Today’s Bloggingheads dialogue features me and writer John Horgan — I will spare you a screen capture of our faces, but here is a good old-fashioned link.
John is the author of The End of Science, in which he argues that much of modern physics has entered an era of “ironic science,” where speculation about unobservable things (inflation, other universes, extra dimensions) has replaced the hard-nosed empiricism of an earlier era. Most of our discussion went over that same territory, focusing primarily on inflation but touching on other examples as well.
You can judge for yourself whether I was persuasive or not, but the case I tried to make was that attitudes along the lines of “that stuff you’re talking about can never be observed, so you’re not doing science, it’s just theology” are woefully simplistic, and simply don’t reflect the way that science works in the real world. Other branches of the wavefunction, or the state of the universe before the Big Bang, may by themselves be unobservable, but they are part of a larger picture that remains tied to what we see around us. (Inflation is a particularly inappropriate example to pick on; while it has by no means been established, and it is undeniably difficult to distinguish definitively between models, it keeps making predictions that are tested and come out correct — spatial flatness of the universe, density fluctuations larger than the Hubble radius, correlations between perturbations in matter and radiation, fluctuation amplitudes on different scales that are almost equal but not quite…)
If you are firmly convinced that talking about the multiverse and other unobservable things is deeply unscientific and a leading indicator of the Decline of the West, nothing I say will change your mind. In particular, you may judge that the question which inflation tries to answer — “Why was the early universe like that?” — is a priori unscientific, and we should just accept the universe as it is. That’s an intellectually consistent position that you are welcome to take. The good news is that the overwhelming majority of interesting science being done today remains closely connected to tangible phenomena just as it (usually!) has been through the history of modern science. But if you instead ask in good faith why sensible people would be led to hypothesize all of this unobservable superstructure, there are perfectly good answers to be had.
The most important point is that the underlying goal of science is not simply making predictions — it’s developing an understanding of the mechanisms underlying the operation of the natural world. This point is made very eloquently by David Deutsch in his book The Fabric of Reality. As I mention in the dialogue, Deutsch chooses this quote by Steven Weinberg as an exemplar of hard-boiled instrumentalism:
The important thing is to be able to make predictions about images on the astronomers’ photographic plates, frequencies of spectral lines, and so on, and it simply doesn’t matter whether we ascribe these predictions to the physical effects of gravitational fields on the motion of planets and photons or to a curvature of space and time.
That’s crazy, of course — the dynamics through which we derive those predictions matters enormously. (I suspect that Weinberg was trying to emphasize that there may be formulations of the same underlying theory that look different but are actually equivalent; then the distinction truly wouldn’t matter, but saying “the important thing is to make predictions” is going a bit too far.) Deutsch asks us to imagine an “oracle,” a black box which will correctly answer any well-posed empirical question we ask of it. So in principle the oracle can help us make any prediction we like — would that count as the ultimate end-all scientific theory? Of course not, as it would provide no understanding whatsoever. As Deutsch notes, it would be able to predict that a certain rocket-ship design would blow up on take-off, but offer no clue as to how we could fix it. The oracle would serve as a replacement for experiments, but not for theories. No scientist, armed with an infinite array of answers to specific questions but zero understanding of how they were obtained, would declare their work completed.
If making predictions were all that mattered, we would have stopped doing particle physics some time around the early 1980’s. The problem with the Standard Model of particle physics, remember, is that (until we learned more about neutrino physics and dark matter) it kept making predictions that fit all of our experiments! We’ve been working very hard, and spending a lot of money, just to do experiments for which the Standard Model would be unable to make an accurate prediction. And we do so because we’re not satisfied with predicting the outcome of experiments; we want to understand the underlying mechanism, and the Standard Model (especially the breaking of electroweak symmetry) falls short on that score.
The next thing to understand is that all of these crazy speculations about multiverses and extra dimensions originate in the attempt to understand phenomena that we observe right here in the nearby world. Gravity and quantum mechanics both exist — very few people doubt that. And therefore, we want a theory that can encompass both of them. By a very explicit chain of reasoning — trying to understand perturbation theory, getting anomalies to cancel, etc. — we are led to superstrings in ten dimensions. And then we try to bring that theory back into contact with the observed world around us, compactifying those extra dimensions and trying to match onto particle physics and cosmology. The program may or may not work — it’s certainly hard, and we may ultimately decide that it’s just too hard, or find an idea that works just as well without all the extra-dimensional superstructure. Theories of what happened before the Big Bang are the same way; we’re not tossing out scenarios because we think it’s amusing, but because we are trying to understand features of the world we actually do observe, and that attempt drives us to these hypotheses.
Ultimately, of course, we do need to make contact with observation and experiment. But the final point to emphasize is that not every prediction of every theory needs to be testable; what needs to be testable is the framework as a whole. If we do manage to construct a theory that makes a set of specific and unambiguous testable predictions, and those predictions are tested and the theory comes through with flying colors, and that theory also predicts unambiguously that inflation happened or there are multiple universes or extra dimensions, I will be very happy to believe in the reality of those ideas. That happy situation does not seem to be around the corner — right now the data are offering us a few clues, on the basis of which invent new hypotheses, and we have a long way to go before some of those hypotheses grow into frameworks which can be tested against data. If anyone is skeptical that this is likely to happen, that is certainly their prerogative, and they should feel fortunate that the overwhelming majority of contemporary science is not forced to work that way. Others, meanwhile, will remain interested in questions that do seem to call for this kind of bold speculation, and are willing to push the program forward for a while to see what happens. Keeping in mind, of course, that when Boltzmann was grounding the laws of thermodynamics using kinetic theory, most physicists scoffed at the notion of these “atoms” and rolled their eyes at the invocation of unobservable entities to explain everyday phenomena.
There is also a less rosy possibility, which may very well come to pass: that we develop more than one theory that fits all of the experimental data we know how to collect, such that they differ in specific predictions that are beyond our technological reach. That would, indeed, be too bad. But at the moment, we seem to be in little danger of this embarrassment of theoretical riches. We don’t even have one theory that reconciles gravity and quantum mechanics while matching cleanly onto our low-energy world, or a comprehensive model of the early universe that explains our initial conditions. If we actually do develop more than one, science will be faced with an interesting kind of existential dilemma that doesn’t have a lot of precedent in history. (Can anyone think of an example?) But I’m not losing sleep over this possibility; and in the meantime, I’ll keep trying to develop at least one such idea.
John Ramsden on Mar 20th, 2008 at 7:16 pm
In #40 Lawrence sketched a picture of (if I understand it) one eigenstate dominating the others, which then cancel out and fade into the background.
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The decoherence is related to the unitary inequivalence of vacua. Hawking radiation from black holes and the related Unruh radiation result in thermal states due to this. Technically it is a Bogoliubov transformation. As a result there is a coarse grained thermalization of states and decoherence.
Lawrence B. Crowell
John,
I suppose my point about two arrows of time, with energy and information going opposite directions, amounts to a duality, that, as you point out about dualities, seems whole from either perspective, but like a coin can be turned over and seen from the other side as equally whole. Such as why relativity treats it as a linear dimension, yet it functions as a quality of relative motion.
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Lawrence, John,
Question about string theory; Can strings essentially vibrate away and form at the intersection of vibrations? This would accord with the macrocosmic relationship of process and product, form and function, nodes and networks, nouns and verbs, etc.
“Probability” is not falsifiable per Popperian constructs! I wish I had thought to mention this related issuee arlier, since verification and observability are related. Probability is a very important parameter but “meaningless” by strict construction of the standard of falsifiability! For example, given a claimed 50/50 chance, no particular run of heads or tails could be given as dispositive of that claim – it would just have 1/2^n chance of happening, along a continuum of lesser chance. You could make an arbitrary decision that you couldn’t find the claim credible anymore, but you couldn’t justify drawing the line just there (or at all really, as I explained.) Tough luck! So I don’t want to hear anyone say, “If it’s not falsifiable, it isn’t science” without acknowledging this big fly in the ointment.
John Merryman on Mar 22nd, 2008 at 11:08 am
Question about string theory; Can strings essentially vibrate away and form at the intersection of vibrations? This would accord with the macrocosmic relationship of process and product, form and function, nodes and networks, nouns and verbs, etc.
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There is the M-theory due to Ed Witten, which accounts for various string types according to how they couple to higher dimensional vibrating objects called p-branes. We have vibrating strings, but we can put them on a sound board or instrument which has dimension = 2, such as a violin, piano or guitar. Then the modes of one type of string are compatible with the vibrations on the p-brane, and since these are compatible with vibrations of another string type these p-branes define S or T duality relationships between strings.
There is an interesting comparison between music and strings. A music theorist a couple of years ago found that cord progressions were mathematically isomorphic to orbifolds, which are the manifold of compactified strings. I’d have to dig the reference. I sat down at a piano and played through some of the constructions. Yes I am one of those ever rarer “birds” who has a piano at home.
Lawrence B. Crowell
Lawrence,
It is interesting that String Theory would reflect the relationships of musical chords, though my question is more basic; Are the vibrations a function of the strings, or the other way around? It’s obvious that any particular musical rendition is a consequence of the instrument(and its player) but the creation of that instrument is a consequence of the interest in playing the music and when it is worn out, it will be retired and replaced. So the instrument is equally a consequence of the music. My sense of string threory is that it’s an effort to get beyond the particular focus on particles as the basis of physics and emphasize their activity equally. That the noun is as much a function of the verb, as the verb is of the noun. That there is an institutional bias against this seems to be the elephant in the room. Obviously science is inherently reductionistic, so focusing on the hard parts, rather then the fuzzy stuff, poses a problem, since everything becomes fuzzy if you look hard enough, thus the tendency is to look harder at smaller parts, not accept that in the relationship between being and doing is fuzzy all the way down.
String theory within the context of M-theory is a theory of n-branes for the dimension n = 0, 1, 2, … 11. So what has transpired is that there is now the 0-brane, which is a field at a point. This is a particle. These come about from Chan-Paton factors for open strings “tied” to higher dimensional branes. These endpoints define 0-branes, and there are some ideas that the whole of M- theory can be reduced to sigma models or soliton field theories of these point-like particles. So, … we might in some ways be back to particles.
Strings have an interesting history. The started out as a model for hadrons, and they had a spectrum given by Regge poles. The competing idea was gauge field theory and QCD — it was California’s physics war between Cal Tech and UC Berkeley. Cal Tech generally won, but they did not smash the idea. Two quarks in a meson are bound by QCD gauge fields termed gluons. Gluons carry the “charge” or color for the QCD force and thus attract each other. Hence two quarks in a meson are connected by this gluon-chromo-flux tube. At a distance this looks remarkably like a string. With the Regge trajectories there was this spin = 2 field with stringy properties. Thus the old hadron bootstrap theory was resurrected in string theory.
So what is going on? It almost appears that the same thing is taking place. I also think that the 0-branes and their spinor field content define the spin networks of Smolin and the rest of the LQG mafia, where by the way some of their developments of late involve ribbons and stringy like things. So the 1960s armwrestling match between Cal Tech and Berkeley has in some recherche manner been resurrected and it will be curious to see how this ultimately transpires.
Lawrence B. Crowell
Lawrence,
Through all the details, it still seems as though the intention is to give form to function, to explain the network as extensions of the nodes.
I still think it is a consequence of assuming the linear narrative of time is a physical dimension and any point on it is as subjective as any point in space. The result being higher dimensional strings of process as physical reality, rather than real change.
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Lawrence,
Another example of the issue would be with the dichotomy of the Uncertainty Principle, that you can’t measure both position and momentum of quanta. I would say the notion of position is a fallacy, for if any such particle had an absolute position, its temperature would be absolute zero, so it would esstentially not exist, since measuring it requires some degree of motion. While I’m not an expert on the methods used, it would seem that measuring position actually means measuring force, since by actually stopping the particle, you measure the amount of resistance required to do so. While measuring momentum measures the direction of resistance.
So my argument is the reason reality is fuzzy is because there is no clear distinction between object and action and this applies at all scales. Describing time as a dimension, rather than a measurement, simply tries to make all action a series of objects.
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Fascinating article by a neuroscientist about her experience as victim of a stroke and the insights it gave on the relationship between the left and right hemispheres of the brain and how they process energy and information.
http://blog.ted.com/2008/03/jill_bolte_tayl.php#more
Of course making accurate predictions is not sufficient for a theory to be a good one. But it is necessary. A theory that makes predictions without giving us understanding of the mechanisms involved is far inferior to one that delivers both predictions and understanding. But a theory that makes no predictions is of no use at all. That is simple and should be obvious.
We don’t even have one theory that reconciles gravity and quantum mechanics while matching cleanly onto our low-energy world, or a comprehensive model of the early universe that explains our initial conditions.
I am positive, that you do have such a theory. An observable object over a certain size simply is not effected by quantum physics, because a quantum field is weaker than gravity field. Where’s the link in that?
Qubit
In what Qubit writes above this assumes certain things about the quantum/classical correspondence. Zurek demonstrates that quantum effects have resulted in certain changes in the motion of the Saturnian moon Iapitus. Quantum fluctuations can be amplified by classical effects with Lyapunov exponents.
Lawrence B. Crowell
Neil (Post 80):
Disclaimer#1. I have not read all the posts here so if anyone has already made this point, I apologize for repeating).
Disclaimer#2. I left physics decades ago early in my career for many reasons, but I now conduct clinical work in inflammatory diseases and cancer, so I encounter similar problems in my field. Many people put out both testable and un-testable speculations, but in our case the regulatory environment limits us from going too far. Despite this, some really unlikely speculations are entertained and studies conducted, all due to the influence of a few well known and powerful people. They are bright and honest, yet end up producing what some would uncharitably call “bullshit.” I for one, see it in terms of human fallibility, nothing else.
The Popperian construct (at least these days) refers to actual experiment that can be conducted to prove or disprove something. In other words, it is not just about a mathematical abstraction like “probability”. Mathematics is a tool or a means to an end in the physical sciences, something you imply as well. If probability simply refers to the likelihood of an event from happening and nothing more, a Popperian analysis should not apply to the abstraction itself. Taking this a step further, anything goes as long as it has a non-zero probability. Could you imagine the number of crackpot contentions that will demand attention? I am not implying that String Theorists are cranks, just that they have badly oversold it. In that sense, both Woit and Horgan are right. Nonsensical theories can sometimes produce occasional predictions that come out true, but that is no reason to go after it. This where Truzzi and his band go off in their Zetetic discussions and end up entertaining ESP, Homoeopathy, paranormal, Velikoskian stuff etc., all in an attempt to be neutral or agnostic as he calls it. And the rest of us are called pseudo skeptics to boot. Some things have to be rejected outright, because they don’t fit in with elementary logic and reason i.e., what we call science. In that sense, I don’t see any fly in the ointment.
Every hardware has its definite software:
Cosmic Equator of self-contradiction (pair of everything), is the Absolute Logic of self-creation and Gluon of All in all. – Aiya-Oba.
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