a bunch of academics get together for a circle jerk.

Do you really not know how the peer review process works? You send in a paper, it gets sent out to a few anonymous reviewers, they write reviews. Maybe you go back and forth on some revisions, but ultimately a *binary* decision is made with regards to publication or not. And if the decision is "not" you can go journal-shopping until you find one that will accept. The reviewers chosen to look at your paper may or may not be the "most able." They may or may not write their reviews free from conflict of interest or other bias.

The formal academic peer review process is badly broken and everyone knows it. There are efforts underway to try to fix it, but it's a political process so progress is slow. In the meantime, like I said, anyone with an internet connection is free to offer criticism of my work. That set is much more likely to contain "the people most able to critique" than the editorial board of an academic journal.

By way of very stark contrast, you have *not* put your position out there for critique (AFAIK). So you haven't really earned the right to give me a hard time about this yet.

> Must I stop all commenting on your blog to avoid the kind of snide remark you have made, here?

No. It will be suffice if you just stop the stupid commenting.

> This is entirely predicated upon the quality and knowledge and expertise of those who have investigated those "answers".

Certainly. But that's always the case for anyone. It's entirely possible that I'm completely wrong about everything, but the person who is in a position to explain it to me in a way that I will understand thinks I'm such a moron that it isn't even worth their time to bother. That is a possibility that everyone should always keep in the back of their mind.

> Does this constitute "excessive focus on formal peer review":

Given that the passage you cite doesn't mention it at all, I would say no.

> Why is your "Cosmic Turing Machine" the only logical possibility for nonlocal hidden variables which is consistent with the empirical evidence gathered by humanity to-date?

It isn't. There are an infinite number of other possibilities. But there are only two possibilities for any one of those theories: either it is an IPU, or it makes a testable experimental prediction that is at odds with quantum mechanics, and hence points the way to a Nobel prize in physics. The Cosmic Turing Machine is just my canonical IPU for non-local hidden variables, the intent being to kind of drive home the point that the reason to reject it is not that it's at odds with the data (it isn't). The reason to reject it is because it's stupid.

Don Geddis said...

@Luke: "Pilot waves propagate faster-than-light and represent nonlocal state, so it doesn't seem reasonable to consider them "part of the photon"."

They're a necessary part of the description of where the photon goes next. They are not detectable separately from the photon. (They have no effect on the universe other than determining where the photon goes next.) No photon exists without them.

At some point, whether you consider it "part of the photon" is just a personal preference. But it's certainly reasonable to consider it just another add-on aspect of the original photon, much like electrons have charge or spin.

"Randomness is not the same as determinism!"

Not quite as different as you seem to think. For all quantum theories, the wavefunction evolves deterministically. And then, at the end, are the Born probabilities. Only the Born probabilities are "random". (Understanding what they are, and why, is probably the greatest mystery in quantum mechanics, and underlies all of the different QM "interpretations".)

Luke said...

@Ron:

> > Peer review is where the people most able to critique a thing get a chance to critique that thing.

> No. Peer review is where a bunch of academics get together for a circle jerk.

You're right, I made two errors:

     (1) conflating the Platonic Form with the currently reified thing
     (2) excluding the citation record that does or does not accrue, and builds and/or critiques

Although, I didn't entirely exclude (2):

> Luke: Well, I don't understand your understanding of "how scientific theories actually work". And I have reason to think that your understanding is not a particularly helpful understanding for actually doing science.

> Luke: What really weirds me out is that you seem to think you have answers when (to my knowledge) you haven't actually exposed those answers to being tested by reality and peer review. This seems utterly antithetical to the spirit of EE&R. Furthermore, how are you—from your own point of view—not sitting on a pile of pure gold which could immensely help scientists do better science and thus improve humanity far more than it currently is being improved?

Correct me if I'm wrong, but: a major indicator of whether a given article in a peer-reviewed journal has stoked further science is whether it is well-cited. The longer it is in the past the greater the danger major aspects have been overturned of course.

> By way of very stark contrast, you have *not* put your position out there for critique (AFAIK). So you haven't really earned the right to give me a hard time about this yet.

I have put out bits and pieces of my position on various different places on the internet, usually in places where my view is a minority position so that it will get the severest criticism available. (People, I find, are almost always harshest on the Other to their own tribe.) But I haven't put it all together—I'm working on that.

> No. It will be suffice if you just stop the stupid commenting.

So if I'm too stupid to figure out what is stupid, I should just stop?

Ron said...

@Luke:

> I'm working on that.

Happy to hear it.

> So if I'm too stupid to figure out what is stupid, I should just stop?

That kind of depends on what your goals are, but I would suggest putting some effort into honing your stupid-comment-detection skills.

Luke said...

@Don Geddis:

> > Pilot waves propagate faster-than-light and represent nonlocal state, so it doesn't seem reasonable to consider them "part of the photon".

> They're a necessary part of the description of where the photon goes next. They are not detectable separately from the photon. (They have no effect on the universe other than determining where the photon goes next.) No photon exists without them.

The particular pilot wave of the two-slit experiment would not exist if not for both slits being open. So to characterize it as "part of the photon" seems quite wrong.

> > Randomness is not the same as determinism!

> Not quite as different as you seem to think. For all quantum theories, the wavefunction evolves deterministically. And then, at the end, are the Born probabilities. Only the Born probabilities are "random". (Understanding what they are, and why, is probably the greatest mystery in quantum mechanics, and underlies all of the different QM "interpretations".)

Fully deterministic processes can generally be modeled by some other deterministic process, plus randomness. True, or false? If true, then depending on what model you adopt, could it be that without drastic changes, you cannot reduce the required random component beyond some minimum?

By the way, I had an interesting experience some years ago, after somehow revisiting Heisenberg's unsharpness relation. I was walking along the Embarcadero in San Francisco, looking at The Bay Lights. What I realized is that there are patterns you cannot see if you zoom in too closely. So any science which is philosophically reductive might have zoomed in too closely to see all the structure there is to see. This was amplified by reading Ilya Prigogine's discussion of the failure to compute individual trajectories in statistical mechanics:

>>     Is this difficulty merely a practical one? Yes, if we consider that trajectories have now become uncomputable. But there is more: Probability distribution permits us to incorporate within the framework of the dynamical description the complex microstructure of the phase space. It therefore contains additional information that is lacking at the level of individual trajectories. As we shall see in Chapter 4, this has fundamental consequences. At the level of distribution functions ρ, we obtain a new dynamical description that permits us to predict the future evolution of the ensemble, including characteristic time scales. (The End of Certainty, 37)

I haven't seen a good argument for why one cannot describe said "additional information" as "nonlocal state". Perhaps that is the same as "correlated noise"? Point being, if you look at individual particles there will be more noise than if you look at multiple correlated particles, together. What is unsharp when zoomed in looks rather sharper when zoomed out.

Don Geddis said...

@Luke: "The particular pilot wave of the two-slit experiment would not exist if not for both slits being open. So to characterize it as "part of the photon" seems quite wrong."

This isn't a matter of "right" and "wrong". It's more a matter of "helpful", "useful", etc. Perhaps so far as "personal preference". I (and others) find the description you are putting forth to be "not helpful". It seems vastly simpler and cleaner to just say "the single photon is spread out in space, and goes through both slits simultaneously, and interferes with itself." We all agree on what is happening, but you want to take the "both slits" part and the "interferes" part, and separate that description into a "piece #1" (pilot wave) that does the interesting stuff, and a separate "piece #2" ("the" photon) that is detected in the end.

I see that you have added considerable complexity to the description, for no additional benefit. That would seem to make it a substandard choice for describing the physics. Why bother breaking apart the concept into those two pieces, when a single unified description works perfectly well?

It's not "wrong". There's just no point to it. It's a distinction without a difference, and unmotivated by the actual physics. (Motivated only by preference.)

"you cannot reduce the required random component beyond some minimum?"

The Born probabilities are definitely "random", in any quantum description. It is not possible to "get rid" of them. And, essentially, nobody has any deeper theory of where they come from, or "why" they exist (in just that particular form). They're just observed, not understood.

"the complex microstructure of the phase space. It therefore contains additional information that is lacking at the level of individual trajectories"

Yes, that's true throughout science. Just because a "higher level" of description is fundamentally based on some "lower level" components (reductionism works!), doesn't mean that there aren't new relationships and science at the higher level, that cannot be usefully explained only at the lower level.

Chemistry is not "just" physics. Biology is not "just" chemistry. You can't explain kin selection, or the rate of diffusion of a gene throughout a population, using only the language of chemistry. Weather is not "just" fluid mechanics. The concept of a "hurricane", or Jupiter's Great Red Spot persisting over centuries, is not usefully expressed at the level of individual gas molecules. Macroeconomics is not "just" a collection of microeconomics.

But I have to admit that I don't quite get the connection you're trying to make with pilot waves.

Ron said...

@Luke:

> Fully deterministic processes can generally be modeled by some other deterministic process, plus randomness. True, or false?

False. Fully deterministic processes do not have a random component. That is what "fully deterministic" means.

(You have apparently not heeded my advice to hone your stupid comment detection skills.)

> It's not "wrong". There's just no point to it.

It should be emphasized that it is demonstrably not the case that there *might* be a point to it that Don and I are simply too stupid to see. The problem is that Bohm's formulation is provably mathematically equivalent to standard QM. Bohm makes exactly the same predictions as regular QM. This is usually cited by Bohmian advocates as a feature but in fact it's a bug. It means that 1) there is no way, not even in principle, to experimentally test whether Bohm is right (as contrasted with, for example, GRW collapse theories which are experimentally testable, at least in principle) and 2) the claim that Bohm is deterministic is a flat-out lie. If it makes all the same predictions (and it does), if it is mathematically equivalent (and it is) then the Born rule has to be hiding in there somewhere. And in fact it is easy to identify where it is hiding: it's in the so-called "particle positions" which are supposedly "real" but which, like an Invisible Pink Unicorn, can never be observed. Calling the unobservable thing a "position" rather than an IPU doesn't add any explanatory power. It simply a lie, a marketing tool.

It is also not, as Don says, simply a matter of taste. Accepting the "particles have positions" lie because it makes you feel warm and fuzzy forces you to accept additional lies like "Spacetime has a preferred foliation (but we can never know what it is)" and "electrons don't really have spins, the wave function just conspired to make it look that way" about which it is much more difficult to feel warm and fuzzy. It's like joining a cult. It sucks you in with promises of making all the confusing shit make sense. But then it extracts a terrible cost.

Luke said...

@Ron:

> > Fully deterministic processes can generally be modeled by some other deterministic process, plus randomness. True, or false?

> False. Fully deterministic processes do not have a random component. That is what "fully deterministic" means.

I spoke in terms of:

     (I) fully deterministic
    (II) deterministic + randomness

Do you object to saying that something "deterministic" could involve any randomness whatsoever? If so, this would be another counterexample to "As you should know by now, I don't like quibbling over terminology." A good example of modeling a system which could well be fully deterministic via using a different deterministic/​«insert term here» system + randomness, see WP: Kalman filter. For a more general treatment of this matter, WP: Central limit theorem becomes relevant.

By the way, I happened to run into someone who does machine learning at Google Brain, and asked for a good example of "Fully deterministic processes which can be modeled by simpler deterministic processes plus randomness/​noise." He immediately treated the question as sensible—pace your "(You have apparently not heeded my advice to hone your stupid comment detection skills.)"—and brought up fluid mechanics as an example of approximating a system which may be fully deterministic, but which is too complex and/or chaotic to model precisely. Theoretically, wind is entirely deterministic, but we use simplified models with randomness to model air foils and such.

May I suggest that the smarter you are, the more capable you are of making someone else's words seem like they are dumb, even when they aren't? One way you can do this is to simply ignore things that I've stated, such as:

> Luke: The trouble with de Broglie–Bohm mechanics, unlike quarks and atoms-back-in-the-day, is that the unobservable ontology has yet to help predict more than the alternatives.

Perhaps you cannot conceive of why I'd continue to want to talk about de Broglie-Bohm given that, and so instead of treating the above as falsifying your model of me like a proper Popperian, you decided to just ignore anomalous evidence and push forward with the old model? I know I sometimes do this to others by mistake—I can be like a freight train which can't always stop on a dime.

Luke said...

@Don Geddis:

> This isn't a matter of "right" and "wrong". It's more a matter of "helpful", "useful", etc.

Ok. I think that if there are multiple causes required to make X what it is, it is factually incorrect to identify X with just one of the causes. But you can always discard the pilot wave interpretation.

As to the photon passing through both slits, does that ontologize Feynman's path integral formulation—perhaps "restrict[ed] … to lie within a finite causally complete region"? I am aware of it being very questionable to assume that there are classical trajectories, which is suggested by naive observation of excitations in bubble and cloud chambers. We could try getting into the arXiv preprint Towards a realistic parsing of the Feynman path integral if you're interested.

> I see that you have added considerable complexity to the description, for no additional benefit.

Well I did say this earlier:

> Luke: The trouble with de Broglie–Bohm mechanics, unlike quarks and atoms-back-in-the-day, is that the unobservable ontology has yet to help predict more than the alternatives.

But I'm not sure that every step in a discussion of these things must predict something new, in order to be on the route toward something which predicts something new. Such a stance would seem to be anti-scientific revolution and therefore dogmatic and stunting. Galileo did his impetus experiments because he found a loophole in Aristotelian physics; I think it can be fun to look for loopholes in quantum physics. If you disagree, then you are not the right interlocutor for me on this topic.

> It's a distinction without a difference, and unmotivated by the actual physics. (Motivated only by preference.)

How many interpretations of QM would you delete from existence on the basis of them being "[m]otivated only by preference"?

> The Born probabilities are definitely "random", in any quantum description. It is not possible to "get rid" of them.

So the theory mandates that said randomness cannot ever be correlated? It cannot ever be the case that you can tell more about two particles by describing both at the same time than you can tell by having independent descriptions of each particle?

> >> … the complex microstructure of the phase space. It therefore contains additional information that is lacking at the level of individual trajectories. … (The End of Certainty, 37)

> Yes, that's true throughout science. Just because a "higher level" of description is fundamentally based on some "lower level" components (reductionism works!), doesn't mean that there aren't new relationships and science at the higher level, that cannot be usefully explained only at the lower level.

You seem to be ignoring "information that is lacking at the level of individual trajectories". If it cannot be measured, does it exist?

> Chemistry is not "just" physics.

There is a crucial difference between simplifications required for human comprehension and the possibility that behavior exists at the ensemble level which does not exist as a simple "sum" of individual elements. Consider for example the trajectory resulting from a spacecraft traveling through an unstable Lagrangian point at just the right angle. The resultant trajectory is simply not computable as a result of the forces of gravity. It's not a matter of insufficient computational resources—unless you try to quantize spacetime and there are some problems with that.

Ron said...

@Luke:

> I happened to run into someone who does machine learning at Google Brain, and asked for A GOOD EXAMPLE [emphasis added] of "Fully deterministic processes which can be modeled by simpler deterministic processes plus randomness/​noise." He immediately treated the question as sensible

That's because that question *is* sensible. But that is a very different question than the stupid one you asked before:

> Fully deterministic processes can GENERALLY be modeled by some other deterministic process, plus randomness. True, or false? [Emphasis added.]

They cannot GENERALLY be modeled this way. They can OCCASIONALLY under VERY PARTICULAR CIRCUMSTANCES be modeled this way. And so, yes, it is possible to give SOME EXAMPLES of processes that can be modeled this way. It is nonetheless FALSE that they can GENERALLY be modeled this way. And the fact that I have to point all this out to you is the reason that your comment was STUPID. You need to start paying attention to detail.

Also, your implication that chaos theory can be applied to quantum mechanics is likewise stupid. Seriously, if it was that simple, don't you think someone would have pointed it out by now? If you think quantum randomness can be explained by chaos then you have not understood either chaos theory or quantum mechanics. (Or both.)

(Here's a hint: chaos is a purely classical theory.)

> May I suggest that the smarter you are, the more capable you are of making someone else's words seem like they are dumb, even when they aren't?

If you really believe that what is going on here is that I'm making you look stupid, as opposed to you actually making stupid comments, why are you still here? Why subject yourself to this abuse? What are you hoping to get out of it?

(And, while you're at it, what do you think my motive would be for gratuitously making you look stupid?)

Don Geddis said...

@Luke: "I think that if there are multiple causes required to make X what it is, it is factually incorrect to identify X with just one of the causes."

I don't know how to interpret this comment, as relevant to our discussion. Are you claiming that there are "multiple causes" to determine what happens to a photon? I don't know what that means. Are you claiming that I'm "identifying" a photon "with just one of the causes"? Which one? I really can't understand you here.

"does that ontologize Feynman's path integral formulation"

Sure, I suppose it's possible to look at it that way. At the end of the day, all the potential explanations need to predict the same experimental results, so: sure.

"I'm not sure that every step in a discussion of these things must predict something new, in order to be on the route toward something which predicts something new."

I agree, I wouldn't necessarily require that. But why do you keep bringing up pilot waves? What is the appeal?

After all, there are an infinite number of theories that are consistent with any data set. Mere consistency is not very interesting. Epicycles upon epicycles still predict the positions of planets. We adopt a heliocentric solar system model based on more than mere predictive ability.

"I think it can be fun to look for loopholes in quantum physics."

That would be. But I haven't seen you identify any loophole. Instead, you just seem to be fascinated by (metaphorical) epicycles, for no good reason.

"How many interpretations of QM would you delete from existence on the basis of them being "[m]otivated only by preference"?"

The standard Copenhagen QM interpretation with the "collapse" of the wavefunction, for sure. That's about as bad an example of philosophy of science as we have in history.

"So the theory mandates that said randomness cannot ever be correlated? It cannot ever be the case that you can tell more about two particles by describing both at the same time than you can tell by having independent descriptions of each particle?"

I can't make sense of the point you're trying to make here, sorry. I don't understand what you mean. There are always the two particles, and also the interaction between them.

"the possibility that behavior exists at the ensemble level which does not exist as a simple "sum" of individual elements"

You seem to be suggesting an actual failure of reductionism. I know of no example in all of science where reductionism fails. High level behavior is always explained by a collection of lower-level entities. You never get new behavior at an abstract level, which has no origin at all at the lower level.

"The resultant trajectory is simply not computable as a result of the forces of gravity."

"Computability" is an entire different criteria. Lots of things get simplified for practical reasons, for the convenience of humans. But the universe doesn't do that. The universe only operates at the very lowest level. Everything higher are just our approximate simplified models.

"It's not a matter of insufficient computational resources"

Yes, it is. There is nothing going on in your spacecraft example, aside from the various ordinary forces. Chaos Theory is still deterministic. It is only uncomputable in practice; it is not uncomputable in theory.

Luke said...

@Ron:

> Luke: Fully deterministic processes can generally be modeled by some other deterministic process, plus randomness. True, or false?

> Ron: False. Fully deterministic processes do not have a random component. That is what "fully deterministic" means.

> Luke: [Engages point about "fully deterministic".]

> Ron: They cannot GENERALLY be modeled this way.

So … you're dropping the complaint about "fully deterministic"?

As to "generally", I intended to talk about the space of processes we encounter in reality, not in mathematics land. I'm thinking of how Fourier's mathematics worked for the systems he focused on and guessed that the physicality of them (e.g. obedience of conservation laws) provided the right restriction to get a "generally" in his case. Does that make sense? If so, my bad for not making clear that I was talking about "in reality". If it doesn't make sense, then how do we robustly test your "cannot"?

> Also, your implication that chaos theory can be applied to quantum mechanics is likewise stupid.

This is a great example of you finding something to make me look stupid. The bit about unstable Lagrangian points (I didn't use the word "chaos") was in response to a comment about reductionism, not interpretations of quantum mechanics.

> If you really believe that what is going on here is that I'm making you look stupid, as opposed to you actually making stupid comments, why are you still here? Why subject yourself to this abuse? What are you hoping to get out of it?

I proposed a model for the observed behavior; I did not say it was the only model. I constantly work with "superpositions" of models for people, hoping the better ones are more accurate and trying to bias my interactions with them to make the better models more likely. But I do try to keep open the possibility of failure, because being a Pollyanna is ultimately more harmful.

As to why subject myself to the abuse: I find I learn more in the long term from this than from any available alternative. Participating in domains where I am not a member of the socially dominant group means my views will generally (heh) get critiqued more harshly than if I'm the one with the mod powers or have others willing to defend me. What better way to pursue rationality over against feeling good about myself and my views of the world?

> (And, while you're at it, what do you think my motive would be for gratuitously making you look stupid?)

The general pattern I recall—noting that memory can be iffy on such things—is that you tend to focus more on what I have wrong than what I have right—or close enough that you can see a way to "repair" it. An example is your point about "fully deterministic". It seems like you jumped on something that kinda-sorta appeared wrong; the fact that you completely pivoted to something else was a bit weird to me, but this model does predict that with higher probability.

Now, you might not know any better way of interacting with people than how you do with me. If for example you yourself have been treated this way by many people, you might merely be imitating that behavior. I find that people rarely question their own rightness or righteousness (including that which they're mimicking), and so generally just keep on truckin'.

Ron said...

> > Ron: They cannot GENERALLY be modeled this way.

> So … you're dropping the complaint about "fully deterministic"?

I have no idea what "complaint" you are referring to here, but the antecedent of "they" is (quoting you) "fully deterministic processes."

> This is a great example of you finding something to make me look stupid.

There's not a lot of sport in it, I'm afraid. You seem to be very capable of making yourself look stupid without any help from me. Case in point:

> The bit about unstable Lagrangian points (I didn't use the word "chaos") was in response to a comment about reductionism, not interpretations of quantum mechanics.

There is so much stupid here I don't even know where to begin.

It's true, you didn't use the word chaos. So what? That's still what you were talking about even if you didn't refer to it by its name. The study of deterministic processes that yield (apparently) random results is called chaos theory. (Did you really not know that?)

I have no idea why you're bringing up "The bit about unstable Lagrangian points." The first reference to Lagrange points was AFTER your question about "fully deterministic processes", which you posed in response to this quote from Don:

> Not quite as different as you seem to think. For all quantum theories, the wavefunction evolves deterministically. And then, at the end, are the Born probabilities. Only the Born probabilities are "random". (Understanding what they are, and why, is probably the greatest mystery in quantum mechanics, and underlies all of the different QM "interpretations".)

So your question about "fully deterministic processes" was clearly in reference to quantum mechanics.

> you tend to focus more on what I have wrong than what I have right

Because you get so much wrong it's impossible to have a coherent discussion with you. And when I try to point out what you get wrong you don't seem to make any effort to understand what you've gotten wrong and why and you make no effort to try to improve, you just respond with more stupidity and non-sequiturs. And this has been going on quite literally for YEARS.

I honestly can't tell whether you actually care about any of this, or if you're intentionally trolling. I'm leaning towards the latter.

Luke said...

@Don Geddis: (1/2)

> [1] Are you claiming that there are "multiple causes" to determine what happens to a photon? … [2] Are you claiming that I'm "identifying" a photon "with just one of the causes"?

[1] No, I'm saying there are multiple causes which determine the pilot wave.

[2] Yes:

> Don Geddis: It's a mere matter of language definition whether you choose not to include the critical "pilot wave" as part of what "is" a "photon".

> > … does that ontologize Feynman's path integral formulation …

> Sure, I suppose it's possible to look at it that way.

Why not just pursue a "shut up and calculate" approach, as that would be more parsimonious than working with any interpretation of QM?

> But why do you keep bringing up pilot waves? What is the appeal?

(1) It is a fully deterministic interpretation of QM which nevertheless predicts everything that indeterministic interpretations predict. It demonstrates that QM is not necessarily indeterministic.

(2) I find it a helpful stepping stone away from classical physics. I have an incredibly hard time working with only abstract equations; my brain seems to need some sort of ontology, some sort of substrate. It doesn't have to be the One True substrate.

> But I haven't seen you identify any loophole. Instead, you just seem to be fascinated by (metaphorical) epicycles, for no good reason.

The only truly demonstrable justification is an increase in prediction powers. Before one gets there, all there is is aesthetic matters which will be at least somewhat idiosyncratic. Maybe another reason I'm on about pilot waves is that Bohm's book Causality and Chance in Modern Physics seems much more philosophically precise than either laypeople or physicsts tend to be, about exactly what is and what is not entailed by QM. Perhaps holding onto pilot wave theory as a truly valid interpretation of QM keeps one from slipping into false conclusions.

> > So the theory mandates that said randomness cannot ever be correlated? It cannot ever be the case that you can tell more about two particles by describing both at the same time than you can tell by having independent descriptions of each particle?

> I can't make sense of the point you're trying to make here, sorry. I don't understand what you mean. There are always the two particles, and also the interaction between them.

You know that in order to say as much as you can about one photon in an entangled pair, you end up saying as much as you can about the other photon as well, right?

Luke said...

@Don Geddis: (2/2)

> You seem to be suggesting an actual failure of reductionism. I know of no example in all of science where reductionism fails. High level behavior is always explained by a collection of lower-level entities. You never get new behavior at an abstract level, which has no origin at all at the lower level.

I am suggesting that the lower level can partially determine what happens at the higher level, but not fully determine it. Sean Carroll argues against this in his Discover article Downward Causation, as well as his own blog post Consciousness and Downward Causation. A helpful article for driving me in the direction of partially-but-not-fully is Massimo Pigliucci's Essays on emergence, part I. Feel free to skip to the first paragraph containing "Batterman".

> > The resultant trajectory is simply not computable as a result of the forces of gravity.

> "Computability" is an entire different criteria. Lots of things get simplified for practical reasons, for the convenience of humans. But the universe doesn't do that. The universe only operates at the very lowest level. Everything higher are just our approximate simplified models.

Well, if you assume there's infinite precision on the trajectory (contra Ron's stance in How do we know that quantum randomness is really random?) and you presuppose that there are no infinitesimal point-forces, you can fall back on [deterministic] chaos theory. So in that sense, point taken and I was wrong.

> Yes, it is. There is nothing going on in your spacecraft example, aside from the various ordinary forces. Chaos Theory is still deterministic. It is only uncomputable in practice; it is not uncomputable in theory.

Infinite-precision arithmetic is not computable in theory. You would need to set a maximum needed precision. Suppose that you bottom out at Heisenberg's unsharpness relation: then wouldn't you have the same kind of problems we have been discussing with regard to having no theoretical way to arbitrarily precisely measure the positions of de Broglie–Bohm particles?

The same would seem to apply to the kind of statistical mechanics Ilya Prigogine was studying: not only are the trajectories computationally intractable, but even if you could you would have a classical computation which ignores quantum phenomena. You can have non-classical correlations between parts though: WP: Quantum discord.

Luke said...

@Ron:

> Luke: Fully deterministic processes can generally be modeled by some other deterministic process, plus randomness. True, or false?

> Ron: False. Fully deterministic processes do not have a random component. That is what "fully deterministic" means.

> Luke: [Engages point about "fully deterministic".]

> Ron: They cannot GENERALLY be modeled this way.

> Luke: So … you're dropping the complaint about "fully deterministic"?
>
> As to "generally", I intended to talk about the space of processes we encounter in reality, not in mathematics land. I'm thinking of how Fourier's mathematics worked for the systems he focused on and guessed that the physicality of them (e.g. obedience of conservation laws) provided the right restriction to get a "generally" in his case. Does that make sense? If so, my bad for not making clear that I was talking about "in reality". If it doesn't make sense, then how do we robustly test your "cannot"?

> Ron: I have no idea what "complaint" you are referring to here, but the antecedent of "they" is (quoting you) "fully deterministic processes."

Your complaint is right there in the quote history: "Fully deterministic processes do not have a random component. That is what "fully deterministic" means." I had to compare and contrast "fully deterministic" and "deterministic" for you.

Now you've dropped the investigation into what class of fully deterministic processes can be approximated by simpler deterministic processes plus randomness. That's unfortunate, because I want to know if I were wrong. If in fact the class of fully deterministic processes in our reality actually can be approximated that way, it'll be very enlightening to find you judging my thinking not based on our reality, but based on logical possibility space.

> I have no idea why you're bringing up "The bit about unstable Lagrangian points." The first reference to Lagrange points was AFTER your question about "fully deterministic processes", which you posed in response to this quote from Don: "Not quite as different …"

Technically my response was after that, but I wasn't responding to that comment. Instead, I was responding to the reductionism in the section starting "Yes, that's true throughout science. … ⋮".

> So your question about "fully deterministic processes" was clearly in reference to quantum mechanics.

Correct. My bit on unstable Lagrangian points, on the other hand, was not. You're conflating the two.

> And when I try to point out what you get wrong you don't seem to make any effort to understand what you've gotten wrong and why and you make no effort to try to improve, you just respond with more stupidity and non-sequiturs.

That's bullshit, as is clearly demonstrated by my paragraph starting "As to "generally", I intended to talk about …".

> I honestly can't tell whether you actually care about any of this, or if you're intentionally trolling. I'm leaning towards the latter.

Then you can join the long line of atheists who have decided that what I claim about my own intentions can be steam-rolled and replaced with their evil models of my intentions.

Don Geddis said...

@Luke: "Why not just pursue a "shut up and calculate" approach, as that would be more parsimonious than working with any interpretation of QM?"

Because the very point of science -- a la Deutsch -- is to come up with "explanations": an ontology of what things "exist", how they relate to each other, how things evolve in time. And counterfactuals: what else would be different, if this part were to change?

"Mere prediction" is not sufficient. We ask for more, from science.

"It is a fully deterministic interpretation of QM"

Not really. Every interpretation of QM still needs to include the Born rule. You always have to take the squared modulus of the wave function, to get a probability of detection.

"The only truly demonstrable justification is an increase in prediction powers."

No, that's not correct. There are other criteria (such as simplicity) in play as well. Again, there are always an infinite number of theories that explain all available data. For example, Last Thursdayism offers the same predictions as ordinary science. Yet I suspect you prefer some alternate theory of the universe, for a reason other than "an increase in prediction powers".

"I am suggesting that the lower level can partially determine what happens at the higher level, but not fully determine it."

Yes, I understand what you are suggesting. Your suggestion is false.

"Sean Carroll argues against this"

Really? Did you bother to read your own links? Some quotes: "I think it’s a misguided/unhelpful notion ... it seems completely wrong-headed to me." And: "There is no reason to think that anything like downward causation really happens in the world"

"Infinite-precision arithmetic is not computable in theory."

You're confusing the physical universe, with math. There are no infinities in the physical universe. And it isn't doing arithmetic. "Infinite-precision arithmetic" is a mathematical model; it isn't what the universe does.

Ron said...

@Luke:

> what I claim about my own intentions

But you haven't actually claimed anything about your intentions. You are constantly cagey about your motives and beliefs. I've been hounding you for YEARS to write a guest blog post here outlining and defending your beliefs. Where is it? Why are you wasting your time commenting instead of working on it?

This is one of the many annoying troll-y tactics you regularly deploy: you say something that sounds like you meant to say X, but you never actually say X so that when X turns out to be wrong (which it very often is) you can (and often do) respond, "But I never said X." In this case, X="I am not trolling. I really do want to learn." Well, IF you really aren't trolling and you really do want to learn then you need to change some very fundamental things about your behavior. For starters, when someone you want to learn from gives you a homework assignment, you need to do it.

On which note:

> Why not just pursue a "shut up and calculate" approach, as that would be more parsimonious than working with any interpretation of QM?

> I have an incredibly hard time working with only abstract equations

There's your problem right there. There are some deep insights to be had from certain interpretations of QM, but before you can really understand them you have to understand the math. At the very least you need to understand its basic structure -- the fact that the Schroedinger equation is linear and why that matters, the fact that the wave function is complex-valued and why that matters, how spin is modeled, and so on. You would benefit greatly from shutting up and doing some calculating for a while. Yes, it's hard. Worthwhile things usually are.

So, homework: get a copy of Griffiths. Read it (at least the first five chapters). Work through some of the problems. Come back in six months.

Here's something to think about while you're reading: what is the domain of the wave function? In other words, the wave function is a *function*, so it has an *input*. What is it? Don't EVEN THINK about trying to answer that until you've gotten to the end of chapter 5. Hint: the answer is NOT "a location in physical space."

One last bit of advice:

> I find it a helpful stepping stone away from classical physics.

It's not helpful, it's holding you back. If you're going to learn relativity you have to let go of the idea that space and time are separate things because they aren't. If you want to learn QM you have to let go of the idea that the world is classical because it isn't.

Luke said...

@Don Geddis:

> > Why not just pursue a "shut up and calculate" approach, as that would be more parsimonious than working with any interpretation of QM?

> Because the very point of science -- a la Deutsch -- is to come up with "explanations": an ontology of what things "exist", how they relate to each other, how things evolve in time. And counterfactuals: what else would be different, if this part were to change?

Is "ontology" essentially a calculating device, in your mind? Incidentally, the many-worlds interpretation "is a realist, deterministic, arguably local theory, akin to classical physics (including the theory of relativity), at the expense of losing counterfactual definiteness." So do you reject it, on the basis that it doesn't permit counterfactuals any realist interpretation?

> "Mere prediction" is not sufficient. We ask for more, from science.

I am aware of how some physics problems are more easily solved via kinematics and others more easily solved via tracking total energy of the system in some way. In some representations, calculation is nigh impossible while in others it is trivial. But these are all instrumental uses; they don't tell you "what really exists". They just give you a psychologically convenient representation. I suspect that in some cases, what one scientist finds psychologically convenient will be different from what another scientist finds psychologically convenient.

> Every interpretation of QM still needs to include the Born rule.

As far as I know, the limitation can be epistemic rather than ontological. See for example WP: Quantum non-equilibrium.

> There are other criteria (such as simplicity) in play as well.

There are three reasons I know of for prioritizing simplicity:

     (1) it seems to point the way toward future discoveries
     (2) it is most tractable
     (3) humans seem to work via successive approximation

The only way in which these connect to a realist ontology is if we suspect that true reality has a kind of structure which is amenable to prioritizing "simplicity" (and "simplicity" understood a certain way).

> For example, Last Thursdayism offers the same predictions as ordinary science.

Last Thursdayism violates parsimony for no gain in prediction or tractability.

> Your suggestion is false.

How would we attempt falsification of your view?

> > I am suggesting that the lower level can partially determine what happens at the higher level, but not fully determine it. Sean Carroll argues against this

> Really? Did you bother to read your own links?

"this" = "I am suggesting that the lower level can partially determine what happens at the higher level, but not fully determine it." That is, Sean Carroll rejects my suggestion.

> There are no infinities in the physical universe.

So how precisely do you have to track a spacecraft passing precisely through an unstable Lagrangian point, to calculate (in principle) its resultant trajectory? Presume as much finite computing power as necessary.

Luke said...

@Ron:

> But you haven't actually claimed anything about your intentions.

Incorrect:

> Luke: It saddens me that you think "Luke is a troll" has appreciable probability by this point in our interactions with each other, but I shall accept full responsibility for that.

But just so there is no ambiguity: I hereby claim that I have never intended to troll you Ron, in any interaction we have ever had. Furthermore, I claim I never intend to troll you in the future, and would prefer that God strike me from existence than for that to change. Is that sufficient, or do I need to find a way to word things more strongly?

> I've been hounding you for YEARS to write a guest blog post here outlining and defending your beliefs. Where is it? Why are you wasting your time commenting instead of working on it?

You've asked a few times, but the term "hounding" seems metaphorically utterly inaccurate given the textual evidence. However, I shall take this as the new model of you and stop replying to you (≠ to Don) until I have submitted a guest blog post. Unless you request I also stop discussing anything with anyone on your blog until I get that guest blog post finished.

Why do I do what you consider "wasting [my] time"? Because I find the present topic interesting and frankly, easier than writing a guest blog post which is properly fortified against stupid-filters. Of all the people with whom I've interacted in life—online or IRL—you have shown the greatest ability to construe what I say as stupid. Discussions like the present one aid my model of what you would consider stupid, but I am still extremely dissatisfied with that model. Well, too bad for me: I shall now either finish that guest blog post or never attempt to talk to you again.

> This is one of the many annoying troll-y tactics you regularly deploy: you say something that sounds like you meant to say X, but you never actually say X so that when X turns out to be wrong (which it very often is) you can (and often do) respond, "But I never said X."

An alternative model is that you continually adopt a "Luke is stupid" filter and when I demonstrate that the textual evidence supports a plausible alternative, you get frustrated. Incidentally, no other person I have interacted in person has had nearly as much trouble as you do. For whatever that statistical fact is worth.

> So, homework: get a copy of Griffiths. Read it (at least the first five chapters). Work through some of the problems. Come back in six months.

Ok, if and until I do this, I will never again attempt to discuss quantum physics with you. Unless, that is, you choose to relax this restriction. But I may choose to have discussions with others on your blog about QM, unless you request I do not.

Don Geddis said...

@Luke: "So do you reject it, on the basis that it doesn't permit counterfactuals any realist interpretation?"

No, of course not. But I suspect you don't really know what these words in your sentence mean. And also perhaps not what the MWI actually is. In any case, a simple enough response to your direct question would probably be: "The many-worlds interpretation is not only counterfactually indefinite, it is factually indefinite as well." (Guy Blaylock). Meaning, as wikipedia says, that "instead of not assigning a value to measurements that were not performed, it ascribes many values". But that's actually no different for measurements that were performed! Nothing special about counterfactuals.

"Last Thursdayism violates parsimony for no gain in prediction or tractability."

I wonder if you realize that you are now apparently agreeing with me, and contradicting your previous claim. Because you earlier wrote: "The only truly demonstrable justification is an increase in prediction powers." But you now seem to have come up with additional justifications (aside from "increase in prediction") on your own.

"How would we attempt falsification of your view?"

Find a real-world example of causality at the higher abstract level, which has no possible explanation at the lower level. I know of no such examples today.

"That is, Sean Carroll rejects my suggestion."

Ah. Thank you. I misinterpreted your original paragraph.

"So how precisely do you have to track ... to calculate ... its resultant trajectory?"

You now seem to be asking a practical question. But perhaps you've lost the point? This new question has nothing at all to do with the point we were discussing. If you go back, your spacecraft example was intended to demonstrate this claim of yours: "the possibility that behavior exists at the ensemble level which does not exist as a simple "sum" of individual elements". How we use real-world noisy measurements, and real-world limited computation devices, has nothing at all to do with the fundamental epistemological claim (of yours) that reductionism might break down somewhere in the actual universe.

To more directly answer a version of your question: if you have a particle travelling on a mountain ridge, balanced between falling off to the left or to the right, and the direction depends on which side exactly its center of mass is as compared to the ridge, but the particle itself is spread out sufficiently in probability space that it could be on either side ... then MWI says that "the" particle winds up falling both to the left and to the right. Similarly, you are mistaken to imagine "its resultant trajectory" as a single unique thing. Just like a photon through the double slit, the single spacecraft will take multiple trajectories through the unstable point. Any calculation that attempts to predict a single outcome, will not match our actual universe.

Ron said...

[Arrgh, I accidentally posted an incomplete draft of this comment that included something I didn't mean to include.]

@Luke:

> I hereby claim that I have never intended to troll you

I will take you at your word. But note that this is just a statement of what your motivation is *not*. You have yet to tell me what your motivations actually *are*. That I still have to guess.

Also:

> It saddens me that you think "Luke is a troll" has appreciable probability by this point in our interactions with each other, but I shall accept full responsibility for that.

Do you? Because what this means it that you acknowledge that I was *justified* in assigning a non-zero probability to your being a troll. And if that saddens you, then your sadness is a result of *your actions*. So unless you like being sad, you need to *change your behavior*. You've not shown much of a willingness to do that.

It's not enough to repent. You have to actually stop sinning, or at least demonstrate that you are making a good-faith effort to try to stop sinning.

@Don & Luke:

> if you have a particle travelling on a mountain ridge

It's worth noting that there is a salient difference between particles and spacecraft, namely, spacecraft are macroscopic. This matters because the uncertainty relations apply to *momentum*, not *velocity*, which is what matters when navigating spacecraft. Velocity is momentum *divided by mass*, so if you have a very large mass you can have a very large uncertainty in momentum but still a very low uncertainty in velocity. So for a spacecraft you actually can measure its position and *velocity* simultaneously with very high accuracy. The actual errors in practice are the result of technological limitations, not quantum-mechanical ones.

It's not hard to do the math on this and work out, for example, how much uncertainty there is in the velocity of a spacecraft if you measure its position to an accuracy of, say, the diameter of an atom. It's a worthwhile exercise.

It's also worth noting that it is an open question what would happen *if* you could put a macroscopic object in a superposition of position states by sending it precisely through a Lagrange point. Predicting that would require a theory of quantum gravity, which we do not yet have. In fact, *if* you could do this experiment, the result would be extremely interesting and enlightening. Given that, and given that we have the technology to fly spacecraft and control their trajectories quite precisely, it is worth reflecting on why this experiment has not been attempted.

Ron said...

@Luke:

One more thing, very important:

> An alternative model is that you continually adopt a "Luke is stupid" filter

"Luke posts stupid comments" != "Luke is stupid."

Also "Luke posts stupid comments" does not imply that you don't also occasionally say things that are constructive and worthwhile.

> unless you request I do not

The only rule I have ever enforced here is that you have to be civil. (Which, I admit, I have been on the hairy edge of violating in this thread. So I am going to remove myself from this discussion and await your guest post.)

Don Geddis said...

@Ron: "it is worth reflecting on why this experiment has not been attempted."

I was enjoying your description of the spacecraft Lagrange example. Until the final sentence, where it felt a little like a cliffhanger. I have to admit, I'm honestly confused. Was this intended to be a rhetorical question? Was it a Socratic question, that you thought the reader had a good chance of answering? Was it just an ordinary question, that you don't know the answer to either?

Personally, I would love to hear you continuing to discuss the answer to your own question!

One thing I don't understand from your description: surely you can also measure the rest mass of the spacecraft very accurately as well. So if you know its mass accurately, and you know its velocity accurately, how do you become uncertain again about its momentum? That would seem to be merely the product of two accurate measurements. (I had thought the stability of macroscopic objects came from the various subatomic uncertainties canceling each other out, on average. So the average momentum of a large population of particles can be known more precisely than the momentum of any given single particle. Or at least the expected value is more sharply peaked.)

Ron said...

@Don:

I was in the middle of elaborating on that question and realized that I don't actually know the answer. I thought I did, and I'm pretty sure I'm right, but I haven't done the math. Then I ran out of time (which I'm about to do again).

But since you ask, this is as far as I got: imagine an idealized experiment where you sent a spacecraft through a Lagrange point. Pick some values for the mass of the spacecraft and the accuracy with which you can measure its position (I was going to suggest values at the extremes of what might be technologically possible: 1 mg mass whose location is measured to within the diameter of an atom). Calculate how long you would have to wait until its superposed positions diverged far enough to be gravitationally distinct (e.g. 1 cm). I conjecture that the answer will turn out to be longer than the age of the universe. But the truth is I have no idea.

> if you know its mass accurately, and you know its velocity accurately, how do you become uncertain again about its momentum

By measuring its position. (Isn't that obvious?)

Note that for the thought experiment what matters is only its position with respect to the direction(s) perpendicular to its velocity.

Ron said...

Also, @Luke:

> I shall now either finish that guest blog post or never attempt to talk to you again.

If you choose the former option (and I really hope you do) I would be particularly interested in hearing what persuaded you to no longer consider yourself a YEC.

Peter Donis said...

I'll take a crack at this. Since we're just looking at orders of magnitude, I'm going to use 10^-34 for Planck's constant (which is pretty close to hbar). Then we have m = 10^-6 kg and Delta x = 10^-10 m (rough value for "size of an atom"), so we get

Delta v = hbar / m Delta x = 10^-34 / 10^-16 = 10^-18 m/s. So for the difference in the two superposed positions to equal 10^-2 m (1 cm) will require 10^-2 m / 10^-18 m/s = 10^16 s, or about 3 x 10^8 years.

I'm not sure where the 1 cm criterion for "gravitationally distinct" is coming from; a 1 mg mass could be quite a bit smaller than that in size. So the time could be a couple of orders of magnitude shorter than the above.

Ron said...

> I'm not sure where the 1 cm criterion for "gravitationally distinct" is coming from; a 1 mg mass could be quite a bit smaller than that in size.

That's the minimum distance that the positions would have to be separated to distinguish them *gravitationally*. The thing that would make this experiment interesting is to somehow isolate the test mass so that its position can *only* be determined by its gravitational effects. (We already know what would happen if we just *looked* at it.)

The time could still be quite a bit shorter than the 10^8 years because you haven't taken into account the "amplifying" effect that sending the mass through the Lagrange point would have (that was Luke's original point, at least AFAICT).

Luke said...

@Don Geddis: (1/2)

> But I suspect you don't really know what these words in your sentence mean.

I have done some reading on counterfactual definiteness, but I generally only come to understand terms through dialogue, not through articles. So, what would you say Wikipedia means when it says:

>> The Many Worlds interpretation rejects counterfactual definiteness in a different sense; instead of not assigning a value to measurements that were not performed, it ascribes many values. When measurements are performed each of these values gets realized as the resulting value in a different world of a branching reality. Thus although unperformed experiments have values, they cannot be used in statistical calculations as one would the single value of a performed experiment. As Prof. Guy Blaylock of the University of Massachusetts Amherst puts it, "The many-worlds interpretation is not only counterfactually indefinite, it is factually indefinite as well." [19] (WP: Counterfactual definiteness § Many Worlds)

? What are the implications of this, over against other QM interpretations? Yes I see that single sentence in the section I excerpted, but what are [some of] the practical outworkings of said "cannot be used"?

> Nothing special about counterfactuals.

So none of our intuitions depend on "counterfactual definiteness"? Because if some do, I want to know how MWI impacts those intuitions.

Luke said...

@Don Geddis: (2/2)

> I wonder if you realize that you are now apparently agreeing with me, and contradicting your previous claim. Because you earlier wrote: "The only truly demonstrable justification is an increase in prediction powers." But you now seem to have come up with additional justifications (aside from "increase in prediction") on your own.

There is a key difference between in principle prediction powers and in [human] practice prediction powers. I meant the former all along, but it appears you were allowing the latter to be a distinct possibility. In general, unless otherwise stated, I implicitly scope my claims to be connected to this reality rather than some ostensible logical possibility space.

> Find a real-world example of causality at the higher abstract level, which has no possible explanation at the lower level.

I thought I did, with the End of Certainty excerpt. But you objected, arguing that in principle, "It therefore contains additional information that is lacking at the level of individual trajectories." is false. To the extent that there is quantum discord going on in what Prigogine describes, you appear to be wrong. But I'm guessing you have a retort to this (which I am interested in hearing).

I'm left wondering whether it is logically possible to find what you describe, or if any way of describing phenomena, which you'll accept, entails that you'll always be able to find a reductionistic explanation [which you'll contstrue as better] from logical possibility space.

> Ah. Thank you. I misinterpreted your original paragraph.

No worries. The very title of his article is a little obnoxious. In my snippets.html, I therefore have "Sean Carroll's reductionist Downward Causation", but I decided to omit the "reductionist" in this case. Oops.

> If you go back, your spacecraft example was intended to demonstrate this claim of yours: "the possibility that behavior exists at the ensemble level which does not exist as a simple "sum" of individual elements".

Actually, it was meant to cleanly distinguish between:

     (1) "simplifications required for human comprehension"
     (2) "the possibility that behavior exists at the ensemble level which does not exist as a simple "sum" of individual elements"

It was meant to be an example where you can't just model something as (1). Logically, ¬(1) ⇏ (2), but I could plausibly be accused of making that mistake. The crux of the matter is whether a deterministic ontology is realistic or actually just a calculating device which works well in some domains for some purposes. On the one hand, you want to allow [deterministic] chaos theory to deal with the spacecraft, and on the other hand Ron wants to ban the [deterministic] de Broglie-Bohm theory. This seems like a philosophical contradiction to me if we have in the back of our minds "fundamental reality" for both systems.

> ... then MWI says that "the" particle winds up falling both to the left and to the right. Similarly, you are mistaken to imagine "its resultant trajectory" as a single unique thing.

Sure. And it seems that one must pay some philosophical costs to posit things you cannot possibly observe.

> Any calculation that attempts to predict a single outcome, will not match our actual universe.

Sure, and this could be due to our having incomplete information—which we have more completely at some point in the future. See how the Born rule is just a hypothesis in de Broglie–Bohm at WP: Quantum non-equilibrium.

Don Geddis said...

@Luke: "what are [some of] the practical outworkings of said "cannot be used""

I don't know. It doesn't seem important to me. I haven't given it much thought.

"I want to know how MWI impacts those intuitions."

All of quantum mechanics, is different from common sense intuitions. The entire field, and all the data, "impacts" those intuitions. The Born Rule (shared by every QM interpretation) impacts common sense intuitions. Superposition impacts intuitions. The double slit experiment impacts intuitions.

In that whole intuitive mess of being in the quantum world in the first place, I don't know that MWI stands out as being particularly strange. The strangeness is already there, in QM. MWI is just one attempt to make some sense out of all of it.

"it seems that one must pay some philosophical costs to posit things you cannot possibly observe."

Not really, no. Let me give you a simpler example: you have some idea how the sun works, right? Nuclear fusion, making heat and photons? And some of those photons leave the sun and head in our direction, and we can see them here on earth, right? Now, the sun is pretty symmetric, isn't it? You would expect a few photons to happen to leave the sun, and head in a direction other than the earth, maybe opposite the earth? Perhaps even most of them?

Tell me your theory about these photons leaving the sun, but not towards the earth. Do they "exist"? They are energy packets outside of your future light cone. According to relativity, they are things "you cannot possibly observe." Either now, or any time for all of humanity in the far distant future. They are no longer part of your observable universe.

Do they exist?

The answer, of course, is: "yes". Our theories of how the sun works, and how fusion works, and how matter and energy work, require that there are lots of photons streaming from the sun out to universe, than we could never possibly observe, but which nonetheless still exist.

And it provides clear answers to counterfactual questions: if we had decided to put a spacecraft orbiting the sun on the far side of earth, we're pretty confident that it would have detected the photons from the bright shining sun, just like we do here on earth. The fact that we happened not to launch such a spacecraft, does not significantly change our expectations that the photons are still there.

MWI is like that.

"this could be due to our having incomplete information—which we have more completely at some point in the future"

No. Experimental QM data cannot be explained by our current, temporary, lack of information. It is more fundamental than that. For example: Can You Prove Two Particles Are Identical?. You remind me of the "one who is wise in philosophy but not in physics" in the story. I'm curious if you can answer this question: "what kind of universe could you possibly live in, where a simple experiment can tell you whether it's possible in principle to tell two things apart?"

Ron said...

@Don:

> MWI is like that.

Not quite. In the case of a photon heading away from the sun there is always the possibility that it could be reflected back to us and we could see it. When a universe "splits" (a better metaphor would be "peels apart") there is absolutely no possibility of ever observing one branch from the other. Each branch is an IPU relative to the other branch.

The reason to believe in parallel universes is that there are only two possibilities: either they exist, or they don't and there is some as-yet-unidentified non-unitary physical process at work in the (one) universe. Pick your poison.