People Keep Making Einstein's Greatest Blunder

"We are all agreed that your theory is crazy. The question which divides us is whether it is crazy enough to have a chance of being correct. My own feeling is that it is not crazy enough." -Niels Bohr

You know who Einstein is, I'm sure. The E=mc2 guy, the speed of light guy, and -- perhaps most prestigiously -- as the inventor of the best theory of gravity that we have: general relativity.

One of the notable things about gravity -- which is also true of all of Einstein's theories -- is that it's completely deterministic.

What does that word mean, deterministic, to a physicist?

It means that, if I tell you all the initial information about a system -- like the positions, momenta, etc., of all its particles -- you can tell me, without any doubt or uncertainty, everything I could possibly want to know about its final state at some later time.

And when quantum mechanics was first discovered, there were a series of hotly contested public debates on the topic. Between two titans of physics: Albert Einstein and Neils Bohr.

Photo by Paul Ehrenfest, in December of 1925. If you are having a geekgasm right now, you may secretly be a physicist.

It was in these debates that Einstein declared his real greatest blunder:

"God does not play dice with the Universe."

This was, of course, in reference to the fact that quantum mechanics is not a deterministic theory. Rather, if I give you all of that initial information -- positions, momenta, quantum states, etc. -- all you can give me, by the laws of quantum mechanics, are probabilities of what the final state will be. One of the greatest demonstrations of this is the double slit experiment.

If you take a single particle, like an electron, and shoot it at a double slit (two parallel slits spaced slightly apart from one another), a deterministic picture tells you that the electron will go through either the slit on the left or the slit on the right. But if you allow the electron to be an indeterminate object, it can, perhaps, pass partially through both slits, and interfere with itself!

Sounds like something out of science fiction, doesn't it? Well, that's why we do the experiments, isn't it? And what happens if you actually send electrons through a double slit, one-at-a-time?

You have no idea where any one particular electron is going to end up! You can compute the probabilities that it will wind up at any location, but that's hardly the deterministic result you were after. So you do what any self-respecting experimentalist would do. You say to yourself, "Alright, I'm going to look."

And you design an experiment the same exact way, except this time you measure which of the two slits the electron goes through. Perhaps you shine a photon across both slits, and when one gets absorbed, that tells you which slit the electron goes through. And when you do that, what do you get?

You get no interference pattern. By measuring which slit the particle goes through, you change the outcome!

As bizarre as it seems, this is something that is predicted and well-understood about quantum mechanics. In principle, there are three possible explanations for why this happens:

  1. Properties of these quantum particles are not real, as we understand "real" numbers. (See, for example, the "i" in the Schrodinger equation.)
  2. All properties of quantum particles are real, but there is non-local phenomena, sometimes colloquially called faster-than-light transmission of information.
  3. Or, perhaps everything is real and nothing gets transmitted faster than light. Called local realism, there must be some sort of "hidden variable" that -- although we do not observe it -- determines what the final states are.

Perhaps maddeningly, all of these are possible in principle. They are just different interpretations of quantum mechanics. (For example, my favorite is the Copenhagen Interpretation, which falls in the first category, although one can argue about its locality.) Others favor the second type, like the de Broglie-Bohm Interpretation, which is just as valid, but no different in its predictions from the Copenhagen Interpretation for any experiment we've devised. Currently, there are no ways to distinguish between most of the interpretations of types one and two.

But what about the third type, the types where everything is predetermined from the outset?, as was favored by Einstein, determined by some unobservable but local (with nothing being transmitted faster than light) and real variables?

Amazingly, there are some very clever tests of this that have been devised, and the experiments performed. The resultant theorem, known as Bell's Theorem, demonstrates very definitively that the "Hidden Variables" approach fails when confronted with experiment.

So what do we learn from all this?

Sorry, Einstein, your steadfast belief that "God does not play dice" has been demonstrated to be wrong, no matter how much people try to resurrect it. Not only that, but you have to accept that these "dice" obey rules that may make you very uncomfortable, and there's no way around it. Whether you give up realism or give up locality (or both), you simply can't have it all in this Universe.

I first addressed this topic years ago on the old blog, and was pointed to this paper in the comments. I sort of flippantly replied something to the effect of, "Well, you can devise math to do whatever you want, but the math needs to make physical predictions. And in this case, the predictions do not agree with the experiments, and therefore this math doesn't describe our reality." I was so sure of myself because, well, I had read this excellent book on Quantum Mechanics, which I now believe is the most underrated and underused graduate text on the subject. If only that were the end of it. After all, "local realism" means that the following three things must be true (taken from this site):

  • First, the assumption that real things exist regardless of whether or not we observe them.
  • Second, the assumption that we can legitimately reach general conclusions from consistent observations and experiments.
  • Third, the assumption that no form of matter or energy can propagate faster than the speed of light.

Three years later, I got an email from Sascha of alpha-meme, who asked me to weigh in on an exchange he had with the author of that same paper, who has written more papers reaching the same erroneous conclusions. Let it be known that Sascha is correct, and all known quantum mechanical interpretations that demand both locality and realism, as far as we know today, conflict with experiments that are sensitive to such predictions. If you want to agree with the experiments of quantum physics, at least one of the above three statements must be false. Since we really, really place importance on the second one -- that, to put it bluntly, seein' is believin' -- it means that the Universe really does play dice in some form or other.

As much as we all admire Einstein, don't keep making his greatest blunder. I'll leave the last word to Bohr, who allegedly said,

"Don't tell God what to do with his dice."

Update 07/02/2011: To clarify, it isn't simply that there's randomness; that at some level, "God plays dice." Even local, real interpretations of quantum mechanics with hidden variables can do that. It's that we know something about the type of dice that the Universe plays. And the dice cannot be both local and real; people claiming otherwise have experimental data to answer to.


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Thank you very much indeed for your support on this, Ethan. I wonder though why you brought it down to the issue of whether there are dice involved (rather than the issue of clearly fraudulent pseudo-science that we privately discussed for example). There are non-deterministic classical theories. Dice, as well as many worlds, do not imply quantum physics (not without interference between parallel worlds for instance), and so it is kind of beside the non-locality versus anti-realism debate.

Good rundown of the tradition up until recently, however: you didn't note the idea that decoherence somehow can explain the collapse in itself (sometimes combined with the many-worlds idea) is more and more popular. Since they claim "continued Shrodinger evolution", in that sense it's deterministic (but of course must account for our world "appearing" (don't you hate that word) to be random. I think it's a crock, no time to explain here except to briefly note its mostly based on a circular argument and violates conservation laws in principle despite tricks about non-interaction. (Uh, what about the fields from developments of the alternative world splits, aren't they filling up the supposed common space hosting all those branches?) Of course, getting correct probabilities without BS is a bear. That's why I too like Copenhagen, challengingly mysterious it may be. (And indeed we cannot have the local realism. Of course in MWI, they just match up sets of possible outcomes and say, so what, AFAICT.) See my description of an experiment to test their basic point, as well as some logical rebuttal, at name link.

PS: that climate change thread, what a swamp ... the denialist trolls were simply incredible.

By Neil Bates (not verified) on 01 Jul 2011 #permalink

I'm shocked! I would have been sure that an astronomer of all people would know that "Einstein's greatest blunder" was his addition of a cosmological constant term in his equations to allow for a static solution.

Of course, the irony is that there may be a nonzero cosmological constant after all, and on analytic grounds it should at least be allowed. But still, that's how he described it himself.

"[T]he speed of light guy"? Shouldn't that be Rømer, Fizeau, Foucault, or someone like that? Though Einstein's connected with it, and in the common public perception might be such, I wouldn't call him that.

"One of the notable things about gravity -- which is also true of all of Einstein's theories -- is that it's completely deterministic."
Even the Brownian motion & photoelectric effect? I'm not a professional or anything, but I wouldn't have thought those were deterministic. Perhaps they're just determinism-agnostic?

By Randy Owens (not verified) on 01 Jul 2011 #permalink

@Neil Bates: "See my description of an experiment to test their basic point, as well as some logical rebuttal, at name link."

Uhh, what name link? Indulge us, please!

By Randy Owens (not verified) on 01 Jul 2011 #permalink

Oddly, the wave/particle duality of light was what first got Einstein publishing in 1905, on the photoelectric effect, building on Planck's idea of quanta. But when experiment and theory pushed it beyond his taste, he recoiled from its implications.

If you've ever sat in a little boat in a heavy swell and watched waves, they're kind of odd things. They're there. They make the boat go up and down, they can make you seasick if you watch them too much (like when you're not getting a bite), but they're also kind of not really there. They just kind of pass through the water and leave it right where it was. That's the best analogy I can offer.

By Douglas Watts (not verified) on 01 Jul 2011 #permalink

First, what's this "god" thing? That outdated game of telephone based on a fiction?

Second, geekgasm: Squee! = OMFG2

"that demand both locality and realism"

I'm not sure I understand "locality".

Can someone give me a link please? Or maybe Ethan might write a a post on it.

Is it possible to set up this experiment with entangled photons.
Send 1 to the slits and the other of in the opposite direction. Then have some form of detector for the second that is triggered after the first has passed the slits.
This is possible from what I know (as layman that is).
The question is can the detectors be setup in such a way that by measuring where the second photon is you can determine which slit the first photon had to pass?

By Who Cares (not verified) on 01 Jul 2011 #permalink

Even the Brownian motion & photoelectric effect? I'm not a professional or anything, but I wouldn't have thought those were deterministic.

Outside of quantum physics, they are both completely deterministic, because all particles (photons included) are treated as billiard balls. Sure, they soon become too complicated to calculate (deterministic chaos), but they're still completely deterministic. In classical physics, there is no such thing as random at all... and things like radioactive decay simply cannot be explained.

The question is can the detectors be setup in such a way that by measuring where the second photon is you can determine which slit the first photon had to pass?

Of course. Has been done, gives the same result as with electrons: the wave behavior disappears.

By David MarjanoviÄ (not verified) on 01 Jul 2011 #permalink

Please be faster-than-light, please be faster-than-light, please! please! please!! ;)

David thank you for the answer.

By Who Cares (not verified) on 02 Jul 2011 #permalink

I do not grok, yet. One reason is when reading this: "After all, "local realism" means that the following three things must be true (taken from this site): First, the assumption that real things exist regardless of whether or not we observe them...." I keep getting Berkeley's tree stuck in my brain!

I'll keep reading!

By Tom of Sweetwa… (not verified) on 02 Jul 2011 #permalink

Imagine how backward they were in those days when they thought scientific disputes could be debated in public. Almost as niave as the ancient Greeks who thought democracy could be achieved through public debates on the subject.

Nowadays we understand that science is all about a bunch of government paid officials and journalists declaring that there is a "scientific consensus" and any "debate is over" before it starts. Woe betide anybody who tries to dispute a "consensus" - they will be demounced as "fuckwits" and censored, at least on "scienceblogs".

Politics works the same way. The media decide what issues may be mentioned, ensure that no actual debate is ever shown to the people ("Presidential debates" are nothing of the sort), that nothing more complicated than a soundbite is ever aired and explains that anybody who disagrees with what they have decreed is an extremist and thus not to be allowed to spesk (though they may be denounced).

By Neil Craig (not verified) on 02 Jul 2011 #permalink

Randy, others: I could have sworn I filled the "URL" tab but must not have. To be sure, here it is too:

Neil Craig: most of the professors in private schools agree with the various consensuses offered by "government scientists" (put in quotes if you meant to include anyone paid even indirectly by a government, like public colleges, U of [State] etc. - uh, BTW a guy at my alma mater UVA is a notable climate skeptic, how did he get away with that?) If you have some terrific survey showing any big rift other than those specifically derived from literal religious constraints - between the two camps - the only thing to make your gripe credible - you better lay it on.

I note that the issue of AGW was indeed debated in this very blog, and I just replied to your bitter yet uncensored latest rant there. You seem to be censoring yourself, apparently embarrassed to link to your own blog where readers could see your wonderful arguments (my apologies if you just forgot like me.) My apologies also to the crew here if this just encourages NC to rant on - but I will congratulate him if he provides even one mature and rational sounding comment.

Omniscience is presumed perhaps even for Einstein's God. As such his statement that "God does not play dice" could more correctly be stated as "God cannot play dice" since God would already know the results of any toss well beforehand even though we as yet are limited to using statistics. Such is the problem with interjecting any assumed absolutes of God into the ever-evolving assumptions which must be relied upon by practical scientists. Cosmological constant? That might seem to be an absolute... Uhh, let's just use whatever number seems to work at our end of the stick and see what happens... OK now let's change it and see something else.

By Lloyd Hargrove (not verified) on 02 Jul 2011 #permalink

By pondering upon the difficult UFT problem for more than seven thousand hours, an elite genius at mathematics and extremely creative, I created a very interesting Unified Field Theory of Physics that I believe is much more appropriate than conjectures by Albert Einstein, Stephen Hawking or anybody else. I call it 'Beyond Albert Einstein's Relativity: UFT Physics'. Go to or the copy in the National Library of Australia.
(Note that I am 57 and suffering progressive brain damage. Therefore, although still a genius for my age-group, I do not want to delve deeply into equations anymore. Further, it is possible that your computer is not reading my formulae correctly.) Peter D Rodgers, Australia

Ethan, you use the word "real", and, may be, this is where the problem starts. The "things" physicists talk about are artefacts produced by the cultural process of the science of physics. They should not be confounded with any proposed "things" outside in the, well, "real" world, containing stones, plants, stars, light, etc., the world which is there outside of our mind. Making statements like "properties of quantum particles are (not) real" may be problematic in a way you haven't taken account of.

And: "as we understand 'real' numbers" -- well, numbers are artefacts too. They and (many) other parts of mathematics are useful, because they have been constructed in a cultural process just to be useful for us. Because of this we can successfully use them in physics. But just trying to define "real, as we understand real numbers", does not help here.

Let me tell you about another blunder, starting with the notorious words (bah) "Einstein once said", that mathematics has nothing to do with reality, and that we don't know why mathematics work (there are mathematicians still believing this; by the way, I'm a mathematician too). As I said, mathematics (more correctly: many parts of it) has just been constructed in a way that it works for us in our life, and mathematics very well has to do something with reality. Einstein as a physicist -- and as a non-mathematician -- should have been able to realize this. But, well, Einstein is fallible, and it's human, and it's okay. But it's a blunder.

By Duncan Ivry (not verified) on 02 Jul 2011 #permalink

My impression was that there are still loopholes in the experiments that have been run. Is this not the case?

In classical physics, there is no such thing as random at all... and things like radioactive decay simply cannot be explained. -- David M.


It helps to understand this if you have a chunk of uraninite on your porch. I have some from a nearby old feldspar quarry in Topsham, Maine.. With a Geiger counter, this stuff clicks like crazy, but each 'click' is, approximately, just a few hundred in a few trillion uranium atoms going into alpha or beta decay. The rest are not, or the porch would melt. But what if I took a razor and kept breaking that uraninite crystal into smaller parts? And what if my razor was so sharp I could isolate just one U-238 crystal? When would this one U-238 atom decay? We don't know. There's no way to predict. With a 4 billion year half life, perhaps quite a long time, but also maybe in a couple seconds.

By Douglas Watts (not verified) on 02 Jul 2011 #permalink

The argument does not really show that Einstein was wrong about the dice. It shows that he was wrong about local hidden variables.

If the electron is a wave, and not a particle, would you then say that the electron is not "real"?

I've been under the impression that the wave - particle duality is really a misnomer. I was convinced (I'm not sure when) that an electron is niether one. The author convinced me that it was merely what we saw when we measured - tested to find a particle or find a wave. The electron itself was something else and we needed to find some other construct to measure.

As you might be able to tell, my confusion about this is quite high. Is there something else we could attempt to determine other than particle or wave? I've heard it's unlikely we'll ever be able to determine anything about strings experimentally.

By Dave the curious (not verified) on 03 Jul 2011 #permalink

That's right, quantum mechanics teaches that electrons are not really waves or particles. The double-slit is confusing if you refuse to accept that, and insist that an electron is a particle.

Neil Bates AFAICT tries to understand the phenomenon of decoherence by starting from what we observe, rather than starting from the math and assuming that it represents reality. I think this has confused him.

Ethan, could you help clear this up? On the mathematical level that every non-kook agrees on, could you tell us the problem (if any) with the "sensitive thingy" explanation of decoherence that starts from amplitudes?(Everyone else: the author spells out roughly what this means for the math here. Neil B: as near as I could tell, your attempt at refutation said that we could further split one of the "blobs" at the end and use it to produce a situation like the one we started with in terms of the detectable patterns they make. This would not mean that we've recombined the original blobs, just that we can't tell the difference by looking at the end result.)

I assume that if the linked explanation holds, we can probably interpret these "configurations" in a local way. At least, I get the impression we can define "sensitive thingy" as anything that reacts to a particle's amplitude in a way which changes the state of space at that amplitude's destination.

About local realism: one way to consider, is forget particle nature for awhile and just imagine wave trains of polarized light. If you know about polarization, you know it's possible to represent any polarized wave, even for any ordinary unentangled photon, in terms of a specific individual superposition like a|xâ© + bÏ|yâ©. This shows amplitudes for horizontal and vertical polarization and the phase angle between them. With any in-phase combination (Ï = 0) you have linear polarized light at some angle. If for example you have a = b and 90 degrees out of phase, you get circular, and other combinations make elliptical polarization etc. Well, it's "a wave" but still "locally real" because I can represent that photon in a specified, unique, unambiguous way (in principle, even if I don't know.)

However, entangled photons aren't like that. If one of them reads linear at 20 degrees, then the other one must also etc. for any setting. Bell's work and the experiments show that there is no way to represent each of the EPs separately in the manner I wrote. Their status is simply not a matter of separate properties.

(PS, other Neil, did you have to say "deliberate false implication"? - couldn't I have really thought what I said? What the hell is your problem? Doesn't it make you look like a f**kwit, after all? BTW no congratulations yet.)

Fight! Fight! Fight!

*coughs* Anyway, I had a question held for moderation about a feature of the math which might explain Bell in terms of local reality.

â[Ballentine's book] I now believe is the most underrated and underused graduate text on the subject.â

Second that. A wonderful âmodel of clarityâ of a QM book with all the hand-wavy bullshit and misconceptions removed. I think it's wise to supplement it with a good 'foundations' book though (e.g. Isham's).

No Mr Bates. Your suggestion that i was lying about being censored wouyld have had to be based on some slight ttrace of evidence for it not to be deliberately false. If your automatic reaction to anything is to proclaim that a person is lying thenI doubt you could function in any society.

Perhaps you might like to apologise for displaying the contempt for honesty common among "scienceblog" cammenters. You certainly would if you aspire to honesty. Being honest on my part I think it unlikely you will but will not assert, as a matter of fact, that you won't.

Neil Craig, why don't you realize that you act like the standard, reprehensible troll? You come in there with an bitter rant that isn't to the point of the topic of quantum mechanics, and then complain about people's understandably edgy and critical rebuttals. Also I just offered the example that you were allowed to post here to show you weren't banned over all of scienceblogs. I can't know about other blogs and esp. knowing who was banned any specific place (AFAIK only PZM lists his bannedees.)

What do most people do, who really want and deserve apologies, corrections, etc? They calmly complain, without flaming, that they deserve better. I'd be happy to give you credit thereby, and already tried at the other thread - remember? Now, you think I should apologize to you - again - after all that abuse and provocation from you? No. You don't deserve it on principle.

BTW if mods want to cut out the entire back and forth between us two Neils, go ahead, pls, just don't let it affect my on-topic stuff. tx

Hf, thanks for the link and looking over my piece (I have a shorter version for anyone interested.) Check my own blog too. Briefly for now: First it would be odd to disdain observations as the key ground, when after all the theory is something we put together to try and explain them. To assume the math from that represents reality is treacherous, esp. in QM.

As for the issue in your link: that is the finding that an object that could have absorbed the light influences results even if not interacted with (ironically disproving the QM urban legend that "you can't observe something without disturbing it"! That basically means, the wave function is re-allocated by the presence of the blockage. There is no logically clean way to represent that. It is IMHO even worse than "collapse" because the extended WF must suddenly (?) change shape when it encounters the barrier. None of that is classic "decoherence" nor explains why the photon ends up being reallocated instead of absorbed by the barrier.

My complaint about DI and MWI are based on specific flaws and unexpectedly finding an experimental way to test the strong DI claim that decoherence in any way makes mixtures out of superpositions. I am rather sure I am not confused but criticizing on understood demerits. I say, proponents are confused. Like I said, they make a circular argument involving comparison of statistics without realizing that getting any statistics at all, not the type, is the issue. The "blobs" in such discussions represent alternative distributions of a WF. There is no explanation of why one of them becomes absent from our universe, esp. in the case of simple split by BS when there is no direct issue of interference anyway.

As for my specific experiment: if DI was right then mixture output from BS2 (readers, please check it out at , I name-urled my own blog) would preclude being able to later get back the asymmetry information about BS1. Maybe you got confused, writing "... we could further split one of the "blobs" at the end and use it to produce a situation like the one we started with in terms of the detectable patterns they make. This would not mean that we've recombined the original blobs, just that we can't tell the difference by looking at the end result.)" Yes it does mean we recombined the OBs (heh), that's the only way we *can* tell the difference - which we should be able to do, against DI expectations - at the other end.

REM also that MWI violates conservation laws, despite sophistry dodges. A given WF represents a *given amount of mass-energy." It should be applied to the same normalization that gives a sum probability density of "one" - use that to also work back to mass-energy *density* in space. That should stay consistent in definition throughout, but will not in MWI. A theorist cheats the moment he imagines - whatever the excuse - that the concentration entailed by a detection entails (like, the whole energy of the photon is "captured" by one of various possible absorbing atoms ...) redefining the mass energy so anyone can consider "all of it" to be in place A yet still another observer "in another world" can consider that original quantity to be also in place B, etc.

Then consider the composition of E and g fields etc that should be summed projection from mass-energy distributions of WFs according to basic rules. That precludes separation of worlds for any excuse. That has nothing to do with "interference" which is a red herring - just a way to have proven to model originally but not the basis of all possible interaction.

Radioactive decay, esp. for stuff like thorium, is like the lottery. The chances of your ticket winning is infinitesimal, but every week, someone does win.

By Douglas Watts (not verified) on 04 Jul 2011 #permalink

"One of the notable things about gravity -- which is also true of all of Einstein's theories -- is that it's completely deterministic." - The grvitational N-body problem has no analytical solution, it is chaotic (for N > 2).

Yes, yes that should be called Einstein's greatest blunder. But I find the links to Sascha and his debate with whomever confusing and gratuitous.

Thanks for the Ballentine's Quantum Mechanic's reference. I'll check it out.

I don't understand this talk of experiments in which photons move about like particles. It's not the wave/particle bit as that is clear from the results. It's things like: what's the momentum of the photon? What's the uncertainty in momentum? Uncertainty of position? Surely if you accept Heisenberg, there can be no locality.

Alan, in most discussions "deterministic" means as a matte of principle, that the bodies move exactly as required by g = Gm/r^2 regardless of whether we can compute that or not. It does raise interesting questions of whether our universe is "computable" or could ever be a "simulation" or mathematical process, etc., see for example Penrose. One way to look at it: the equation above allows only one unique outcome in principle, even if we can't find out what it is. (IOW, once started, it can't turn out differently, different times it's done - unlike QM as we really experience it.)

the wave particle duality problem is easy to solve. if i had a web site i would link you to it and you could go and marvel at my explanation. plus my choice of fonts and flourescent blinky text would mesmerize you.

Ethan: i will go and check out the QM book you recommended. when i took QM the emphasis was on the Copenhagen interpretation.

Let me suggest rather that this was "Einstein's most important blunder".

To quote Alain Aspect, "in 1935.. the article by Einstein, Podolsky, and Rosen (EPR), whose title raised the question, "Can Quantum-Mechanical description of physical reality be considered complete?"... concluded that quantum mechanics was incomplete... Neils Bohr was apparently bowled over by this argument, which rests on quantum mechanics itself... His writing show his profound conviction that if EPR reasoning were correct... it would be all of quantum mechanics that would collapse. He immediately contested the EPR reasoning... In contrast to Bohr, Schrodinget reacted positively to the EPR paper, and coined the term 'entanglement'... in 1935, quantum mechanics was being crowned with one success after another, so apart from Bohr and Schrodinger, most physicists ignored this debate... We had to wait thirty years to see a resounding counter-argument... In 1964, a now famous short article changed the situation dramatically. In this paper, John Bell takes the EPR argument seriously... (his) result, known as Bell's theorem, continues to surprise today."

Quote from Alain Aspect's Introduction to the 2004 (revised 2nd edition) of J.S.Bell's book Speakable and Unspeakable in Quantum Mechanics.

Einstein's most important blunder was not a trivial blunder. Neils Bohr argued immediately against Einstein's interpretation; but for a decisive argument physicists waited and contemplated for 30 years! Yes, it took 30 years to understand the new quantum mechanical reasoning necessary to correctly interpret Einstein's EPR problem.

Alain Aspect further says, "The most remarkable feature of Bell's work was undoutably the possibility it offered to determine experimentally whether or not Einstein's ideas could be kept. The experimental tests of Bell inequalities gave an unambiguous answer: entanglement cannot be understood as usual correlations, whose interpretation relies on the existence of common properties, originating in a common preparation, and remaining attached to each individual object after separation, as components of their physical reality... Starting in 1970s, another concept has progressively become more and more importatn in quantum physics: the description of single objects, in contrast to the statistical use of quantum mechanics to describe only properties of large ensembles... As a witness of that period I would like to argue that John Bell also played, indirectly, an important role in the emergence of the new theoretical approaches clarifying the quantum description of individual objects... It is my claim that Bell's example helped physicists to free themselves from the belief that the conceptual understanding that had been achieved by the 1940s was the end of the story."

My point regarding Einstein's most important blunder is:
1) It was not a trivial blunder; rather it was deep and profound.
2) Einstein's critical EPR idea focused Bohr and then John Bell upon a conceptual cornerstone idea of quantum mechanics (entanglement) whose importance was not recognized until Einstein.
3) Einstein's clear critical mind focused upon a foundation problem in quantum physics that took 30 years before anyone (i.e. only John Bell) clearly understood the problem which Einstein had posed.

To further quote Alain Aspect, "I think it is not an exaggeration to say that the realization of the importance of entanglement and the clarification of the quantum description of single objects have been at the root of a second quantum revolution, and John Bell was its prophet. And it may well be that this once purely intellectual pursuit will also lead to a new technological revolution."

By the way, Alain Aspect did the experiments suggested by John Bell's understanding of the problem that neither Einstein nor Bohr could decisively interpret.

The debates between Einstein and Bohr were of the most scientifically productive in the history of science. The winner of these debates was quantum mechanics. Einstein's ideas even when incorrect were powerfully focused upon cornerstone ideas which have led to new physics insight. We should not trivialize his mistaken idea by calling it his greatest blunder; we should honor it by calling it "Einstein's most important blunder".

"The grvitational N-body problem has no analytical solution, it is chaotic (for N > 2)" Indeed, and it is deterministic as well.

By Trulu Anomalous (not verified) on 06 Jul 2011 #permalink

Mr Bates if that is an apology for saying that you "really thought" I was lying about being censored I accept it.

I do not think my initial post here #15 can correctly be construed as a "rant". Gentle irony is the worst as anybody reading it will see.

"there must be some sort of "hidden variable" that -- although we do not observe it -- determines what the final states are."

A possibility, mind, is that your second system has a difference: it can discern which slit the particle came through.

That means that it must be able to separate the energies of either location into discrete elements.

E.g. it uncovers a degeneracy in the two-slit experiment.

There would then be no hidden variable, just an effect that we don't yet include.

"In classical physics, there is no such thing as random at all... and things like radioactive decay simply cannot be explained."

Sorry, that's complete codswallop.

Two infinitesimal balls hitting each other (required for thermodynamics of an ideal gas) will recoil in any direction. The determinism that leads to the laws of thermodynamics and definitions of things like temperature and entropy are results of the determination of means which becomes entirely deterministic in the limit of infinite numbers of occasions.

An absolutely fair coin will roll an average of 3.5, asymptotically. That value is calculated from randomness yet is entirely deterministic.

Likewise the random walk (distance traveled varies with the square root of time) is random yet deterministic.

Randy is right with the Brownian motion but not with thermoelectric effect.

Childish Neil Craig, your post at 15 *IS* a rant:

"Nowadays we understand that science is all about a bunch of government paid officials and journalists declaring that there is a "scientific consensus" and any "debate is over" before it starts."

Is most definitely a rant (see for the history of the hundred and fifty years of discussion before consensus was reached on the facts, a debate is over when it's finished, but you refuse to realise that the debate has happened).

And a conspiracy nutcase rant too.

tx Trulu for reinforcing my point about gravity.

Wow, we can't realistically use "infinitesimal points" in classical physics becasue there is indeed 1. no way to model just what happens when they collide, given no clear "angle of attack" and 2. no finite chance of them hitting each other: of course, you could just arrange for them to. But any "mathematical model" is deterministic because math produces unique (even if uncomputable) results from itself, it is logically perfect in that sense even with set theory paradoxes. Supposed "randomness" is really pseudorandom, just an expression of ignorance of all the relevant data. Laplace was right about the consequences of such a universe, wrong that our universe was like that. (See my article at name link.)

However - ! - even that is not so simple since collisions do require some "modeling" of the substance of the colliding bodies. But if "math" does it, then any randomness (non unique inevitability) would have been "put in by hand" by a psuedorandom generator.

Brendan: sure, the Schroedinger Equation is deterministic as usually given (assuming we have a right to regard something we infer by many measurements to be "real" and despite it not expressing definite values e.g. of polarization while "in flight" during entanglement), but we don't get to see that: something "happens" to force an outcome. If you think that MWI scam can work, please read my essay at name link and also consider that MWI does not, as claimed, represent simple continued SE with no extra assumptions. For one thing, the definition of total mass-energy of the system has to change context when more than one observer/"world" is allowed to claim localization of the entire original amount but at separated positions. A piece I'm writing about that and decoherence may be in upcoming "The Quantum Times", keep an eye out.

"Wow, we can't realistically use "infinitesimal points" in classical physics"

No, we HAVE to use infinitesimal points. The theory of an ideal gas REQUIRES it (the gas itself occupies no volume within the container) and that modification of the ideal gas law is required when high pressures mean that three-body collisions occur enough to make a difference.

Unless you want to tell me thermodynamics isn't part of classical dynamics.

PS collisions don't have to be inter-gas. they can be gas/wall/gas collusion, with the gas never colliding with another gas molecule and you still get the same result.

And the inter-gas collision was never *actually* modelled, just asserted.

The "gas doesn't occupy any space" is EXPLICIT however, in Dalton's Law of Partial Pressures. Again, classical.

NOTE: if the gas were not counted infinitesimally small, then the ideal gas wouldn't have an isotropic recoil: remember the demonstration by Rutherford showing a small dense nucleus was the heart of an atom which was otherwise mostly empty space?

Higher energy particles didn't recoil with the same pattern as lower energy ones.

God doesn't play dice with gravitons. There, a triple play.

Wow: OK, in a certain idealization for making simple *math* but no classical physicist thought that atoms *really were* infinitesimal points! Anyway, the nature of "math" as a representation is the key issue. BTW I have an answer for you anyway: by symmetry, "point" collisions would just be whatever preservers conservation laws in the IRF of a give particle P1. So I can just be there, see another "point" P2 coming along a line that either connects with P1 or does not (in latter case no collision anyway, and if field effect that follows whatever the field law says.) If connects with P1 then P1 and P2 go off according to whatever conserves momentum and energy.

However you bring up some interesting challenges overall, so I wonder why people keep saying how deterministic classical physics was?

"in a certain idealization for making simple *math* but no classical physicist thought that atoms *really were* infinitesimal points!"

But nobody thinks that the spin of an electron is actually rotation around an axis.

And, as far as is possible to detect, electrons are infinitesimal.

Since the laws are written as mathematical rules, your point is false: the maths is the physics is the maths and the maths uses infinitesimials and infinities all the time. To say that classical physics doesn't have infinitesimals is false.

Your illustration with momentum/energy conservation is correct, but misses the point I believe. These are conserved if the collision is always head-on. That isn't isotropic. The isotropy is a result of infinitesimals: the collision can be infinitesimally off-axis, still hit, but be a glancing blow. Whilst an infinitesimally off-axis hit will be more solid and cause a greater deflection. However, the difference between two infinitesmials is infinitesimally small. Therefore they are all equally valid. Therefore the deflection paths are isotropic.

And, since being completely isotropic means you can say the AVERAGE difference is deterministically 90 degrees from the direction of the incoming particle, you get the random walk, square-root-of-n determinism of classical physics.

It's when you take reality with a sphere of finite size that you can no longer be deterministic until you delineate the interaction probabilities and permissible paths to work out what, other than a 90 degree deflection, your actual collision will on average take.

The randomness of classical mechanics is more hidden than nonexistent. With quantum mechanics, the random is front-and-center.

But note that you can get the deterministic F=ma from Schrodinger's equation IF you take the quantities as averages.

And that makes QM's version of F=ma just as deterministic as classical.

That's because the 1970's global cooling scare didn't happen in science. It happened in the media.

But you want fear and loathing of anything that may get in the way of rapacious greed.

"Here's one I made earlier"

Notice another lie from our resident pathalogical parasite.…

Has exactly the same text. Yet the "about" gives a contact detail:

Whereas "A place to stand" has this to say about the owner:

"Comments from Scotland on politics, technology & all related matters (ie everything)"

So why does a scot have an australian email address?

Or is he a thief too?

Wow, you can't have a "glancing blow" with infinitesimals unless you "cheat" (term in philos. discourse not meaning deceit) by using nonstandard analysis or other jiggery: literal "points" either hit head-on (intersecting paths) or not at all. And it doesn't matter what their relative angles are to some given observer, that can of course be transformed away. Only real "balls" can have vectors (dyadics?) of mutual normal contact at various angles relative to the approach. That is all aside from whatever the heck our universe is "really like."

And, that depends on *arbitrary* given of parameters. Maybe you confuse "arbitrary" or "unknown" with literal non-deterministic *inevitability* from *specified* earlier conditions. You seem not to understand that latter concept or realize that I am presenting the orthodox distinction (aside from whether it's true, spirit points to you for going against that but no cigar unless you turn out to be right too.)

As for QM, sure the Schrödinger evolution is deterministic because it is a "field" that does what math says it does. The "collapse" is literally non-deterministic because nothing "in" the Eq. tells us which way the measurement will turn out. Any making that happen cannot be controlled by a genuine math process as I argued at that FQXi link. (Actual outcomes, not to be confused with the generalized abstraction of their unpredictable existence as in thermodynamics etc.) must be "put in by hand" as I'm sure you at least understand that notion.

As for whether MWI can offer a way out of "real randomness" by saying the WF continues to evolve: again, it cheats: The alleged mechanism of separation, decoherence, is just a complication of the WF and can't isolate the mass energy of the original particle in more than one place. Actual "continued SE evolution" would simply redistribute the same original mass-energy.

No, you just assume that they happen. Just like we assume electrons have a position.

"Maybe you confuse "arbitrary" or "unknown" with literal non-deterministic *inevitability* from *specified* earlier conditions. You seem not to understand that latter concept"

Maybe because

a) you've only just brought that up

b) you haven't explained what you mean

"The "collapse" is literally non-deterministic because nothing "in" the Eq. tells us which way the measurement will turn out."

I'm not talking about the collapse of the dead cat/live cat situation.

I'm talking about the deterministic classical equation F=ma turns out from the QM Schroedinger's equation. No collapse. No cat. No many-worlds or decoherence. F=ma falls out from the field theory of QM if you extract the expectation values from the QM equations.

And F=ma is deterministic.

In Classical Mechanics, this is just stated. In QM it's a result of taking the expectation value.

No decoherence.

Wow, you said somewhere
"...square-root-of-n determinism of classical physics."
Could you please give me a hint, what that is? Thnx in adv.

Anybody British may, if they choose, explain the derivation of "one I made earlier" to Wow.

By Neil Craiog (not verified) on 10 Jul 2011 #permalink

The one you made earlier was one someone else made earlier, you thief.

Mr. Craig, this is an interesting thread, minus the fork you introduced--which might be interesting in a thread in which it is relevant. All of your posts have been off-topic. #15 was a thinly disguised segue to a different subject. That is trolling. Please be courteous and post on-topic here; if you have nothing to add that is relevant to the comments to the post in question, post on another thread. It is rude to decrease the signal-to-noise ratio.

By Christopher Booth (not verified) on 11 Jul 2011 #permalink

Dang, my notion of determinism had grown fuzzy over the years; I was thinking it was an aggregate effect. I'll need to refine my thoughts on the 'no free will' debate.

By MadScientist (not verified) on 13 Jul 2011 #permalink

I'm also sad we don't seem to have grand debates like Bohr / Einstein anymore. It seems like so many of the current so-called debates have scientists on one side,and trolls on the other. Biologists vs creationists, epidemiologists vs anti-vaxers, climate scientists vs CO2 emitting windbags.

Are you being supressed? Prove it. Show me publication-ready papers, the journals they were submitted to, and the rejection letters. Don't send me blog posts. Show me that you are taking part in the debate. If you aren't submitting papers to journals, then you're just some random guy on the Internet. If you haven't had a paper irrationally rejected by a journal, then by definition the scientific community has not rejected you any more than that cute guy at the gym you're too nervous to ask out has rejected you.

By Gopiballava (not verified) on 16 Jul 2011 #permalink

No, my greatest blunder was thinking that those 3D glasses (the old ones, with the red and blue lenses)that make two dimensions look like three would, if I wore them all the time, make three dimensions look like four and thus help me with my unified field theory. All they did was make it impossible to match my socks, resulting in much mockery.
And now I'm dead. What a pisser.

"Properties of these quantum particles are not real, as we understand "real" numbers."

I'm not sure where you get this limited view of the realism problem. There's no reason you couldn't say a complex number is the value a property really has, even if it sounds awkward.

And it isn't just about randomness ("dice") either. Merely inserting an uncaused randomness doesn't help.

The problem is that the basic premise of physics itself is being called into question. Physics assumes that there is an external reality independent of our perception of it. Some people debate this, but if you perform a scientific physical experiment you are automatically cancelling the debate and assuming reality exists on faith. Because if you had any doubt about the reality of what you were testing, you wouldn't be compelled to report honestly about the weird results upon which modern physics is based.

This means that scientific physics starts by assuming that there is a true nature of the system being studied. You may conclude it's not what you thought. You may conclude you don't know what it is. But you cannot conclude with words you claim it embodies, because that would break your commitment to collecting scientific data.

If experiments in quantum mechanics are described solely in terms of the laws verified by science, then the description always includes a narrative twist, leading to the above contradiction. The only way out of this is to allow laws that we cannot yet verify, with the restriction that they must be "necessary and proper" to ensure that we are theorizing about what happened in the actual experiment, rather than just a narrative of it.

Such speculative laws must agree with everything verified about quantum mechanics, and also with the classical limits, which is a tall order always open to improvement. Quantum mechanics thus brought as near as we can to completion is not strictly scientific, but strongly constrained by science. Conversely, quantum mechanics based on pure science cannot admit its lack of completeness.

If this speculation is honestly constructed to fulfill the original purpose -- honoring the commitment to reality that justifies the science it's based on, it's incapable of producing any of the nonsense for which quantum philosophy is notorious. Whereas without it, the nonsense seems natural.

Note that MWI fails this commitment, because quantum experiments measure probabilities of random events, and MWI denies that anything random happened.

So how can Neil Bates denounce the denialism inherent in MWI, and yet agree with those who deny global warming?

By https://me.yah… (not verified) on 16 Oct 2011 #permalink

Meh. Bell's Theorem is the most overrated bit of QM there is. It proves exactly zip about local theories, because it still assumes you add probability amplitudes, and not probabilities. Hence you get interference -- what a surprise!

You have proved nothing about genuine local hidden variables, because ipso facto if these existed it would NOT be correct to compute probabilities by summing probability amplitudes and then finding the modulus.

This is just Quantum Religion, a cut about Deepak.

By Carl Pham (not verified) on 13 Dec 2012 #permalink

The electric field of one photon will add to the electric field at the location you have your sensor. Another photon will add ITS electric field to the same place. If the electric fields are equal and opposite, then the sum electric field there is zero and remains so.

And a photon absorption/emission event with zero electric field value changing between zero and zero is what?

No photon.

This is why adding probability amplitudes works. You cannot add probabilities in this case because the photon doesn't just have a location. It has an E and M field too.