In a couple of days, the final results on the search for the Higgs boson at CERN will be publicised, so in the meantime, I would like to dwell a bit on what comes after. Indeed, if the Higgs is found, this will only have confirmed, once more, that the Standard Model of Particle Physics was right, and was able to predict the existence of a new, exotic particle.
But the Standard Model has been around since the 70s, and, for all its predictive power in particle physics, it suffers from major shortcomings: for instance, it becomes completely inappropriate when dealing with gravity. For this reason, most of the work of theoretical physicists for the last 40 years has endeavoured to find a deeper, all-encompassing theory, a Grand Unified Theory (a GUT...).
One of the serious contenders for the title today is superstring theory, a rather elegant theory that postulates that all known phenomena are actually manifestations of the vibrations of microscopic strings (too small to be observed with our present technology), in nine or 10 dimensions of space.
Fascinating on a purely aesthetic level (as Brian Greene puts it, the Universe of string theory is "nothing but music"), this theory has also sparked a truly interesting controversy in the physics community, best illustrated by the publication in the past decade of books such as The Elegant Universe (Brian Greene) or The Cosmic Landscape (Leonard Susskind) on the "pro-string" side, and The Trouble With Physics (Lee Smolin) or Not Even Wrong (Peter Woit) on the other side (Greene's and Smolin's books especially provide a good, balanced overview of the subject).
Indeed, string theory today occupies a rather unique position in the world of theoretical research: it has, for nearly 30 years, concentrated the efforts of hundreds among the brightest physicists of our generation, and yet has still, as even string theorists themselves admit, not been formulated definitely in the form of a unique set of equations, making equally unique (and falsifiable) predictions, which is how most scientists define a physical theory. In fact, the name "string theory" is somewhat misleading, in that the "theory" today is more of a set of intuitions and ideas on what the end product may look like (although it must be conceded that even in its incomplete form, some rather interesting predictions have been extracted from it, such as those concerning black-hole entropy).
This curious state of affairs has led scientists to adopt different attitudes towards string theory: some claim it is "not even wrong", in that it can, in its current form, neither be proved nor disproved using experimental data, while others believe that eventually a unique theory will emerge, making predictions about our world, but that this would necessitate a better understanding of the theory than we have today.
An even more extreme attitude (though more marginal) is that string theory is right, but that humans are simply not clever enough to grasp it fully, the argument being that if you asked a dog to understand even rudimentary physics, this would prove beyond its intellectual means, so that in the end there is no reason why the human mind should not possess similar limits in understanding the physical world.
This last example is of course quite extreme, but usefully illustrates one of the most common reproaches made to string theorists: they have come up with something that is nothing more than an interesting hypothesis, and when they find that this hypothesis leads to unmanageable equations, they try and change the "rules of the game" rather than admit they have hit a dead end, which raises the question as to whether or not string theory may actually be damaging to science.
Indeed, although the idea that string theory will eventually prove beyond the grasp of humans is not one shared by the majority of the string community, the fact that some scientists are in such awe of their own creation that they are willing to believe it true but ineffable does reveal an alarming streak of fanaticism in this area of research.
But, in the end, what must be borne in mind is that the over-confidence of some string theorists is simply the result of their brainchild being "the only game in town" (or if not the only one, certainly the most popular), and unfortunately, as Lee Smolin argues in his book, this has got more to do with academic sociology than science...
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How the Discovery of the Higgs Boson Could Break Physics | Wired ...
Having said that, it may have quite a bit of significance for physics. Maybe not as a theory of everything, quite yet, but it's certainly an interesting stepping stone on the way to such a theory.
I have no objection to all those very smart people spending their days trying to work something out that they have not quite managed to do yet... and they can keep doing that as long as they like so long as they don't try and change the definition of what "worked out" means to shift the goalposts and claim success when they have not succeeded.
Success is formulating a theory that makes real, testable, falsifiable predictions and thus demonstrates real explanatory power... and then following through on the testing and figuring out if they are right or wrong. That is the goal line and you do not get to move it and still call yourself a scientist. You abandon the falsifiability requirements of science and you have just switched to doing religion instead.
String theory is clearly falsifiable, so that's not even an issue.
"so long as they don't try and change the definition of what "worked out" "
String theorists make no such scientific claim. So, that, again, is nothing to be concerned about.
"Success is formulating a theory that makes real, testable, falsifiable predictions and thus demonstrates real explanatory power."
And string theory is not a theory but a model that people work on because it has some really interesting properties. It does not have any explanatory power right now. So that's all pretty dandy, too.
"That is the goal line and you do not get to move it and still call yourself a scientist. "
Working on far out models does not exclude you from being a scientist. If it did, Einstein would have given up being a scientist when he worked on general relativity.
"You abandon the falsifiability requirements of science and you have just switched to doing religion instead."
Very good. Now name a string theorist who did. Quick!
http://www.higgs-boson.org/
I had a sixty second introduction to one of these models in my introductory class on general relativity decades ago. That class was held by a solid state physicist and because defects in lattices are a bread-and-butter phenomenon in solid state physics, he was personally interested in defect models. Other than that, they are probably mostly ignored by most classes on GR. Having said that, the mathematicians have explored these concepts in differential geometry for a long time, see e.g.
http://www.sciencedirect.com/science/article/pii/0020722581900732
for a professional treatment. No need to go to the amateurs here, the professionals have been on top of this thing forever. Without success, as you can tell from the fact that the problem is still far open.
The most significant problem with the naive defect picture is that is uses a metric dependent background field, and is therefor not Lorentz invariant. The correct general relativistic version of these seem to re-appear in loop quantum gravity in form of spin networks and spin foams... which seem to preserve background independence and Lorentz invariance.
Hope this helps.
Yet the conjecture of distributed strings, in an 11 dimensional universe, is the closest thing to a Grand Unified Theory. 11 dimensional M-theory is so universal it has eaten all the other string conjectures.
There again is the problem. Being everything to everybody, it ends up being nothing to anyone.
We have known physical constraints. Scales of forces, etc. Any conjecture that does not START with those is really just counting angels on the head on a pin. We have 1/R scale invariance, and the scale inversion between EM and gravity as compared to strong and weak forces. Throw the Higgs field in there and you have a nice soup. But until and unless you use it to make testable assertions about the real world, it really is little more than "World of Warcraft" for mathematicians. You may become a 17th level mage, but your spells don't work in the real world.
The string landscape is an argument from ignorance.
If you don't construct your calabi-yau manifold correctly, you'll never get to your string landscape, much less Narnia.
:-(
String theory, as beautiful as it is mathematically, is simply an "it's not even wrong" kind of affair, still. There are, of course, very serious theoretical charges against it. For a model that supposedly can deal with quantum gravity, which may not even exist, it relies very heavily on pre-geometry, which any TOE supposedly needs to be able to explain from first principles as an effect, rather than use as a starting point to describe itself. So there is a rather curious inconsistency in the very structure of string theory, already.
The safe bet, at this point, is to wait for the full LHC data set. If it contains signs of supersymmetry, then the program of real physics will continue along the lines of standard model extensions, and unless string theory, or any other similar model can produce the complete spectrum of the standard model from first principles, it will stay just that... not even wrong.
BEEP! End of theory.
Huh? Why would that be? If the energy required to make a real SUSY particle is above the energy of our largest accelerator, we can't make any. That't just below the TeV scale right now, which means it only excludes sub TeV SUSYs. If the cross sections for virtual SUSY particles are small (because their masses are large), they won't show up as corrections in experiments until large amounts of data have been collected. LHC hasn't done that, yet. The lowest energy SUSY candidate is a WIMP... it won't even show in your detector, except as missing ET (and if you think that means extraterrestrial, you won't even have to comment, again). It will, on the other hand, have been produced copiously during the very early big bang and have hung around as... you guessed it... dark matter.
:-)
:-)
This is known as linguistic determinism, essentially meaning our understanding of the world is limited by our capacity to describe it. http://en.wikipedia.org/wiki/Linguistic_determinism
:-)
String theory begins right where that model ends. So it might take a while until we know whether or not it can be knocked down or not.
In other words: those 99.9% may not apply within the community of string theorists. For sheer lack of knocking power.
What comes after the standard model are the supersymmetric extensions of the standard model. You don't need any string theory for that.
Diogenes, get a better barrel. One that can hold a physics library.
There is an equation. Always wrong somewhere, always backfitted to data.
The Standard Model of December 1st, 1950 bears little resemblance to the standard Model of December 1st, 2010. And that one bears little resemblance to the one of December 1st, 2012.
It is an equation, that gets terms added to it and removed from it every week. It is astoundingly accurate in matching our experiments (to 17 decimal places in many cases). It is absolutely incompetent in predicting anything about gravity, or the source of mass. Higgs equations are being grafted on, and tested, but it still won't be predictive.
Mathematical models are very good for looking backward at what you already know. String conjectures show us we know nothing, and can test even less.
No, you can't knock down the Standard Model of Physics (version 7.5.2012), because version 7.12.2012 will have new terms that correct for whatever you found.
And that is a beautiful thing, called progress, because science improves its understanding.
Stephen Fry postulates that proof of comprehension is confirmed, on creation of devices functioning though the application of those theories previously proposed. Except that we have the grandfather clock. But what is gravity exactly?
"a Grand Unified Theory (a GUT...)."
Presumably ratified on the initiation of a gut reaction?
"on a purely aesthetic level"
if all this is indeed possible, why classify “god” as being an obviously preposterous possibility?
"a set of intuitions and ideas on what the end product may look like"
Given its mooted that believing it makes sense, reveals a lack of understanding regarding the implications. Do humans have minds of a form capable of such envisionment?
"it can, in its current form, neither be proved nor disproved"
Watch out then. For the rise of Stringists and Athestringists.
"a better understanding of the theory than we have today."
If observations do not conform to the theories devised. Maybe those notions are ill-conceived.
"whether or not string theory may actually be damaging to science."
What’s damaging to science is mistaking expertise for infallibility.
"some scientists are in such awe of their own creation"
it might as well be a religion? That can come from not daring to challenge books.
GUT reaction? So little confidence in your religion you have to take words out of context? Acronym. Look it up.
God is not a preposterous possibility. A God that intervenes, yes. One who set the rules for the Universe, maybe not. But you would never calculate those likelihoods, much less admit they are so very small.
Intuition on the end result implies that one must model the Universe, then improve that model. You don't. Your model is the mutterings of goatherders from 6,000 years ago when they were still Egyptian slaves. A lot has happened since then.
You are equating your belief in a God to string conjecture, neither provable nor disprovable. Good job!
Ill-conceived notions which get modified with new evidence are better than ill conceived beliefs that never get updated.
Science isn't infallible, and never claims to be. It's predictions are right 99.999999999% of the time, while yours are less than 1% of that.
No, science isn't a religion. Tenets change. Evidence is acquired. New ideas are accepted.
Reread Matthew 25:34-40, John 14:12, and John 8:32-47. Realize you are COMMANDED to LEARN the truth, heal people better than Jesus, and take care of those worse off than yourself..
:-)
On a side not, it's curious how scornful many (although certainly not all) theoretical physicists are toward philosophy. It's as though they know that some of them are perilously close to what philosophers do and feel the need to distance themselves.
Philosophies are, of course, a dime a dozen. Physical theories, on the other hand, are rare. We don't have more than a handful of them. String theory, not being one of them, is one of hundreds of models that have been explored to see if they have a reflection in nature. String theory is testable and it is being tested as we speak. The initial signs seem to show that it will fail spectacularly, and that will be the end of it. Can't say the same things about monads...
I've read and heard conflicting statements from physicists about whether or not string theory is actually testable. Most non-string theorists seem to doubt that it is. From what I understand, it's actually a collection of theories. Maybe some are testable and others not?
:-)