The BBC on the LHC

By Mark Trodden | January 4, 2006 1:04 am

The BBC has a nice article about CERN’s Large Hadron Collider (LHC).

I’ve mentioned the LHC before, and what we expect will be its central role in providing insights into some of the biggest questions in particle physics and cosmology. The BBC article provides a summary of the magnitude of the construction effort, discusses the roles played by the different experiments and talks a little about the physics we hope will come out. I hope you have fun reading it. I’ll leave you with the beginning paragraph, which is short, simple and sensible, at least to me.

“We are at a point where experiments must guide us, we cannot make progress without them,” explains Jim Virdee, a particle physicist at Imperial College London.

“We must wait for the data to speak.”

I hope, as opposed to this, or that, no one considers Dr. Virdee’s statement a particularly dangerous idea.

CATEGORIZED UNDER: Science, Science and the Media
  • bittergradstudent

    Here’s to hoping that they find all sorts of unexpected and “dangerous” things, so that I’ll have plenty of work to do when I’m done being a bitter gradstudent and have moved on to being a bitter postdoc!

  • Frank

    I wouldn’t worry, bittergradstudent. There’s always more bitterness to be had in the world!

  • Dissident

    Regarding danger, I guess we could always revive the old worry that a sufficiently high energy collider could accidentally create a black hole or a bubble of a different vacuum which then proceeds to gobble up the planet. That would provide an interesting answer to Fermi’s paradox: before an intelligent species becomes sufficiently advanced to build starships, it typically builds an LHC – and so wipes itself out. Not because of atavistic warmongering, mind you, but out of the curiosity which led it to advance that far in the first place. Oops.

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  • Dumb Biologist

    I honestly don’t know how ostensibly likely this outcome is, given current, well-tested theory, so perhaps someone here could elaborate:

    I’ve heard and seen it stated that the LHC may be only just powerful enough to generate an unequivocal Higgs signature, and will otherwise yield more of the same, only to more decimal places. No SUSY, no micro-black holes, no good pointers to a GUT, and most certainly nothing of great significance to the field of quantum gravity, except that maybe it would rule out some of the hypotheses that require extra dimensions large enough to be probable at LHC energies.

    Anyone seriously betting this is what’s going to happen?

  • Ben L

    Dissident – There was a study performed when the RHIC accelerator was being build to study disaster scenarios. I think either that study or another one covered potential problems at the LHC as well. One basic conclusion was that, if the LHC could destroy the world, then collisions initiated by ultra-high-energy cosmic rays would already have done it.

  • bittergradstudent

    (not so) Dumb Biologist–

    that is certainly a possible scenario. It could very well be the case that all the LHC does is generate a Higgs signiture (or rule out the Higgs model… Wouldn’t that be fun?). To my understanding, current theory does little to predict what the supersymmetry breaking scale or the sice of the extra dimensions should be in string theory, and non-string theories do even less. So, we might begin to see signatures of these things, or we might not.

    Another possibiity, one, given the history of experimental science, that I find quite likely, is that we see something totally and completely unexpected. But who knows, really?

  • Dissident

    #6: I know, that’s what I meant by “old worry”. I must admit that it’s not completely obvious to me that what we intend to do at the LHC has natural equivalents involving cosmic rays… but I’ve never been sufficiently worried about it to read the report either.

  • Dissident

    #7: But if supersymmetry fails to turn up this time too, it will definitely have lost its main selling point as far as particle physicists proper are concerned (alleviation of the hierarchy problem). Superstringers will obviously cling to it no matter what, but…

    Another thing that’s not obvious to me (plenty of those) is that the LHC could definitely rule out the Higgs.

  • Dumb Biologist

    OK. Thanks, bittergs.

    My understanding is that, unless there’s something seriously wrong with our current understanding of the SM (which appears exceedingly unlikely), something which can be implicated in the Higgs mechanism will be found at the LHC. It might be a single or multiple Higgses, or some composite which does the same thing for the purpose of giving mass to the Ws and Z. To this it is added that by far the most likely mediator of the Higgs mechanism is a “massive scalar field” (the quanta being, obviously, one or many Higgses) and not some composite of, say, the Top quark something else of the “vector field” ilk.

    Anyway, this pessimistic view of the LHC comes to me originally from a former-bitter-grad-student-turned-bitter-postdoc-turned-bitter-administrator who lamented the scrapping of the SSC and thinks we should have leapt straight ahead to some mega-humongous linear collider. In short, if I understood and remember his words correctly, the LHC will be seriously anticlimactic in what it produces, that confirming the Higgs, while swell and all, won’t surprise anyone, and that “new physics” will continue to elude us for quite some time. From what my poor brain can absorb, he’s possibly not alone in this assessment.

    I really don’t have an opinion on what this guy said one way or another. He may just be a knee-jerk pessimist denying all contrary data, the data may say nothing conclusive at all, and hence he’s the half-empty sort, or the hopes for the LHC are wishful thinking based on unlikely best-case scenerios, and he’s essentially correct.

    I’ve really no idea, honest. Just wondering. Seems like what you’re saying supports the second hypotheses: He’s a half-empty type, and we’ll just have to wait and see with open expectations.

  • Dissident

    #10: The funny thing is that after two decades of talking about it, now that the LHC is almost ready (knock on wood) it turns out that it’s not only Dumb Biologists who wonder exactly what meaning we’ll be able to glean from the expected avalanche of raw data:

    Maybe we should have given that some thought before designing those megabuck detectors…

  • Dumb Biologist

    Again, I’m not wondering from the position of having an opinion or even a good reason to think one or another. I’m wondering about the opinions of some pessimistic folks and, basically, whether or not they’re full of baloney.

  • Dissident

    #12: They are not full of baloney. The fear that the LHC will see nothing particularly interesting – maybe a Higgs, no superstuff – is common. Imagine trying to sell an even bigger hole in the ground to politicians after that. As a corollary, you can expect anything coming out of the LHC to be hailed as Great Progress, no matter how insignificant it actually is.

  • bittergradstudent


    My understanding was that the renormalization group equations didn’t really allow the Higgs mass to be much bigger at all than what the LHC would be able to rule out without making the other Standard Model masses different from what they were already experimentally measured to be. Is that incorrect? Having not actually done the calculation myself yet, I don’t know.

  • Ben L

    Dissident – the paper of Arkani-Hamed et. al. talks about how to extract parameters *after* new physics is discovered. The machine and the detectors were designed to find the Higgs, and to be general search experiments for new physics. If there is new physics to be found, it’s very likely the LHC can see it. Whether we can then uniquely identify the nature of what’s been found is a different question, and our ability to answer it depends a lot on the nature of the new physics.

    What Arkani-Hamed et. al. showed was that, in the case of supersymmetry, unique identification is generically not possible without either new techniques or a new machine. This has actually been known for a long time. To make a unique identification, you need precision measurements, and in many cases the LHC can’t make measurements that precise. This is one of the biggest motivations for building another machine, the International Linear Collider, which can do incredibly precise measurements, but isn’t as good of a discovery machine as the LHC.

  • Ben L

    bgs – that’s correct. If there is only the Standard Model, the LHC will certainly be able to see the Higgs. If there is new physics things can get more complicated and the Higgs might slip through some “cracks”. Of course, in such models that I know about, there is always other stuff around that the LHC will see.

  • Dumb Biologist

    Ben L:

    By the “nature of what’s been found” do you mean to say, for instance, LHC researchers will probably see something new, know that it behaves as a SUSY particle or particles should, but they won’t know if it’s a neutralino or something else?

  • Mark

    Ben has done a nice job of summarizing the situation. What he says is essentially what most people who know what they’re talking about think.

    One hears a lot of comments in science these days along the lines of “most probably …” or “the most likely thing is …”. However, I think the right way to look at this is that we have some very well-motivated and exciting ideas of what could be seen at the TeV scale, and some very compelling and intriguing hints, both theoretical and from precision experimental tests of the standard model, that there will be something new at the LHC. Beyond that I’d say we have to work hard and keep our expectations open.

    The kind of comments Dissident is making are not really justified in my opinion. It is logically possible that nothing interesting will bee seen at the LHC, but there are many reasons to think that this won’t be the case.

    In any case, almost no matter what theory tells us, probing the world at the highest energies we can afford, to see what new facets of reality pop out seems like an exciting scientific goal.

  • Mark

    DB, that’s essentially right. Identifying the detailed structure of whatever new is discovered at the LHC will require the inputs of both this hadron machine and a later lepton machine (the ILC) for precison work.

  • Ben L

    DB – it could mean a number of things. What we’ll know is that there are some new particles, we’ll know something about their masses and what they decay into. This will be enough to say, for example, that the data is or is not compatible with Supersymmetry, but won’t be enough to tell for sure that it is SUSY. There’s an example model know called Universal Extra Dimentions that can look almost identical to SUSY at the LHC. To differentiate these two models in that case, you need to know the spins of the new particles. That is a measurement that is almost impossible at the LHC, but quite easy at a Linear Collider.

    Another thing you’d want to know is: say you were convinced that the LHC had found SUSY. What do we then learn about other fundamental physics questions? Such as – does grand unification really happen? In principle, measureing the properties of the superpartners can tell us quite a lot about such questions, but you need to be sure that you have interpreted the measurements correctly. The Arkani-Hamed paper presented examples of pairs of supersymmetric models which had identical signatures at the LHC, but two superparters, a chargino and a slepton, switched masses. Identical phenomenology, but vastly different implications for the underlying physics.

    Incidentally, I wouldn’t view any of this as disturbing. There are interesting questions about interpretation of LHC data that need to be addressed, and that’s exactly what people are doing. There are disaster scenarios where not much interesting comes out of the program, but those are very special, and most indications suggest that there will be lots of interesting data produced.

  • Dissident

    #18: Mark, would you care to clarify which comment of mine you find “not really justified”? Surely you are not denying that many in the HEP community are worried that the LHC will fail to find anything interesting and turn out to the the last of the big accelerator experiments?

  • Dumb Biologist


    Seems there’s all kinds of opinions out there, and the consensus is, apparently, that it’s a very good bet the LHC will be “big enough” to see something new. This may be Higgs, and nothing more, Higgs+other stuff (probably SUSY), or other stuff (again, probably SUSY), but no Higgs (precisely because of the nature of the other stuff). Only in the first case is it expected to be a bit of a disappointment, and finding nothing new is not to be seriously expected. Further, the nothing-but-Higgs scenerio doesn’t really fit the available data well (maybe this is informed phenomenologically best by the anomalous muon magnetic moment, and how good our understanding of the QCD contribution to that calculation turns out being?).

    Also (and perhaps because I’m misremembering something I heard, in defense of whom I heard it from), skipping past the LHC to save money for some mondo linear collider is a bad strategy, because they complement each other in some essential way.

    Am I getting this right at all?

  • Dumb Biologist

    Oops, didn’t see Ben L’s post before mine. Thank you!

  • Dissident

    #16: Ben L, last time I checked the LHC would have problems seeing a minimal SM Higgs with mass 650 GeV. The LEP2 limit is a mass > 115 GeV; triviality would set in around 1 TeV. So it doesn’t look quite so definite to me.

  • Dissident

    Oh dear, my “greater than” and “smaller than” are being parsed as HTML tags… previous post was supposed to say that the LHC would have problems seeing a minimal SM Higgs with mass smaller than 180 GeV or larger than 650 GeV.

  • JoAnne

    In the Standard Model without the addition of a Higgs boson, the scattering of W bosons, i.e., WW -> WW, violates unitarity at energies of 1.7 Tera electron Volts. (Tera = 10^12) A violation of unitarity means a violation of the optical theorm in Quantum Mechanics which is basically a violation of probability (the chance of something happening being greater than unity). There are 3 possibilities:

    (1) When a Higgs boson is added to the Standard Model, it participates in WW scattering and unitarity is preserved as long as the Higgs has a mass less than approximately 800 Giga electron Volts (Giga = 10^9).

    (2) It is quite possible that there is no Higgs, but some other, completely unknown, piece of physics which preserves unitarity in WW scattering. This piece of physics has to kick in before energies of 1.7 Tera electron Volts.

    (3) It is also possible that nothing preserves unitarity and that WW scattering will occur at increasingly stronger rates at large energies.

    The LHC was designed to have just the right energy to explore all of the above possibilities. The LHC experiments will discover the Higgs, if it behaves as predicted by the Standard Model, and it has a wide capability to discover a variety of classes of new physics.

    There are 2 worries: (i) the Higgs is non-standard and behaves in such a way that once produced it cannot be distinguished from Standard Model background processes. Ditto for certain types of new physics. (ii) it doesn’t have enough energy to thoroughly study the case where WW scattering becomes strong. That’s why the SSC was designed to have higher energy beams – to cover this case of strong WW scattering.

    I won’t even enter into the discussion of whether the LHC can identify the Higgs, or anything else, once something new is discovered. That will be the subject of many future posts!

    Whatever Nature has in store for us, we cannot yet say. We may have prejudices one way versus another (the present prejudice is the existence of a light Higgs, which is predicted by current data if one considers the Standard Model alone with no new physics). But in all truthfulness, we don’t know what happens at the Tera electron Volt scale – we can only list the possibilities. We will begin to explore that region when the LHC begins operations. That, of course, is the magic and excitement of science!

  • Ben L

    DB – There are lots of reasons that the LHC was built before a Linear Collider; physics reasons – there are lots of kinds of new physics that the ILC simply can’t discover; technological reasons – people knew how to build the LHC before they knew how to build a linear collider; political reasons – no short summary here :) .

    Dissident – The unitarity bound comes in at around 850 GeV, and my understanding was that, while it certainly gets hard to find that heavy of a Higgs, it’s possible right up to the bound. More than that, though, is that if there is only the SM the precision electroweak fit bounds the mass to be less than about 250 GeV at 95% confidence, so it’s highly unlikely that the Higgs is that heavy.

  • Mark

    DB, seems like you’ve got a good bead on it now. One small comment would be that I personally wouldnt use the word “probably” with regard to any specific framework.

    Dissident, what I’m saying is that although people will occasionally say things like “wouldn’t it be a nightmare if there was nothing at the LHC!?”, in fact, basically no one in the field expects that this will happen because of the reasons I mentioned. So yes, I’m suggesting that this statement of yours is not really justified.

    Also, while a very heavy Higgs would be a problem for the LHC, the effects on precision electroweak measurements push one to even more extreme tunings in that case, implying that one expects to see something else at the LHC. It is always true of course that things could just be fine-tuned just so, but science seeks to explain fine-tunings, not accept them, and that’s why people think this logical possibility is not in any way an expected outcome.

  • Dissident

    #27: …so by Murphy’s Law, we should expect a minimal SM Higgs with mass 150 GeV. 😉

  • JoAnne

    DB: There are two reaons while the LHC is being constructed before a high energy Linear Collider: (i) the Linear Collider technology was not (and is still not quite) ready to build such a machine, and (ii) the tunnel for the LHC was already built, so it is comparatively cheap.

    In fact, CERN conducted a study in 1987 (I still have a copy of the proceedings!) which concluded that the physics capabilities of a 1 TeV Linear Collider surpassed that of the LHC! But nobody knew how to build one at the time.

    Ben: As to your comment in #27, please name one, just one, piece of new physics that a Linear Collider cannot discover. I think you will have a difficult time.

  • Ben L

    2 TeV gluino. :)

    If you meant model, then sure, there isn’t one that I know of.

  • Dissident

    #28: Mark, I guess we’ll just have to disagree on this one (too). I sure envy your unwavering optimism, but it doesn’t strike me as typical.

    #30: JoAnne, could you set me and Ben L straight on the upper (minimal SM) Higgs mass detectable at the LHC? I remember 650 GeV, Ben L says 850.

  • spyder

    Maybe it is because today is the 45th anniversary of Camus’ tragic death, i am not sure, but there seems to be something in the synchronicity of his Sisyphean allegory that is making itself present in so much of the blogsphere today. The range of possible outcomes discussed above for the LHC cover a fine spectrum of pessimistic to optimistic. At its worst i suppose the LHC will be another of our Sisyphus moments on the planet. However, for the cost of a bit more than a week of Iraq war dollars, the LHC will provide an example of humanity’s quest to understand the universe rather than destroy lives and human rights. Even if nothing of significant value comes out of it, the LHC as a model of human endeavor, is vastly more worth our efforts and positive “vibrations” than silly wasteful wars.

  • JoAnne

    Ben: Actually, I wasn’t putting an energy constraint on my challenge. CLIC can see a 2 TeV gluino. The LHC can’t detect a 4 TeV gluino, so that’s not really a fair example. My point was more along the lines that a Linear Collider can observe everything within its energy reach (and some things way beyond), whereas the converse is not true of the LHC. It is possible for things to be produced at the LHC and not observed as they are swamped by background (such as 500 GeV sleptons).

    Dissident #32: The LHC can indeed detect a Higgs all the way to 850 GeV and probably slightly above as well. For a Higgs above 200 GeV or so, they use the ZZ decay channel of the Higgs. Up to Higgs masses around 500-600 GeV, they use the lepton (electron or muon, not tau) decay modes for both Z’s. So the signature is H -> ZZ -> 4 leptons. For higher Higgs masses, they start to run out of rate, so they use Z decay modes with higher branching fractions for one of the Z’s. So, the signal is one Z decaying leptonically (so they have something to trigger on) and the other decays hadronically to jets, H -> ZZ -> 2 leptons + 2 jets.

  • Dissident

    #34: Thanks!

  • Dumb Biologist


    Big amen to that, but we all know real science gets a sliver of the pie, wars or no wars. When you consider the bone-crushing inanity of abandoning the SSC when 1/4 of the money was already spent, in favor of the ISS, and juxtapose that with the galactically monstrous stupidity of some obscenely expensive current events, it’s painfully obvious the “accelerators are cheaper than war” cost-benefit analysis is not applicable to the real world. Never mind that it makes perfect sense. How presidents and parliaments spend money typically ranges from the inscrutable to the insane, so kvetching over a measley billion or two in science funding is unfortunately entirely justified.

    Hence, it’s still very comforting to hear the LHC probably (sorry, I can’t help using that word, limited vocabulary, etc.) will give particle physicists plenty to sink their teeth into., no matter what.

  • Count Iblis

    What happened to the light gluino hypothesis, see e.g. here:

    Are they now ruled out?

  • Dumb Biologist

    Last question, hopefully not too controversial:

    This “universal extra dimensions” model…

    A quick google tells me this is a Kaluza-Klein theory in which all the SM fields propagate into extra dimensions, maybe one or two more than the three we’re used to. There’s no other necessary connection to stringy physics except that it’s a KK theory (I guess the compactified dimensions can still be pretty big compared to the Planck length…perhaps they have to be?). It’s not obviously related to quantum gravity, anyway. And…these other dimensions allow for a “mixing” of SM particles, the decay products of which behave sufficiently like those of SUSY particles that, if we see SUSY-like phenomena in the LHC data, we won’t be able to be sure if it’s SUSY or these other…things.

    So, before my head blows up, is this the basic gist, and will the situation really be that confusing?

  • Mark

    DB – I like this “probably” – it’s just the use when applied to any specific framework that I’m avoiding :)

  • Plato

    I was looking for a place in which to start counting?

  • Dumb Biologist

    Holy crap…you quoted me? When I’m asking a question that could be so stupid I’m not even posing it correctly?


  • Dumb Biologist

    Anyhow, in an effort to get some answers to my questions (which, of course, led to more questions…like “Why might ‘penguins’ be marching around the innards of the LHC?”), I stumbled upon the file linked below…it’s a PDF…

    While it’s got its fair share of jargon, I could sort of follow along. If one is “counting”, it appears this is a good source of unvarnished info. about the challenges facing particle physicists once they get the sort of data they’re expecting. It’s gotta be better than anything I could say on the subject.

  • Mark

    I also usually find Joe to be an excellent source of wisdom on such matters.

  • Plato

    I’m all for unvarnished truth.:)

    INtroduction of “other concepts” are interesting even if they come from the “uneducated?” Those “biased” with education, leading us down the path of “no regard” for?:) Opposition too? Why? Revealing the infalibility of, and how such a deception was perpetrated on us innocent lay people.

    Hearing him describe things like dark matter and superparticles and extra dimensions leaves you feeling that you almost understand them.

    Of course, we have to admit that we are less then sure. Yet, it is your spirit of inquiry I acknowledge. :)

  • Steve W

    Going back to Dissident’s comment at #3, has anyone looked carefully at the arguments at concerning micro black holes (MBH) as a potential danger? (Have a look at the various pages there.) I have been in contact with the web site author, James Blodgett, who is not a physicist but has has a special interest in risk assessment (and better maths than me.) He has had great trouble getting physicists to take the issue seriously.

    His basic argument is that the current risk assessment issued by CERN in 2003 ( see is patently inadequate, and I think he is definitely correct on this, as it does rely on Hawking evaporation solely.

    It ignores the possibility that Hawking radiation either does not exist at all, or does not “work” at this tiny scale. James Blodgett notes at least one avXir paper which disputes that it exists at all, and my own scan through recent papers (written in the last 6 months or so) found 2 that talked of the possiblity that Hawking radiation may leave “stable black hole remnants” which may be captured by electrical charge.
    See : arXiv:hep-ph/0507140v1
    and arXiv:hep-ph/0510236v1

    These papers do not describe the nature of such remnants at all (or not in terms a layman like me can see), so possibly they are thought incapable of acquiring mass – I just don’t know. What I do know is that the CERN risk assessment does not talk of this possibility at all, perhaps because it had not been thought of in 2003.

    The other reason for doubting that MBHs could be a danger is based on the same argument used to qwell concern about “strangelets”; namely the assumption that ones created “naturally” by cosmic rays would already exist and haven’t eaten the sun or planets, so they can’t be a danger. The Risk Evaluation Forum site deals with this in much detail, arguing that it is likely that natural ones would usually all have high speed and may zip through stars and planets with almost no interaction, whereas some of those made in the LHC can be expected to be at very low speed (below earth’s escape velocity), and could therefore end up in the earth’s core. Then the question would turn on possible accretion rates, especially in the high pressure environment of our planet (about which I would also suspect there is a lack of detailed knowledge).

    (I would also wonder whether it is possible that their accretion behaviour may be inherently different in the earth’s core compared to floating around in stars. Could they be harmless to stars or gas giants but harmful to rocky, hot core planets?)

    Blodgett acknowledges that it is possible that the worst possible accretion rate may be so small that it is still not a significant risk. However, the point is that CERN’s risk assessment does not address these arguments at all.

    The issue has been covered in some other forums on the internet, but none seem to have addressed the Blodgett arguments fully.

    It seems to me, as a layman, that the state of the physics papers shows that there is indeed a high degree of uncertainty as to the exact characteristics and behaviour of MBHs that might be created at the LHC. (It is, of course, entirely possible that none at all will be created, if large extra dimensions just aren’t there.) To me, given that the premature end of the earth is the worst possible outcome, physicists should be looking at all of the possible scenarios; not just the simple ones (such as Hawking radiation as a given). Remember the Fermi paradox too!

  • Mark

    I took a cursory look at this page. It does not seem to be serious at all and in fact, I don’t know what it means that a non-physicist is “doing calculations” to check out what will happen. These issues have been discussed at length by physicists (and he is entirely wrong that we don’t take them seriously) and the results have been mentioned earlier in this thread. I don’t think anythig this “risk assessment” person has to say changes anything.

  • Dissident

    Mark, as I noted way up there I’ve never actually worried enough about this stuff to read the report(s) on it. Assuming that you did, maybe you can answer the question at the core of Steve’s remarks: how model dependent are those studies?

    After all, the whole idea with the LHC is to find new physics. That’s “new” as in “unknown”, hopefully even “surprising”. Is it really possible to construct watertight arguments against lethal consequences of unknown new physics before having actually seen and studied it? [Tune in theme song from The Twilight Zone.]

  • Count Iblis

    You can’t rule out for 100% that we live in a simulation. A particle accelerator we build may cause the computer simulating us to crash. :)

  • Dumb Biologist

    I’ve managed to determine that a “penguin” is a loop in a Feynman diagram that, I guess, is supposed to look like a penguin. And I thought “sonic hedgehog” was a silly name.

    I’m amused by the thought of a “conspiratorial” WIMP. Perhaps, being so weak in their interactions, they have to organize in secret in influence the MACHOs.

  • Plato


    Your paper linked

    Mircostate blackholes

    Sometimes, these things have to be placed in perspective.

    It opens up the mind abilities to comprehend what is going on around them? While the experiment is controlled, this does not disawow what is taking place in nature.

  • Plato
  • Steve W

    Mark: I actually don’t want to alienate someone who presumably has the capacity to reasonably explain the faults in the Blodgett arguments, but I find your response unhelpful, to say the least.

    I note that you mention that “these issues have been discussed at length by physicists…and the results have been mentioned earlier in this thread”. I may have missed something here, but apart from those items that discuss how the LHC may turn up nothing much at all, I don’t see anything on this thread that deals with the argument about adequacy of the risk assessment.

    You appear to be very dismissive of Blodgett’s site, but is it too much trouble to be precise about what errors you presumably found from a “cursory look” at his pages. What made it “non serious”?. Does he get his maths wrong? Does he misunderstand something fundamental?

    He openly acknowledges that he needs help to look at limits to the model, to better define what the worst case scenarios are. It is clear from his website, if it is read throughly, that he is quite willing to be convinced that there is in fact such a small risk that it is not worth worrying about.

    Don’t non-physicists, of the non lunatic kind at least (and I am reasonably satisfied that is not what we are dealing with here,) deserve more than dismissal if they raise questions asking “have you thought of this?”

  • Mark

    Don’t worry Steve W, you’ll have to much more to alienate me. You make a fair point -I was somewhat dismissive and I mostly apologize for that. But I find Blodgett’s arguments a little unfair. They seem to boil down to “Physicists have come up with an idea – the large extra dimensions idea. Within this framework small black holes could be created at colliders – we have to take this seriously. Within this framework the black holes are predicted to Hawking radiate – we should imagine that they won’t and worry about the consequences.” I don’t really buy this. Let me just focus on one thing from his site

    7) The mechanism behind Hawking radiation requires some of the same principles as the mechanism behind mini black hole creation. If one is true, then the other must be true.

    Black hole creation is enabled by the multidimensional models of string theory. String theorists have derived Hawking radiation based on principles of string theory. If both black hole creation and Hawking radiation are true, then mini black holes are not dangerous. At the moment, the extent to which one requires the other is not clear to us.

    Some of this is just inaccurate – the large extra dimension idea does not logically depend on string theory. If I just take it as a phenomenological model (in which I can do calculations), then indeed if the calculations of black hole production are correct (requiring semi-classical gravity), then I expect the Hawking radiation results will also be reliable.

    Anyway, hope this helps – you were right to take me to task for being dismissive. The existence of this site is, I hope, evidence of my commitment to taking seriously the comments of non-crazy non-physicists.

  • Steve W

    Mark: thanks for the apology. Now how about 2 very specific points I raised:

    Blodgett specifically cites a 2003 paper disputing the existence of Hawking radiation:

    I find this lengthy paper hard, (well, impossible) to digest, but to quote from the abstract:

    “simple dimensional arguments show that quantum-gravitational effects might well alter the evaporation process outlined by Hawking. Thus a definitive theoretical treatment will require an understanding of quantum gravity in at least some regimes. Until then, no compelling theoretical case for or against radiation by black holes is likely to be made.

    The possibility that non-radiating “mini” black holes exist should be taken seriously; such holes could be part of the dark matter in the Universe. Attempts to place observational limits on the number of “mini” black holes (independent of the assumption that they radiate) would be most welcome.”

    If the arguments in this paper have not been “debunked” by other physicists yet, it clearly supports Blodgett’s concerns, doesn’t it?

    Secondly, as I mentioned in my original post, I found 2 recent papers on arXiv which talk of “stable black hole remnants” from the LHC being a distinct possibility. Being “remnants”, presumably we are talking of something even “tinier” than the original MBH, and maybe they are not conceiveably dangerous. But were these considered at all in the 2003 CERN paper?

  • Plato

    Risk Evaluation forum added, with References

    So one gets a sense of who is coming from where. :)

  • fh

    As a general point, we are not able to fuck up nature seriously outside of our own scales. It’s really stable the way it is, which is why it is the way it is.

    I actually did a couple of back of the envelope calculations on this a while ago. Can’t find them right now, but even without HR the crosssection of BH growth is so miniscule that it couldn’t gobble up the earth during the next couple of millenia.

  • Adi

    @ Dumb Biologist
    Are you actually a biologist ? Or are you really a
    former-not-so-bitter-physics-grad-student-turned-postdoc-turned-rich-and-wealthy- owner-of-a-biotech-startup-looking-back-to-good-old-times ?

  • Dissident

    fh, remember the story of a man who falls out of a skyscraper and, while passing an open window on the 30th floor, is overheard saying “so far so good”?

    The rates of exponential processes – e.g. the growth of a cancer tumour – always looks insignificant initially. Then they explode. If your calculations show that a mini-BH accreting eating the planet from inside would need a couple thousand years to start growing rapidly, it may be reassuring to us who are here right now, but future generations may view the premature termination of their planet in a slightly different light. 2000 years, 80 generations, is not all that long a time.

    Getting back to #47, what really bothers me now that you got me thinking about it (I was just goofing off!) is the model dependence of the risk assessments. We really do not know what the LHC will see, so there’s a built-in contradiction here: if it’s truly new physics, as we certainly hope, how can we know that it won’t blow up on us?

  • Peter Armitage

    Ironic that this thread about experimental verification of the Higg’s bosons is going on right next door to a thread concerning the discoverer of the Anderson-Higgs mechanism.

  • Mark

    Hi Steve W. Unfortunately I don’t have time to go through the first paper you mention in detail. However, you can look at for a careful discussion of related issues, and if you like, there are a few sentences in section 7.1 that discuss how the HR results from string theory agree with the semiclassical results. Jacobson is an extremely well-known and reliable relativist – which I mention not as a substitute for going through the other paper in detail, but just to explain why I pick this one as a good reference.

    The last 2 papers are really only one paper, since the last one is a conference proceedings summarizing the earlier results. The thing is that this paper is devoted entirely to the physics of an existing mini-BH. They do not address the question of how the formation and radiation rates are related, so I stand behind that seemingly sensible argument for now.

  • fh

    Dissident, google is a wonderfull tool to do back of the envelope stuff if you’re used to G=c=h=1. So let’s put things in perspective. Let’s say we are looking at a E=14Tev MBH. It has Schwarzschild radius R = 2GE/c^4, therefore an area of R^2*Pi. It’s speed has to be smaller then escape velocity, v = 11200 m/s, so it scoops a volume of R^2*Pi * v now multiply with density of earth to get mass accretion: rho = 5515 kg/m^3 or converting.

    Now google will do the calculation for you even, just google for:
    (2* G * (14TeV)/(c^4))^2 * Pi * (11200m/s) * 5515kg/m^3 *c^2 * 1s in TeV

    Energy accretion is 10^-67 TeV/s

    Now approximately speaking we need 10^67 seconds to gain a single TeV. Age of the universe

  • fh

    (…continued from accidental html tag) less then 10^18 seconds.

    No need to finish your tea quite yet.

    So what does that tell us? If I take just classical considerations we’ll have other things to worry about long before this becomes a problem.
    The accretion rates the risk studies cite are actually orders of magnitude larger, because they use semiclassical arguments that are actually neccessary to get a serious estimate.
    Also these semiclassical modells suggest that we might be able to create them in the first place but predict evaporation as well.
    In general the easier it is to create something the more natural ways it will have to decay.
    We can fuck up reality on our own scales, but not fundamentally, our facilities are far to small for that.

    As for the, it’s new physics so it might be dangerous, let me freely quote Peter Woit:
    “if dragons emerge from the LHC interaction regions, we will have been wrong”

  • Dissident

    fh, the 2000 years mentioned in #58 are in reference to your own “couple of millennia” in #56. If you now want to revise your estimates, fine, but as I’ve said a couple of times now, I’m not really worried about things which we can predict based on existing models.

    To reiterate: what bothers me is that I can see no way to make a truly model-independent risk assessment.

    The mini-BH story is a good example. The old risk assessments apparently did not consider black holes at all, since the energies involved are much too small for them given only standard 3+1 spacetime and GR. Then Randall & Sundrum dreamed up large extra dimensions, and all of a sudden black holes became a possibility. Now, you may know in what regard I happen to hold this particular idea, but it illustrates the point: we can only evaluate known models, i.e. possibilities which somebody has thought of. If there is one safe bet, it is that we haven’t thought of all possible things which may be lurking around 1 TeV. If anything, we expect – and hope – to be surprised by what we find.

    Large extra dimensions and mini black holes won’t keep me awake at night. The unknown might.

  • fh

    With the millenia I was being fa·ce·tious, guess the tone was lost.

    “Large extra dimensions and mini black holes won’t keep me awake at night. The unknown might.”

    You’re either a lot more knowledgeable then we all or must be getting very little sleep…

    Nature is stable against our pesky probings. They are miniscule compared to the dynamics this cosmos holds within itself.

  • Dissident

    fh, I just had this great idea for an experiment: take 5 kg of U235, make a gun shell of it and fire it into a massive slab of 100 kg more U235. Film the whole thing at high speed to study how this exceptionally dense material behaves on impact. Use X ray diffraction to compare its crystal structure before and after the experiment and see if it’s changed in interesting ways.

    I promise I won’t use more than 20 kg of high explosives for the whole experiment, so maverick of quick estimates that you are I’m sure you’ll agree that the release of chemical energy couldn’t possibly pose any danger to anyone, provided standard precautions are taken. I’ll be doing this in the cellar of the physics department, behind a solid cement wall reinforced with sand bags, so what could possibly go wrong? After all, nature is stable against our pesky probings.

  • Dumb Biologist

    I am completely, totally, 100% a dumb biologist whose mathematical deficiencies border on dyscalclia (though I think I’ve got something of a good head for the more qualitative aspects of some physics concepts). I am neither old, rich, nor brilliant, just a working-class benchmonkey doing my small part. My tendency to go toe-to-toe in debates with my intellectual superiors is something of a compulsive illness driven by equal parts chutzpah and the annoying tendency to care too much.

  • Dumb Biologist

    Gah, that was in response to Adi…

  • Mark

    I love the word “benchmonkey”! Haven’t heard it before. Might take it out for a spin at a faculty meeting or two :)

  • fh

    Dissident, that will hardly “fuck up nature”, maybe blow up a town, probably not even that, just release a lot of radiation with a small explosion.

    As I said, we can mess up thing on our scale, but not much beyond. Nothing like a sun swallowing BlackHole. And certainly not an unlimitable exponential runaway reaction.

    Furthermore the physics we know do put tight constraints on what can happen in new physics. For example the is a maximum energy released in your experiment would be E=mc^2. Same thing here.

    What does a risk analysis that is not model dependent even mean? A risk analysis that is entirely based on currently known physics? Any fundamental instability triggerable in LHC would have been triggered by cosmic processes long ago. The energy in a beam is enough to melt a block of lead, but not to blow things up. Even if the entire LHC would suddenly mysteriously transform into pure thermal energy it would probably not wipe out much more then Europe (which would be a real pity, I like it here). There you go.

    If you want to evaluate the risks of new physics, well, the new physics is only new to us, it’s been here all the time and it hasn’t killed us so thumbs pressed.

    If you worry so much about mankind destroying itself there are uncountably many more urgent risks out there to worry about then LHC. Try improving car safety for a start. Your energy will be much better spent.

  • Dissident

    #69: “we can mess up thing on our scale, but not much beyond”

    How do you know?

    “the physics we know do put tight constraints on what can happen in new physics. For example the is a maximum energy released in your experiment would be E=mc^2”

    Yes, we know that – now. But if you had asked a physicist back in 1900, you would have been told that the maximum energy released would be that of 20 kg of conventional explosives. See the point?

    “Same thing here.”

    Yes, but not the way you seem to think. What makes fission useful is that you only need to input a small amount of energy to get back a whole lot. What you put in is just a catalyst to release what was there all along. Do you know that the LHC won’t catalyse something? If so, how?

    “Any fundamental instability triggerable in LHC would have been triggered by cosmic processes long ago.”

    This sounds like a reasonable ansatz for a model-independent risk assessment, but the mini-BH example shows that it’s not watertight (the rest frame of cosmic rays colliding with Earth does not coincide with that of beams colliding in the LHC, so whatever is produced by the former is less likely to be captured by gravity).

    “Even if the entire LHC would suddenly mysteriously transform into pure thermal energy it would probably not wipe out much more then Europe”

    Gee, that’s reassuring. But it still misses the point. Again: think “catalyst”.

  • Steve W

    MarK: I don’t follow your last point about the paper on remnants. They are talking about the LHC and how stable remnants may be left, aren’t they? I also note one other short paper discussing black hole remnants:

    Another paper mentions possible “long lived” relics:

    where it says:

    “it is not quite clear what happens to the remnant without a more complete theory but within the present framework we are left with a stable remnant.”

    I gather that these papers don’t deny HR, they just say that it may not mean complete “evaporation” a MBH.

    My question as to what would be the characteristics of such a proposed remnant (with a particular view to whether they are capable of growing) remains.

  • Plato
  • fh

    I have been talking about catalyst the whole time. That’s what instability means, a meta stable state is made unstable and goes on a runaway reaction.

    Perhaps you should actually read what people have been writing in their risk analysis? (They probably don’t include these absurd “Dragons will emerge” scenarios. And my arguments are probably a bit off)

    How do I know there’s not more energy there then E=mc^2? Gravity. That energy would couple to Gravity, and it’s not.

    This all depends only on well known physics. Fact is, we know a lot more now about the LHC region then Marie Curie knew about the nuclear region. That was a happier time when experimenters could still easily probe regions far beyond the understood.

    Your worrying about risk is like worrying that Curries experiments might bring together a specific combination of elements that just happen to be instable and whose instability catalyses the instability of all other matter, and leads to all matter being radiated away.
    That’s a conspiracy theorists risk, not a science risk. A science risk is that several of the early researchers in radioactivity die of cancer.

    The mini-BH example is not dangerous, hence your supposed example is none.

  • James Blodgett

    I appreciate the calculations of “fh”. However, they need to be extended. The Schwarzschild radius is many orders of magnitude larger given extra dimensions. See Also, there is an area beyond the Schwarzschild where gravity is still intense and will attract most particles.

  • Dissident

    fh, are you being serious?

    For the umpteenth time: the mini-BH example shows that we only know how to compute numbers, hence evaluate risks, given a model. Before someone thought of large extra dimensions, mini-BH production at colliders was not an issue. Then somebody thought of the possibility of extra dimensions, and so there was a whole new risk to analyze.

    Have we now thought of all possible ways new physics might behave around 1 TeV? Of course not.

    As for your gravity comment, I guess you haven’t been paying attention, or you would be aware of that little discrepancy of 120 orders of magnitude between estimated (by your naive kind of argument) and apparent zero point energy of quantum fields coupled to gravity. Bottom line: we haven’t got a clue as to how much vacuum energy there really is. For all we know we could be sitting in a false vacuum just waiting to get knocked out by the right kind of event.

  • Plato

    Extended yes, and the process held in context of what we actually are getting from such collision processes?

  • fh

    “The right kind of event.”

    That’s precisely what you fail to appreciate. None of the events generated at LHC will be extraordinary or different or unusual in any way if seen in a cosmic/natural context.
    They are extraordinary for humans but it’s nothing new to the universe.

    And yes, of course this “calculation” (rather a guesstimate), is ridiculously inadequate, but you can put in 50 orders of magnitude without changing the result, and I doubt a change of 50 orders of magnitude in the input would still be compatible with established physics.

    I will stop this discussion, your arguments are of the nature of conspiracy theory, and in this context it’s impossible to disprove that everything is possible.

    Perhaps the very words I type out now are an ancient spell that will accidentally trigger a gateway to hell and unleash armaggedon, unlikely given what we know, but can you give a “model independent” analysis that excludes this risk?

  • Dissident

    fh, there is nothing conspiratorial about it at all. Quite why you keep denying with such vigor the obvious fact that we can’t predict the behaviour of unknown physics precisely because it’s, duh, unknown, I’ll leave it to others more interested in your psychology to figure out.

    Meanwhile, may I suggest that you read up a bit on the various cataclysmic phenomena which astronomers observe all the time? Try gamma ray bursts for a start. Even if you were right about the events to take place in the LHC being nothing unusual in the grand scheme of things, that would not rule out something literally Earth-shattering.

  • fh

    A last comment:
    Can we rule it out with absolute certainty? No. Can we assess how likely these things are based on what we know? Yes.

    Will a reasonable analysis find that the possibility of LHC destroying the Earth differs from the possibility of it producing dragons? No.
    Why? Both events would mean that known physics are wrong or have conspired in an extremely unlikely way to keep these phenomena hidden from us.

  • James Blodgett

    “Fh” says: “Will a reasonable analysis find that the possibility of LHC destroying the Earth differs from the possibility of it producing dragons?”

    I think this is a fair question. We at are mainly asking that physics produce that reasonable analysis. To give them credit, they have tried, twice. The RHIC risk assessment said that black hole production required impossible energy. Now some string theorists are predicting black hole production. The CERN risk assessment relies on “thermal processes.” Now a very good paper questions the existence of Hawking radiation and similar thermal processes. Both risk papers rely on the cosmic ray/collider analogy which we claim is inexact. “Fh” produces calculations on accretion but does not respond to a simple challenge to those calculations.

    The precautionary principle can be overdone, but in this case I think it applies. I think it incumbent on physics to produce that “reasonable analysis” before taking this risk. I think we have asked questions that deserve an answer. It is not fair methodology to presume the results of a reasonable analysis before it is produced. To turn the tables, I suggest that the reason for the lack of a reasonable analysis is because it can not be produced.

    If anyone would like to help, or help prove us wrong, we can use all the help we can get.

    For example, I am working on a paper on the cosmic ray / collider analogy. I would love to have someone review my math. Send me an email; see our “contact” page.

  • Dissident

    #79: fh, you are wrong, period. It is not at all obvious that new, potentially disastrous physics living at a higher energy scale E_disaster > E_known must be in conflict with what we know about physics at E_known, nor is any “conspiracy” necessary to keep it “hidden from us”, any more than a conspiracy is needed to keep nuclear physics hidden from ordinary chemical processes, or QCD hidden from (relatively speaking) low energy nuclear physics. As for assessing the risks from such unknown physics, I reiterate once more (hoping that sooner or later it might sink in): as long as it’s unknown, it’s unknown. How do you quantify risks from something unknown? Beats me.

  • Plato

    Layman becoming very nervous, as if there is a new game being played, and someone, is going to come out a winner?

    It reminds me, of the extra-dimensional scenario and those who thought it poppy cock, while here, we see the talk and such, exmplifying strategies, that would have easily been dismissed by that same crowd.

    So what’s going on here?

    I would not be the one to instgate such fears, other then to say, that you guys fix this, or somebody with a higher skill set intrude here to lay it at rest, and let me assume my way through all the wonders about those extra-dimensions.

  • Dissident

    Plato, remember what I wrote back in

    ? “Sure, it’s possible. But there’s no reason to expect it.”

    I don’t EXPECT the LHC to destroy the planet (or I wouldn’t just be sitting here doing nothing about it). I’m just musing (if that’s the word) that there doesn’t seem to be a way to prove (short of actually running the experiment) that it’s not POSSIBLE, and noting that I can’t even come up with a sensible way to put numbers (i.e. a probability) on that possibility.

  • Plato

    Ah, I see. Thank you dissident for clearing this up. :)

  • James Blodgett

    “Mark” objected to the following statement:

    “The mechanism behind Hawking radiation requires some of the same principles as the mechanism behind mini black hole creation. If one is true, then the other must be true.”

    I do not think he understands the origin of this statement.

    A typical reaction of physicists to our message is to fire off some quick reason why nothing could possibly go wrong. This is one of those reasons. Mark thinks it is wrong. So do I.

    But ultimately it would be nice to find a reason why we are wrong, a limit to our model. Therefore we are cataloging the objections to our model, in hopes that one will be solid.

    Also, however, we would hope that the safety of the earth would rest on something other than a bunch of reasons that have proved to be flimsy.

    We think that physics owes it to the world to devote more attention to this. As “Plato” says, paraphrased, “somebody please fix this.”

    Our model might be right. We concede that it might be wrong. With the fate of the earth in the balance, we need a very high probability that we are wrong, and we do not concede that. The precautionary principle can be overdone, but in this case precautionary principle methodology applies. It should be incumbent upon physicists to demonstrate that their proposed activities are safe. To be fair, they have tried, but we think it is clear that their risk assessments are inadequate. Someone needs to tell them that. We are not having great success. People assume we are wrong, as Mark did. But if a few others, a few of you perhaps, chime in, perhaps we can put this issue on the intellectual agenda. The point it to get physics to take this seriously enough to take another look.

  • Mark

    Exactly what is it you’d like to tell people you think I don’t understand, James Blodgett? I don’t think I took issue with the statement you said that I did. In fact, I was saying that within many contexts it seems correct.

    In any case, feel free to email me if you’d like to explain how, based on the short comments here, you feel that your understanding of quantum field theory (in both Minkowski and curved space-times) and semiclassical gravity calculations, is superior to mine and therefore allows you to make this statement.

  • Plato

    This process in itself might be telling in terms of how scientists and the experiments that are put forward, are responded too, before the actually implementation.

    Do you think this risk assessment, was ongoing from 1955, from the time of divergence and from how cosmic analysis took place, plays a key role?

    I mean, I see gravitatinal waves predominante in our views of acceptance, yet, the move to extra dimensional understanding, far from understood from those who critize string/M theory’s work.

    Have I missed something here?

  • Steve W

    Mark: I think you may be right in that James may have misunderstood your post. However, please don’t throw the baby out with the bathwater yet…

    While roaming the internet I have come across another paper: which again is so technical as to be impossible for me to follow the detail. However, it does contain these lines:

    “As the known equations of quantum fields in curved space-times are expected
    to break down at such wavenumbers, the derivation of the Hawking radiation has the flaw that it applies a theory beyond its region of validity.” And:

    “Therefore, whether real black holes emit Hawking radiation remains an open question and could give non-trivial information about Planckian physics.”

    It may be that I am misunderstanding this paper, but it seems to be suggesting that HR works under certain assumptions, but there are other possible assumptions that may make it not “work”.

    How these “assumptions” relate to MBH that might be created in the LHC, I don’t know.

    My earlier question about black hole “remnants” also is left open. I am not sure if your earlier post means that you don’t think they will happen at all. However, if they do happen, as some say is a possibility, will they definitely not interact with matter (or each other) in any way that could be dangerous? ( I am expecting that they won’t be dangerous, but just asking!)

    I know that you may not have time to address all these issues in detail right now. But, I suppose the fundamental point that Blodgett is making is that if there is any legitimate theory work which suggests that MBH may not disppear due to HR, and there is no “real life” observations to confirm it one way or the other, should not the risk assessment for LHC have looked at this scenario and spent time on the issue of “worst possible” accretion rates for a MBH (or indeed, hundreds of them) in the earth?

    Just to be clear here: no one seems to think there is any chance at all of accretion rates being so high as mean the earth would disappear in a day, a year or even a thousand years. However, if it was barely possible within (say) 10,000 or 100,000 years, how would people would think about it then?

    And also to be clear: the cosmolgical argument (about “naturally” created MBH not causing apparent problems) might “win” the risk issue for LHC too, but I think (as a layman) that Blodgett proposes interesting criticisms of the analogy that (as far as my internet searching so far indicates) have not yet been addressed in any published detail.

    What I hope is not happening here is analogous to the way the first Shuttle disaster happened. Namely, a few people recognized a possible danger, but their concern got lost in the clamour to get a project going. (Not a perfect analogy, as Blodgett has apparently not got any actual physicist perfectly on side!) But you get my drift.

  • Plato
  • James Blodgett

    “Plato” mentions colliders and cosmic rays. The collider / cosmic ray analogy is a fairly good argument. Cosmic rays sometimes have more energy than colliders and they have been hitting earth for billions of years. If colliders could produce something that could do damage, then one would think that cosmic rays would produce the same something and earth would not remain. The continued existence of earth (and also the moon, where cosmic rays hit larger atoms) demonstrates that colliders are safe.

    Unfortunately the analogy is not exact. A cosmic ray particle moving at close to light speed hits an earth particle that is moving slowly with respect to earth. If this creates a mini black hole, it would be moving much faster than escape velocity from earth. If it accretes slowly like a neutrino it will zip right through earth with very low probability of hitting anything. It would have to accrete millions of particles to slow it below escape velocity, the probability of this happening even once in trillions of trials over billions of years is essentially zero. On the other hand, when two particles collide in a collider, their velocity more or less cancels. They would drop into earth and have forever to accrete. There are several possible accretion mechanisms.

    Actually, “more or less cancels” happens only occasionally. The collision of consequence is the collision of the quarks, and they carry a random proportion of proton energy. This is expressed in proton structure functions. Landsberg did some calculations, and I have been working on replicating them, that show that a bunch of black holes per year would be moving at less than escape velocity.

    I would love to have someone help check the math behind these statements.

    Incidently, the collider / cosmic ray analogy does suggest that accelerators producing particles that hit fixed targets would be safe. These might be used to explore higher energy ranges first.

  • Paul Valletta

    One has to remind one self, that in the early Universe epoch, Blackholes are “Particle-creators”, via HR:

    The experiments one can do by accelerating Particles, and colliding them is opposite the above:Blackhole’s created from Particles.

    The “reverse engeneering” process needed to create conditions that are close to the big-bang, are all based upon “what we actually know”?

    The inner products from accelerated particle collisions, are all quark oriented:

    The fact that the “reverse” process is being investigated, is no way sure that there may be a particle phase that is not fully understood, and this does not rult out the appearance of some form of “NEGATIVE” phased matter?

  • Paul Valletta

    What would be really interesting is if T Violation, out of the K-0 Creation products, produced a little-bang ?..

    If there was ever an understatement previous to hindsight, the maybe :Let there be Darkness

    just might be such an understatement?

    T-violating muon polarizations, are as far as I am aware, beyond the standard model?

  • Steve W

    Mark: I have now had a look at the Jacobson paper you refered me to at #60.

    You have to remember that these are hard for the layman to follow. However, I note that Jacobson says this:

    “To predict the state of the positive free-fall frequency modes T+ and T− from the initial state thus seems to require trans-Planckian physics. This is a breakdown of the usual separation of scales invoked in the application of effective field theory and it leaves some room for doubt[52, 30, 53] about the existence of the Hawking effect.

    While the physical arguments for the Hawking effect do seem quite plausible, the
    trans-Planckian question is nevertheless pressing.”

    The paper he cites at 53 is the Helfer paper I originally mentioned. Thus, he does not seem to be dismissing it out of hand. (In fact, the other 2 papers he cites are earlier papers by Jacobson himself.)

    Now, in section 7.1 which you specifically referred me to, I take it to mean (in a paraphrase) that string theory suggests that, at least for some black holes, there isn’t a problem with this trans planckian issue. However, the section finishes with this fairly opaque (to me) sentence:

    ” However, neither of these approaches from string theory has so far been exploited to address the origin of the outgoing modes, since a local spacetime picture of the black hole horizon is lacking. This seems to be a question worth pursuing.”

    Correct me if I am wrong, but this seems to leave the question open somewhat, even if Jacobson seems to lean towards the idea that there really is no problem.

    Now I think I may be coming to the heart of the issue. Your position is that:
    “indeed if the calculations of black hole production are correct (requiring semi-classical gravity), then I expect the Hawking radiation results will also be reliable.”

    However, it comes down to whether one necessarily follows the other. Are you saying that it is a matter of “calculations showing the possible creation of MBH also show that they must evaporate via HR” or is it more the case that if one happens, it suggests the other will also happen (or if you prefer, strongly suggests the other).

    The way I read Jacobson, and your earlier comment, it is more the second case.

    If my understanding is correct (and feel free to tell me I do not understand you or Jacobson correctly) then I would think that there is in fact sufficient reason to say a risk assessment should include the possibility of HR not occurring.

    It is clear from all of this thread that there is a lot of legitimate speculation as to what the LHC might or might not reveal. Now, my concerns are not those that Dissident raised, because by his own argument, you can’t predict risk on something that is completely unforeseen and outside of your current “model”. However, unless I am misunderstanding you, you think the failure of HR would be extremely unlikely, but not impossible. But surely as long as it can be modeled, then risk assessment can be done. I think….

  • Plato

    If one is given a bulk perception to take hold of, is it reasonable to think of gravitonic concentrations?

  • Plato

    It’s a shame we would leave this as it is, while I had presented a speculative post above, it is of course from corruption of accepting certain model assumptions:)

    So if that’s not real, then what use are the accretion disks of risk assessment, and I find myself all over the map, but still trying to understand.

  • Richard Reddy

    Killer black hole?

    I like the real world view, where parades of scientists develop consensus around the ideas of a few. For example, the earth is completely flat, and the center of the universe. It’s easy to forget how our whole species believed this, with the same conviction we believe black holes will evaporate with a puff of Hawking Radiation.

    CERN is the first device with enough energy to create an artificial black hole. Unfortunately, there are those who object to all the new colliders, creating the impression of a paranoid fringe, proven to be scientifically ignorant. CERN is a very big gun, able to probe matter on the scale of the weak force, the first device with this level of energy. I honestly wonder if physicists are better informed than the paranoid fringe–it’s absolutely new territory.

    If everything goes according to plan, black holes created in the matter stream will quickly evaporate as Hawking radiation. Though we have confirmed the existence of black holes, we have never observed Hawking Radiation, so there does seem to be a risk that a black hole might be stable.

    I guess we will find out. Such is the way of the world, with big science and
    big money, gathering solid political support. We freak-out if Iran has a nuclear program, but dismiss the minority report on dangers in high-energy particle
    physics, as crying wolf. Will the real fanatics please stand up? Probably not.
    Self-awareness is just what fanatics lack.

    I don’t think cosmic rays are good model for what will happen at CERN.
    At CERN we have much lower momentum, inside a closed system. If a stable black hole were formed, we could see the demolition of our planet
    in less than ten minutes–the most efficient weapon ever tested, or the final industrial accident.

    The current accepted theory is one where no proposed experiement is dangerous, and experimenters have a green light for any experiment they
    wish to conduct at high-energy.

    I am also enjoying this adventure, but believe France should be much more serious in matters of risk accessment. It is risk accessment–not risk–that is
    nonexistent. Leading scientists should reflect on the history of science, where a minority of one, frequently leads to a breakthrough in scientific thought, by individuals who reject accepted theory. They should admit we have never been able to tell the difference between blowhards and geniuses, before a
    particular view of nature runs its course–which often takes decades.

    We have years before CERN’s collider is operational. Why not assemble teams of teams of physicists to play the devil’s advocate? There are certainly credible scientists who worry about the risks of probing matter at these energies. We should listen attentively to the minority view, given what is proven knowledge on black holes (self-propagating collapse of matter), and
    what is theory (Hawking Radiation never observed, cosmic ray interactions never observed).

    The brute force approach of big money, big names, big theory and a project of unprecedented scope, runs over opposition like a steamroller. I would like to see CERN go forward as much as anyone else–but waving our arms to dismiss the minority reports is reckless and irresponsible. Sometimes, what we don’t want to hear–ideas can only delay or harm the CERN project–are exactly what we should hear. For a few dollars more–a very small cost in relation to CERN’s budget, and allow ourselves the benefits of open-minded debate.

    Could this kill the project? That’s the whole point of risk accessment!
    CERN would not be stopped by objections that don’t hold water, but we might find chilling reasons to proceed with caution, or not at all. We really don’t know if the reflex is censorship, and anyone expressing concerns is percieved as a
    menace to progress. In examining all the risks, we only employ more scientists, engineers, mathematicians–just what drives CERN in the first place.

    What could definitely kill the project is the public perception that CERN experiments are recklessly irresponsible. Censoring those who urge caution
    and reflection certainly creates this impression. The risk we dismiss so
    easily is the utter destruction of our planet. If there was ever a good time to listen, it is right now.

    There is another danger. Suppose a group of scientists develop a resolutely convincing model for stable black holes when CERN is operational? Any state or nation is well within it’s rights to nuke the facility, if they believe they are in grave danger. So, should scientists present their objections to CERN, or should they present their findings to host governments and military establishments?
    We don’t know what discoveries will happen before 2010–CERN could very well be shut down at gunpoint, by states or nations who think the risks are too great. No nation, including France, has the right to put everyone in jeapordy.

    For working scientists, what would you do with new research assigning a 92 percent probability of stable black holes forming in the particle stream? How about a 1 percent probability? CERN is not listening, so who gets your paper?

    Every war in history is based upon smaller issues than complete destruction of
    our planet. I really think we need greater consensus and less pomp in matters of risk accessment.

    While reading Steven Hawking’s excellent book “Universe in Nutshell”, I was struck by how he characterized science in the information age. In his field, papers are being published at a continuous rate of 7 per minute. In terms of raw information, a professional physicist is marginally better informed than
    janitors who mop the floor. The bias towards accepted theories, which are often wrong, is simply enormous.

    I would love to see Dr. Hawking get a Nobel Prize when small black holes in the CERN particle stream disappear with a puff of Hawking Radiation. He’s really a wonderful guy. If we get a stable black hole, all life on earth–and the planet–would evaporate instead. The CERN project is certainly among the wonders of the world, but refusal of the French governent to explore and manage possible risks could be called insanity. I think every nation supporting CERN should insist upon exhaustive accessment of risks, and examine ALL relevant theories as if our lives depended on it (this might very well be true).

    Lacking momentum, a heavy object like a stable black hole, would simply
    sink to the earth’s core, where it would do what black holes are proven to do:
    Eat all the matter the crosses an expanding event horizon. The CERN experiment will mass-produce black holes, which we hope will be unstable and disappear in nanoseconds, or less. If they do not, it will be our final experiment.

    If France does not provide an atmosphere of careful risk-accessment, that doesn’t mean nobody else will. Our bias, proven to be enormous, for the entire history of science, could be our undoing. It is especially disturbing when we favor theory and seem to ignore established facts–or act as though working scientists are just trouble-makers, because they urge caution.

    I guess I’m a little worried . . . (blab, blab, blab). Let me leave you with this thought for reflection. How many physicists, who believe that risk of a stable black hole is zero—also believe the universe was created a point of zero volume and infinite density? If you believe that, contrary to conservation of
    mass/energy, it’s possible to believe in most anything. If physics is an experimental science–which is what CERN is all about–then we should base our perception of risk on experimental facts, not popular or accepted theory, having no empirical validation.


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Cosmic Variance

Random samplings from a universe of ideas.

About Mark Trodden

Mark Trodden holds the Fay R. and Eugene L. Langberg Endowed Chair in Physics and is co-director of the Center for Particle Cosmology at the University of Pennsylvania. He is a theoretical physicist working on particle physics and gravity— in particular on the roles they play in the evolution and structure of the universe. When asked for a short phrase to describe his research area, he says he is a particle cosmologist.


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