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String Theory Tested, Fails Black Hole Predictions
eldavojohn writes "Back in 2006 there was a lot of talk of testing String Theory. Well, today CERN has released a statement for the Compact Muon Solenoid Experiment. The short of it is simply that as far as they could tell, 'No experimental evidence for microscopic black holes has been found.' The long statement indicates that since the highly precise CMS detector found no spray of sub-atomic particles of normal matter while LHC smashed particles together, the hypothesis by String Theory that micro black holes would be formed and quickly evaporated in this experiment was incorrect. These tests have given the team confidence to say that they can exclude a 'variety of theoretical models' for the cases of black holes with a mass of 3.5-4.5 TeV (1012 electron volts). Not Even Wrong points us to the arxiv prepublication for those of you well versed in Greek. While you may not be able to run around claiming that String Theory is dead and disproved, evidently there are some adjustments that need to be made."
Simple. The Creator obviously didn't NULL-terminate. Hence his strings have no black hole at the end.
One day, Bob the Scientist was puffing on some buddha. He smoked and smoked, and smoked some more. Suddenly, Bob the scientist looked down: the lines between the tiles on the floor started to wiggle this way and that, giving the tiles the impression that they were vibrating. Bob the Scientist blinked his eyes twice, only to see the lines still wiggling, enticing them with their random, chaotic dance.
"That's it!" Bob shouted. "That's the answer, man!"
Bob the Scientist went and grabbed Bill the Scientist. He pointed at the floor, saying over and over again "The lines, man! Look at the lines! Wooooooaaaaaahhhhh."
Bill the Scientist sniffed, and said to Bob "Bob...have you been smoking that crazy ganja again?"
"Yes, but so what? Duuuuude...the liinnnes...their taaaalking to meeeee..."
"Give me some of that shit." Bill the Scientist took a big drag, looked down at the floor, and they both stared. "Woooooaaaaaaah...we better write this down, so we don't forget!"
And thus, string theory was born.
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It shows string theory is testable after all.
Even failing still sheds light on what is wrong with our theory (or reality if you're an economist :-).
How can we be sure that the black holes were not created?
As one might suspect, the very opening to the paper in the arxiv explains this. After lengthy explanation of several peer reviewed papers that have been widely accepted on detection of black holes, they state:
The microscopic black holes produced at the LHC would be distinguished by high multiplicity, democratic, and highly isotropic decays with the final-state particles carrying hundreds of GeV of energy. Most of these particles would be reconstructed as jets of hadrons. Observation of such spectacular signatures would provide direct information on the nature of black holes as well as the structure and dimensionality of space-time [1]. Microscopic black hole properties are reviewed in more detail in [15, 16].
Now, as you can see by the [1], [15] and [16] references, each of these claims will lead you to a further longer paper on the concept of black holes themselves. Is it possible this method is flawed? I'm not a particle physicist so I'm not authorized to answer that. But I will say that this experiment has been a long time coming and I'm certain the authors of this paper were very careful in all their statements about String Theory.
String theory posits that there exist physical dimensions outside of our 4 dimensional universe, in fact that these are part and parcel of our universe. However, given our tools are all limited to 4 dimensions, it makes sense that there could be phenomena that is unobservable in our universe yet occurring in those other unexperienceable dimensions.
I know what you're saying but String Theory turns a lot of people off when its nature seems to be "unobservable" as you so put it. You'd have just as easy a time proving God exists as you would proving String Theory. The joke about String Theory is that it is conceived to make it untestable so it can never be wrong. This is dangerous ground and whenever a prediction is made by the theory that can be tested, it must be taken seriously. "Unexperienceable dimension?" Ahhh, I wouldn't go around talking to scientists about 'unexperienceable' things. I do not believe the scientific process looks kindly on such things.
I agree with the summary, this isn't the defeat of String Theory. It is a chance to refine and improve it.
I am the submitter, I don't think I said anything too far one way or the other. Usually Not Even Wrong points me in the correct direction but they gave this paper an unusually short nod with little correspondence or refutation. I think this is a good indication that everyone is waiting for the real scientists (not my lame armchair ass) to look this over and weigh in. You know, if you make predictions and they're wrong and you stretch your model to always avoid any sort of direct contradiction but you never get anything correct, then you look more like a fortune teller than a theoretical physicist. They should have the option to revise but my prediction is that this result will lose them a large amount of support in the community. It doesn't outright disqualify them but it sure is a vote of no confidence in a lot of the popular String Theory models.
My work here is dung.
String theory is one of those theories
No it isn't. 'String theory' is an informal term used to describe a collection of theories with some common principles. Not all of them make the same predictions. It works as a pretty good filter when reading scientific journalism. Any article that contains the phrase 'string theory says' is almost certainly written by someone who doesn't know what they are talking about.
that get changed around every time they run into trouble
Uh, that's how science works. You observe, hypothesise, test, and then refine the hypothesis. Sometimes it takes a lot of testing before you find a case where the hypothesis makes predictions that are wrong (e.g. Newtonian gravity), sometimes it takes very little. If a theory is sufficiently high profile, a lot of effort (e.g. building the LHC) will go into testing it, so hopefully you'll find errors quickly.
Very occasionally, someone will come up with a completely new theory that makes the same predictions as an existing one (or more accurate ones) but is simpler. When this happens, it generally displaces the old theory, but it's very rare.
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I happen to be an actual theoretical particle physicist. The headline and summary are completely misleading/sensationalist and this has essentially nothing to do with string theory. If I hadn't seen the string-theory connection here on slashdot, "string theory" would not even have crossed my mind reading this. If you happen to actual read the so-called "long statement" (which is only half a page really) you would have noticed that it doesn't say anything about string theory. What this measurement has ruled out are certain theories that have some small extra dimensions that would predict these tiny black holes. Those theories don't really have anything to do with string theory per se. The only conceived connection is that string theory also has more than 4 spacetime dimensions.
Calling this "string theory tested, fails prediction" is close to the following analogy: Someone comes up with a crazy theory according to which once a while (say 1 in 100) an apple that gets detached from a tree should rise into the sky (say by using complex numbers to cleverly generate a minus sign in Newton's laws). After having observed sufficiently many apples all fall down, we can now say with confidence that apples don't rise but in fact always fall. The slashdot headline would be: "Complex numbers tested, fail apple prediction."
So rest assured, no string theorist will have a sleepless night and none of them will make any adjustments whatsoever. The main reaction in the particle physics world to this will be a lunch conversation along the lines of: "Told you so, this whole idea about mini-blackholes was ridiculous in the first place, in any case, glad they rule it out, so hopefully this will quiet down this whole black-hole circus now."
Good, I'm glad someone said this so I don't have to. As it happens, the very fact that there are so many string theories available is my #1 reason for being disillusioned with the theory. Not only does this data slow down any string theory research program, but they have not even described any possible data that could. String theories (or I should say M-theory) is so empirically slippery that it serves more as an explanatory framework and less a scientific theory.
An explanatory framework is a normative constraint on how we should interpret the world, not a set of statements that entails to observational predictions that can be falsified. The Enlightenment view that "the universe is a clocklike mechanism" is clearly not a scientific theory, but it sort of provides a framework for things that are. They basically said "we don't want to hear any theories that don't represent the universe as a clock-like mechanism." That's why I said "normative." M-theory evangelists are best understood as people who try to commit us to a new normative framework ("we only want theories that can be expressed in 'elegant' M-theory math'), rather than to a scientific theory.
No, "layman" doesn't mean "someone who understands a subject and can even work with it to some extent but is NOT an expert." It means simply "someone who is not a member of a particular profession", full stop. (That's actually the second, but relevant, definition, which evolved from the earlier and still primary definition, which is specifically someone who is not a member of the clergy.)
"Layman" is sometimes prefixed with an adjective like "experienced", and so modified may mean something like what you suggest, but that isn't what it means on its own.
The summary is completely incorrect. Whoever wrote the summary simply didn't understand the paper. String theory does not predict the production of microscopic black holes at LHC eneries. The paper's abstract says, "Limits on the minimum black hole mass are set, in the range 3.5 -- 4.5 TeV, for a variety of parameters in a model with large extra dimensions, along with model-independent limits on new physics in these final states." Note that phrase "large extra dimensions." Here is the WP article on large extra dimensions. String theory has *small* extra dimensions: extra dimensions that wrap around on themselves at the Planck scale. The LHC doesn't probe the Planck scale. Theories with large extra dimensions have, er, *large* extra dimensions. This experiment falsifies those theories, not string theory.
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