Well, I'm sure this famous quote by Werner Heisenberg will clear everything up for you.
Oh, and you want to know what space actually is? Here's Heisenberg again clearing the matter up completely!

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Everyone is entitled to his own opinion, but not his own facts.

Or, if you prefer, GR is a 'background-independent' theory (and that's built into the math it's expressed in), and QM is a 'background-dependent' theory (ditto).

In simpler English (and I'm not sure this is accurate):

* QM assumes 'the background' (aka 'space') is fixed, static, unchanging, ... just always there ... but it does assume a background.

* in GR, in contrast, there is no 'background' (no 'space') which exists ... 'space' is dynamic, it depends on what's 'in it', it changes as the things 'in it' change, ...

That's where the infinities which Tensor referred to come from ... in QM (thank you Werner) virtual particles do not change the 'space' in which they pop in and out of existence within (if that's a legal English sentence!); however, in GR, they do ... the more massive the virtual particles, the more space-time is warped, bent, twisted, shaken (and stirred) ... until the virtual particles are so massive that they form black holes ... oops!

In my experience, that's how science seems to operate as it probes nature.

yep. that's how I "understand" it.

This is quite accurate (for the simplicity you want) and a much improved version of mine. The only thing I would add would be to clarify that it is the real particles that pop into existance, not the virtual particles that cause the change in space-time. I moved the bolded from your last paragraph for clarity.

This isn't quite right. The infinities arise when you try to account for the different ways the coupling between two electrons can take place. You would think that the small corrections would give you a better calculation, but they don't, they produce infinities.

In regards to Phil's comment about foamy space-time, in a sense, he's correct. The Lorentzian Manifold that provides the model for space-time in GR is assumed to be continuous (or smooth) all the way down to a zero distance. In QM, the values would be discreet and not continuous.

Nereid, I'm not sure you can find a simple mathless explanation for all of the incompatibilities. Several are quite amendeble to a word picture. There are several (the infinity thing being the most obvious) where it is more or less strickly math related. I now realize that there are shortcomings in my attempt to paint a word picture. Maybe I'll think about it some more and try an edit and add a few things I've been thinking about.

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Some try to tell me, thoughts they cannot defend,... - Moody Blues.

Neptune- The original Dark Matter.

The author feels that this technique of deliberately lying will actually make it easier for you to learn the ideas. - Donald Knuth

I would instead characterize it as an argument that the burden of proof falls on those who claim they have cornered a piece of reality's "truths", so is accuracy in a calculation going to be accepted as such proof? Consider Newton's laws of gravity. They were extremely accurate in many situations, and are still used, but we now know they did not corner a piece of reality, if you will-- they were completely wrong in quality and philosophy, they just happen to work for basically coincidental reasons. I would claim that all our laws are exactly like that. Useful, yes. "True"? No, in science, the only definition of truth is usefulness.
Again, are Newton's laws of gravity what the "universe is really like"?
That is the issue in a nutshell-- is an inexact theory a piece of the reality, just not the whole tamale, or is it more like a replacement for reality that happens to work? I'd say the latter, considering the Newton example.

Indeed, that is a paradox-- if I had evidence that reality is unknowable, I'd have to know a lot about reality! Yes, it's intuition, but it stems from a kind of intellectual modesty that I think we've forgotten amongst all our achievements.
I'll take that bet, in the following form. I'll bet that it would be possible to derive an equivalent treatment of photon/atom interactions, for example, with no reference at all to protons or electrons. Furthermore, I'll be that it could be done without even using numbers in any way. It would be a great challenge, I grant you, we'd feel hamstrung. But I'll bet it's possible. Indeed, I would argue that the ultimate example of precisely this is nature itself-- it is the true "theory of everything", but only the "mind" of nature itself can "understand" this theory. (I'll leave it to the philosophers to define the "mind" of nature, but I don't doubt that a reasonable definition is possible if it is possible to define "mind" at all without reference to our own. And note that if it is not possible to define "mind" in an independent way from ours, then my point is even more obvious, as then we are certainly trapped in our own minds.)
Why stop at 500 years-- let's take 500 million years, and hope our descendants are still around. Would you still take that bet?

It's actually not obvious to me which side of the debate that statement puts you on. Note that I never contested that the concept of "proton" is spectacularly useful, and that's really all you have said. The issue is, does usefulness imply there's something real to it, or is science stuck with defining real the same way as useful? I claim the latter. At one level, this observation rather makes the argument moot, but at another level, it does interject a certain level of "reality check" into the scientific process.
My favorite definition is, "reality is that which doesn't go away when you stop believing in it." I forget who said it, sadly. But what I'm saying is, that's the scientific definition of reality. It is circular logic to let science define reality as that which science works on, and then claim that as evidence that science works on reality. The real question is: is there anything real that science doesn't work on? (Take: the origin of the Big Bang, for example.)
Yes, that is very much in the spirit of my intention. But it is for the physicists, too, not just the nonscientists.
Granted-- no doubt this is why we do science when we actually want a paycheck!

Why do we have two different gravities one for GR and one for QM. Surely both would operate under the same gravity if we could pick the right one to fit. Newton up and down or attracting force, Einstein a plane of gravity where up close planets fall into the dip of the planes depression extending beyond the mass.

Has there been a 3D model tested on GR and QM that applies such that density affects both. Sure GR handles it very well but in a 3D gravity QM model wouldn't matter have to shrink or expand just like GR moves structures i.e. orbital velocity v.s. distance.
I did read somewhere once that for the most part matter, the phlogiston is empty. Just as a side question is there anything wrong with a different gravity also effecting QM if that is possible?

I know there is possibly only one supporter for 3D gravity but has it been given a go. Newton got the line, Einstein the plane I sure wouldn't mind going for the bottle.

Cheers

We don't.

QM is blind to gravity.

There is no quantum theory of gravity; or, more precisely, no such theory has been developed and tested yet, to the point where we could call it a viable theory.I don't know what you mean, but it seems you have a quite confused understanding of the two - perhaps you'd like to start a separate thread, "What's the difference between the Newtonian and GR view of gravity?" perhaps?In one reading of this, the answer is "yes!" - that's what modern cosmology is (it incorporates GR and QM, as they apply to real things like electrons and protons). QM enters cosmology via particle interactions, which are described by the standard model (of particle physics); this model is extremely good, but incomplete.If you could point me to a paper which describes this "3D gravity", maybe I could better answer this.

What I would like to see/comprehend is the boundary where this state transition occurs, i.e. zooming in from things to "not things". For example, is the boundary clear-cut or is there an intermediate "quasi-thing" state.

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“He who asks a question is a fool for five minutes; he who does not ask a question remains a fool forever”
Chinese proverb
"All you need in this life is ignorance and confidence - and then success is sure." - Mark Twain.

One attempt at a quantum theory of gravity, is LQG, loop quantum gravity, which quantizes spacetime. Here the familiar Planck length and time appear as the smallest quants of spacetime.

http://en.wikipedia.org/wiki/Loop_quantum_gravity

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“He who asks a question is a fool for five minutes; he who does not ask a question remains a fool forever”
Chinese proverb
"All you need in this life is ignorance and confidence - and then success is sure." - Mark Twain.

And Penrose's twistor theory is another.

As of today, I think the consensus is that LQG may have legs (no knock-out blows have landed yet, nor any heavy hits), but that twistor theory will need to be modified quite a lot if it is to have legs.

Otherwise known as looped gravity.

As I appear to be the only proponent of this 3D gravity it is the effect down to the tenth dimension in quantum mechanics. Gravity is the strong nuclear force by virtue of massively overpowering the natural tendancy of like charge particles from flying apart. It connects fundamentally down to string level.

Its negative field is due to the overall positive nature of the protons in mass which give gravity its cathode like nature. Gravity not a conductor but has an overall capacitor effect due to its relationship with matter. The energy density of gravity is slightly weaker on earth. Please note one of the errors in a previous post due to the Hubble telescope being built on earth the "y" axis was correctly accounted for on Newtonian gravity a pull downwards.

This had the effect of the "x","z" plane shrinking in the higher density gravity of space, increasing the curvature evenly. The correction of the "y" axis vertically on Earth mean't it shrunk also in the higher density of space and was corrected the other way as it was thought to get longer.
The curvature of the lens was equally thought to change marginally.

The gravity density in space is greater than that on earth where we fall into its weakened field, or if you like push gravity. Gravity is hard not so see as coming from matter as it connects down to string level to hold all matter in filaments through ponderous force in organised lines through the galaxy.

So Newtonian up and down, yes we fall into a weakened field.
Einstein has the fall into a weakened field also objects in a plane dropping into the well of gravity that very large objects extend beyond their mass.
3D if a star can bend a ray of light then imagine what 100 billion stars in a galaxy could do ti it.
The effect is to connect through shape so that all mass is connected in a galaxy from string to around the loop of structured space back to string.

Gravity density in 3D will not make you fall. It will if removed have you fly apart at sub molecular level due to the repulsive effect of protons. We are held together by gravity which determines our size.

An interesting side note is that if the results are in from gravity probe B yet there should be echoing of any generated gravity effect every one to eight minutes depending on how many galaxies we link to.

Cheers

I believe Witten is trying to integrate twistor theory with string theory...

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“He who asks a question is a fool for five minutes; he who does not ask a question remains a fool forever”
Chinese proverb
"All you need in this life is ignorance and confidence - and then success is sure." - Mark Twain.

Actually, I am not taking either side here. And you've cleared up something that I (and perhaps Grey) weren't quite sure about.

I too have heard that said, and I like it as well. According to several searches, it's attributed to Phillip K. Dick, an American author.

That wasn't quite what I was referring to. I wasn't addressing the meaning or nature of "global reality", but rather what I thought what was being asked above: along the lines of what are the natures of things scientists call space, time, electrons, protons, photons, etc. And so what I meant is that the physicist/scientist builds working models of nature based on what we observe, and within the realm of scientific inquery that's really all we can say (e.g., about the nature of an electron). Thus no circular argument.

Ah yes, that's it, thanks.
I think that is a perfectly accurate statement of what science does, and I wager that you, I, and Grey all agree on that score perfectly well. I think the issue that is really under consideration, which gets a lot stickier, is that given that we are applying the scientific approach as you've defined it, does this imply that all we ever get out of it is something useful for building bridges and giving ourselves a sense of understanding of "how things work", or do we really get such an understanding of something true in a sense that is outside of the purely scientific approach itself? Put differently, would an alien intellect that is vastly more scientifically advanced say "yes, protons, that concept is so supremely useful that even we see it as very unlikely there is not a great deal of "objective truth" associated with it." I think that's what Grey is suggesting. What I'm suggesting is, they would instead say "ah yes, protons, particles, all that biz-- very useful indeed, and much simpler than the real situation, so much so that we still teach it to our elementary school children. Of course, as they advance past their larval phase, we sequentially bring in the six higher levels of understanding that our approach has evolved through, such that we now think of "proton" as a kind of toy model that works fine in many situations."

To choose a more concrete example, I think Newton's vs. Einstein's gravity is a good one. In 1800, the world's best physicists, it seems to me, would be likely to hold Grey's opinion as applied to Newton's gravity model. It just works too beautifully to not hold at least a kernel of the truth about gravity. But now that we have Einstein's view, isn't it really a vastly different explanation of what gravity "truly" is? Do we not see Newton's gravity as a kind of toy model that we teach introductory physics students because it's simpler than the "real" model? I just don't see that physics ever escapes this conundrum, they're all toy models, when compared to reality. But I share your statement that this isn't a problem for science, because it's exactly what science is supposed to do-- science was never about finding truth in any way outside of how science defines it, which is pretty much in terms of usefulness and quantitative accuracy, rather than philosophical or qualitative content. But we are not always true to this statement when we use science as a bludgeon against other approaches to the most profound types of questions that humanity encounters, questions that fall in the more proper domain of philosophy and religion. (And don't get me wrong, depending on how the questions are phrased, it is often true that philosophy and religion tackle issues that are far better left to science.) To me, the big issue is objectivity, not truth-- if something is objectively determinable, then the approach to use is science. However, the $64,000 question is, are there profound issues worthy of human consideration that do not admit to objective resolution? I argue, certainly yes, riddled throughout the human condition, but some are even at the very edges of science itself-- like the collapse of a wavefunction, or the origin of the Big Bang, or can intelligence ever fully understand itself. The more physics I learn, the more clearly the picture emerges to me that reality involves more than objective science can ever address, even in principle. Thus even as our understanding grows in leaps and bounds, so should also our humility about this amazing place we find ourselves. Or put more succinctly: science has no answer for the problem that the more you know, the more you don't know.

Thanks for those interesting thoughts, although it might be nice to hear from Grey once again.

The noted "problem", which I've bolded, is a strength of the scientific methodolgy of investigating nature, and it is this (and human beings' natural curiosity) that pushes us on to ask more and deeper questions. If we ever come to think we KNOW everything there is to know about a particular phenomenon, science will have ground to a halt.

I once heard somebody say, "as the sphere of our knowledge expands, the surface area contacting the unknown grows still larger", or something like that.

Yes, I second all of those sentiments. I think it is especially important to recognize that these are indeed the strengths of science, but every strength comes with a limitation. Someone with no vertical leap at all can only pretend to have athletic ability, but in pretending, they are superhuman, whereas the best high jumper in the world must come to terms with the fact that he cannot jump a skyscraper no matter how supremely adept he becomes at his art.

Ken G wrote, “. . . science has no answer for the problem that the more you know, the more you don't know.”

Since scientists generally attempt to know, and science in general attempts to know more, would the statement above mean that science is part of “the problem“? If not, then maybe there is no problem in the apparent simultaneous increase in known and unknown. (And is the unknown really a function of the known in this equation?) If so, maybe “reality” is a problem only for scientists who believe they are “working” to increase ignorance. How useful is that, and if the purpose of knowledge is strictly utilitarian, what is the purpose for which it is being used? Is it a useful purpose? What is the use, or purpose, of cosmology? Is it just useful for employing smart apes at large salaries?

The OP appears to be interested in defining “space”, “time” and “energy” in a way that “works” or is “useful” in harmonizing two theories that don’t “work” very well together. Would Ken G agree that the words “space”, “time” and “energy” represent something “real”? If so, would the “reality” exist at an “energy” level that cannot now be probed? Or is it a useless exercise? And would those words ultimately be defined only in mathematical terms and put to “use“? If so, why are forum participants using English words to talk about the idea of reality? Maybe words are useful - science! Maybe thought is useful. Maybe what we imagine is as real as what we imagine to be real. Maybe every imaginative creature holds part of what is real, and the parts we don‘t know are less of a problem than the parts we know, and not knowing why we know is the biggest problem, which may be the problem with scientists and the reason they “work” for people who don’t know. Strangely, the universe may show us its purpose, and if we follow it, we may find our own purpose, and start to put our knowledge to good use rather than a use that may or may not be good (which we in our knowledgeable ignorance cannot tell).

I believe “space” and “time” are units we use to measure events, the assumption being that events follow one another. “Energy” (I believe I have said before) ought to be defined as the ability to move (because at its root I believe that is what it is) which then necessitates spacetime as an effect of energy. Where GR cannot go is to measure spacetime by spacetime. If everything is made of spacetime, GR cannot measure everything. It has to stop where spacetime “lives“, which is in material bodies. If material bodies are “made of” spacetime, how do you measure something with itself? It’s like measuring a ruler with a ruler. If they disagree, which is right? It seems to me that somewhere around the Planck region is where spacetime meets spacetime. Then you have to start dealing with energy itself.

I think one of the things that Grey was trying to convey is that when science does make a leap to a new paradigm or new understanding of the workings of nature, it doesn't do so by "erasing the blackboard" and declaring the previous theory "all wrong". Instead, improvements in our understanding are nearly always built around our earlier understanding of how nature behaves. The new scientific theory is more general (i.e., it explains more phenomena) and has greater predictive power, amongst other useful attributes.

A lot of hot air has been generated by many who look at the historical progress of science and come to the conclusion that there is no progress, that science just invents theories to throw them away in favor of something different, and we therefore essentially know nothing. From the point of view that we live in a rational universe, that is certainly not the case. Perhaps this is in part what Grey was arguing against.

I am not suggesting that you don't understand this, but that perhaps some of the readers might not.

Ok, I've said enough on this digression. ngeo, above, raises some more pertinent points to the original purpose of this thread....

I agree that is what he is saying, and of course science does indeed progress that way, but still the issue is at what point do we admit that a deeply held theory of the past really does not contain even a kernel of "the truth", other than as being a way to achieve much the same answer as "the truth". Another example of this is the geocentric model of the solar system-- was that a kernel of the truth? In some ways, yes, it did hold that planets moved around. But it was not just quantitatively inaccurate, it is now viewed as essentially wrong, that is, wrong in its essence. Usually when we replace a theory that was wrong in its essence, we tend to think the new theory is right in its essence, but the fallacy there is historically evident (as Nereid pointed out earlier).
Yes, well that is just silly postmodernism. The advancement of science is very obvious. What I'm saying is that the advancement means our toy models are getting more sophisticated, like those hypothetical aliens I described. We are more accurate, and more powerful, but not closer to "the truth" because that is so sublime that with each discovery, in one sense we actually get farther from the truth-- by learning how much more sublime things are than we appreciated.
Perhaps, and I don't dispute that at all-- science does advance, no question about that.
Indeed, that must be clarified.

I'll let you find your own answer to this question-- what do you think is the usefulness of cosmology?

Indeed. But my point is, given that the Planck domain is drastically separated from any regime that we have actually probed or tested in any way, I view it as no more than a kind of intellectual pastime to try to make QM and GR compatible at that scale. The point is, what we are saying is, if we take two of the best theories we've ever generated, and because they are so good we drastically extrapolate them way beyond any realm of observational testing, should we really be surprised or bothered that the extrapolations are not compatible? Had they been compatible, quite frankly I'd see it as nothing more than an amusing coincidence anyway, given the extreme qualitative differences in the general approaches of those theories.

In short, I don't see anything wrong in trying to unite QM and GR, in the spirit of yielding a more concise and powerful theory (as far as it goes), but I see the whole issue as being like taking a dog's concept of "master", and a cat's concept of master, and extrapolating them to a description of how they expect humans to act in situations that have no relationship to pets. Then the dog and cat get together to check if their extrapolations are consistent. What difference would it make? What would we think if we overheard them (other than, hey, talking animals!) saying "that's odd, our two extrapolations to expected human behaviors in non-pet interactions are not consistent with each other, that's distressing", or if we heard them say "say, our extrapolations agree on how we expect humans to feel when they listen to opera, for example, all is well with our understanding of humans". What difference would it make, neither a cat nor a dog has any concept of a human perception of opera, regardless of whether or not they are consistent with each other.

There was an interesting thread in General Science on "Theories", you might want to check that out-- all these types of issues were hashed out there.

I'm confused, now you are citing the usefulness of science when a moment ago you objected to that standard.

Indeed, and maybe humans really are just the way dogs imagine us to be. Or maybe not. The burden of proof is on the claim that science really does capture the essence of reality, just as the burden is on those who claim UFOs are real. Mind you, none of that is required by science-- science's self-evaluation standard is that it be useful, not real. Indeed, there's no way to even separate the meaning of those words in science, yet they are different words in nonscience applications.
That is an optimistic and perfectly valid philosophy, and I would equate it on a par with people with optimistic and perfectly valid religious views as well. But they are in the realm of the subjective, not science's realm. You are speculating on what might happen if we play the game of science expertly and by the rules, but science only tells us how we win, not what we win.

This is just the kind of analysis I'm talking about-- when you push our scientific constructs, really push them, what you find quickly is a whole handful of limitations to those constructs. That doesn't diminish their usefulness, but it does diminish their truthfulness.

I'll try to catch up with the thread in a bit (it was busy over the weekend, I see!). But I want to respond to this bit first.
That would be the case if your statment were something like "we can never be sure that our models really reflect reality", which is a statement that I'd agree with. However, I'm challenging your assertion that it's "...overwhelmingly obvious that this is not "really" what reality is doing. It's just a model that works, and often works quite well, amazingly." That's a much stronger claim. Not just that we have not (and maybe can not) prove that a theory really reflects the underlying reality, but that it's obvious that it definitely doesn't reflect that reality. It's especially odd coupled with your amazement that the theory can work so well. What better reason for it to work well than that it does model (at least some) elements of reality, even if not perfectly.

I'm not certain, and I'd actually be the first to saythat the forces seem to be more mysterious than matter, as far as that goes. But at it's most basic, even Newton's model of gravity says that masses will move closer together over time, depending of course on other movement they may have. But it seems like you're claiming that "mass", "movement", "time", and all the other primitive terms used in that statement are themselves not representative of reality, so that the statement itself doesn't really make sense.

Well, that's more or less my point. By claiming that it's obvious that we must be wrong, I think you're assuming just about as much about reality as someone insisting that we must be right. I think a middle ground wouold be more appropriate.

Sorry, not good enough. Yes, I expect you could come up with a model that would predict the results of photons with atoms without referring to protons and electrons. Now, try to come up with a model that can accurately describe and predict not only that, but the quantization of atomic weights, the pattern of the periodic table and chemicacl interactions, the quantization of charge on ions, various types of nuclear decay, as well as fission and fusion, the results of scattering experiments, including ones where we've used opposed beams of protons and anti-protons (or at least, what we think are protons and anti-protons ), and a whole host of other phenomena. Frankly, I don't think it would be possible. The success of the nuclear model of the atom is not just that it explains one thing well, but that it helps understand a wide range of observations that in some cases are remarkably unrelated.

I think we are indeed best to leave discussions of what "mind" is to the philosophers, but I don't think your point logically follows. Even if there's a broader definition of mind, it does not follow that we are "trapped" within our own minds, nor does it follow that our minds are therefore incapable of comprehending reality.

Yes, actually, I would. I think that a model that includes protons and electrons, among other things, is so incredibly accurate and useful precisely because there really are elements of reality that correspond to them. I'd would say that any sufficiently advanced alien species that we might hypothetically encounter, even if they had a development and history of knowledge far different from ours, would have an analogous concept. Now, it's certainly also clear that whatver protons are, exactly, it's pretty strange. They are clearly not like the things that we think we experience in the macroscopic world. What exactly are they like? I'm not sure, but I don't think it's necessary to completely understand somethign in order to claim that it exists.

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Conserve energy. Commute with the Hamiltonian.

We've had this discussion before, of course, and I think this is the crux of the problem. You want a "sensorial visualization" of things at the smallest scales, but I'm not certain that the properties that subatomic particles possess necessarily line up with the senses that we have. Our sensory experience is one of color, motion, sound, light, taste, smell, and so forth. We know right off the bat that some of these don't apply. Smell and taste are both chemical reactions with various molecules, and can't possibly apply at a scales smaller than individual atoms. You'd know I was speaking nonsense if I suggested that an electron tastes salty, or smells like roast turkey. A lot of what we get from sight clearly doesn't apply either. Electrons certainly don't have a color, and though they have something like what we call motion, it's not like the classical sort of path we'd envision. In our previous conversations, it has ended up coming down then to touch and shape. You're convinced that it has to have one, but I'm just not so sure.

But, since you're asking, let me try to give you such a description anyway. So, you've just been shrunk down to a subatomic scale, and you're hanging around the electron cloud of an atom. Let's assume that not only has the size of everything been magnified, but all other properties as well. What do you experience? Well, an electron has an electric charge, so perhaps you'd feel that prickly sensation when your hair stands on end that you feel in the presence of charge. An electron has an intrinsic spin, which would affect magnetic fields. Maybe if you were like a carrier pigeon and could feel which way the fields lines go, you'd be able to sense that, too. What would you see of the electron itself? Well, as far as we can tell, you wouldn't see any kind of shape to it no matter how small you were, though we can't be certain about that. But you probably wouoldn't see much of it anyway. It can't be in a single spot for more than an instant (to do so, it would have to have a definite position as well as a definite zero momentum, which can't be the case at the same time). So perhaps you'd simply catch glimpses out of the corner of your eye where you think you see it briefly, but when you turn around to focus on it, it's not there anymore. I have no idea at all what you might taste or smell. How's that?

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Conserve energy. Commute with the Hamiltonian.

I think it's a fuzzy transition, and it happens just about at the level of atoms. Although there is some atomic behavior that requires quantum theory to describe, for many purposes, individual atoms can be viewed for most purposes as very small macroscopic objects. Interestingly, that's even sometimes true of their components. For example, the correspondence principle says that in the limit of large quantum numbers, you start to approach classical behavior. For the largest atoms, the outermost electrons actually have pretty big quantum numbers, and so they actually behave much more like classical orbiting particles than do their lower quantum number counterparts. I understand that was sometimes helpful in the early days of quantum theory.

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Conserve energy. Commute with the Hamiltonian.

The difficulty is in not allowing the discussion to fall into semantics. If one takes an extremely literal interpretation of the meaning of the words, everything I've said is essentially tautologically true, and given another entirely operational interpretation, then Grey's points come to the fore. So the real question is, what is the meaning that we are using for words like "representative of reality"? To me, the key word there is representative-- science is representative of reality, because it works on reality, but the real question is, does it work on all reality, or just the subset of reality that is actually intellectually and objectively addressible using the methods of science? Look at the questions science addresses-- are these really the only questions that have to do with what is "real"? That seems like quite a stretch to me, is basically all I'm saying. The connection to the OP is, I'm asking, should we really care if two theories are self-consistent in a domain where there are no observational constraints? I think we're taking ourselves too seriously to even make that an important goal.


The reason that I think it would be possible is because in my opinion, reality does it. Take the entire particle concept. Wave functions showed us that particles are not what we think they are, they don't actually have "existence" in the normal sense, instead they have more to do with the way measurements get done, and yield quantized results. So we have a new word, "quantum". We still use "particle" because it's a useful concept for organizing these quantized results of measurements, but we now have a much more sophisticated understanding of the limitations of that word. I would say, the limitations are to the point that reality itself must use a different concept altogether, one without those limitations. That's my basic point-- we generate concepts that work, but every concept has limitations. Reality is not allowed to have those limitations, it has to work perfectly because it is what it is.

Perhaps a statement that we both agree on is that science is the study of the projection of reality onto our ability to make measurements and observations of reality. We must fit reality into boxes that make sense to us, and of course in the process we leave bits out because they don't fit. What you are saying is that as the boxes get better and better and more and more useful, we asymptotically approach a complete understanding of what reality is. Or, if our intellect never reaches convergence on that "full" truth, at least what we do is bringing us closer. What I'm saying is, the very nature of the boxes, the whole basis of this approach, is guaranteed to leave out very important elements of reality. Those elements simply aren't addressible this way, just as the act of projecting a shadow on the wall will always leave out elements of the object being shadowed. It's an inherent part of science, and leaves us with limitations we should study and understand, rather than overextend our concept of truth into realms that science is ill-equipped for. Like the Planck realm, or the origin of the Big Bang, or what happens when a wave function is collapsed, or how intelligence can be used to study itself (sticking to scientific frontier topics-- obviously the realm of art and aesthetics is another one.) Put succinctly: when the observation is impossible, then so is the science.
Fair enough, but I'd still like your opinion on the two examples I've mentioned so far, the geocentric universe and Newton's gravity. Note that both of those could certainly be described as "so incredibly accurate and useful" by the measurement standards of their day. Would you then also say that there really are elements of reality that correspond to them? A lot is hidden in the word "elements", and again we come against semantics. Most likely, there is much to be said for the points that we are both making, so the real issue is, what are the various valid ways to interpret the words we're using such that our arguments have something important to say?

Perhaps one day this hypothesis will receive its test. Not sure that would be such a good thing for the advancement of humanity's knowledge, or humanity itself for that matter!

The way I would have phrased this is, it's clear that whatever element of reality corresponds to what we now conceptualize as a "proton" is really strange, and is clearly not like the macroscopic things that we use concepts like "trajectory" on. But just because measurements achieve quantized results does not prove that reality itself is "made" of quanta-- it just means that if you do a particle number measurement, you get a quantized result, just as if you do an angular momentum measurement, you get a quantized result. Reality can't be bothered by that, because it has to allow the possibilities for different numbers of particles in a given box, in high energy conditions.


And this depends on what means by "exists". I grant you that there is plenty of usefulness in the scientific meaning of this word, that's not at issue. What is at issue is, are there alternative meanings to the word that don't fit into the scientific methodology? The tendency is for scientists to say "no-- if it's real, our science will plumb its depths in time". But I am saying that when we analyze the meanings we are using for these words, we find that the statement is circular. Science never offers a solution to the problem that the more you know, the more you don't know.

Alright, on to more general comments. Spiff, I wasn't sure which side you were on either by your statement. You seemed to be claiming to agree with me, but then making a statement that was closer to Ken's. Ken is right that there isn't really that much difference in our points of view.

Yup, absolutely.

Ah, I see we were both thinking along the lines of what an alien civilization might think, even before I got to this post. Great minds think alike (or is it "fools never differ", I never can keep that straight... ). So I do actually think the former, at least about some things. Other things (the wave equation of quantum mechanics, say), I'm not at all sure. Of course, it's pretty much a speculative or philosophical point, I think, so we're not likely to have much concrete to go by. What I objected to was suggesting that it was obvious that the second must be the case, when I don't think that's necessarily obvious at all.

I'd agree that why forces seem to behave the way they do is something that is less well understood. And that in some sense these are "toy models". But even a toy often has many things in common with the real thing it represents, and that's the question here. Sometimes, of course, we find that two views of how things work that seem to be distinct turn out to be essentially two ways of looking at the same thing. To tie back into the OP, my own guess as far as unifying general relativity and quantum theory is that it will happen when someone figures ouot a way that an exchange of virtual gravitons and a curvature of space can be seen as two different ways of looking at the same thing. I have no idea how you would do that, of course.

I don't actually agree that trying to unify the two would be wholly academic. For example, using just our knowledge of particle physics, we can make predictions about what should have happened when the universe was very hot and dense. From that, we get a prediction about abundances of various elements from a time just a few minutes after the big bang, which can be tested and shown to be in line with what we observe. A theory of quantum gravity would allow us to do something similar, but from an even earlier time.

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Conserve energy. Commute with the Hamiltonian.

Thanks Grey! Good explanation...

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“He who asks a question is a fool for five minutes; he who does not ask a question remains a fool forever”
Chinese proverb
"All you need in this life is ignorance and confidence - and then success is sure." - Mark Twain.

Which is the reason why you can't tell what side I'm on.

Slightly more seriously - I find myself largely in agreement with your arguments, but I find that Ken G's slightly different "spin" brings some interesting light to bear as well. However, Ken G - occasionally some of your statements seem overly Platonic, or at least in my opinion could be mistaken as such. In which case some readers might interpret this in a squishy, post-modernist know-nothingism sort of way. I think this is largely a problem of semantics and perhaps in expressing oneself on short notice in a forum such as this; to this I certainly plead guilty.

We've drifted off the OP - but that's OK, this is a very interesting topic.

(ngeo: I will address your post, in the next day or so, promise ...)

There's one angle which we've only just touched on - changes in the nature of science itself.

We can look back and identify - imperfectly - what elements of 'modern science' we see in the work of the ancients; we can look to the more recent past and see how 'modern science' is continuing to change ... but can we project into the future? With what degree of confidence can we say that what we are doing today, as physics, as cosmology, will be regarded as solid 500 years from now? 5 million?? Or the converse - what will a future Robin Dunbar tease out of the dusty records of the 20th/21st century to show correspondence with the then consensus view of 'modern science' (and point out just a few examples of where it falls way short)?