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Arrogance and the Large Hadron Collider

I see they're going to fire up the Large Hadron Collider at half power. For those who haven't been following this story, your life is being put at risk.

The Large Hadron Collider (LHC) is a project by The European Organization for Nuclear Research, known as CERN. Back in 1964, a physicist called Peter Higgs found an elegant mathematical theory by which he explained one of the great puzzles of particle physics, why mass exists.

There is some background to this question. The twentieth century produced two great theories of physics: relativity and quantum mechanics. Quantum mechanics explained many curious puzzles in the subatomic realm, for example, why atoms don't collapse. Atoms have a field of electrons orbiting the nucleus; according to classical mechanics, any accelerating charged particle (like an electron orbiting an atom) should radiate energy. This means the electron should spiral into the nucleus and the atom should collapse. Obviously they don't because we are still here, made of functioning atoms! Another example is the radiation from black bodies. Only quantum theory can explain why the spectrum is what it is.

It is no exaggeration to say that the modern world only exists because of quantum mechanics: every piece of electronics that exists only works because of quantum mechanics, and a great deal of it was only discovered because we understood the theory behind it all. It is the most successful scientific theory ever. It has passed every experimental test ever thrown at it. But it doesn't explain gravity.

Relativity, on the other hand, has an answer to the gravity question: the bending of space-time. It is a classical theory: in it the world is continuous, not discrete; everything exists in one definite place; influences cannot travel faster than light; and so on. It also has some impressive evidence on its side, such as the unexplained shift in the perihelion of Mercury, and the bending of starlight around the sun, and the slowing of clocks in a gravitational field.

But these two theories are incompatible. One or the other must be wrong. So it is only natural that any theory that helps us make sense of this conundrum will have a huge emotional and curiosity attraction for scientists. So when Higgs proposed that mass came into existence because of a certain subatomic particle (later named by others the Higgs boson), searching for it became a top priority for many scientists. If the Higgs boson were discovered, it would allow us to clarify many of our ideas about basic physics.

Enter the Large Hadron Collider. At a cost of something like 4 billion Euros, the European Union is mounting a search for the Higgs boson. The problem is this:

Matter, from which everything in the Universe is made, is believed to have originated from a dense and hot cocktail of fundamental particles. Today, the ordinary matter of the Universe is made of atoms, which contain a nucleus composed of protons and neutrons, which in turn are made of quarks bound together by other particles called gluons. The bond is very strong, but in the very early Universe conditions would have been too hot and energetic for the gluons to hold the quarks together. Instead, it seems likely that during the first microseconds after the Big Bang the Universe would have contained a very hot and dense mixture of quarks and gluons called quark–gluon plasma.

The ALICE experiment will use the LHC to recreate conditions similar to those just after the Big Bang, in particular to analyse the properties of the quark-gluon plasma.

That's from the official CERN website. But is it safe to replicate the conditions of the early universe? Dangers include creating "strange matter" which would make the existence of ordinary matter like you and me impossible, and creating mini black holes, which, some say, might suck in the entire planet into a black hole.

Now I want to make one thing very clear here: CERN and almost every physicist on Earth, agree that these scenarios are highly unlikely; some say they cannot happen. And I agree with them.

However! If CERN, the world's scientists, and my humble self are wrong, the entire planet will be destroyed. Where I differ from CERN, the scientists, and the governments that approved this experiment is that I do not believe I have the moral right to risk the very existence of the planet on my assessment of this risk. When asked about this risk, CERN said something very odd indeed:

According to the well-established properties of gravity, described by Einstein’s relativity, it is impossible for microscopic black holes to be produced at the LHC. There are, however, some speculative theories that predict the production of such particles at the LHC. All these theories predict that these particles would disintegrate immediately. Black holes, therefore, would have no time to start accreting matter and to cause macroscopic effects.

Now hang on: One or the other or both of relativity or quantum mechanics must be wrong. Since QM is passing every single test ever thrown at it, it is at least a possibility (in fact I believe close to a certainty) that the wrong one is relativity. In fact, the very realm in which relativity does not work is the subatomic. So their argument might be reasonable in some circumstances, but in the context of whether we might destroy the only planet known to have life in all the universe, using an argument from relativity theory is hopelessly inadequate. Moving on, they then say that all the speculative (meaning disagreeing with the probably wrong theory of relativity) theories so far invented that allow mini black holes to form also predict their disintegration. So? What about speculative theories we haven't invented yet? Who says we have an understanding of physics so very good that we can stake the life of every person and every living creature upon it? And we don't even know which one of our two incompatible theories of basic physics is the wrong one—or if both of them are!

Again I have to remind readers that I am not alleging that the LHC will (or even likely will) destroy Earth. But I am alleging that there is an arrogance and an irresponsibility in building this machine merely to answer scientific curiosity. Yes, I want to know whether the Higgs boson exists as much as any other lover of science, but I don't put my curiosity ahead of the rights of others not to have their lives risked. Yes, the likelihood of error is small, perhaps extremely small, but the stakes are so very big. It might be a different matter if this experiment were needed to solve some problem that was in itself pressing, such as solving the controlled nuclear fusion problem, which would release us from dependence on fossil fuels. In that case not having the answer in itself causes harm, and the experiment would almost certainly reduce our exposure to harm. But that's not the case here.

Unfortunately we humans are congenitally handicapped in assessing low probabilities and big numbers. I have seen the risk of the LHC quoted as one in 50 million. I don't believe that these figures have a precise meaning, but let's run with it. With a world population of nine billion, the expected deaths—"expected" in the statistical sense—from turning on the LHC is the ratio of these numbers: 180. When the outcome is either none or a huge number, the expected outcome is largely meaningless, but what it does tell us is that if we did a very large number of experiments, each one as risky as the LHC, then the average death rate from each one would be about 180. Is 180 deaths, plus many times more animal deaths, worth it for more knowledge of physics? Is it even morally permissible? Some will say the "greater good" says yes, but if you look up the Principle of Goodness, which is the grounding moral vision for this site, according to which we must not deliberately harm even one innocent, you will know immediately that my answer is no.

Lastly, the cost of the LHC is in the same ballpark as the cost of experimental fusion reactors such as ITER. Yet fusion finds it hard to get funding, even in the current panic environment over fictitious anthropogenic global warming. We simply must find ways to deal with the fact that humans are such poor thinkers about the really big and the really unlikely.

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Re: Arrogance and the Large Hadron Collider

Hi Ron

Interesting thoughts. You do pretty well for having moderate official expertise in this field; I perceive you are a generalist. I too like to read widely and try to formulate pertinent ways of understanding such things without becoming bulked up with technical detail.

I understand your call for caution, and you are not alone. I'm sort of in the same place, though I think a certain amount of the perceived risk is just fear of the unknown. I remember the fear of fission reactors "melting down", forming a big ball of fire that drops through the earth's mantle, punching a big hole and spewing hot liquid rock all over the surface, resulting in disaster of unprecedented scales. Or repeated Chernobyls, on larger scales. People are afraid of what would be the consequence of a runaway fusion reaction too. All of these "risks" can be quantified as highly unlikely with numbers just as meaningless as the "one in 50 million". But unquestionably small.

We make choices associated with such risks everyday. What if it is, after all, wrong to eat pork? (To pick an example out of the blue.) And what if God gets really angry and sends people to Hell for this, and what if Hell is exactly as some would have it--eternal agony of burning in unrelenting fire?

I'm not going to assess all of the above risks, but they are all accepted by at least some intelligent people as nonzero. And the stakes are high. Some might say infinitely high (taking "eternity" as a rough proxy for "infinity"). The resulting imbalance of probabilities is not mitigated by my assessment making the chances of going to Hell for eating port very, very, very tiny. Should I risk such stakes on my confidence in my own view of metaphysical reality? I know that Pascal's wager makes it a dubious proposition. So do you. Yet I bite into that pork chop with immense pleasure, and with nary a concern about the eternal consequences. Don't you?

So, while I'm sympathetic to your line of thought, I'm thinking we're putting an awful burden on the LHC scientists by considering their risk unacceptable while we make daily choices having similar risk imbalances without batting an eyelid.

The only point where you appear to have a serious misunderstanding is in your repeated insistence that one of Quantum Mechanics or General Relativity must be wrong.

Actually, few competent cosmologists would agree with such a statement, and those who do would not do so on the basis you give. The most common belief is that the two theories will be superceded by a more general theory that encompasses both -- a "grand unifying theory" (GUT). There are many thoughts about what such a theory may look like but in general none of them simply discard quantum theory or general relativity, but produce finer strokes showing how they fit into a bigger picture.

In other words, the general consensus is that quantum and relativity theory are both right. If you wonder how this can be, given the apparent contradictions between them, then first, you must understand that "apparent" is the operative word, and you must have a proper understanding of how the words "right" and "wrong" apply to scientific theories. It is not simply that a theory is one or the other---we must speak of the degree to which the theory accurately describes/explains the universe. Is Newton's theory of physics wrong? Well, it has been superceded by general relativity theory. Yet it is still taught -- indeed, it is a prerequisite for learning about relativity, just as arithmetic is a prerequisite for learning algebra, and algebra for calculus. So it is wrong to say that Newton's theory is "wrong". It is right as a first stage of understanding how the universe works. But if we try to apply it strictly we run into problems, say with objects travelling near the speed of light, the nature of gravity, and the behavior of tiny particles. But it fits nicely and "correctly" into a larger theory as a first approximation, quite appropriate in certain contexts.

The following essay, " The Relativity of Wrong" by Asimov, is a really good read on this point. I think you'll find it worthwhile.

Re: Arrogance and the Large Hadron Collider

Thank you both for a very interesting post and discussion.

I tend to agree with the comment above, all activities are life threatening, and although the LHC is potentially humanity threatening, not to go ahead with its development would be to kowtow to the green's simplistic "precautionary principle."

Re: Arrogance and the Large Hadron Collider

Hi craigen, Thank you for such a carefully thought through comment on the article.

Yes, the question of risk is a sensitive as well as a subtle one. There are two things that separate this case, IMHO, from the others you mention: firstly, the others all have payoffs for the same people who are risked. Even if we might predict that, in a lifetime, the benefits of nuclear power will not flow through to African villagers, we might hope that they do so in their children's time, which is a benefit of successful reproduction even for the ones alive now. And so on.

But the LHC benefits the curious, like you and me, and if everyone were equally curious, I would withdraw my objection, as I think the risk is indeed negligible. But they don't. I am risking others, who couldn't give a fig for a Higgs boson, to satisfy my curiosity. I also agree we do even this 'in the small': I drive a car to town, knowing that an extreme unlikelihood might result in my hitting someone who cares not whether I ever see a supermarket again. So I take your point here. I think the difference is the complete all-encompassing nature of the LHC. If I drive to town despite the minuscule risk (I am a good and careful driver), equally I grant to others the right to take similar minuscule risks with my interests for their own purposes. In the combined situation (we all drive around town), we all benefit compared to if none of us drove to town. But with the LHC, no such averaging of our combined interests can occur: if it does go wrong, it destroys everything there is. No one else can ever make good or make up for the loss.

(As an aside, I actually don't buy Pascal's wager at all. I had an atheist friend (Hi Paul!) at uni in my student days, who has an extremely creative mind. One day he came in and proudly announced that he had become an anti-Christian. He was joshing, of course, but he had a very interesting argument for why, in fact, God will send to hell Christians and only Christians. The point is that the wager makes assumptions about the alternatives that might be very far from the truth. The wager is even worse when it is applied to beliefs rather than actions, because whether something is true is not related to whether I like it.)

The right and wrong question is interesting and, as you point out, there is a lot of subtlety around it, such as the considerations Asimov recounts. Thanks for that link, I edited your post to make it clickable-I think the quote before it confused drupal somehow. I do find dim recollections of having read it before surfacing, but I greatly enjoyed seeing it again.

In that regard, one of my firm principles is that you cannot discover facts about reality from word definitions (except facts like "The German for 'yellow' is 'Gelb'", of course). So I must define my words. Not having thought about these words in this context before, I would tentatively say that what I had in mind was "A theory is right if all its predictions are in accord with what will actually happen" and contrariwise for "wrong". Now under those definitions, QM and GR are certainly inconsistent; they predict different things in the same situation, and therefore one of them or both must be 'wrong'. To see this, QM assumes the world is a complex-valued 3N-dimensional Euclidean space (N is the number of particles in the universe) with an independent scalar parameter, time. GR assumes the universe is a 4-dimensional curved space where time is one of the four dimensions.

Nextly, QM's Schroedinger equation is linear: it scales up linearly, so those who say it doesn't 'apply' to macroscopic quantities are mistaken. So each theory has a realm in which, on the surface, its predictions fail: QM in the macroscopic, where we don't seem to notice people being in two places at once (although there are very good arguments as to why the theory can indeed cope with this - which is why I have a great deal of respect for QM); and GR in the microscopic, where it simply cannot replicate observed quantised phenomena as well as tunneling, superpositions of states, etc., and its failure is certain.

Getting back to my original post, whether more all-embracing theories exist doesn't really matter because these results are all I need to establish the 'oddness' of the remark by CERN on their website. "According to the well-established properties of gravity, described by Einstein’s relativity, it is impossible for microscopic black holes to be produced at the LHC." This is exactly the realm, the subatomic, where GR is known to give incorrect predictions.

But returning to your wider theme, I find the discussion fascinating, as obviously do you, so let's chat some more about it. One way to make a 'right' theory out of GR would be to narrow it: say that, except for the subatomic, the universe is as depicted by these equations. And if you don't 'buy' one of the solutions to the fade-out of quantum effects in the macroscopic (such as the IMHO right answer, decoherence), then you can similarly narrow QM by making a new theory: "subatomic phenomena behave this this - no predictions for macroscopic phenomena." By eliminating the overlap, maybe both can be 'right'.

The question of a more embracing theory therefore boils down to: can we devise a single postulated framework to model the universe, and a single set of equations in that framework, such that we can predict all the correct predictions of both QM and GR, and none of their incorrect ones? So the GUTs and the TOEs (theories of everything) alter the fundamental mathematical framework of at least one theory. As you point out, whether we should be using words like 'right' and 'wrong' for this is problematic. I do so because a lot of people seem to think that the unaltered individual theories can be enhanced somehow, maybe with additional terms in the equations, to produce a single theory with both sets of properties. Now my own mathematical skills are far too low to make a confident pronouncement on that score, but I very much doubt it. AFAIK, the candidates generated so far do indeed differ fundamentally from one or the other of QM or GR. But there is that other sense, which you explain, in which other ways of talking about it seem to fit what's going on much better than the approach I was using.

Re: Arrogance and the Large Hadron Collider

Hi mikh, I recently discovered your Mickey's Muses - great site, congratulations!

I do adhere to the precautionary principle: the next great climate movement scheduled by the regular astronomical cycles the Earth passes through will be a killer ice age. So anything we can do to warm the place a bit in advance is good stuff. All perfectly consistent!


Re: Arrogance and the Large Hadron Collider

Hi Ron. While I suspect it will be a VERY long time before physicists are happy about something that approximates being a TOE or even a GUT, I do think it is possible that a theory of Quantum Gravity is around the corner. This would fall something short of a GUT but would be a massive improvement on the current "standoff" between QT and GR.

Although he is considered marginal by many in the field, I think Roger Penrose is onto something very substantial in this regard. He has been chuckled at before, and proven right repeatedly on many things such as the existence of stable solutions to GR in which black holes exist, the nature of black holes, the development of Twistor theory, and many other things. A maverick, but not a quack.

A nice feature about his proposal is that it promises to give a framework in which conscious intelligence makes sense. He argues, quite convincingly, that neither QT nor GR explains the conscious mind, but that the most obvious approaches to quantum gravity do. If one accepts even a weak version of the Anthropic Principle, this is pretty strong evidence in favour of such approaches, for we cannot accept a "unification theory" that is inconsistent with the most fundamental part of our observation of the universe, namely our conscious experience of it.

Re: Arrogance and the Large Hadron Collider

Hi Craigen, thanks for reminding me about Roger Penrose. I agree with you about his proposal. My confusion in this regard is as follows: I see his point about the point at which gravity starts to influence QM and water down quantum phenomena. On the other hand, decoherence is such a compelling and complete in itself explanation of the lack of odd QM phenomena at the macroscopic scale that it surely must be correct. If so, what room is there left for the ideas Penrose is advancing? It seems we have two answers to the same problem. Decoherence is more than just a possible answer: it is basically nothing more than statistics applied to the chances of two parts of the wave function interfering with each other. The more particles involved, the more complicated the wave function gets, and the less chance there is for structured interference. Seems more or less a process that has to happen, whatever else is going on. Maybe there really are two reasons, not one, for the fading out of quantum effects?

Re: Arrogance and the Large Hadron Collider

Hi Ron. I'm not sure what you mean by "Decoherence". Are you referring to a coherent and well-known theory? You seem only vaguely familiar with Penrose's proposal. Check out his book, Road to Reality, which some regard as an immediate successor to Newton's Principia in terms of scope and importance. It's a BIG read, though so you'll have to set some time aside. Don't worry about it being full of fluffy nonsense. It's basically a physics textbook that spends some time talking about big ideas in the process.

His specific proposal about quantum gravity is fairly simple and -- once one grasps the idea -- pretty straightforward. He says, first, that it is nonsense to suppose that the reduction phase of quantum mechanics (wherein the waveform is reduced to a classical state) is fiction. He takes it at face value: It's an actual phenomenon that occurs; the methods used by physicists work because they reflect something REAL that's happening. In terms of the world of serious physicists, this is a bit radical, as it's a bit more sexy to regard phase reduction as a mere practical necessity for getting results, and that ultimately it will disappear when put into the proper framework -- such as is proposed in the Many Worlds Hypothesis.

So it's a bit bold of Penrose to say, no, reduction is Real.

Further, he proposes that two kinds of reduction take place. This is even bolder. But if you read his book Shadows of the Mind you'll see that he spells out what I believe are very intuitively pleasing reasons for this. Basically, it is because he requires a universe in which it is possible for minds to function. (Anyone who says otherwise must be living in a different universe, or not have a mind of their own!)

Further, he demonstrates that there are natural, physics based, ways to think of the two kinds of reduction; I understand them, in a rough sort of way, to be space-constrained and time-constrained (treating a time axis as special). But it's actually more in terms of the gravitational energy of superposed states. When one (space-constrained) of the kinds of reduction takes place, he posits an actual phenomenon that is probablistic, exactly like physicist "do" in practise though they take no epistemological stock in its meaning.

When the other kind takes place, it is for a slightly different reason, and is precipitated differently. He calls this OR, or "Orchestrated Reduction". For OR, essentially the universe sits down and says, "Oh boy, I'd better reduce this waveform to a single state, it's gravitational energy cost is getting too big. Let's consider all possible states and make a decision".

The upshot is that, while there is such a thing as "all possible states", it is computationally impossible to "consider" them all, ie a computer can't do it! I don't mean that the problem is too big and it's infeasible. It is impossible in principle. It matters not how large or fast one's computer is, it simply can't be done.

Incidentally, what is sought is a non-computational result. It is not necessarily either "deterministic" or "probabilistic" -- Penrose doesn't say, but I infer that he leaves open the possibility for "other". I, leaning a bit toward a mystical interpretation, want to call it "will", or "volition", but I won't accuse Penrose of any such sentiment. He is a non-mystic. But he does say he's friendly toward the mystics because if he's right, physics will necessarily move in a direction that validates a certain kinds of mystical thinking (this is not the way he would put it). What I think he's validating is what the great logician Kurt Godel said about the mind: "A human mind is a computer with a spirit attached". If you read Godel's thoughts on the matter you find that he wasn't a misty-eyed mystic either, he was led to this conclusion by an earlier version of essentially the same train of thought as Godel.

This is a huge oversimplification but when such a reduction takes place Penrose allows that it MIGHT correspond to a fundamental event of consciousness. I realise that bit sounds pretty silly but it's largely because it is ripped out of context and put into common, and not altogether appropriate terms. Penrose arrives at this point more-or-less deductively. Rather, he puts pretty good theoretical chops on each of the following propositions:

- The universe, as described by QT and GR, does not support consciousness as manifest by the human brain
- This particular way of unifying QT and GR, however, does support events that fill in the gap -- that is, they permit that aspect of consciousness he has identified that doesn't fit into classical physics (QT and GR)

He does not argue that by force of necessity his approach is the unique solution or that just because it fills the gap he has identified between theory and reality this means it "explains" conscousness, only that it appears to fix the problem he had identified in the existing theories.

- Further, he identifies brain substructures (note: NOT the neurons themselves) that can believably act as physical substrates for large-scale OR events. These structures are unique to brain cells (at least in the formations that occur there -- the basic building blocks occur in all Eukaryotic cells).
- Further, he does the "Einstein thing": assuming only that SOME extension of QR and GR has to permit this kind of non-computational outcome, plus his insistence that reduction is "real", he arrives at a basic equation that has to dictate how it occurs. By "Einstein thing" I mean he assumes almost nothing besides one or two philosophically lightweight fundamental principles, and arrives at down & dirty equations that actually put meat on the theory and arrives at real predictions, with real laws that say precisely what happens.
- Armed with these simple equations he dumps in some standard constants and does back-of-the-envelope calculations to try to determine what lower limit of complexity would permit what psychologists call "protoconsciousness". It seems this happens at about the complexity of the nervous system of a worm. Given that the basic constants he's using to all the way from Planck's constant up to parameters relating to the age and size of the universe, it is remarkable that he arrives at a very believable scale on which consciousness "begins". Of course, this proves nothing; figures don't lie but liars figure as they say. One has to read through the process and decide whether or not pleases in the same intangible way that Einstein's GR did -- and convinced many scientists of its truth long before it was validated by experiment.

Perhaps you're thinking along Penrose' lines in the last sentence of your comment above?

Re: Arrogance and the Large Hadron Collider

Hi Craigen, thank you for that explanation of Penrose's idea. I have read Shadows of the Mind, but not Road to Reality, so from that you can judge how familiar I am with his work. It is some considerable time since I read SotM, but my recollection is that he explains his idea in what might be called summary-style - that is, he explains it but doesn't give detailed development of it. If I could locate my copy I'd check that memory out.

Decoherence in QM is not an informal term (such as if we said a dance or a piece of music had "coherence"). It is a technical term for a very well-defined discovery about the way the Schroedinger wave function behaves when a quantum system interacts with a macroscopic object such as a measuring device (or a human mind). You can find a very good explanation of it in Roland Omnes's book Understanding Quantum Mechanics, and also in his less technical Quantum Philosophy.

The problem of how or why superpositions seemingly disappear as a quantum system influences a macroscopic object is one I attempted and failed to solve in the '70s, when I was personally tutored in the physics of the problem by one of the last students and collaborators of Schroedinger. The failure was all mine, as some combination of my mathematical skills and my insight was not good enough to see the answer, but I sure did recognise the answer when I saw it; and it is decoherence. It's a subtle idea, and in fact was discovered twice before its importance was understood.

The idea basically is this: A quantum system (say, a photon passing through a two-slit experiment), has a wave function something like:

W(x) = aw1(x) + bw2(x)            (1)

where I am using W and w for the normal Greek letters usually used for wave functions. w1 represents a photon passing through slit 1, and likewise w2 and slit 2. The resulting wave function W can have obvious characteristics of interference because of the simple nature of the two w's, just as with water waves passing through slits in a barricade, spreading out, and creating 'choppy' waves behind the barriers. The patterns are in fact almost identical, as everyone knows.

But now what happens if we place two detectors (macroscopic objects), one behind each slit, measure whether a photon went through, and later try to force the two signals to interfere? Devising an experimental way to do this would be tricky, but not impossible. But for sure no interference pattern will be observed. Our question is why?

The answer proposed by decoherence is that, unlike the simple wave function shown above, the wave function after being transmitted through a macroscopic component now looks like this:

W(x, y) = aw1(x, y) + bw2(x, y)         (2)

What are the y's that have turned up? They are coordinates representing all the particles that have been affected in the macroscopic apparatus, untold gazillions of them, all interacting (bumping against each other, shifting electrons around and so on) in a hopelessly unpredictable way. Now look back at equation (1): for any given value of x, W might or might not be non-zero - which is why interference effects can be observed. But look at equation (2): the hopeless mess of phase shifts in the y's means that W(x,y) can be hopelessly out of phase with W(x,y'), even if y' is incredibly close to y. For example, a tiny shift in one insignificant electron somewhere in the measuring apparatus might completely invert the phase of the wave function. And there are hopelessly many particles involved, all of them equally important in distorting the final wave function. Sorting out the phases and getting the waves to "add up" in the way needed for interference is hopeless.

This is inherently a statistical problem: what are the chances that, if you disturb a few moles of atoms, photons, electrons, etc., you can retain the phase of your wave function in its pristine condition, given that any one of these particles can and will do any amount of disturbance, up to and including completely inverting the phase? It is easy to see that the task of keeping things pristine is utterly hopeless.

This explanation is, IMHO, more or less nothing other than a very careful examination of how the wave function would work if it interacted with a macroscopic object: it proposes no new physics, doesn't change the QM equations, or make any other speculative assumptions. It is simply a light shone on how the thing would work, and that light shows us how and why we expect to lose the coherence needed for interference phenomena to operate. And we do. If this explanation is not the reason, I would be as staggered as if I suddenly found I could get milkshakes by wishing for them.

So the question I have for - well, for Penrose, I suppose - is: is it indeed the case that a second, entirely different, mechanism is also operating that also causes collapse of wave functions in the very same places that this mechanism is also doing so? My physics intuition tells me that is a doubtful proposition. Of course it might be true. It violates Occam's razor, since the additional proposals by Penrose don't solve a problem (decoherence must be happening and therefore has already solved it), so I would be looking for additional evidence for another process if I were to give credence to its existence.

Now that, I dare say, is where the consciousness issues you mention come in. I agree with you that we need to explain why it feels like something to do something. Why isn't the world doing what it does, but without awareness? That needs explaining. If I am to accept Penrose's idea, then, it would have to justify itself entirely on this score, and not in any way on explaining why quantum effects die out in the macroscopic.

Looks like I'll have to get his other book. Thanks for filling us in on it.

Re: Arrogance and the Large Hadron Collider

Thanks for the explanation of decoherence. I have never seen it used for a precise explanation of anything, only as a description of the general behavior of quantum systems, sort of a negation of quantum coherence. I think I see the point you're getting at. Note that the most complete explanation of the Penrose-Hameroff proposal for a theory of consciousness involves large-scale quantum coherent phenomena that collapses with the gelation cycle in one's neurons. So the *theme* of coherence and its breakdown is very much a part of their proposal, though perhaps not in the sense of which you speak.

I'm afraid I'm not enough of a physicist to answer your "question for Penrose". But as I understand his two kinds of collapse, the second is not an "entirely different, mechanism", as you say. I'm sorry if I had given that impression. In fact, I think he would say that they are one mechanism, but which manifests in two very different modes. A loose, but imperfect analogy might be electric fields versus magnetic fields. I'm not even sure whether he would insist that the modes are completely distinct; perhaps they can be "mixed" according to some spectrum. However, there is a sharp and rigorously definable distinction between outcomes that are computable versus noncomputable, so the distinction is very real and there exists some clear boundary at which it can be said that one of the modes is qualitatively different from the other.

I don't know if it helps your physics-trained mind, but my mathematically-trained mind pictures a cube in some abstract space, with a time-line passing through opposite faces. If it passes through the East/West faces then we have probabilistic wave-form reduction and if through the North/South then Orchestrated Reduction. In both cases it is reduction of the waveform, and it is the same cube being passed through.

The faces of the cube are distinguished by how the event of reduction (represented by the cube) is precipitated, or approached. For probabilistic reduction, we have an energy barrier transgressed. It's been a long time since I read it, but I believe it means that, when universes representing the states of the two particles differ by gravitational energy exceeding a bound defined in terms of Planck's constant, Reduction is forced. For orchestrated reduction it is more of a time barrier; gravitational energy, itself, does not increase past the barrier, but remains at some level for too long, and the "same" threshold is crossed, but in a different direction. So, loosely, East/West in my thought-picture represents space, or rather energy associated with space-wise superposition, and North/South represents energy associated with a time-wise superposition. As Penrose articulates the energy is calculated in both cases by a single equation, so he is not really talking about two different "mechanisms", only two different qualitative outcomes from the same mechanism.

I'm not completely convinced that decoherence (I mean as you describe it in terms of a precise mechanism, not as a general descriptive term) "explains" anything; it looks to me more like another way of discussing the sum-over-all-histories approach, or something a bit more general (As I read sum-over-histories) it focuses on how a single particle's state may "behave" classically by following one history line and considering the statistical implication of all histories taken together. But when I find the time I may pick up one of Omnes' books and see how he lays it out.

Re: Arrogance and the Large Hadron Collider

Hi again Craigen,

I think I'll have to chase up Penrose's second book, so thanks for putting me onto it. Yes, I think you are right about the sum over histories. Decoherence effects are just the result of statistical probabilities, which is what sum over histories amounts to, looked at in a different way. If we take the many worlds interpretation of QM, it amounts to this: in a system that retains quantum properties (usually, but not necessarily microscopic), different branches of the world-line retain enough coherence (like waves emerging from a two-slit experiment) to later interfere and produce the characteristic pattern that then raises such conceptual difficulties for us. But in a system in which this coherence is lost (as will certainly happen when chaotic behav iour of large numbers of particles gets involved), the two branches are so unlike each other that no effects of one world-line can filter through into the other: the universe 'splits in two', each version seeing only one of the possible outcomes. This is a poor analogy, but it would be a bit like being in a rowboat way out to sea as a tsunami passes underneath. We could put our finger in the water and make little waves, which we would see, but the vast wave of the tsunami passes by us without our even noticing it.

I like your analogy of the cube, but I find it makes my head spin a bit. There is so much we still don't know - but it's fun trying to find it out! Cheers.