[acqq]

So please explain in a few sentences what is that that Yudkowski writes, did he make any new contribution to the standard model or made something else or do you agree that the standard model is the most researched and most usable model up to now, and he just made a lot of posts where he just writes a lot of text?

I see a lot of links in the article you gave, but I don't understand what we're supposed to discover in Yudkowski's writings after trying to follow most of them. There's a lot of free text, not much physics. The standard model is a lot of smart formulas supported by the decades of expensive elaborate measurements (and vice versa), however his texts look more like writings of some philosophy student who knows a little of the math than like a physicist's material. I'd also really welcome opinions of professional physicists.

Edit: Wikipedia entry about him seems to fit my impression: http://en.wikipedia.org/wiki/Eliezer_Yudkowsky "Yudkowsky (...) is an American blogger, writer, and advocate for Friendly artificial intelligence (...) Largely self-educated."

[Sharlin]

The Standard Model does not concern itself with the various interpretations of quantum mechanics. It can, as of now, neither verify or falsify any of the interpretations which, consequently, are not scientific theories or even hypotheses, but firmly on the side of philosophy of physics. The interpretations are attempts to answer why Nature works as it does, within the framework of the Standard Model which only appears to answer the question how.

Yudkowsky certainly hasn't invented the many worlds interpretation, which was originally formulated by the physicist Hugh Everett in 1957. Even though originally scorned, in the more recent times it has gained popularity among physicists. The series of blog posts by Yudkowsky are (in my opinion, at least) a persuasive argument in its favor against the competing interpretations, and are very much recommended reading for anyone who would like to better understand the issue.

[acqq]

> the interpretations which, consequently, are not scientific theories or even hypotheses, but firmly on the side of philosophy of physics.

Thanks, that's exactly what I wanted to know.

I'm completely satisfied with the "shut up and calculate" approach. For me, until somebody shows that he/she can calculate (that is, predict) more than what physicists achieve, they are the ones the closest to "the truth" and not the "interpreter."

[spacehome]

Bring it back to the scientific method. The way to differentiate between competing hypotheses is by devising experiments that falsify some of them, and then running the experiments and either falsifying or failing to falsify them.

The issue here is subtle, and it's that the most popular interpretation, Copenhagen, isn't a complete theory because it doesn't tell you algorithmically when collapse occurs. For any possible algorithmic way to handle collapse, there's a corresponding experiment that could (at least in theory) differentiate between Copenhagen and Many Worlds. But the Copenhagen is inordinately slippery in that collapse is defined to occur ex post facto in whatever way is needed to make the experimental results match the theoretical results.

It's perhaps not so surprising that this shortcoming was overlooked in the beginning because Copenhagen was hypothesized before we really had a clear handle on the study of algorithms. But the fact that Copenhagen is still as popular as it is means that Yudkowski needs to spend a lot of time on philosophy of science, because that's what's holding back most people from seeing the problems with Copenhagen, and why at first glance it looks like philosophy.

[sriku]

spacehome suggested reading Elizer's posts on quantum physics precisely to not bother to deal with outdated statements like "the most popular interpretation, Copenhagen". Afaik, no serious physicist uses this any more, not even to explain quantum theory. To use wavefunction collapse to "explain" QM is like invoking "God" to explain the universe - i.e. it is not much of an explanation, and it raises more questions than it answers.

Text books ought to be rewritten to teach decoherence instead of outdated stuff like wave-particle duality, wavefunction collapse and such. That is the history of the development of QM and not QM as it is known today, in my limited knowledge.

If you get decoherence, much of the "mysteriousness" and "spookiness" that's talked about in such magazines just disappears and you find them all, every one of them, shallow.

[acqq]

I think I can agree with your first paragraph, even if I'd phrase it somewhat differently, but I don't see the connection between it and the next two.

[spacehome]

I certainly meant those three paragraphs to be connected; perhaps I'm just poor at explaining. As I mentioned, the shortcomings of the Copenhagen Interpretation are subtle, and I originally linked to Yudkowski's treatment because I believe he does much better job of explaining it than I ever could.

[acqq]

Allow me to not agree with your classification of the top article as "garbage." I've got from it more than from the text you linked to and I'm even less satisfied with your explanations whereas Natalie Wolchover did a rather good article. Please tell me if you have any background in physics, or what is your background?

The major thing missing from the article for me is that she didn't mention that the co-author of the most recent paper on the topic is much more known as the security researcher than as somebody who does anything related to quantum physics:

http://arxiv.org/abs/1401.4356

http://en.wikipedia.org/wiki/Ross_J._Anderson

http://www.cl.cam.ac.uk/~rja14/

He's author of (to me) very useful book "Security Engineering":

http://www.cl.cam.ac.uk/~rja14/book.html

[scott_s]

Last week, I wrote a comment replying to someone asking, if we can't use experiments to determine which interpretation is better, what's the point? Rather than repeat myself, I'll just link to it: https://news.ycombinator.com/item?id=7940647

[acqq]

You say there: "How they lean will influence what sort of questions they investigate, how they investigate it, and what sort of outcomes they will look for."

If I understand you, we can expect that somebody is maybe going to be the first to discover something new thanks to the way he's used to think about the subject. Still, before that happens, what do we have?

Edit: Only real hard science. The discoverer we expect of course must decide from which side to attack the matter to reach the new discoveries.

[scott_s]

I don't know, but I'm not sure what you're asking. Kuhn's point (and mine, by transitivity) is that scientists are human with unavoidable biases, and these biases will influence what work they do.

The reason I don't know how to answer your question is that I interpret it to mean: what tangible result do we have before we have our first tangible result?

Of course, if that's not what you mean, then please clarify. You may want to read his book, though, as this concept is central to some of it. If you're saying, "what is the effect of such paradigms before they change," then it's best to read his book. One point he makes is that everyone operates under a paradigm, whether conscious of it or not. That is, we must think about our scientific work in some way, and whatever way we think about it will influence what scientific work we do. It is generally the case, though, that many people have some form of agreement on that "some way." When we do, that sets informal bounds on what is "acceptable science."

He does use quantum mechanics as an example, but that's loaded because we're still hashing it out. Another example he uses is phlogiston chemistry (http://en.wikipedia.org/wiki/Phlogiston_theory), which has thoroughly been supplanted. Those who first encountered oxygen were unable to recognize what it was because the paradigm in which they operated didn't contain the concept.

[acqq]

Thanks Scott. I understand that phlogiston thrived until real honest scientific experiments disproved it. Thanks to which "interpretation" before that point? Can't we call it "shut up, experiment and calculate"? Or, simpler, "do the science."

[GregBuchholz]

If you can get the same answers, with a simpler or more elegant theory, you might consider that a "better" theory. IIRC, initially the heliocentric theory of the solar system gave worse approximations of planetary positions than the highly refined epicycles of the geocentric models.

[danbruc]

IMHO the many worlds interpretation is one of the least appealing interpretation - millions of millions of millions of universes for nothing. What do you think about the following similar argument? Why are the laws of physics and the physical constants the way they are? There is a universe for every possible set of laws and constants and our universe just happens to be compatible with life. You can just render almost every interesting question moot with similar arguments - I would really prefer something more interesting at the heart of the universe.

[acqq]

On that level I don't have any problem with "many worlds" as it can be seen just a one more extrapolation of "we're not in the designed special position" principle: first we're not the center around which the planets circle, then our Sun also isn't the center of our set of stars, then our set of stars is one of many other galaxies... if our physical universe is just a lucky variant of other possible (and mostly uninteresting) universes, it at least doesn't appear surprising.

[danbruc]

But there is an important difference - you can observe the other stuff in our universe and therefore know that we are not (exceptionally) special in our universe. Other universes are usually per definition completely outside of our reach, as hard to grab as a god or Russell's teapot.

[acqq]

> completely outside of our reach, as hard to grab as a god or Russell's teapot.

I agree! As in my other comments here, as long as there isn't any scientific result, I also won't regard the products of the proponents of such "interpretations" better than you.

[spacehome]

Well, they're not completely outside our reach. Interference between our worlds and nearby ones is very testable, and the reason the theory exists.

[alphydan]

That makes it out of reach. You cannot falsify the many-worlds-interpretation simply with interference. All other interpretations make the very same predictions.

[DavidPlumpton]

What's more likely? That quantum interference appears because many worlds perpetually exist, or because they seem to exist but somehow don't, or because they sometimes briefly come into existence, hang around for a bit and then randomly collapse breaking all sorts of laws (Liouville thereom, CPT invariance etc.)?

Many Worlds is much tidier than all the alternatives.hh

[eli_gottlieb]

Actually, I'd say the "illusion" option is the simplest and tidiest. It is more likely that we interpret a complicated reality from incomplete information than that reality truly is complicated.

[Jach]

Have you read Feynman's QED? It's a bit like that, in that it's meant for a layman, but with more algebra. Instead of abstract arrows, EY goes straight to complex numbers. It goes through a basic approach to quantum mechanics (taking diagrams from here for instance: http://www.qi.damtp.cam.ac.uk/node/60) in a modern way and tries to build an intuitive understanding of the subject, especially demolishing a lot of confusions one may have gained through popular media. He then departs from the basic theory to elaborate on why the collapse interpretation is ridiculous and why Many-Worlds makes more sense. You can stop when you get to the Timeless stuff.

You're not really going to find anything ground-breaking, but it may help your intuitions about QM even if you're a physicist. As a chapter from the Aaronson book (http://www.scottaaronson.com/democritus/lec9.html) I linked to in a cousin comment says in the first two paragraphs:

There are two ways to teach quantum mechanics. The first way -- which for most physicists today is still the only way -- follows the historical order in which the ideas were discovered. So, you start with classical mechanics and electrodynamics, solving lots of grueling differential equations at every step. Then you learn about the "blackbody paradox" and various strange experimental results, and the great crisis these things posed for physics. Next you learn a complicated patchwork of ideas that physicists invented between 1900 and 1926 to try to make the crisis go away. Then, if you're lucky, after years of study you finally get around to the central conceptual point: that nature is described not by probabilities (which are always nonnegative), but by numbers called amplitudes that can be positive, negative, or even complex.

Today, in the quantum information age, the fact that all the physicists had to learn quantum this way seems increasingly humorous. For example, I've had experts in quantum field theory -- people who've spent years calculating path integrals of mind-boggling complexity -- ask me to explain the Bell inequality to them. That's like Andrew Wiles asking me to explain the Pythagorean Theorem.

(And on EY himself, just read the million or so words of the Sequences and you'll see he is actually really smart across multiple domains. ;))

[acqq]

I never claimed that EY isn't smart, only that what he writes is not actually physics.

As much as I remember Feynman's lectures, he introduced the amplitudes very early?

[Jach]

Fair enough. I agree a large part of it isn't strictly physics, though I think in the beginning it's like the first couple weeks of a high school Mechanics class. Low on math, but you get to do or hear about experiments and how they ought to shape your view of what's going on. (Thinking of masses and acceleration and forces, thinking of complex amplitudes and decoherence.)

[sriku]

Yudkowsky's contribution is pedagogical rather than anything fundamentally new. He explains quite well in short the process of "decoherence" and links it well to the many worlds interpretation. He makes a case for why the "many worlds interpretation" is not really an "interpretation", but is just stating what the mathematics says on its face anyway .. and hence is the one we should adopt. In particular, he does a good job of connecting this to "timeless physics" - i.e. the Weyl equation for the "wavefunction of the universe" which does not have time in it.

[sriku]

edit: Sorry! Tongue of the slip. I was referring to the "Wheeler-DeWitt equation" [1] and not the "Weyl equation" [2].

[1] http://en.wikipedia.org/wiki/Wheeler%E2%80%93DeWitt_equation

[2] http://en.wikipedia.org/wiki/Weyl_equation

[DavidPlumpton]

Yudkowsky is more of an expert in reasoning than in Physics. For example, imagine you are a world class expert in Quantum Mechanics and you are asked to give a talk at a science club. You cover a lot of stuff and think "that was great". But somebody else tells you "that was terrible, you mumbled, you wrote illegible stuff on the board etc." and you realise it wasn't about QM, it was about public speaking.

Similarly physicists have done amazing work over the decades, and now it's time to draw conclusions from all that evidence. But it turns out that physicists are not domain experts in drawing conclusions from evidence. That kind of skill is a separate domain in its own right.

[gohrt]

The Standard Model is a model, not an interpretation. Whether Yudkowsky is right or wrong, anyone's interpretation is going to be text, not physics.