schrodinger's backside

No. The CI does not posit an "intelligent observer", "conscious observer" or even just "observer". There is a measurement provcess, and it is in extrapolations of this measurement process that some have suggested the neceesity of a conscious observer. It has nothing to do with the CI of QM, and has no solid foundation.I think it is safe to say most physcists do not believe that an "observer" is necessary in QM. Decoherence is one way of formalising the measurement process as part of QM and actually leads to a very aesthetic, natural and sensible realisation of the CI. The Particpatory Anthropic Principle... I still have a soft spot for it But even if there is something to it (definitely a meta-physical/religious belief) I do not think it is involved in the measurement process of the CI.

But what do you call the quantum realm? We see quantum effects extend to the molecular level, and way beyond to classical distances in the case of entangled particles. The trick seems to be avoiding the environment - other particles. If you can do this at classical scales, then your quantum realm should extend to classical scales.One idea of which I am particularly fond is that the ubiquitous gravitons are the great reducers of quantum to classical behaviour - not that there is anything magical about the graviton compared to say the photon, just that they are everywhere and interact with everything (unlike the photon). When we (physicists) talk of fine-tuning, we do not imply any entity. We are looking for reasons why the constants are such that they are comptaible with our existence. The usual explanation is some large enough population to create all possibilities, and then we simply apply the Weak Anthropic Principle. However, there are interesting mechanisms such as inflation that actually produce some level of fine-tuning without having to become boring (applying the WAP). Exactly, and no small feat. In fact stars are more of mystery of fine-tuning than almost anything else. Of course, neatly explained by large population and WAP, dull as it is... Why? If all that is required for the Universe to exist is sentient life existing somewhere in its (4d) expanse, then surely we should see the minimum effort expended in producing that sentience?Or to put it another way...a universe with an abundance of life requires a far tighter tuning than one with minimal life
only universes with life are observed
an essentially infininte number of possible universes are provided
the probability is very high that we live in a universe where we are alone/very far away from other sentience.

The Universe is (or appears to be) a 4d entity. When we say the Universe contains sentient life, it is not necessary to specify at what specific (4d) coordinates such sentience is located.The Universe did not "begin" to exist at the Big Bang... the Universe just exists. Existence is not a property of time: time is a property of existence. And given that we have very lttle clue as to what existence is, it is difficult to make statements as absolute as yours. Yes, it is most definitely your opinion. But I have already pointed out that your reasoning is not sound. Tuning to the point of abundance of life may be 1) undesirable by the active agent 2) unnecessary by the WAP selective process 3) incompatible with the natural constraints placed upon the parameters. Given what we know of the physics of life, stellar abundance is an absolute necessity, even for a marginal content of sentient life. The two are most certainly not independent. Fine-tuning via a WAP mechanism is actually the one way out of positing either Design or some more meta-physical connection between ourselves and the fundemental nature of the Universe. Well, you're forcing me into a corner - of large distances and long time-scales - difficult. But give me any of the other three options and no problem (large distance over small timescales, small distances over long timescales, etc) I sometimes entertain the idea of preserving a long-lived macroscopic quantum state in a gravitational Faraday cage - say a planet sized hollow sphere... I'm not sure I understand you... I would say that as distance is irrelevant to entanglement it is obvious that the quantum realm extends into "classical" distances.

This is one of the big conceptual difficulties with GR and space-time physics. Infinities don't mean that much. I still visualise a universe with no temporal beginning and end as a compact object I can hold in my hand - even when the spatial dimensions are infinite as well The dimensions are properties of the universe and the parameter space of the dimensions are properties of the dimensions - so whether T spans from 0 to Tmax, or from -inf to +inf, doesn't really concern me when I'm considering the big picture... they're just labels. It's only when we zoom in to look at the geometry of the universe, that the diferent parameter possibilities make a significant difference.

I guess my thought is that SR/GR works to such an extraordinary degree, and relativity shows us that time is inextricably linked with space in quite a geometrically non-trivial way. We now have a harder time separating the two - we can't simply visualise 4d space-time as an ordering of 3d events, which we can with Newtonian cosmology. I like Barbor's work at thsi point, although I think that our own illusion of time develops at a much a higher level that he suggests. Otherwise I have a hard time reconciling his ideas with GR.

Out of the parameter space of implements of the order of 0.1-1m in size, then I would agree. If the parameter space is of any conceivable object, on the scale of Planck length to radius of observable universe, I would say your chop-stick is incredibly fine-tuned. And observing over such a scale, I would really not be able to distinguish between the chop-stick and the soup-spoon. Perhaps, but that is not a fine-tuning of THIS universe. As I mention in (3), it is possible that no amount of tuning will create prodigious life within this universe.Even if such a tuning is possible, this says nothing of (2)... given the entire possible parameter space, it is easy to imgaine "no life" vastly dominating, followed by some very small measure of "sparse-life" and finally "abdundant-life" would be some microscopic corner of the space, barely visible. If we then take random samples of this parameter space, "no life" universes are discounted as they are not observed. We are left with "sparse-life" and "abundant-life", and the probability of drawing from the latter is fairly close to zero.IF our (observable) universe is one of an essentially infinte number of trials with varying parameters, then the overwhelming odds are that we inhabit a universe with sparse-life.

Maybe, but would you like to suggest how? Let's take a number of the most commonly considered parameters - the fine structure constants, G, masses of the particles of the Standard Model, number of families in the Standard Model, Lambda, etc. Now how would you go about arranging those to make a Universe full to the brim of life?I'm not sure you are on the same page as to what we call fine-tuning in phsyics - we are talking about getting a usable universe. One that hangs around for longer than a few seconds-to-years. One that doesn't expand so fast that all there is is ionised hydrogen. One that has its fine structure constants such that atoms are stable, that stars can burn, etc, etc. This is what we need for life.If all these parameters can vary from universe to universe (or area of universe to area) then we have our explanation in the WAP. The universe appears finely tuned because we only see those universes that support us.

You are missing the point. It is the complex, long-lived universe that is "surprising" and which requires an explanation. You actually provide the very one I have expounded... Namely, the assumption of multiple universes - which then allows us to appeal to the WAP. Without that assumption, we are left looking for an alternative explanation...Welcome to EvC, BTW

That is because they don't know what they are talking about. Just becasue a concept of theoretical cosmology is incorrectly usurped by the design crowd does not invalidate the original concept. I see a great deal of misunderstanding here concerning what fine-tuning is actually about. Us physicists do not let the design crowd define our terms for us. Just becasue they talk about fine-tuning in terms of making our universe habitable does not mean that fine-tuning is now synonymous with design and designer... I don't know. It is my conjecture for which I have some evidence, but it needs exploring. When you want to learn about theoretical cosmology, you don't go to "most people". We need the assumption that the universe repeats in some fashion in order to be able to appeal to the WAP to explain why we see the values that we see. Otherwise as I said we are left looking for other explanations. Again, "other explanations" does not imply a cosmic designer. Despite what you may have heard, we don't go running to God every time we find a gap in our knowledge...

I'm sure this is true. Check out here for the original paper. Interestingly to me, these guys are currently working with an old colleague of mine who went on to great things.Read the intro for some background on what I am talking about. Their work is fascinating and wonderfully counterintuitive. BUT it doesn't invalidate the prior work, and merely shows that some parameters are more flexible than others. Hmmm, and these planets and observers are going to just coalesce from the hydrogen? There's a reason we observe a universe of Pop I, II, and III stars! Edited by cavediver, : No reason given.

Well, Paul certainly ranks as one of "us physicists"... are you suggesting that we shouldn't be discussing our own field? you could try, but if you check out what I said it essentially boils down to: A... if not, then not A. I like my arguments to be tight But let's take some of your ideas: You've got some major sources in Paul's paper, and you better check out Weinberg's work very sigificant work on the cosmological constant (references in the Harnik, et al paper). Show me you know better...

I think you are confused. I was castigating design. I myself have been talking about WAP (Weak Anthropic Principle) fine tuning in most of this sub-topic. The Anthropic Principle... IS NOT DESIGN!!!! Arrgghh anthropic fine tuning REQUIRES* a "multiverse" by definition - a multiverse in this context refers to a population of possible universes over which various parameters can vary - this population could be provided by a sequential oscillating type universe, or through multiple parallel universes via say Linde's chaotic inflation scenario, or simply through a huge 10/11d megaspace where branes span and intersect, forming an infinitude of sub-universes with varying dimensions. This enables even our 3+1 dimensions to be anthropically picked, as Tegmark discusses.There are not many theoretical cosmologists that don't believe in a multiverse of one form or another - nothing to do with the WAP - but simply just about every theory we have predicts it. Even boring old inflation gives us millions of observable-universe sized volumes to play with. Consequently, it would be simply amazing if some aspects of the universe are not anthropically fine-tuned. My apologies... but you need to back up a little and understand this topic before being so ready to critique it.ABE: *I guess a caveat to this is possibly the most obvious example of anthropic fine (actually very coarse) tuning, which is the age of the universe. The universe cannot possiby be much younger than we obseve it, as sentient life almost certainly requires the heavier elements... a generation of stars and their dying supernovae are required before we get chance to play.Edited by cavediver, : No reason given.Edited by cavediver, : No reason given.

All fine tuning is anthropic - it is an anthropocentric viewpoint so how could it be otherwise? We are only ever going to see an observer-friendly universe.The issue of habitability is the argument often used by the design crowd - that our universe can support *our type of life* - that there is a suitable star, planet, right place in the Galaxy, etc. This is all rather us-specific. As many will point out (as you did yourself), life could exist in any number of unimaginable niches.On the contrary, give me a suitably large, long-lived complex universe and observers start to become possible.That is why it is the reasons for the universe to be large, long-lived and complex that interest me - becasue that is what I need to exist. Bingo! Science looks for problems to solve/understand... while we're still looking, there are always those that say "heh, heh, you stupid scientists - God did it!" Once we have solved that particular problem and moved on to our next, those same hecklers follow us along and repeat their mantra. Just look in the QM and Thermodynamics thread for recent examples of this. Buz in this case seems to be under the impression that we just make stuff up to conceal our ignorance. Same with some type of multiverse - just becasue it sounds sci-fi and ludicrous does not mean that we're making stuff up to weasle out of difficult problems. This is all pretty basic and mundane when you're in the field. We're just in rather an esoteric field.

Try! Make the argument. Why do we see this particular heavy element have this particular stability? Fine-tuned by what? Try making the above argument work. Again, please make the argument. Let me see it work. Huh? If something is anthropically selected it's not a coincidence. And of course coincidences exist, and these are not anthropically selected, else they wouldn't be coincidences! So what? There are many values and parameters in the Universe that are probably not anthropically selected...