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What the micro black hole fear mongering really is about June 12, 2008

Posted by dorigo in personal, physics, science.
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I was slightly surprised this morning to read the following comment from my friend Kea, after I had answered in slightly provocative terms to the umpteenth comment of some anti-LHC activist promoting the modern-day equivalent of a raid with torches:

Tommaso, to be honest, I am a bit tired of this LHC-safety-case bashing. Even given all the usual reasonable arguments, how sure are you that you have accounted for all your hidden assumptions? I’m a theorist, and the only I thing I know for sure is that NOBODY knows what we’ll see at the LHC.

I wish to paste here my answer to Kea, because I think the heart of the matter must not be mistaken.

I am of course unable to be sure of what the LHC will produce, if black holes or red dragons. But I am sure that the advancement of science calls for boldness in opening doors leading into the unknown. And I am in favor of the small risks the package includes. The question, to me, is not whether the risk is zero or tiny. It is whether we must insist for rationality in our choices or be led by hysteria. And I have my own answer. Therefore I will, sorry, insist in bashing these clowns whenever they pester this site with their oddities.

Now, I am sure Kea agrees with my statement. I think she just wants to communicate that we might end up feigning more confidence than we really possess. After all, it is not so uncommon to find fanatics among scientists too: we are humans. Granted: but fear mongering is to be addressed before we clean up our own home.

UPDATE: on a second thought, there is nothing wrong in principle with raising objections about the LHC or whatever other scientific endeavour, if done respectfully. And following Voltaire, I have to remind myself that I defend the right to speak of those who disagree with me. So I have to offer a partial retractatio: I will not “bash those clowns” as they “pester this site with their oddities”, but rather counter their arguments with rationality. Not forgetting that I want to have my share of fun as I do it 😉



1. Ronald - June 12, 2008

I agree that science is not about working within any spectrum, but to take one step further than anyone else has.

2. Andrea Giammanco - June 12, 2008

All this story recalls an amusining short story by Asimov: a guy, placidly sitting in his porch, assists to the sudden appearance of a man coming from the future.
The man from the future explains that his Time Machine had the only defect of requiring so much energy to destroy planet Earth; but he comments that the achievement of traveling in time is so great that this was worth of.
The man in the porch nods in agreement, then asks: “By the way, how far in the future are you coming from?”
The time-traveler guy asks what time is it, then answers “two hours”.

3. bozox - June 12, 2008

This isn’t even about hysteria vs. rational thinking. There’s gonna be nothing at LHC that Mother Nature doesn’t already do on daily basis. I’m talking about high-energy cosmic rays – LHC’s p/pbars are small potatoes compared to those. Luminosity-wise, the whole volume of Earth was showered by those for billions of years, yet shill remains in place somehow…


4. dorigo - June 12, 2008

Hi Andrea,

I do not remember that story – I must have read it though, because I basically devoured all of Asimov (including non-scifi stuff such as the black widowers’ club series) in my youth. He remains among my favorite writers overall.

Hi Bozox,
the question is a bit more complicated than that, despite mother nature (the bitch) doing what she likes every day. I fear that simplifying the matter too much appears as too much handwaving for the kind of case we have to fight. A thorough investigation is about to come out on the issue, stay tuned – I will comment it here.


5. Louise - June 12, 2008

The idea that LHC might produce mini-black holes is based upon the very, very speculative idea of extra dimensions. Furthermore, even if a mini-hole were produced it would quickly evaporate and not suck us up. This shows that there is massive media attention to speculative ideas like extra dimensions, and nobody considering that a Black Hole could exist in the Earth. Tommaso and Kea are both right.

6. bozox - June 12, 2008

I’d appreciate an explanation why did anyone think, in the first place, that nontrivial gravity (i. e. nontrivial spacetime effects) starts at TeV scale, as opposed to Planck scale.

7. dorigo - June 12, 2008

Bozox, that is in fact one problem. Another is why it starts at the TeV scale and not 200 GeV, where it would have already destroyed the world (in combination with non-hawking radiation, non-escape velocity from earth, etc., etc.)…


8. bozox - June 12, 2008

Heh, 200 GeV is kinda ruled out by observation data – we’re still here 🙂 I personally think that TeV scale is ruled out, too – see cosmic rays. But someone who knows better than me obviously disagrees, and I’m not talking about the fearmongers in the journalist crowd. I’m not being sarcastic here, I honestly wonder what was the theoretical motivation.

9. Luboš Motl - June 12, 2008

The best joke in the conversation is Kea’s “I am a theorist”. Cool! 😉

She is right about the essence, of course: we don’t know what will happen. That’s partly why we paid for the collider in the first place.

But still, science is also about getting qualified opinions about the things that are more likely and those that are less likely.

Mini black holes accessible to a doable collider are around 1% but dangerous black holes that could eat someone are extremely unlikely, something like 10^{-20} or much less.

Louise’s point is as wrong as Kea’s point is right. Extra dimensions are no more “speculative” than the hypothesis that there are no extra dimensions. In fact, the opinion that the number of extra dimensions is exactly zero is a very unlikely, speculative hypothesis. A “measure zero” opinion, in some sense.

Extra dimensions are a natural, self-consistent part of the theoretical physics toolkit – that is compatible with all observations we know and that may explain some features of Nature and that is required by other deeper explanations in string theory – and if their mere existence were enough for the LHC to destroy the Earth, I would surely join the LHC alarmists, too.

It is far from enough.

10. dorigo - June 12, 2008

But the point, Bozox, is exactly that anti-LHC activists continue to offer a doomsday scenario “around the corner”, as we escalate to higher energy colliders.

For a sort of motivation for tev-scale gravity, however, see the post about Lisa Randall’s seminar at CERN from last September.


11. dorigo - June 12, 2008

Lubos, I disagree. One could by the same token argue that the existence of zero or even one god (as opposed to a gazillion gods) is a null-measure set, and thus highly unlikely. I prefer to keep it within the realm of science. Speculations open an infinite-dimensional space of worlds, but the very fact that one can speculate does not mean that ours is unlikely or whatever: it means precisely nothing.

We have to keep it in the tracks of scientific investigations as we have in the last four hundred years: we have no hints that there are extra dimensions, so they remain a highly unlikely speculation, despite how fancy the theories are.


12. Andrea Giammanco - June 12, 2008

Indeed, there are more religions with a gazillion gods than monotheistic religions. I think that this a sign of something.

13. bozox - June 12, 2008

Extra dimensions != TeV-scale black holes, right? 🙂 Even if the radius of compactification is ~TeV.

The doomsday/BH scenario was tossed around as early as RHIC, if I remember correctly. Nothing new.

14. dorigo - June 12, 2008

Oh, and – Lubos: Kea is definitely a theorist, while you are not one any longer if I understand your current position. A science advisor is more a bureaucrat to me than a scientist. Please correct me if I am wrong…


15. Kea - June 13, 2008

I think she just wants to communicate that we might end up feigning more confidence than we really possess.

Yes, this is basically right, but of course I was also reacting to the harsh treatment of the doomsday people, who are simply acting in what they consider to be the best interests of humanity, and from what I gather they are not all completely ignorant of the facts.

LOL, Lubos. I think it’s fair to say that neither of us is a theorist: me because I wait tables for a living, you because ….

16. Ed Darrell - June 13, 2008

1. Astounding that when real scientists working on the real frontiers of real science take extra pains to be careful and safe, they get hammered for letting the public — the “booboisie” as H. L. Mencken called them — know that thought has been given to all potential dangers. It’s as if people can’t believe that real scientists function in sunlight.

2. I’m reminded of Ernst Mach, who despite having taught so many of the people who developed atomic theory, had difficulty himself with the idea. “Atoms?” he’d say. “No one has ever seen one.”

But despite Mach’s skepticism, he didn’t denounce his students and try to stop their work.

Mach was a wise man. Others would do well to follow his example.

17. Luboš Motl - June 13, 2008

Dear Tommaso,

if you are closer to Kea’s type of being a “theorist” than mine, then you are a crackpot, too – which is the case even without the assumption, after all. 😉

Extra dimensions have different degrees of probability than God, and indeed, theories that they are “right around the corner” are rather likely, but that is hard to explain to you. It might be easier to explain it to Kea.

I am no advisor to anybody.


18. dorigo - June 13, 2008

Boo-hoo, I’m now labeled with the infamous word. I wonder if I will have the guts to go back home and look at my children in their eyes.

LEDs are a fascinating, if quite improbable, way by which we might see something beyond the SM horizon. I like to be open, but not gullible… I have bet 1000$ dollars one way, you have bet 1000$ another if I understand correctly. Unfortunately, these are two separate bets. We will still have a chance of mocking each other in a few years, depeding on who wins and who loses… Only, if I lose I will be happy anyway, while if you lose you will be doubly sad 🙂

And ok, I acknowledge your correction: you are not a science advisor. I had been picking up a rumor I heard who knows where.


19. island - June 13, 2008

Okay, let’s see if I have this right…

The LEP experiments have yet to find any evidence for MSSM Higgs boson production despite the fact that they have combined their results from data taken at center of mass energies from 91 to 183 GeV to place lower benchmark limits of 78.8 and 79.1 GeV.

Meanwhile, the results from individual experiments from 189 GeV have confirmed the combined results 83.5 and 84.5 GeV, and in addition, exclusions at 175 GeV are becoming available for any stop-mixing scenario.

Not to mention the fact that the expectation for the standard model higgs at 160 GeV has been eliminated to a 95% CL, while Lumo sits there just as confident and arrogant as he can possibly be, showing none of the expected humility, as none of this even gives him pause, which is not what one would expect from a scientist who is watching his best theories fall apart before his eyes, but is something that is quite common among crackpots and creationists.

So I’ll take Dorigo’s uncanny crackpot’ intuition over Lubos’ arrogant confidence any day.

20. island - June 13, 2008

Oh crap, it just hit me.

Lumo had previously indicated that he thinks that a lack of evidence for the existence of something, constitutes evidence for the existence of something, as long as his favorite theory says that it’s the only way, and that explains his confidence… doh!

My mistake… 😉

21. goffredo - June 14, 2008

I was on vacation. Please keep this exchange going. It is quite remarkable. I am not being sarcastic. Well, not entirely, just a little

22. Evil String Theorist - June 14, 2008

The MSSM Higgs boson is expected to be in the range 114-130 GeV, which has definitely NOT been excluded. So why should an exclusion at 160 GeV give us pause?

23. island - June 15, 2008

EST… I said that the SM higgs has been (mostly) excluded at 160 GeV, which *should* make you stop dead in your tracks, but my information about the mssm higgs was outdated, so I could use a little help there… …Dorigo.

24. dorigo - June 15, 2008

Island, the MSSM Higgs is a more complex business than the SM one. It is way too hard for a Sunday afternoon for me to try and make a summary of recent numbers… The bottomline though is that limits have been derived for some benchmark channels which assume values for many of the 100+ parameters. And then again, if you go past “minimality” you will have more freedom to set your Higgs mass where you want it… I am sure all of that is familiar to you though.


25. island - June 15, 2008


And I’m sorry if I woke you up… 😉

26. Tom O'Bulls - June 16, 2008

I really *still* don’t understand why there is a debate about LHC destroy-the-world scenarios. It’s very simple: ask yourself how many human lives you would be willing to sacrifice to make it work. Let’s say the number is 6. Then you should be prepared to let it run if you can substantiate an argument showing that, over the full lifetime of the LHC, the probability that it will ever destroy the world is less than one in a trillion. Here I am estimating that the total number of human beings who are alive or who will be alive throughout the lifetime of the solar system is about 6 trillion — you can adjust this number if you are more pessimistic/optimistic.

OK, I am partly joking, but [a] calculations of exactly this kind are routinely made when large engineering projects are projected: there is a whole field [risk analysis] devoted to such calculations, and [b] if we want to call ourselves scientists, we have to be quantitative about this. It is true that the risks of running the LHC are very very small, but the costs of getting it wrong are very very large. What is the product of [very very small] with [very very large]? The point I am making is that we are not accustomed to dealing with costs of this magnitude, so assurances that the risk is “small” are *absolutely meaningless*. The sooner we realise this the better.
The Lumotic suggests that the probability [of what exactly?] is about 10^(-20). I would regard that as acceptable, *if* he could substantiate this number, which I strongly doubt. But at least he is generating NUMBERS, so he is on the right track!

27. dorigo - June 16, 2008

Hi Tom,
sure, I understand the “risk assessment” point of view, but as you note, the whole paradigm of insurance and premium fails with exceedingly rare events which can break the house.

Numbers are useless, because of the trouble with agreeing on an “acceptable” level of risk, and on the impossibility of a credible estimate of the latter. The only meaningful way to proceed is to demonstrate experimentally that black holes do not get created in high-energy collisions in the Universe. That, I think, is the goal of the review in progress by CERN theorists. It is due out soon.


28. Tom O'Bulls - June 17, 2008

I’m sorry, I just don’t agree. Consider for example the construction of a nuclear reactor. In the UK at any rate, the engineers *do* have to compute the expected number of deaths per year from all kinds of failures [including catastrophic ones], and they are required to keep this *actual number* below a certain level. If you told the nuclear regulatory authorities that you propose to build a reactor, and that you don’t know the number of expected deaths but that you are sure that the number is “small”, then you would be stopped [by law] from building it. It’s that simple. Also I am perturbed that you think it “impossible” to agree on what would constitute acceptable risk. You live in a democratic society [of sorts…..] so you have to convince your fellow citizens. If you can’t, then you should abandon the project. Again, if the CERN theorists really can’t come up with a concrete number, then the project should be stopped. I know, the risk is ridiculously small. But the cost is ridiculously large. I don’t want your children to be converted into strange matter, or to consider the possibility that all recordings of Beethoven Opus 132 will be destroyed. We need a *number*, and it had better be *really* small. By the way, the RHIC people did produce numbers regarding strangelets etc, so this kind of thing can be done. [Of course, their analysis was sloppy and their [initial] numbers were pretty stupid, but I’m sure the CERN people are more careful…..]

29. goffredo - June 17, 2008

Hi Tom O’Bulls.
Good point and it poses a nice challenge to HEP “theorists” at LHC.

30. dorigo - June 17, 2008

Hi Tom,

you seem unwilling to get the point. We do research because we do NOT know. We do not know whether there are extra dimensions, we do not know whether micro black holes can be produced in collisions. We know they radiate, however, and decay very fast.

Given that there are things we know and things we totally do not, we could well assign probability one to those we do not know, and see whether the product of the others (of not destroying the earth) comes up at less than one in a billion. But this staying on the safe side would be a potentially very silly way of dealing with unknown effects: Anybody could come up with some unforeseen, improbable effect for any project, and nothing would be built, nuclear reactors included. The heart of the matter is that the concept of “probability” is very fuzzy.

I think the paper that will soon come out about these issues will however address your doubts, because from the observation that some objects exist in the universe together with high energy cosmic rays allows one to determine that high-energy collisions are not harmful for us.


31. goffredo - June 18, 2008

There are also things we don’t know we don’t know!

I feel that it would be INTERESTING if someone sat down and made the excercise of a psuedo-risk-analysis on the basis of what we know, allowing for what we know we don’t know, and try to set some benchmark questions and numbers that exotic theorists and even crack-pots could then try answering and challenging.

32. rationalpsychic - July 30, 2008

It’s heartening for a liberal arts major to read a physicist quoting Voltaire. It’s also understandable to think that there are at least a few clowns who appear to be begging for a good old-fashioned rhetorical bashing.

33. dorigo - July 31, 2008

Hi rational psychic (did not know such a combination existed in nature – it must have been due to some pretty odd union). Thanks for the visit. Yes, people who ask for it are all around. A small number is always good, but too many of them are a distraction.


34. vonwao - August 21, 2008

Hi, I’m wondering if the review or paper that was mentioned a couple months ago that was supposed to be due out soon, is it out? Can someone point me to this?

I am not a physicist but I have a friend who is, who brought up the topic and said to me that one prudent way to proceed might be to set up experiments to find evidence of Hawking radiation, since it has actually never been observed. From my limited understanding, this would ensure that if a mini-hole is created, it would not pose a threat. If anyone is still watching this thread, could you comment on this?


35. dorigo - August 21, 2008

Hi otto,

yes, the report has been out since a couple of months ago. Please see in

About testing hawking radiation, I am afraid there is no way to do it other than try and produce black holes. Which we do not really know how to do. Despite speculations, the chances that LHC will produce black holes are objectively tiny, since they depend on adjusting a parameter to a very particular value, in a theory which nobody has ever proven.


36. vonwao - August 22, 2008

Hi dorigo,

Thanks for your reply. I realize there may be no way of testing hawking radiation, but might there be a way to find indirect evidence of it, by using telescopes, etc., the same way we find evidence for other phenomena in the universe?

About your mention that producing black holes “depends on adjusting a parameter to a very particular value”… like I said I don’t know much about physics, can you tell me and explain what this parameter is or point me to a source?


ps. I appreciate the respectful and non-fear mongering discussion on your blog 🙂

37. dorigo - August 22, 2008

Well, I am not sure. Black holes are only found through their gravitational effects, and the temperature of Hawking radiation, I am told, is inversely proportional to their mass: for reasonably-sized ones the temperature is too low to be detected with ordinary means such as x-ray probes etc.. What might, one day, be seen is some evidence of H.r. by measuring the evolution with time of their mass. But it seems far-fetched.

The parameter I mention is the scale of quantum gravity. I suggest you to read the Mangano-Giddings paper for a start.


38. Klü Lés - September 11, 2008

I’m no scientist so forgive me if my questions sound ridiculous.

If a micro black hole was actually created, would it have enough mass for it’s gravitational field to pull apart atoms and/or molecules? Isn’t gravitation the weakest force? especially at very small sizes?


39. dorigo - September 11, 2008

Hi Klu,

no question is ridiculous, if it is asked with the intent of furthering one’s knowledge.

If a micro black hole was indeed created, it would vaporize instantly, because it would be very hot and it would radiate off all its energy in a very small time.

However, assuming radiation is not allowed, the black hole would move away from the point where it has been created, and in its path it would find nuclei. It could, in principle, absorb some mass, and grow as it encounters more nuclei. Gravity is weak, however, so this would indeed be a slow process. A black hole would traverse the earth and cross just maybe a dozen nuclei. The problem might be that it could in principle be captured in the earth’s gravitational field, thus staying around, and eventually grow.

This is what some people are fearing. Now, we know it is not happening because 1) black holes do not get created in proton-proton collisions (the theory “predicting” this is a speculation, and itself requires very special conditions to enable BH creation); 2) black holes radiate, so they decay very quickly; 3) black holes would then be created daily in the solar system and in the whole universe, and we would have very clear effects of the process, which we do not see.


40. hamburgler - January 19, 2009

I’m on the web looking up these terms and the hawking radiation and just black holes in general are all theoretical. The stuff i’ve been reading suggest black holes dont really even exist. they don’t know what it really is. So, you would think some one with a scientific mind would want to do more research before he or she takes a risk that they may or may not harm innocent people who dont know or care about any of this. Thats why its become such a big deal i think. CERN is sort of forcing people to say ” hey! if your not 100% sure what your doing, then why are you doing it! My life shouldnt be jeperodized due to the irresponsibility of a group of scientist on a quest to find there meaning in life. If it’s that important then find another way that leaves the rest of us 100% out of your equation. Thats all i have to say.

dorigo - January 19, 2009

Dear hamburgler,
what is it that you care about, your ipod ? If you like it, you’ve got to like the research that brought it to you. Since you do not seem to understand the details, leave them to people who do, and who also have a life they care about.
Also, please do not confuse matters: scientists are not after the meaning of life, but after the improvement of life through a better understanding of the way the world works. For the meaning of life, please address your complaints to the closest church.


41. paul - July 2, 2009

how much ignorance my friends. the Nuclear company is not about improving our knwoeldge of the Universe, for that we have thought eperiments and theorists. Nor teh Higgs exist, but it is a top quark written with other equations and sold to Reagan as ‘god’s particles’ to get money. This is a crooked company that has nothing to do with the ideals of science. On the contrary it debases science and the opinion we have of it, with its callousness. Black holes dont evaproate, and after the Haifa experiment with soundholes we know a densely packed bosonic state of quarks will form one. So that is what probably will happen. quarks will form a black hole, it wontevaproate and we will all die. this is the fermi paradox *why there are no sings of intelligent life in a universe filled with planets. cern is the response

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