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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
"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.
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
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?
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.
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.
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
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.
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
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);}
There are background independent formulations of string theory, but none that give (4D, non-supersymmetric) GR in an obvious way. However, formal background independence is a matter of philosophical preference, not physical necessity. 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? I wouldn't call adding supersymmetry to eliminate tachyons a "kludge", anymore than, say, adding gauge invariance in QFT to eliminate non-renormalizability. As for the positive cosmological constant, I'm not up to date on what is necessary to get that to work out in string theory, but all quantum theories have had notable problems explaining any realistic value of the cosmological constant.
IAAPhysicist, an experimental high energy physicist to be more precise, and I don't like string theory much. I am not opposed to its study, I do not campaign to have funding removed from its proponents, in short, I do not hate it. I just don't care for it, and rather hope that it turns out to be wrong. OTOH, I don't really like the Standard Model (and extensions to it) much either. I think that something different from either is what is needed. Not being a theorist, I am not working on an alternative myself, but I have seen one or two things at various conferences, and thought (just gut reaction) that they looked very promising. One in particular that I found myself unaccountably fond of was a neat little statistical approach from a guy at tamu.
Anyway, my reason for disliking string theory is not at all that I find it "too elegant" or "too cute". You have most of the experimental hep people I know, including myself, pegged quite wrong there. In my opinion, and that of most of my colleagues that I have discussed it with (not a large percentage of all my colleagues), the problem with string theory is that it is not as cute or elegant as it thinks it is. It has precious few free parameters (contrast the standard model), and its first principles are strikingly simple. That ought to be elegance. However, the fact remains, as the GP said, that getting our observable (3,1) universe to appear, even just at low energies, from string theory is quite difficult. Why is this? Primarily because string theory does not tell us how the small extra dimensions are wrapped up around each other. The topology of space presents a huge theory space to search around in.
The standard model is criticised because it does not nail down the values of its free parameters (tautology), and if you don't have the right values of those parameters, then the theory does not describe our universe. However, we can perform experiments which measure various values which depend upon those parameters, and by so doing, obtain values for those parameters with ever increasing precision. Thus, we can find the values such that the standard model describes our universe. Furthermore, the standard model is not chaotic. If you are just a little bit off in the values of your parameters, then your theory describes a universe which is very like ours.
Now, take string theory. The topology of space winds up acting very much like free parameters. However, we can't do experiments to measure the "value" of the topology of space, so finding the right topology is, as I understand it, a huge trial and error process. Furthermore, as I understand it, even if you managed to define some notion of "closeness" to the correct topology, one topology which was "closer" to right than another one would not produce a universe which was necessarily any "closer" in its various properties to correct than the other one. In that sense, string theory is chaotic. So, for all its apparent elegance, it seems to me that string theory is a great deal uglier in the end that QFT and the standard model. This is why I and many others do not like string theory.
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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
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