Slashdot Mirror
String Theory Put to the Test
secretsather writes to mention that scientists have come up with a definitive test that could prove or disprove string theory. The project is described as "Similar to the well known U.S. particle collider at Fermi Lab, the Large Hadron Collider, scheduled for November 2007, is expected to be the largest, and highest energy particle accelerator in existence; it will use liquid helium cooled superconducting magnets to produce electric fields that will propel particles to near light speeds in a 16.7 mile circular tunnel. They then introduce a new particle into the accelerator, which collides with the existing ones, scattering many other mysterious subatomic particles about."
Welcome to slashdot; here's your junk science for the day.
You can't prove string theory through experimentation, all you can do is attempt to disprove it.
Liberty you never use is liberty you lose.
It can't prove string theory. It can *support* it, or it can disprove it, falsify it, contradict it. But it can't confirm it. All the experimental data in the universe can't do that.
The tests proposed would not "prove" string theory. They are only testing some of the fundemental assumptions on which string theory is based.
If the test shows that one or more of these assumptions is incorrect, however, then it would probably force a very fundamental rethinking of string theory... essentially disproving it.
42.
Did anyone honestly think that the answer would be different?
'Loose' is when your pants are three sizes too big. 'Lose' is when you misuse 'loose'.
http://www.xkcd.com/c171.html
-- Too lazy to get a lower UID.
I say, kill all the particles and let science sort 'em out...
I hope, when they die, cartoon characters have to answer for their sins.
Oh...Large Hadron Collider. If it was in the Castro district I would really be suspicious.
I'm by no means an expert in string theory. I barely grasp the basic concepts. However I am an engineer who has taken a LOT of physics classes over the years and I'm not completely ignorant either.
String theory has always struck me as a modern day version of epicycles before it was realized that planets follow ellipses instead of circles. It just seems like we're trying to fit the math to the model instead of modifying the model so that the math makes sense. Add in the fact that it makes no testable predictions (not yet anyway) and it's bordering on not being science anymore. Maybe technology advances will change that but then again maybe not.
Maybe string theory is right, I don't honestly know. But it seems like a lot of group think is going on and little progress is being made.
I think it's funny how the article forgets to mention that the LH collider is located at the CERN (the European nuclear physics institute). As a matter of fact, it is not only in Switzerland, but extends to France as well. The article only mentions it is similar to the U.S. Fermilab accelerator, but then forgets to add that there are many kinds of accelerators world wide.
Funny, ain't it?
The tests being proposed by the physicists in this blog would not test string theory, in that it does not test any prediction of string theory but the underlying assumptions. The write up is very misleading since Lorentz invariance has been tested throughout the past 80 years and always stood up to the tests. I suspect that someone wants to get more funding and mentioned testing string theory to a funding agency.
The number of dimensions isn't that high. When all of the string theories are combined into M-theory, the total number of dimensions is eleven, IIRC. Harder to understand? Yes. Impossible to visualize? Yep. But not abhorrently high.
You can never go home again... but I guess you can shop there.
String theory always seemed to be the most complicated mathematical way you could "force" a unified field theory into existence by adding as many dimensions and undefinable, physically meaningless constants as possible.
And the essential problem in trying to falsify it is that it's so bad it's not even wrong.
KFG
I remember hearing about plans to use the LHC to produce and study miniature black holes. These are supposed to evaporate nearly instantanously due to Hawking radiation, but such radiation is only a theory without any experimental verification, and apparantly quite a few scientists are concerned it will just go ahead and gobble up the earth.
At least it will be quick :)
"The canonical forms of string theory include three mathematical assumptions--Lorentz invariance, analyticity and unitarity. Our test sets bounds on these assumptions." --Benjamin Grinstein
Don't quantum mechanics and GRT also include the above? Meaning if the experements don't confirm the above then more than just string theory is in trouble.
Of course analyticity probably has some very subtle meaning in string theory. Any one here in the know?
November 2007? Sure, what the hell, I've had a good life.
So, who wants to loan me large sums of money? Pay you back in December?
Slashdot Burying Stories About Slashdot Media Owned
It thought this was cleared up years ago:
Scanning/Copying based on a terminator byte pattern is fraught with error and is definitely not secure.
Buffer sizes are terribly problematic when left tot he caller to check on overflow. It must be in the methods, and thus part of the data structure. (see point above).
Strings these days are UTF-7 or 8, which makes them an even better candidate for a object-based construct rather than a memory map.
I'd like to point out the....oh, wait...
Nigel: As you can see, our theories all go to eleven, right across the board. Look: eleven, eleven, eleven.
Marty: Does that mean it's better? Is it any better?
Nigel, well, it's one more, isn't it? Most blokes, their theories only use ten dimensions. They're at ten, where do they have to go from there? When we need that extra push over the cliff, you know what we do?
Marty: Put it up to eleven?
Nigel: Eleven. Exactly. One more!
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
Not at all. You merely have to project one of the dimensions down so that you're only considering a 10-dimensional space.
Ben Hocking
Need a professional organizer?
I don't think it's whining. The public's confusion about science surely stems in part from sloppy reporting.
How often have we heard someone claim that we shouldn't allow something because it has never been proven to be safe? Such comments show serious misunderstanding about the nature of knowledge.
I haven't RTFA (site is returning a database error), but the biggest criticism of string theory so far has been that there aren't many good ways to falsify it, i.e. disprove it, which makes it somewhat suspect as a scientific theory. Having a way to do a test that could disprove it is, in a sense, very good news for the theory. (Besides, you can't ever prove a scientific theory, you can only support it with evidence and fail to disprove it with tests.)
OTOH, a test that actually does disprove string theory could be very bad news for string theorists. But you can bet there'll be a lot of scrambling to rejigger the theory after a failed test...
From the wording in the article it sounds like they actually want string theory to fail. . .
.despite the fact that we have few alternatives so far.
A test in which a theory fails is the most useful sort of test.
. .
I cannot accept a theory simply because I don't know what to replace it with. Make the tests, generate failures; and then new theories which take the failures into account. That's how the alternatives come into being in the first place. That's why the "failures" are the most useful.
"Successes" only make us complacent with the state of our knowledge, which might well be wrong anyway. "Failures" let us know where we lack knowledge. Science is not done where we know, but where "here there be dragons." It's about exploring the dark corners of the map, not sitting in our offices diddling with ourselves.
We leave that sort of thing to the engineers.
And think about this:
Who says we need an alternative? The quest for a Unified Field Theory is an asthetic desire on the part of physicists. The universe is well known for taking our asthetic desires and shoving them up our collective arses.
Perhaps there can be only two.
KFG
In what other endeavor can you persuade people to spend hundreds of millions of dollars to build complicated machinery and pay you a salary based on the following (roughly paraphrased) prospectus:
;-)
"You see, what we'll do is accelerate some shit up to within a hairs-breadth of the speed of light then smash it into some other shit and see what happens."
Gotta love those wacky physicists!
Insisting on "correct" English is like saying that there is only one, definitive recipe for chili.
It's been known since the 1920s that adding extra spacetime dimensions allows you to unify forces; Kaluza and Klein successfully unified classical electromagnetism and gravity that way, with a theory in 5 spacetime dimensions. Unfortunately, this idea can't be readily extended to all the forces in the Standard Model, and the unified theory is at least as difficult to quantize as gravity alone.
From a different perspective, leaving gravity out of it, there are the grand unified theories. They too have "extra dimensions", except that the extra dimensions are not of spacetime, but of an internal "gauge" symmetry space. (Kaluza-Klein theory basically turns these internal gauge dimensions into true space dimensions, paving the way to a gravitational theory.)
String theory also does not add as many "undefinable, physically meaningless constants as possible". Indeed, it has fewer constants than the Standard Model. In fact, it has only one constant, which is certaintly definable: it is the string tension. Furthermore, the dynamics of string theory are unique, unlike the quantum field theories. (You can write down infinitely many different particle physics theories with different particle content and interactions, but all of the string theories are part of the same theory, and all the strings obey the same fundamental laws of interaction.)
In short, string theory is not a totally contrived fudge; pretty much all of the ideas that led to semi-successful unified field theories found their way into string theory in a natural and uniquely determined way.
The energies that will be created in the LHC happen on a daily basis in our upper atmosphere. The only difference is that we will have detectors in the immediate vicinity.
Ben Hocking
Need a professional organizer?
http://arxiv.org/abs/hep-ph/0604255
And furthermore, now that I have read the "article", it turns out to be a freaking BLOG POST containing nine whole sentences. NINE! Sheesh. Secretsather, you deserve some serious downmods for your laziness and obvious lack of subject knowledge.
A quick news search reveals much more informative articles, which allows one to find the original journal article. Here's the abstract...
...most of which is beyond grasp of what I remember from 200-level college physics. Would a domain expert care to jump in now?
String Theory was proven on July 16, 2003, and confirmed after peer review and over 20 separate duplicated efforts, including a lab in Dallas, Texas.
Proven: When you need a piece of string to tie something up, and you find a piece of string in a junk drawer, it will always be too short for use, or too long and when cut to the appropriate length, the remaining piece will be too short for further use.
A similar, but as yet unproven theory is in testing: When you have a piece of string and measure it by "eyeballing" it will always be too short for actual use.
Politics is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly and applying the wrong fix.
That's what experiments are for, you disprove a current theory and then start work on the new theory that fits the observations from the experiment.
String theory has one particle - the string. It has one force which emerges from the very simple dynamics put into it at the outset. A wide spectrum of particles and interactions emerges from it in a natural way. There is little choice for the dimension of spacetime - the theory locks it down from the beginning. Gravity emerges from it naturally - something that doesn't even get mentioned in the standard model. There are close to zero arbitrary constants. And at bottom, the initial assumptions of String Theory are really simple. Simpler than other quantum field theories.
The problem with String Theory is that taken at surface value it doesn't match the universe we see. We don't see a 10-dimensional universe, we don't see the predicted spectrum of particles and so on. The publicised problems we see with String theory are from all the attempts to make our 4D universe emerge from it - and the incredible freedom we have in doing so (eg. by folding up dimensions in various ways). At core, String theory is simple, beautiful and as far from arbitrary as you can imagine. There are all kinds of things wrong with String theory. But they have nothing to do with "adding as many dimensions and undefinable, physically meaningless constants as possible", which sounds more like the ramblings of someone who doesn't have a clue what String Theory is about.
Note that I am neither for nor against String Theory, which makes me part of a tiny minority in the physics world. I certainly doubt it's the ultimate theory of anything, but I also think that there is a lot of uninformed criticism of it. I'm just telling it like it is without my own ax to grind.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
1. Which string theory? There's a few. Anyone who says "M-Theory" will get slapped.
2. What predictions does the string theory in question make?
3. Are the predictions unique to string theory?
it will use liquid helium cooled superconducting magnets to produce electric fields that will propel particles to near light speeds in a 16.7 mile circular tunnel. They then introduce a new particle into the accelerator, which collides with the existing ones, scattering many other mysterious subatomic particles about.
This is why the Mythbusters should not be allowed to design scientific equipment. I can picture Adam dancing about in girlish glee even now...
If I knew the wedgies I gave you back in 6th grade would have resulted in this . . . I might have taken a moments pause.
We can have a raffle! How will the LHC destroy us? Check one: [ ] Microscopic black holes [ ] Trigger collapse of the false vacuum [ ] Strange matter [ ] Magnetic monopoles [ ] Disruption of the Wigner observer cascade causes a universal system reset [ ] God notices and stuffs us all into Carlsbad Caverns
woosh
As a minor nitpick, I think you meant Occam's razor. More important, you clearly don't understand it. Occam's razor simply says that you shouldn't add more assumptions than you need. To pick a real-world example, don't assume there's a Vast Conspiracy behind the War in Iraq if everything can be explained without it. Yes, atheists use Occam's razor to show that you can explain the universe without assuming the existence of God, but that's not all it's good for by any means.
Good, inexpensive web hosting
You can have the weird little string theories in 6 dimensions, and non-critical strings in less than 10. Critical superstring theory lives in 10 dimensions, and M-theory lives in 11 dimensions. Critical bosonic string theory lives in 26 dimensions, although that doesn't contain any fermion particles and hence doesn't describe our universe, unless it turns out to be related nonperturbatively to M-theory in some unknown way.
Thou shalt have four dimensions. No more, no less. Four shall be the number of thy dimensions, and the number of the dimensions shall be four. Five shalt thou not have, neither thou have three, excepting that thou then proceed to four. Six is right out.
Unfortunately, that site is totally bogus. Interesting, but it's entirely unrelated to string theory, which the author seems to mention just to lend his ideas some credibility.
Unfortunately, that site is totally bogus.
Mod parent up. I've seen tons of people pass that link around and it has nothing to do with 10 dimensions in the string theory sense at least.
"...always new atoms but always doing the same dance, remembering what the dance was yesterday." -Richard Feynman
THE EARTH REVOLVES AROUND THE SUN?? You must be joking. I can clearly see the sun rising and setting. Any theory that interferes with the perceptions that I am comfortable with, is obviously bollocks. Last time I checked I couldn't see any evidence for the earth revolving around the sun, even when looking under the sofa.
Censorship is telling a man he can't have a steak just because a baby can't chew it. --Mark Twain
When I first tried to post this I got a message saying that "This user does not exist, no matter how much you want him to." Anecdotal evidence suggested that I do, in fact, exist, since I think, I think, so I attributed the result to experimental error and reran it; failing to falsify my existence in the process.
Keep running the experiment; eventually you'll get the outcome you expect.
"Ladies and gentlemen, my killbot features Lotus Notes and a machine gun. It is the finest available."
As I always like to point out, the most important thing to remember about Occam's Razor is that it's a rule of thumb, not a Law of Nature. If two proposed theories otherwise seem to work similarly well, but one introduces fewer assumptions than the other, Occam's Razor suggests that the former is probably better than the latter, but you can't take this as "proof" -- at best, it lets you make a better educated guess about which avenue is likely to be more fruitful to continue exploring.
David Gould
main(i){putchar(340056100>>(i-1)*5&31|!!(i<6)<< 6)&&main(++i);}
String theory has one particle - the string. It has one force which emerges from the very simple dynamics put into it at the outset. A wide spectrum of particles and interactions emerges from it in a natural way. There is little choice for the dimension of spacetime - the theory locks it down from the beginning. Gravity emerges from it naturally - something that doesn't even get mentioned in the standard model. There are close to zero arbitrary constants. And at bottom, the initial assumptions of String Theory are really simple. Simpler than other quantum field theories.
I think much of the debate over string theory is, at heart, irrational. Some people are attracted to its beauty and elegance, while others find it so elegant that it is therefore suspect. (I.e., the subluminiferous aether was actually pretty beautiful as a theory in a certain way, too, as were epicycles, crystal spheres, and any number of now-disregarded theories; some people would hold that string theory is suspiciously similar to other elegant ideas which have ended up on the scrap heap.)
In some ways, the debate is less of a purely scientific one than an ideological battle between idealists and cynics; lacking experimental evidence, the community seems split mostly between idealists who support string theory, in all its theoretical elegance, while on the other side are cynics who think the whole thing is just too cute to be true, and that it owes itself more to wishful thinking than actual physics.
This is to be expected; until someone can come up with an experiment that will disprove part or all of string theory (or until the theoreticians can find some prediction made by string theory which differs materially from that made by a competing theory), it's an un-winnable argument. There really is little besides "gut reaction" (and other not-quite-rational factors, like the reputations of various people who have already taken sides) to pick sides based on.
"Ladies and gentlemen, my killbot features Lotus Notes and a machine gun. It is the finest available."
- It's not a theory but a collection of theories. The original five different-but-possibly-dual theories and handwaved 'M-theory', plus different flavours with added restrictions or extensions?
- It's not by any means finished: for instance, finiteness hasn't been proven, and there is no explicit background independent formulation which yields GR spacetime?
- The basic idea may seem simple, but is overlaid by a lot of kludges such as supersymmetry to eliminate tachyons and fluxes to get a positive cosmological constant?
But on the other hand, the topological variations on extra dimensions and fluxes add up to 10^500 different theories with different predictions. How does that make an improvement over the twenty variables of the standard model? Granted, string theory attempts to explain more, but... Really? Which? Does the mythical 'M-theory' exist other than as a big 'Maybe'? What does it look like? What predictions does it make? Substitute 'might be' for 'are' and add a 'conjectured' in front of 'theory'... Perhaps. But there seems to be a lot of contrivance in there.Assuming I'm reading it correctly, if the Bosons don't bounce the right way, it means that string theory (as currently formulated) violates one of the fundamental assumptions (Lorenz invariance, analyticity or unitarity). If the string predicted scattering doesn't match the experimental observations, then string theory (in its current form) is "impossible" and at the very least "would have to be reshaped in a highly nontrivial way."
If the Bosons bounce within predicted limits, then string theory still isn't proven - it just survived this elimination round and moves on to next week's physical challenge...
Of course you can project down 4D objects to 3D in several ways, and thus get some feeling about them. But our perception always keeps those images at 3D, so in our brain it's just a 3D image with mentally attached info, unlike in the 3D->2D projected case, where or brain manages to re-create the 3d image without problems. You simply cannot visualize four straight lines staying perpendicular to each other, no matter how hard you try. You can visualize four lines in 3D-space, and can mentally attach the info "that line actually goes to 4th dimension, but was projected here", but that's it. Our mental images are restricted almost the same way the perceptions of real images are. E.g. another thing you just can't do is to visualize a body cell with all its structure in its natural size. You can visualize its structure enlarged (such as you see it in a microscope, or pictured in a book), and mentally attach "like this, but much smaller", or you can mentally shrink it, but then eventually you'll end up in your imagination with a structureless point.
The Tao of math: The numbers you can count are not the real numbers.
String theory has not been "adjusted" to meet experiment. I'm not really quite sure where this notion comes from. For that matter, I'm not sure where the notion that this is entirely a bad thing comes from.
The standard model is "adjusted" all the time by experimental data. That is, our knowledge of the values of the free parameters in the standard model is changed every time someone gets a new analysis finished. Generally, we just get slightly better precision, but an adjustment is made nonetheless. If we claimed particular values for these parameters that turned out to be wrong, then the standard model would not describe our universe. So, the particulars of the theory are constantly adjusted, but the foundation of the theory is not.
String theory is quite similar, except that you replace free parameters with the topology of space. Now, using topology of space as your degrees of freedom presents a particularly nasty problem because topologies are not continuous like real numbers, so we can't just measure and get a good approximation. We're either quite right or quite wrong if we claim that "x is the topology of space". With the standard model, we can be almost right, and the closer we get to the correct parameter values, the closer our theory gets to right. With string theory, as I understand it, it is all or nothing. However, choosing different topologies, although it does count as an "adjustment" based on data, is not at all an adjustment to the fundamentals of the theory.
In other words, your comparison between theories of fundamental physics and theories describing the solar system is way off base. If anything, the standard model is more like the circles and epicycles than string theory is. The standard model is very ad hoc, and was never intended to be a comprehensive theory, merely a stopgap which described all our experimental data until we could get a better theory. Furthermore, the standard model has been disproven already! Neutrinos have been experimentally demonstrated to have mass, a direct contradiction of one of the first assumptions of the standard model.
Now, I am not in favor of string theory. I hope it does turn out to be wrong. But, at the same time, I am very much more opposed to extremely poor and misinformed "criticism" of string theory. If you don't know what you're talking about, shut up.
Disclaimer: I AM a physicist. I am not a theorist, however, but an experimental high energy physicist. There is a quite good chance that I will be working at the LHC in the next few years.
SIGSEGV caught, terminating
wait... not that kind of sig.
Not actually. There were quite a large number of particles around before Gell-mann came up with the Eightfold Way or Path or whatever. They didn't even have much of any way of classifying them (which is why the nomenclature for hadrons is so screwy today). There were certainly not any models predicting the nucleus before Rutherford hit on it, at least not any that carried much weight. Quantum mechanics kind of grew weirdly from various models like the Bohr model of the atom which were entirely based on experiment.
Even string theory has experiment backing it up. No, really, it does. Everyone talks all the time about how string theory has no experimental evidence. Well, no, it has just does not have any predictions which are currently testable which differ from leading other non-string theories. But, think about it. Other, leading, non-string theories don't have any predictions which are currently testable which differ from string theory! That puts it in the same boat as the standard model and friends.
Furthermore, string theory in its original incarnation was motivated by experiment. It was first developed as a rival to QCD. I don't think that any theory ever (with any kind of success) has been just dreamed up in an experimental vaccuum. Certainly not quantum mechanics. Certainly not string theory. Certainly not thermodynamics, nor Newtonian mechanics. Certainly not relativity, either general or special. All have been motivated by some kind of observations. Later, many of them were found to have predictions that were more far-reaching than what had been observed so far.
SIGSEGV caught, terminating
wait... not that kind of sig.
WHAT is your favorite DIMENSION?!?!
"10... no, wait 11!.... AUUUUGGGGHHH"
I hold very few opinions. I hold information based on observation and fact. If you wish to disagree, please use facts.