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Subatomic Darwinism
blamanj writes "In the beginning was Darwinism, then there arose Social Darwinism, now physicists are proposing Quantum Darwinism. According to the Nature article: "If, as quantum mechanics says, observing the world tends to change it, how is it that we can agree on anything at all? Why doesn't each person leave a slightly different version of the world for the next person to find?
Because, say the researchers, certain special states of a system are promoted above others by a quantum form of natural selection, which they call quantum darwinism. Information about these states proliferates and gets imprinted on the environment. So observers coming along and looking at the environment in order to get a picture of the world tend to see the same 'preferred' states."."
i.e. genetic algorithms.
GA's are used to maximize arbitrary functions by a mixture of random mutation and crossover between the solution candidates with better aptitude.
It's hot stuff, and it comes up with good solutions for analytically untractable problems.
The other kind "measuring affects things" is a little harder to grasp, and is exemplified by the schroedinger's cat example. There are situations where a particle/system/etc. can probabalistically be in one of several states. But until someone or something measures it to determine which state it is in, "the universe hasn't decided yet". So it's kind of like telling someone "I'm thinking of either a car or a dog" and not really deciding which one you're thinking of until someone asks you to tell them which it is. It's not the case that someone really has to look at it for it to "determine" itself - something about the universe could depend on the state, which is as good as an observer looking at it.
This is known as the "God of the Gaps" approach; God is assigned responsibility for whatever science can't currently explain. As you point out, the problem with this approach is that God keep shrinking as the gaps get filled in.
When all you have is a hammer, everything looks like a skull.
Quantum Field Theory already explains why macroscopic observations yield a single answer to every observer. The path integral sums over all possible complex-valued histories and it is those histories that constructively interfere that survive. Any graduate level QFT course will carry out the famous single particle example that yields Newton's law of motion. Its the reason while particles macroscopically travel a single path whereas quantum mechanics would suggest it actually travels every single path possible with some probability (in theory yielding different answers to different observers).
To us physicists, there is no mystery at all. The why part is left to philosophers.
No, it seems more like a problem with current theory. QM is very accurate as far as it goes, but it doesn't give the whole picture, even in its own domain. Theories about the causes of decoherence - collapse of superposed states - are still very much under development, which explains why there's so much confusion about the subject.
The naive and typically anthropomorphic idea that human or conscious observation has something to do with decoherence hasn't been credible for a long, long, time, and Nature (the magazine) deserves to have its ass kicked for allowing an abstract to pit its argument against such a nonsensical straw man. For an update on the most credible current work, a good starting point is The Role of Decoherence in Quantum Theory.
Darwanism involves differential rates of replication of two or more differing replicators built from simpler materials. Evolution occurs over several generations, where the more efficient replicators come to outnumber the rest. Because they are built from simpler materials, there is room for slight changes (mutations), some of which will be beneficial.
Take any of these elements away and you don't have darwinian evolution. I haven't read the article yet, so I don't know if it misapplies the term.
Seriously people. If you haven't taken a Quantum Mechanics class of some sort (or had some other real, solid exposure to the mathematics behind it) then don't even attempt to talk about it. Basically, 100% of all attempts I have ever seen to explain QM "conceptually" are complete and utter $hite, and have virtually no relationship to what the math really says. As far as I can tell, there is no good way to conceptually describe quantum mechanics. There are no good analogies. There are gillions of mediocre analogies, but if you really try to understand QM by means of these analogies, you're screwed. Because the analogies work for a small part of QM, and then break down if you try to get at all outside their range. So don't try to extrapolate anything from a conceptual discussion of QM. Don't try to take anything from it other than face value, because you will get it wrong. And in many cases, (such as this one) you will not even get it right from face value.
Case in point: TFA talks a lot about observations. But they also talk about people looking at trees and buildings. You looking at something really doesn't constitute an observation (Quantum mechanically). The photon interacting with the tree (building, etc) is the observation. The photon entering you eye, interacting with your cornea, your lense, and finally your retina is another "observation." But you looking at a tree does not change the tree.
Go read the actual papers referenced by the article, these will actually contain science, and not some journalist's misunderstanding of it.
BTW- IANA physicist... yet. I am halfway through my third year of undergrad physics work. One of the classes I just finished was Intro to Quantum Mechanics I. Just to establish my credentials. If anyone who is a physicist with more education in the subject disagrees with what I have said, I would be glad to talk to him. But if you haven't had any QM class.... shut up. Please. Trust me, unless you have had exposure to infinite dimensional linear algebra and partial differential equations, you do not know what you are talking about.
SIGSEGV caught, terminating
wait... not that kind of sig.
Many-worlds is not intrinsically in opposition to this work, and the authors are not adopting the Copenhagen interpretation. Decoherence, an attempt to explain "measurement" in physical terms, is compatible with the MWI. You imply that the authors are working in a framework that neglects the fact that the measuring apparatus itself lives in a quantum world, but that's the whole point of decoherence: to explain how an apparent dichotomy between "quantum particle" and "classical environment" arises from a "holistic" quantum environment in which there is no hard distinction between "observer" and "observed".
In short, you don't know what you're talking about. This is not pseudoscience, and Zurek is one of the top researchers in this field.
(And yes you do need to prove one or the other, and make your proof solid so no one can come up with arguments to it, otherwise it is just a theory not scientific fact)
Umm, there are no such things as scientific facts beyond the theory, except in logic, philosophy and mathematics. Science is mostly unprovable because of the way logical induction works. And besides, even if something is called a "theory" doesn't mean that it's something completely ephemeral and without any relevance or that it doesn't match the observed world very well. For instance, the theory of evolution is just that, a theory, and cannot be proved in any logically binding way. Yet it explains a lot of the phenomena we have observed, and after some revisions hasn't yet been falsified.
I'm no physicist but that's the impression I get from what I've read.
You are getting a right impression from what you have read, but what you have read is just one rather old-fashioned view of Quantum Mechanics (it's called the Copenhagen Intepretation). There are plenty of alternative (and equally valid) interpretations that don't require any waveform collapse by observation. These include the Many Worlds Interpretation, the Transactional Interpretation (my favourite) of John Cramer, which implies that particles exchange information back and forth through time, and the ideas of Roger Penrose which suggest that quantum states collapse to a single one of the alternatives when the states differ sufficiently in energy to cause significant spacetime curvature.
My view is that at this time, it's foolish to pick any single interpretation of quantum mechanics (such as collapse by observation) and assume that it has any reality. We just don't know enough.
I'm not a physicist so you can shut me up at any time. But I thought the "observation changes the object" was only true because to observe you you have to toss energy at it and see what happens. Then the act of tossing the energy changed it.
This was an early rationalization of the experimental results, but the truth turns out to be more general than that. Physicists have gotten much cleverer in working out ways of gaining information about a system without perturbing it, and the results still hold. (Think of Sherlock Holmes's dog that doesn't bark in the night). But it is not clear whether observation changes the system being observed or the rest of the universe, or even whether that is a meaningful distinction. Another way of looking at things is that observation couples the quantum states of the system being observed with the quantum states of the observing system. So once the Schrodinger's Cat box is opened, all "dead cat" states becomed coupled with "bereaved experimenter" states, which do not appreciably interfere with the "live cat" states that are coupled with "relieved experimenter" states.
Quantum Mechanics is not like 15th century astronomy. The theory is just misunderstood a lot, not only due to bad coverage like this posting on Slashdot and even the Nature article. As a physicist, I find it a pity that nowhere is mentioned that not all physicists agree with the decoherence people (in fact, I would say that it is only a minority).
... MANY particles or small subsystems). I cannot see how this can be satisfactory for any theoretical physicist.
...
The problem with quantum mechanics is that you have a) the theory and b) the interpretation of it. Most people agree on (a) but go terribly wrong when it comes to (b).
Personally, I always have a good laugh when people use environmental decoherence as an argument. That is like saying that the coffee in my cup cools down because of the existance of the Alpha Proxima system. I never understand how people can be fully satisfied by blaming the environment of a system for something happening in it. Remember folks, this is physics, where ideal situations are very common, even a perfectly isolated system! Environmental decoherence arguments are not applicable for such systems, since there is no environment to interact with in the first place.
How can this be an ab-initio explanation for anything ? Take the universe for example, isn't this an isolated system by definition ? Or is the environmental decoherence argument only applicable to parts of the universe but not to the universe as a whole ? Then to imagine that people try to explain emergent phenomena with this argument... (emergent phenomena = things that happen when you take together many, many
There is an alternative way of understanding why we see objects in the state that they are in when we observe them, and it is simply a matter of counting. No decoherence tricks needed! If you look at the _typical_ behaviour of a quantum mechanical system (technically speaking: if you average over a reasonable set of initial conditions), then you immediatelly see how emergent properties like irreversibility and "agreement between observators" arise. It is a matter of doing the maths and concluding that, simply because you work with a large system, composed of many constituents, that the quantum effects disappear on macroscopic levels. Things like measurements have absolutely no effect on the level of the world we live at.
For more info, see the work by people like Lebowitz (Macroscopic behaviour from microscopic laws), Bricmont,
This sounds very interesting, but is it just simply a strange twist on words?
No
Let me explain: Quantum mechanics takes place in the realm of the extremely super small. Einstein's relativity takes place in the realm of extremely large values of velocity.
No, relativity applies just as accurately to a garden snail as a laser beam and quantum mechanics applies to a neutron star just as much as an electron (in fact in many ways neutron stars can be considered large atomic nuclei). The disconnect between quantum physics and relativity comes from the fact that the former describes reality in terms of wave functions (although practicing physicists use a different, equivalent formulation in terms of fields) and the latter in terms of curvature tensors. Reconciling those points of view is the point of a ToE.
The Theory of Everything. The Holy Grail of physics is to find this super theory that unites relativity, quantum mechanics, electricity and magnetism, gravity, mechanics. Although relativity is used in quantum for calculations, there are some contradictions in reconciling the two theories, thus Einstein's famous quote (during his hunt to reconcile relativity with quantum), "God does not play dice with the universe!"
This is wrong on so many levels I don't know where to begin but I'll try. Neither quantum mechanics nor relativity have any problems describing electromagnetism (now more properly known as the electroweak force), there is no succesful theory of quantum gravity yet, but the creation of one does not require a ToE as far as anyone can tell, although a ToE will necessarily have a quantum theory of gravity as one of its consequences. Einstein's "God does not play dice..." quote was in reference to his belief in (now discredited) hidden variable theories which would attempt to remove some of the probabilistic aspects of quantum mechanics.
Look around, and everyone will see that quantum mechanics is not something that happens around us!
Aagh, my computer just vanished thanks to the impossibility of its existence! Given the physical nature of a quantum well (a system that traps a particle in a particular energy state, typically very small and cold) if I could see one I'd probably have several more pressing problems to address than my misunderstanding of quantum physics.
As you observe the movement of the train, does the Heisenberg uncertainty principle come into play?
Yes, but thanks to the fact that uncertainty in the product of position and momentum only has to be larger than Planck's constant divided by 2*pi and Planck's constant is a very small number in SI units given the relatively large errors in the equipment at hand for observing trains I can safely cross train tracks. Or to put it another way, the de Broglie wavelength of a typical train is so small as to be safely ignored.
This uncertainty principle does not conflict with everyday life chiefly because it only applies to the special case of extremely small and extremely fast particles.
To be precise, only when the de Broglie wavelength approaches the spatial extent of a system do quantum mechanical effects become significant. Similarly, although there is no equivalent to the de Broglie wavelength in relativity, when the energy of an object is smaller than a certain threshhold relativistic effects can be safely ignored.
So this comparison, extension and exercise of extending quantum mechanics to Darwinian proportions appears to me to be more than anything a philosophical exercise.
What's a Darwinian proportion?
Anyone else remember Rupert Sheldrake's "Seven Experiments that could change the world"? Sheldrake has a lot of odd probably crackpot theories, but one of his better ones was the idea of a morphogenetic field theory, http://en.wikipedia.org/wiki/Morphogenetic_field to explain both the shapes and behaviors of organisms, a sort of subatomic field effect that worked in conjunction with DNA. The best evidence he had involved the creation of new synthetic compounds that would be extremely unlikely to ever occur naturally. It turned out that the more often people created the compounds over time the molecules would appear to form more quickly. Most people had written this off as anomolous, or just a side effect of more experience in creating the compound. Sheldrake made the conclusion that the universe was building a "memory" of the atomic state of the new compound and was more prone to falling into such a state after it had been observed previously as it had "learned" the shape previously. Now this subatomic darwinism business is sure sounding a lot like these people are inferring a "memory" to the universe, so maybe the morphogenetic field theory isn't quite so odd as it sounds.