The Trouble With Physics

[exile]

Now you've got me thinking. Most specifically about loop quantum gravity. If the theory might have difficulty quantizing gravity into 3+1 dimensions without creating matter and energy artifacts what does it do with antimatter?

You know, I don't really know how loop quantum gravity is supposed to work; all I know is that it's built on a quantized geometry and in effect treats space as a quantum field. But how it does that, and what the final theory looks like...
I really don't know. Elder probably has a much better idea about this, or Arni...

 

[Steel Tiger]

You know, I don't really know how loop quantum gravity is supposed to work; all I know is that it's built on a quantized geometry and in effect treats space as a quantum field. But how it does that, and what the final theory looks like...
I really don't know. Elder probably has a much better idea about this, or Arni...

I've just been reading about it and I have to say I don't really know how it works either. It appears to be a mathematical beast and making predictions with it is extremely difficult computationally. Looks like it is in a similar corner to string theory at the moment, just on the other side of the room.

One thing I did find intriguing was the idea that under LQG the quanta of spacetime are described as discrete. This means that some analogies with fluids are drawn for spacetime. This brings into play group field theory and condensed matter physics uhohh:). I'd like to see where that goes.

 

[Makalakumu]

You got it, Lisa.

The payoff (and not in a good sense) is going to come a couple of decades down the line, when the lack of alternative research (because people now who are pursuing alternatives aren't getting jobs, or postdocs, or research funding, due to the stacked-deck aspect of hiring committees, grant review panels and so on) will leave the field without any way to backtrack to different approaches that might actually prove predictively effective. The field seems to be killing itself by failing to encourage what has always been essential in science: simultaneous pursuit of multiple alternative lines of explanation. That's almost always how we've made progress in the past: a kind of adversarial model (in the legal sense), where people have argued both sides, or all three, or four sides, of a question till the majority of the onlooker finally decided where the most profitable line of future development lay. We don't have that situation now. If string theory continues to go nowhere, there just isn't enough demography supporting any alternatives for the field to actively develop these alternative lines. And the current harsh conditions for non-stringers will drive a number of those who do currently pursue alternatives out of the field, eventually...

This really gets to me because my own field, theoretical syntax, is in exactly the same situation, and has been for the better part of half a century. We may actually be a little better off than the physics community, but the sociology and economics are very, very similar....

What people like Woit and Smolin are calling for isn't abandoment of string theory; they just want some intellectual honesty from the string theorists about the grave foundational problems that 'theory' (it's not, by consensus on both sides of the argument, actually a real theory at this point!) faces. And they want the kind of monoclonal cultivation of physics that seems to become the norm to be replaced by the contending-schools-of-thought model where different view clash and bang against each other till the last one standing can legitimately claim the prize. But that's not what's happening, and the prospects are bleak for the situation they're describing ending any time soon.

...and along comes a patent clerk...

Maybe that's wishful thinking on my part. I am just now starting to take my first steps into academia scientia. My graduate school work will be in geology, however, I still want to beleive that people with powerful ideas make a difference.

I'm a little afraid of your reply, Exile, because I am so prone to cynicism and I am taking the first steps on this journey...

 

[Makalakumu]

Well, as "somebody" stated here years ago :lol:, if it's unmeasurable, and untestable, it's not a theory. It's a "metaphysical wonderland."

I'm not a proponent of string theory or any theory that can't be tested in the regular scientific way. However, I do feel the need to throw out the proposition that perhaps homo sapiens are grappling with concepts that are far beyond or technologic ability to comprehend.

Our language ability is so limited that we cannot hardly even talk about this subject without contradicting ourselves. (wave/particle dualtiy anyone!) Heck, our mathematics, when you consider the history of how this feild has developed, it's almost like a cut a paste collage of concepts.

Some of the questions being addressed by String Theorists are salient, but we really may need to consider the bigger picture in all of this. See the Kardeshev Scale. Humans aren't so great. We are just a fraction of the the skim of life that inhabits the pale blue dot.

E.O Wilson calculated that every human on earth could fit within the volume of the grand canyon.

 

[elder999]

I'm not a proponent of string theory or any theory that can't be tested in the regular scientific way. However, I do feel the need to throw out the proposition that perhaps homo sapiens are grappling with concepts that are far beyond or technologic ability to comprehend.

Our language ability is so limited that we cannot hardly even talk about this subject without contradicting ourselves. (wave/particle dualtiy anyone!) Heck, our mathematics, when you consider the history of how this feild has developed, it's almost like a cut a paste collage of concepts.

Some of the questions being addressed by String Theorists are salient, but we really may need to consider the bigger picture in all of this. See the Kardeshev Scale. Humans aren't so great. We are just a fraction of the the skim of life that inhabits the pale blue dot.

E.O Wilson calculated that every human on earth could fit within the volume of the grand canyon.

Naah-optimistically, I did say some goood maths had come from it, and I did point ouit that the aether theory led to the Lorentz transforms, which led directly to Einstein's work on relativity...

or, as you said earlier, along came a patent clerk. :lol:

On any case, you're partly right- we are wrestling with concepts far beyond our technological ability to comprehend. We always have been; it's called science.

Better computers, new models for measuring, hypotheses about what sort of data we can observe around certain phenomena-all these things could lead to an ability to at least partially measure,test, prove or refute portions of string theory-at which point, it will be a real theory, rather than a mathematical conceit that leads to a "metaphysical wonderland."

 

[exile]

Maybe that's wishful thinking on my part. I am just now starting to take my first steps into academia scientia. My graduate school work will be in geology, however, I still want to beleive that people with powerful ideas make a difference.

I'm a little afraid of your reply, Exile, because I am so prone to cynicism and I am taking the first steps on this journey...

No, you're in a good position, UpN. Geology, and planetary science more generally, is in a very exciting time in its history, I gather. Work on the detailed structure of the planetary core, and its connections with complex processes at intermediate layers, is beginning to reveal a very strange, intricate set of connected structures showing the physical architecture of the planet to be much richer and more complex than people had previously imagined. And there are very powerful mathematical techniques, imaging devices and software environments available now that can lead to rigorous, testable hypotheses... with the right admixture of imagination and insight (always the hard part, of course...)

I
Our language ability is so limited that we cannot hardly even talk about this subject without contradicting ourselves. (wave/particle dualtiy anyone!) Heck, our mathematics, when you consider the history of how this feild has developed, it's almost like a cut a paste collage of concepts.

Well, actually the wave/particle duality is one of the better understood aspects of quantum mechanics; it really follows from what's call the formal axiomatic formulation of QM. There are six of these axioms, or postulates (or five, or seven, depending on how they're formulated). First of all, all information about a physical system is encoded in something called a state vector, whose time evolution under ordinary nonrelativistic conditions is specified by something called the Schrödinger Equation. A state vector is an abstract entity defined in an infinite-dimensioned space of complex numbers called a H(ilbert) space, whose vectors have certain very nice, mathematically tractable properties. Each 'dynamical variable' of classical mechanics corresponds to a particular mathematical operator defined on vectors (vectors being certain complex functions of real variables, functions with those nice properties) in this H-space. [WARNING: observables like position and energy in classical physics correspond to things, to entities, in a way that we can understand intuitively; observables in H-space representations correspond to nothing we can relate to intuitively. Momentum, for example, isn't mass times velocity, but rather the partial derivative operation. We don't actually observe observables, in QM; we measure certain numbers that are the outcome of applying those mathematical operators to vectors. Very unintuitive.] For each such operator O, there is a class of vectors (with those nice properties! ) ø-1, ø-2... such that Oø-n = c-n ø-n with the c's (so-called eigenvalues of ø-n) all real numbers (you know how for example the first derivative wrt x of the logarithmic base e, say eˆ(3x) winds up just multiplying eˆ3x by 3? So that means that eˆ3x is an eigenfunction of the operator (d/dx), since applying that operator to the function eˆ3x just multiplies this function by 3. The second of the axioms, or postulates, of the formal theory of QM states that every H-space operator corresponds to a dynamical variable of the system, and every eigenvalue c-n of an eigenvector ø-n is a measurable value for the dynamical variable corresponding to O. Now remember, the state vector is the only source of information about the properties of the state. It follows from the third axiom of QM, which is a bit too mathematically complex for this site's text display capabilities, that only when the state vector coincides with some eigenvector ø-j of a particular operator corresponding to some variable (e.g. position, momentum, angular momentum, energy, etc.) will there be a probability of 1 for measurement of the eigenvalue c-j of ø-j. If the state vector does not coincide with ø-j, then c-j exists only as a possible value in a smear of probabilities. That's the mathematical background, and it's actually pretty clean. But look at what follows: assume that ø-j is an eigenvector of position. If the state vector happens to coincide with ø-j, then the nature of the operator corresponding to the position operator ˆP, which takes this eigenvector as its function, turns out to yield a real number as the eigenvalue, corresponding to a defined position in space with the value c-j. But if the state vector coincides with an eigenvector of the momentum operator ˆM, then the eigenvalue will turn out—because of what the eigenvectors of the momentum operators have as their mathematical form—to display values corresponding to a periodic function, i.e., a wave, because that is what the momentum eigenvector functions look like mathematically. Thus, the wave/particle 'duality' is nothing more than the fact that the form that the wave function takes is intrinsically indeterminate and unconstrained: under certain conditions it can be forced by the measurement setup to coincide with the eigenvectors of ˆP and under others it can be forced to coincide with one of the eigenvectors of ˆM.

When this rough sketch is fleshed out and made explicit and rigorous, it really corresonds to an extension of ordinary language, and we can indeed talk about wave/particle duality rather easily. That doesn't mean we can understand it, but that problem isn't restricted to the very small quantum range; geneticists used to be able to talk about combinatory genetics without understanding what was going on, because Mendelian genetics was worked out long before the molecular structure of the macromolecule chains, DNA and RNA, whose replication is the basis for the transmission of biological properties over the generations, was known.

Naah-optimistically, I did say some goood maths had come from it, and I did point ouit that the aether theory led to the Lorentz transforms, which led directly to Einstein's work on relativity...

or, as you said earlier, along came a patent clerk. :lol:

On any case, you're partly right- we are wrestling with concepts far beyond our technological ability to comprehend. We always have been; it's called science.

Better computers, new models for measuring, hypotheses about what sort of data we can observe around certain phenomena-all these things could lead to an ability to at least partially measure,test, prove or refute portions of string theory-at which point, it will be a real theory, rather than a mathematical conceit that leads to a "metaphysical wonderland."

What's really needed are predictions that don't require access to energy regimes comparable to those in the Big Bang or very early universe, or even supernova conditions. Something that the LHC would be able to see, say, would do nicely....

 

[Makalakumu]

No, you're in a good position, UpN. Geology, and planetary science more generally, is in a very exciting time in its history, I gather. Work on the detailed structure of the planetary core, and its connections with complex processes at intermediate layers, is beginning to reveal a very strange, intricate set of connected structures showing the physical architecture of the planet to be much richer and more complex than people had previously imagined. And there are very powerful mathematical techniques, imaging devices and software environments available now that can lead to rigorous, testable hypotheses... with the right admixture of imagination and insight (always the hard part, of course...)....

My particular field of study happens to be volcanlogy, however, depending on who has grant money, I may move into that area. Such is the nature of real science...

Well, actually the wave/particle duality is one of the better understood aspects of quantum mechanics; it really follows from what's call the formal axiomatic formulation of QM. There are six of these (or five or seven, depending on how they're formulated. First of all, all information about a physical system is encoded in something call a state vector, whose time evolution under ordinary nonrelativistic conditions is specified by something called the Schrödinger Equation, an abstract entity defined in an infinite-dimensioned space of complex numbers called a H(ilbert) space, which has certain very nice, mathematically tractable properties. Each 'dynamical variable' of classical mechanics corresponds to a particular mathematical operator defined on vectors (vectors being certain complex functions of real variables, functions with those nice properties) in this H-space. For each such operator O, there is a class of vectors (with those nice properties! ) ø-1, ø-2... such that Oø-n = c-nø-n with the c's (So called eigenvalues of ø-n) all real numbers (you know how for example the first derivative wrt x of the logarithmic base e, say eˆ(3x) winds up just multiplying eˆ3x by 3? So that means that eˆ3x is an eigenfunction of the operator (d/dx), since applying that operator to the function eˆ3x just multiplies this function by 3. The second of the axioms, or postulates, of the formal theory of QM states that every H-space operator corresponds to a dynamical variable of the system, and every eigenvalue c-n of an eigenvector ø-n is a measurable value for the dynamical variable corresponding to O. Now remember, the state vector is the only source of information about the properties of the state. It follows from the third axiom of QM, which is a bit too mathematically complex for this site's text display capabilities, that only when the state vector coincides with some eigenvector ø-j of a particular operator corresponding to some variable (e.g. position, momentum, angular momentum, energy, etc.) will there be a probability of 1 for measurement of the eigenvalue c-j of ø-j. If the state vector does not coincide with ø-j, then c-j exists only as a possible value in a smear of probabilities. That's the mathematical background, and it's actually pretty clean. But look at what follows: assume that ø-j is an eigenvector of position. If the state vector happens to coincide with ø-j, then the nature of the operator corresponding to the position operator ˆP, which takes this eigenvector as its function, turns out to yield a real number as the eigenvalue, corresponding to a defined position in space with the value c-j. But if the state vector coincides with an eigenvector of the momentum operator ˆM, then the eigenvalue will turn out—because of what the eigenvectors of the momentum operators have as their mathematical form—to display values corresponding to a periodic function, i.e., a wave, because that is what the momentum eigenvector functions look like mathematically. Thus, the wave/particle 'duality' is nothing more than the fact that the form that the wave function takes is intrinsically indeterminate and unconstrained: under certain conditions it can be forced by the measurement setup to coincide with the eigenvectors of ˆP and under others it can be forced to coincide with ˆM.

When this rough sketch is fleshed out and made explicit and rigorous, it really corresonds to an extension of ordinary language, and we can indeed talk about wave/particle duality rather easily. That doesn't mean we can understand it, but that problem isn't restricted to the very small quantum range; geneticists used to be able to talk about combinatory genetics without understanding what was going on, because Mendelian genetics was worked out long before the molecular structure of the macromolecule chains, DNA and RNA, whose replication is the basis for the transmission of biological properties over the generations, was known.

What's really needed are predictions that don't require access to energy regimes comparable to those in the Big Bang or very early universe, or even supernova conditions. Something that the LHC would be able to see, say, would do nicely....

You are probably the perfect person to present this idea to, so I'll shoot. The semiotics involved in both mathematics and language doesn't seem to mix. When I try to break a simple equation down into a sentance, the language that we use to describe such a thing. All of the options presented by simple algebraic manipulation are obfuscated by the simple words that we utter.

Their seems to be a disconnect between the language that we speak and the mathematic way we view the universe.

 

[Ninjamom]

..It does seem to me ... that mathematical elegance is starting to overtake predictive content as a primary yardstick for the worth of a new theory. .....if a theory admits to no way for it to be tested and disproven then, ...that's not science.

...... The mathematics involved are novel and frighteningly difficult (way more difficult, if I understand what I've read, than the differential tensor geometry that Einstein appropriated from a couple of late-19th century Italian mathematicians as the geometric language which he needed for general relativity, though at the time that was regarded as being at the limits of comprehensibilty, at least so far as working physicists were concerned...

Naah-optimistically, I did say some goood maths had come from it, and I did point ouit that the aether theory led to the Lorentz transforms, which led directly to Einstein's work on relativity...

These three points together paint a somewhat rosier picture than what you gentlemen have been worrying about (at least for me, but then I do tend towards the optimistic side of things).

I have always seen mathematics, in every case of a major scientific breakthrough, as being an answer in search of a good question. Mathematics provide more tools in the tools box. Elegant maths provide power tools on steroids. It is the job of the real scientists to select the right tool from the toolbox that seems to mirror the actual physical behavior of the observable universe. Hence, the division between abstract mathematics and applied math/science is no more or less than what is done with the disproveable hypothesis (good ol' fashioned 'scientific method').

The fact that good maths are coming out of this quest encourages me that good answers will be found - we might just have to change our original question.










Oh,........ and 42

 

[exile]

My particular field of study happens to be volcanlogy, however, depending on who has grant money, I may move into that area. Such is the nature of real science...

Vulcanology... outstanding! I've always been drawn to the more violent aspects of nature (when I was a student, I was thinking for a long time that I would become an astrophysicist/cosmologist, and the violence out there is as violent as it gets; but on Planet Earth, volcanos are about the best we can do, eh?) I lived in Victoria, British Columbia for many years and heard Mt. St. Helens explode that fateful morning—the acoustic shock wave bounced between atmosheric layers of different densities, apparently, so many people much nearer that part of the Oregon coast never heard it (because they were in the wrong part of the bounce pattern), while for us, on Vancouver Island, it sounded like a major train wreck going on in the living room of the people downstairs. I sincerely hope you get to stay with volcanos...

You are probably the perfect person to present this idea to, so I'll shoot. The semiotics involved in both mathematics and language doesn't seem to mix. When I try to break a simple equation down into a sentance, the language that we use to describe such a thing. All of the options presented by simple algebraic manipulation are obfuscated by the simple words that we utter.

Well, part of the problem is that the kinds of relationships that mathematics presents exist outside any chronology: the proof may involve steps, but the relationships all hold simultaneously. And that defies our own real-time perception, in which we sequence things based, in many respects, on the order in which we perceive them, and where before and after really do apply to components of the physical world. And it's true, a lot of mathematical operations correspond to things that absolutely no correspondence with normal experience. An integral—the infinite sum of a set of areas whose width in one of its dimensions is infinitely close to zero? An complex number? A complex function as the exponent of a variable? What the hell do any of these things mean, or correspond to in our experience? But language is something which is intimately connected with the way we partition the world into manipulable units; it couldn't work if it had the kind of unimaginable qualities that so many mathematical structures have.

What happens, I think, is that people who use mathematics as a tool for understanding reality eventually develop a way of thinking about that reality, on the basis of the extension mathematics provides to our ordinary language of experience, so that what seems alien and unacceptably bizarre when you talk about it without benefit of mathematics becomes almost homey and familiar if you allow yourself use of those formal tools. For a lot of wine afficionados, for example, use of certain domains of description—fruit flavors, herb flavors, suggestive adjectives such as 'minerally' and so on—are essential for them to express their experience of wine flavors. They know exactly what they're trying to communicate, but because of the somewhat odd nature of our physical sensoria, it's hard to talk about complex flavors like wine without making certain key comparisons to more familiar kinds of flavor. I think of mathematics in the hands of physicists in much the same way...

Their seems to be a disconnect between the language that we speak and the mathematic way we view the universe.

See, the way I would put it is, the strangeness of the universe, much of which is at odds with our built-in sensory expectations, and the categories we build top of those expectations, become reduced to something like familiary, or at least considerably reduced strangeness, if we can recruit the equally strange language of mathematics, tame that and turn it into a tool, and develop it into an extension of our 'normal' use of language. Set a thief to catch a thief, in effect...

The fact that good maths are coming out of this quest encourages me that good answers will be found - we might just have to change our original question.

Well, yes; and that is almost certainly what the head-against-brick-wall effect currently stalking the the string theorists is try to tell us. I think progress is possible in principle; my real worry is that the sociology of academe, and the way in which research funding has become both so centrally controlled and so scarce, will jointly reduce the critical mass we need of working physicists who can backtrack from the limb that physics has been edging itself further and further out on for the past couple of decades or more.

And yes, our old friend 42... but the truth is, it's almost certainly not 42; it's much more likely to be 137! Read on here!

 

[Sukerkin]

The fact that good maths are coming out of this quest encourages me that good answers will be found - we might just have to change our original question.

What do you get when you multiply six by nine?

Oh,........ and 42

 

[Sukerkin]

it's much more likely to be 137! Read on here!

{click}add to Favourites/Academic{click}

Cheers for that Bob and also for shaking my brain about and getting those synapses firing again :tup:.

 

[exile]

{click}add to Favourites/Academic{click}

Cheers for that Bob and also for shaking my brain about and getting those synapses firing again :tup:.

You're welcome, Mark, and thanks back to you for helping drive this great, crazy thread along....

as a sidelight on that, I read in a collection of physics humor—A Random Walk in Science I think it was called—that the three physicists George Alpher, Hans Bethe and George Gamow, as a prank, collaborated on a short note involving a ridiculously complex (and, of course, carefully contrived) calculation in quantum theory which wound up yielding 137 as the value of one of the coefficients—and given that that's a prime number, that would have been a tour de force all by itself!—and submitted it to a journal of which Eddington was one of the editors, just to tease him... it's not clear that Eddington ever got the joke, or the fact that the author names would have come out Alpher, Bethe and Gamow... AE was a very earnest, serious, scholarly man.... :lol:

 

[Makalakumu]

Time for a larger picture. Isn't this a problem with science in general? Take a look at how scientific research is manipulated in the US in order support policy. One gets the impression that the entire edifice is crumbling.

Science says what the government pays for...

 

[exile]

Time for a larger picture. Isn't this a problem with science in general? Take a look at how scientific research is manipulated in the US in order support policy. One gets the impression that the entire edifice is crumbling.

Science says what the government pays for...

I think that's really a separate problem. The government really has no interest in this stuff whatever; if they did, they'd have funded the superconducting supercollider. There is no spinoff technology foreseeable from string theory for many, many generations, if ever; even the Standard Theory has no technological implications. There's no public policy issue connected with the rivalry between loop quantum gravity and string theory, or anything like that. The problem here is that the standard theory has provided a formalism and a set of field equations which have been confirmed in every single solitary experiment that's been carried out over the past 30 years. The data pool that could possibly challenge the theory seems to be dried up, in the existing energy regime, and there won't be any new data a-coming till the next generation of large colliders is built. And the way it looks, there are certain questions that we simply cannot build a machine large enough to create energies at the range that would supply the answer to. This is a case of being a victim of your own success, with a vengeance. So what's left?

In the past, empirical phenomena always guided the forward thrust of science. Planetary movements in the 17th and 18th century, the relationship between electrical currents and magnetic phenomena that ultimately led, through Faraday's experimental work, to Maxwell's equations; the problem of blackbody radiation, radioactivity, and the scattering of electrons that led to the first quantum theory, and so on and on... in every case, theory was pushed to its limits by new observations. But an ominous element came in with the work of Dirac on the quantum theory of the electromagnetic field, where essentially mathematical considerations led Dirac to propose a wave equation of a radically different type than the celebrated Schrödinger equation (which has the look of a classical wave equation, at least). Dirac's equation required far more mathematical virtuosity to solve; but the solution was highly productive—it predicted antimatter particles, observed a few years later—and reconciled quantum theory with special relativity. A lot of physicists, however, seemed to get the idea from Dirac's work that the right tack was to aim for mathematical elegance, something you can tolerate as long as there's a steady stream of frustrating new data to keep physicists honest and force them to give up beautiful but wrong ideas on a regular basis.

But all that changed when the stream of crucial new experimental results stopped coming in because we had reached the limit of the energy ranges possible with our current accelerators, and because we had gotten to a point where to go one level of explanation deeper, we would need to tap an energy range enormously greater than anything we could conceivably build in the next century or so. After a while, it became evident that all we were doing was repeating the same kind of experiments that had supplied crucial impetus for the terrifically successful Standard Theory, linking the electroweak (electricity/magnetism + the weak nuclear force) field with quantum chromodyanmics (the strong nuclear force). So now physicists could indulge their lust for super-difficult, elegant theory to their heart's content, without fear of being brought up short by unpleasant confrontations with facts. And so far as I can see, that's the real lesson of string theory's cul-de-sac: you can't get by on formal elegance alone. Much as we might hate to admit it, sometimes sheer beauty isn't enough of a reason to abandon our critical scrutiny of some idea and just go with it....

 

[mrhnau]

I think that's really a separate problem. The government really has no interest in this stuff whatever; if they did, they'd have funded the superconducting supercollider. There is no spinoff technology foreseeable from string theory for many, many generations, if ever; even the Standard Theory has no technological implications.

Caused simply by the lack of insight by those physicist, or do you think generations will not find practical applications in time?

Enjoying the convo btw

 

[exile]

Caused simply by the lack of insight by those physicist, or do you think generations will not find practical applications in time?

Well, this is all very speculative, but the technological problem seems to be that even if you could prove string theory, what you'd basically be getting as a benefit was something you already have—namely, the standard theory, but now with the latter enjoying the status of a theorem, rather than something you just have to bite the bullet and accept as Just The Way It Is. You'd know why it is that we have what already have, but the reason has to do with stuff going on at the Planck scale, therefore essentially inaccessible to any manipulations we can carry out, because of the the uncertainty principle: nothing we try to do at that level of smallness can ever be certain to do what we want to do, even if we knew what that was. There are no 'tools' that can serve as probes at that level, where space and time themselves may well turn out to be granular. If there were some way of using string theory to change the properties of matter in ways that met our specifications, you could maybe imagine an application, but given that the extra dimensions in S.T. are compactified into size ranges at such unimaginably small scales, it seems very unlikely that we'll ever be able to do anything that involved them. And that leaves us with just the four familiar dimensions of spacetime that we already know and love... so I don't see how we'll get anything out of S.T. that we can actually use to have an impact on the physical world.

(And this is all predicated on the assumption that S.T., or some other grand unification theory, can be established, or at least made plausible... and that is One Big If, eh?)

Enjoying the convo btw

Nice to hear from you, incidentally!

 

[mrhnau]

Well, this is all very speculative, but the technological problem seems to be that even if you could prove string theory, what you'd basically be getting as a benefit was something you already have—namely, the standard theory, but now with the latter enjoying the status of a theorem, rather than something you just have to bite the bullet and accept as Just The Way It Is. You'd know why it is that we have what already have, but the reason has to do with stuff going on at the Planck scale, therefore essentially inaccessible to any manipulations we can carry out, because of the the uncertainty principle: nothing we try to do at that level of smallness can ever be certain to do what we want to do, even if we knew what that was. There are no 'tools' that can serve as probes at that level, where space and time themselves may well turn out to be granular. If there were some way of using string theory to change the properties of matter in ways that met our specifications, you could maybe imagine an application, but given that the extra dimensions in S.T. are compactified into size ranges at such unimaginably small scales, it seems very unlikely that we'll ever be able to do anything that involved them. And that leaves us with just the four familiar dimensions of spacetime that we already know and love... so I don't see how we'll get anything out of S.T. that we can actually use to have an impact on the physical world.

(And this is all predicated on the assumption that S.T., or some other grand unification theory, can be established, or at least made plausible... and that is One Big If, eh?)

I am thinking less of direct string manipulation, but rather filling out the holes left by the ST. Might we uncover some useful tidbit of previously uncharacterized physics that might prove useful for current global issues? Garner a deeper understanding of and master nuclear fusion perhaps? Map missing/unknown particles/mass? Find some way of detecting gravity waves? Find/Manipulate wormholes perhaps?

I think direct string manipulation is way down the road, if it is even possible... Unless we have some dramatic breakthrough, it sure won't be in my lifetime.