Talk:Safety of high-energy particle collision experiments/Archive 5

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Choptuik-Pretorius article

I see that Oldnoah has added to the section on micro black holes a mention of a paper entitled "Ultra-Relativistic Particle collisions". While the paper appears to be good enough to deserve publication in Physical Review Letters, it is not clear to me why it should be mentioned in our article. There are dozens of serious papers on black hole formation that might even be cited in a dedicated article on black holes, but, for the purposes of the article on the safety of the LHC, the old sentence

Although the Standard Model of particle physics predicts that LHC energies are far too low to create black holes, some extensions of the Standard Model posit the existence of extra spatial dimensions, in which it would be possible to create micro black holes at the LHC at a rate on the order of one per second.[59][60][61][62]

seems informative enough to me. Perhaps Oldnoah would care to elucidate what new and relevant information is contained in his sentence

This was recently updated in a March 17, 2010 Physical Review Letters article by Choptuik and Pretorius in which they offer a proof that micro black holes must form if the energy of two colliding particles is on the order of the Planck energy, and suggesting that that energy might be as low as 1 TeV if theories of extra dimensions are correct.

It is not clear to me how the statements in the second sentence constitute an "update" of the ideas mentioned in the first sentence. The fact that black holes might be copiously created at the LHC if there are extra dimensions and the true Planck scale is of the order of the TeV is well established (see e.g. the references [59]-[62]). The new paper addresses the extremely technical (from the point of view of our readers) question of whether black holes in particle collisions can arise as solution of the equations of classical general relativity (as opposed to quantum gravity, I presume). Do we really need to enter this sort of detail? I mean, does anybody among the editors (let alone the readers) have the background necessary to appreciate these subtleties? In addition, the second part of the sentence: "suggesting that that energy might be as low as 1 TeV if theories of extra dimensions are correct" is quite misleading. The paper just mentions that "Existing experimental bounds on the Planck energy in this context are at around 1 TeV", also a very well-known fact for which the authors cite nothing else than the Particle Data Group review (i.e., the repository of established results in particle physics).

In summary, it seems to me that the sentence on the Choptuik-Pretorius paper only adds noise to the paragraph, and while the paper does appear to be serious it is not particularly relevant to our discussion. I am inclined to remove the sentence but I would like to hear other editors about it. Cheers, Ptrslv72 (talk) 22:31, 22 March 2010 (UTC)

The article is the first computer-modeling proof that black holes should form; previous articles were more speculative. Further, the publication is in a more prestigious journal, Physical Review Letters, than previous articles. Further, the authors are from prestigious universities (Princeton and University of British Columbia). The article itself was initially published on arXiv as a preprint, then accepted for publication and published on March 17, 2010. Certainly the editors of Physical Review Letters believe the article adds something not already published. In particular, it adds the extensive computer modeling, and the article has been referenced in numerous other science-review publications (not cited, but I will obtain those shortly).Oldnoah (talk) 23:03, 22 March 2010 (UTC)Oldnoah Here are two general references to the article, one from the western world, the other from the eastern:http://news.sciencemag.org/sciencenow/2010/01/22-01.html?etoc http://www.blogchina.com/20100220896139.html Oldnoah (talk) 23:16, 22 March 2010 (UTC)Oldnoah

I am aware that the Choptuik-Pretorius paper has been published on a prestigious journal (BTW, the same is true of ref.[60], which has collected hundreds of citations in the scientific literature). What I am arguing above is that it does not add any information relevant to our article. The old sentence already tells all we need (black holes can be created copiously at the LHC if the Planck scale is of the order of the TeV), there is no point in larding the article with technical information that very few of the readers will understand (anybody who can appreciate the relevance of this new paper does certainly not get his information on Wikipedia). It does not seem to me that you have addressed this criticism, but let's see what the other editors think about it. Cheers, Ptrslv72 (talk) 23:50, 22 March 2010 (UTC)

Further, the article is in essence the first application of relativity, via computer modeling, to determine whether or not black holes can form, and found that they would at about the Planck energy. Previous articles were guesses or speculation about that, this article is the 'proof'; the only question then remains as to whether the Planck energy is the high value of our common 4-dimensional space-time, or whether it is lower due to extra dimensions. That speculation, of course, remains the same; the major difference is that this is now a proof that black holes form, not a speculation, when particles collide at ultra-relativistic energies. If anything should be deleted, it should be one of the older articles, not this one which is more informative and authoritative.Oldnoah (talk) 23:23, 22 March 2010 (UTC)Oldnoah

The paper has collected only 5 citations in six months, not exactly the scale of the truly groundbreaking... As I mentioned above, the paper only shows that the equations of classical general relativity do admit a black-hole solution in the collision of two high-energy states. I suspect that the reason why the paper did not become an instant classic is that it is not obvious that physics at the Planck scale is indeed described by the classical (as opposed to quantum) theory of gravity. As I wrote above, Dimopoulos-Lansberg has 605 citations, this one only 5, it will take a while before you can delete the old articles... But this is not even the point: we should not be discussing such technicalities, all the info required by the safety article was already there. Now it's late in my time zone. Cheers Ptrslv72 (talk) 23:50, 22 March 2010 (UTC)

I cannot follow your argumentation; first you say it needs to be peer reviewed and published by a serious magazine to be included, this is the case for the article, and now you are suggesting that "only" 5 citations is not enough. I don't read anywhere that Wikipedia is a popularity reference. Oldnoah's argument "the first computer-modeling proof" is a valid one, it brings something fresh to this article, and I can imagine that it would interest the reader. btw we could also include a reference about the Anomalies and discrepancies of all the gravitation theories. greetings, Michel_sharp (talk) 08:30, 23 March 2010 (UTC) —Preceding unsigned comment added by 80.201.242.140 (talk)

Yet, the argumentation is rather trivial: a lot of papers on black holes are peer-reviewed and published, but not all of them are relevant to this article. My main point is that the sentence written by Oldnoah does not add new information to the sentence that precedes it (at least, new information relevant to the understanding of the safety-of-the-LHC issue by regular readers). This paper might be relevant to an article specialized on black holes, but in our case it simply makes the paragraph heavier. The comparison between the number of citations of the two papers was just in response to Oldnoah's funny claim that this paper is "more informative and authoritative" than the ones referred to at the end of the old sentence (the number of citations by other scientific papers is a commonly accepted measure of the impact of a given paper). If you really want to include this paper in the article, it should be just as an additional reference at the end of the original sentence, which - for the umpteen time - already conveys all the necessary information. BTW, note to Oldnoah: in my opinion there is no need to write the exact publication date of each paper, and please create a single reference for the arXiv version and the journal version (unless there is a special reason for not doing so). Note to Michel_Sharp: please remember to sign with four tildas your comments on the talk page. Cheers, Ptrslv72 (talk) 10:34, 23 March 2010 (UTC)

Let's see, the reference 60 (Dimopoulos, et al.) came out in 2001; and the current one came out in 2010, so yes I would expect the older article to have more cites; give it the same amount of time and this one will have just as many if not more. Not everyone has a paid subscription to Physical Review Letters, so if you want to read the entire article and not just the abstract, I included the arXiv version which is free. This article is not just another black-hole paper. It specifically makes reference to the LHC and its possibility of making micro black holes; it is tailored to this Wikipedia article in that regard. It is indeed a seminal article on the potential for the LHC to make micro black holes, as it provides a proof, not a mere conjecture as was true for all the prior articles.Oldnoah (talk) 12:38, 23 March 2010 (UTC)Oldnoah

From the link I gave above you can see that ref.[60] collected roughly 30 citations in its first six months, and whether the Choptuik-Pretorius paper will get just as many in the foreseeable future is entirely your speculation. However, this is not my point and you keep avoiding the main issue. This Wiki article is not specifically about black holes, it is about the safety concerns at the LHC. Of course we could keep larding each sentence with more and more references to specialized literature, but this would not give any additional information to the average reader and would just make the paragraphs much heavier. In the paragraph that we are discussing, the relevant information is that the LHC can produce black holes copiously if the true Planck scale is of the order of the TeV. This information was already given in the original version, and the sentence that you added simply delays the moment in which the reader gets to the relevant point of the article, i.e. the safety of the hypothetical black holes produced at the LHC. If you are really in love with this Choptuik-Pretorius paper you can add it as a further reference at the end of the original sentence (I mean, as ref.[63]). As to the comment on the arXiv version, I am just suggesting that you link both the arXiv version and the published version in the same reference, as is done for the other papers cited (and please, once again, write title, authors and so on in the reference). Cheers, Ptrslv72 (talk) 16:19, 23 March 2010 (UTC)

"We show, for the first time, that at sufficiently high energies the collision leads to black hole formation ..." That's what the abstract starts out with. This is a unique paper, showing for the first time that micro black holes are not merely conjectured that they might form, but rather must form, if the Planck energy is achieved. I believe that is a significant difference. Further, 30 citations in 6 months for the first article in Physical Review Letters (Dimopoulos), and it is only one week out for this current paper. One can hardly expected it to have been read, let alone cited in other articles. This type of comparison is inherently biased until sufficient time elapses to determine how others will respond to Choptuik-Pretorius. And the arXiv preprint is not the same - theorists much prefer to wait until the article has been published by a peer-reviewed journal, rather than citing to arXiv or viXra. I did take your suggestion and make it to one reference, instead of two.Oldnoah (talk) 22:56, 23 March 2010 (UTC)Oldnoah

Clearly you don't know what you are talking about. The paper has been out on arXiv for seven months, and you can be sure that theorists check arXiv every day and when a paper is good they certainly don't wait for publication in a journal before reacting. If it does show anything, the relatively long delay between the appearence of this paper on arXiv and its publication in PRL shows that at least one referee was not happy with it. Anyway, I have nothing against mentioning this paper in the Wiki article dedicated to micro black holes (as you seem to have already done). My point is that elaborating on it in the Safety article only makes the paragraph heavier without adding relevant information. We already say that theories with extra dimensions predict the formation of micro black holes at the LHC, and this is enough to set the stage for the subsequent discussion. Cheers, Ptrslv72 (talk) 10:33, 24 March 2010 (UTC)

In addition, let me stress a point that I mentioned already twice but that you don't seem to understand. This article shows that classical general relativity does predict the formation of black holes in high-energy collisions. However, this does not mean that, as you seem to believe, micro black holes must be formed in particle collisions at the LHC if the Planck scale is low enough. Black-hole formation at the LHC is a quantum-mechanical (as opposed to classical) process, and we don't have a quantum theory of gravity. Therefore, black-hole formation at the LHC remains a conjecture. Anyway, as I stressed already a million times, this discussion is not relevant to the subject of the article, i.e. the safety of particle collisions at the LHC. Indeed, the safety argument assumes that micro black holes will be created at the LHC, then it goes on to show that they cannot be dangerous. Cheers, Ptrslv72 (talk) 15:13, 24 March 2010 (UTC)

I believe I was quite clear that it remains conjecture as to whether the LHC will reach the Planck energy. Ergo, it remains conjecture whether micro black holes would form at the LHC. The article says they MUST form IF the Planck Energy is accessible at the LHC. Perhaps you have a hard time understanding plain English. Incidentally, as a reminder regarding the safety argument which relies upon black hole evaporation, here's what Helfer said: "The prediction that black holes radiate due to quantum effects is often considered one of the most secure in quantum field theory in curved space-time. Yet this prediction rests on two dubious assumptions: that ordinary physics may be applied to vacuum fluctuations at energy scales increasing exponentially without bound; and that quantum-gravitational effects may be neglected. Various suggestions have been put forward to address these issues: that they might be explained away by lessons from sonic black hole models; that the prediction is indeed successfully reproduced by quantum gravity; that the success of the link provided by the prediction between black holes and thermodynamics justifies the prediction. This paper explains the nature of the difficulties, and reviews the proposals that have been put forward to deal with them. None of the proposals put forward can so far be considered to be really successful, and 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." Adam Helfer "Do Black Holes Radiate"; http://xxx.lanl.gov/abs/gr-qc/0304042 (2003) Oldnoah (talk) 22:05, 24 March 2010 (UTC)Oldnoah

A couple of other quotes regarding the energy requirement for the formation of micro black holes:"The Large Hadron Collider at CERN will have a center-of-mass energy of 14 TeV, i.e. more than an order of magnitude larger than the value of the fundamental Planck scale M∗ = 1 TeV, suggested by the most optimistic scenaria with extra dimensions. It becomes then a natural place to look for strong gravity effects, and possibly for the creation of black holes. Studies have shown that their production can be realised as long as the energy of the collision exceeds at least the value of 8 TeV. At the same time, the produced black holes are expected to have a mass of at least a few times the value of the fundamental Planck scale if we want the classical theory of General Relativity and its predictions to be still applicable. According to the above restrictions, the Large Hadron Collider is found to lie on the edge of both the classical regime and of the black hole creation threshold." Panagiota Kanti, "Black Holes at the LHC" http://arxiv.org/pdf/0802.2218v2 (2008) "We present results from numerical solution of the Einstein field equations describing the head-on collision of two solitons boosted to ultra relativistic energies. We show, for the first time, that at sufficiently high energies the collision leads to black hole formation, consistent with hoop conjecture arguments. This implies that the non-linear gravitational interaction between the kinetic energy of the solitons causes gravitational collapse, and that arguments for black hole formation in super- Planck scale particle collisions are robust." Matthew Choptuik and Frans Pretorius; "Ultra Relativistic Particle Collisions"; http://arxiv.org/pdf/0908.1780v1 (2009) Oldnoah (talk) 22:12, 24 March 2010 (UTC)Oldnoah

You still don't get it, and I don't see the point in continuing this discussion since - as I mentioned 1000 times - it is not relevant to the safety article. Anyway, for the record, I'll try one fourth and last time. The Choptuik-Pretorius paper does not say that "micro black holes must form at the LHC if the Planck scale is of the order of a TeV". It says that classical general relativity predicts that they must form in those conditions. However, as is mentioned even in the first two of your quotes above, we don't know whether or not classical general relativity is the correct theory to describe micro black holes at the LHC. Possibly, to describe micro black hole formation in high-energy collisions we need a theory of quantum gravity that we still don't have. This is why the LSAG argument takes the super-conservative assumptions that black holes i) are created at the LHC and ii) don't evaporate due to Hawking radiation, and goes on to show that even in that case they cannot be dangerous. Cheers, Ptrslv72 (talk) 18:52, 25 March 2010 (UTC)

Well, yes, I do presume that classical general relativity is operable, and not some other weird physics we see in the pseudo-science forum or otherwise cess-pooled. As to whether the assumptions of i) a lower Planck-energy and ii) non-evaporation of micro black holes are "super conservative" or not, I'm not able to answer. They do, however, seem reasonable to numerous theorists who have proceeded along those lines. However, the LSAG when it "goes on to show that even in that case they cannot be dangerous" also makes certain assumptions that have been criticized. In particular, it makes the assumption that relativistic micro black holes are not 'slippery' and will stop in in dense nucleonic matter such as neutron stars/white-dwarfs; and that those galactic bodies have sufficiently weak magnetic fields that inbound cosmic rays aren't deflected and can generate micro black holes that would be stopped. The LSAG makes those unexpressed assumptions without any discourse on them, which is the main subject of objection to the LSAG, as it relates to micro black holes, as I understand it, other than the Rainer Plaga idea which is not even addressed in the LSAG. That having been said, it might also require an inordinate amount of time for a few micro black holes to cause a neutron star to disappear, far longer than their observed lifetimes which are on the order of under 1 million years. Making micro black holes at the LHC in far greater abundance than those that might be stopped by a neutron star during its lifetime therefore also becomes a problematic difficulty for the LSAG. We can, of course, hope that Panagiota Kanti's article ["Black Holes at the LHC" http://arxiv.org/pdf/0802.2218v2 (2008)] is correct, and that the Planck energy is at 8 TeV or higher, and won't be reached with this current proposed round of collisions at 7 TeV.Oldnoah (talk) 19:37, 25 March 2010 (UTC)Oldnoah

If you "do presume that classical general relativity is operable", why do you quote somebody (Helfer) who complains that the argument on Hawking evaporation is flawed because it neglects quantum-gravitational effects? Do you even understand the stuff that you are posting? I can only conclude that the distinction between "classical" and "quantum" is lost on you (sorry for not realizing that earlier). Just for your information: general relativity, like all theories, is "operable" only in its own domain of applicability. If the energy involved in a gravitational process approaches the scale at which quantum effects become important, we can no longer be sure that general relativity gives the correct description. And guess what is the name of that energy scale? It's the Planck scale... If these very basic concepts sound like "weird physics" to you, I suggest that you gather a lot more information before even trying to discuss difficult issues such as black hole production. Anyway, we are once again straying from the purpose of this page, which is discussing improvements to the article. Cheers, Ptrslv72 (talk) 21:29, 25 March 2010 (UTC)

Perhaps a bit off topic, but could you perhaps explain me why something irrational like micro-black-holes is included in the safety-report, and a simple logic autocatalytic event not? greetings, Michel sharp (talk) 12:46, 26 March 2010 (UTC)

There's mentioning of magnetic monopoles and vacuum bubbles, but no explanation.

How exactly do some people think these might cause a doomsday scenario? As for the latter I heard something about a low energy vacuum travelling at close to light speed, but I'm not clear how this results in the destruction of the Earth. Robo37 (talk) 11:57, 22 March 2011 (UTC)

See Vacuum_metastability_event#Particle_accelerator. To put it loosely, if the universe relaxed a bit in some tiny particular spot, then that spot would spread out and eliminate the universe. To make the universe go poof, you'd have to be able to tickle it just right. This is unlikely to occur by accident. If someone figured how to do it, there would be no seeing if it worked - only failure would be observable. - 67.224.51.189 (talk) 20:41, 24 April 2011 (UTC)

External Links

The link [hasthelargehadroncolliderdestroyedtheworldyet.com] has been added to the article. I've reverted it though funny, but it's been re-added and I'm certainly not going to start an edit war with a fellow admin, so better to bring it here. The external link certainly isn't encyclopaedic in my opinion, and I don't see how it fits into WP:EL and I can't see a justfiable reason for it's inclusion and certainly falls foul of WP:ELNO point 1. If so we may as just add all the joke sites that did the tour at the expense of the tin hat brigade, including the video of CMS disappearing into a black hole. cheers ^Khukri 10:33, 17 September 2011 (UTC)

I'll add my thoughts on why it should be in there, but for now I'll revert as a show of good faith since you brought it up on the Talk page. Thanks, Steven Walling • talk 22:52, 17 September 2011 (UTC)

The policy on External Links states:

Some acceptable links include those that contain further research that is accurate and on-topic, information that could not be added to the article for reasons such as copyright or amount of detail, or other meaningful, relevant content that is not suitable for inclusion in an article for reasons unrelated to its accuracy.

In my opinion the operative words here are meaningful, relevant. The website in question may be funny, but it doesn't add any information whatsoever to the article. Moreover, I concur with Khukri's "slippery slope" argument. If we start linking humorous websites just for the sake of it, anybody will be entitled to add their own. Cheers, Ptrslv72 (talk) 17:02, 18 September 2011 (UTC)

Energy differences Cosmic Rays versus LHC

There is no clear overview in the article of what the Energy differences are between the LHC and Cosmic Rays. Therefor I would like to add this topic: Energy differences Cosmic Rays versus LHC

Normal Cosmic Rays: 10^7 eV to 10^10 eV

Man-made: 10^12 to 10^13 eV

OMG Cosmic Rays: 3 x 10^20 eV

Energies:

1 MeV = 10^6 eV

1 GeV = 10^9 eV

1 TeV = 10^12 eV

references:

Cosmic_ray

Large_Hadron_Collider

Ultra-high-energy_cosmic_ray

Electronvolt

Michel_sharp (talk) 20:08, 11 january 2011 (UTC)

Hi Michel, as you know very well the subject of this article is the safety of particle collisions at the LHC. I don't see exactly what you are trying to show with the plot and the numbers that you give above. Anyway, before editing the article, you should prove with reliable sources (i.e., no original research, no personal inferences of yours) that what you want to add is relevant to the subject. Cheers, Ptrslv72 (talk) 15:14, 13 January 2011 (UTC)

Hi Ptrslv, The reason why I want to put it in is because it clarifies this part in the article: One argument raised against doomsday fears was that collisions at energies equivalent to and higher than those of the LHC have been happening in nature for billions of years apparently without hazardous effects, as ultra-high-energy cosmic rays impact Earth's atmosphere and other bodies in the universe. If I am interested in safety I would like to see some numbers that go along with this statement, and the two post I want to add just do that. Regarding reliable sources, I have added the links needed, you can check them if you want. This not a matter of personal research but a presentation of the facts. If there is no good argument against I will add these two topics on friday, kind regards Michel_sharp (talk) 19:38, 13 January 2011 (UTC)

The stuff that you want to add is not really related to the issue of safety. In your first "post", you seem to attach a lot of importance to the fact that the flux of high-energy protons from cosmic rays hitting Earth is much smaller than the rate of collisions at the LHC. But so what? The plot shows you that the rate of cosmic rays hitting Earth with center-of-mass energy equivalent to the one of the LHC (i.e., those in which the proton in the cosmic ray has an energy of 10^17 eV) is somewhere between 1/m^2/year and 1/km^2/year. This means that a lot of proton-proton collisions with center-of-mass energy comparable to (or larger than) that of the LHC collisions have occurred on Earth since its formation. If those collisions could create some planet-destroying monster they would have already done it many times over, but the planet is still there, therefore the collisions are not dangerous. This is the essence of the cosmic rays argument, and it's already spelled clearly in the article. If you want "to put some numbers" you can find out the precise rate for cosmic rays of 10^17 eV and quote it in the article (with a reference), but the other stuff you wrote - i.e., the lengthy description of the plot and the paragraphs on the structure of cosmic rays - is out of place. That's what the cosmic rays article is for.

What you mean with the numbers in the second "post" is even more obscure to me. The plot shows an energy spectrum for the cosmic rays ranging between 10^8 eV and 10^21 eV. How do you decide that the "normal" cosmic rays are those between 10^7 and 10^10 eV? And why should we give in this article a table of conversion between eV, MeV, GeV, and TeV? TeV is hyperlinked in the text (see the section "Particle Accelerator") and the interested reader can just follow the link (as for the cosmic rays plot). Also, the energy of LHC collisions is already given in the text.

Last but not least, despite our earlier discussion, you still don't get that you must compare collisions with equal energy in the center of mass frame (i.e., the relevant value for the cosmic ray energy is 10^17 eV, not 10^12 eV). Please try to understand this important point before coming back. Cheers, Ptrslv72 (talk) 22:58, 13 January 2011 (UTC)

(e.g., you can read again the link that I gave you last time). Ptrslv72 (talk) 23:42, 13 January 2011 (UTC)

Regarding the second topic:

...these very high energy cosmic rays are very rare; the energy of most cosmic rays is between 10 MeV and 10 GeV.

Ultra-high-energy_cosmic_ray

Cosmic rays can have energies of over 10^20 eV, far higher than the 10^12 to 10^13 eV that man-made particle accelerators can produce.

Cosmic_ray

When reading the first quote, I considered most as the norm. If I use 'Man-made: 10^12 to 10^13 eV' isn't that the same as using the 14 TeV (= 1.4 * 10^13 eV) mentioned in the article that you refer to, and that reaches an equivalent energy in the centre of mass of 10^17 eV? Next in that article they look for energies that exceed these energies and they end up in the lower bottom region of the graph, referring to the amount of these collision that happen continuously in space. That is a fair point, but they do not make the comparison of the density of collision at one place, that is why I want to add the first topic where the following is nicely explained:

in one square meter, looking over the whole upper half of the sky (2 pi = 6.2 sr), in a bandwidth of 1 GeV, one sees 1000 particles every second. That is very small compared to the luminosity of the LHC, which is somewhere around 10^30 collisions per square centimeter per second, the difference is 10^27.

btw I thought it would be handy for the reader to add a short table what MeV's, GeV's and TeV's are. I can understand that it is perhaps to much information and a reader could look it up themselves but I just think it gives clarity to the situation where both notations are used. Greetings, Michel_sharp (talk) 12:18, 14 january 2011 (UTC)

1) it was your sentence in the first post "The protons in the LHC have an energy of around 3.5 x 10^12 eV (3.5 TeV). The cosmic ray plot shows that the flux of particles with energies around 10^12 eV is much lower (...)" that made me conclude that you still don't get the center of mass issue.

2) it does not matter if most cosmic rays have energies lower than 10^17 eV. The plot shows that there are still a lot of cosmic rays with energy at or above 10^17 eV, i.e. those that matter for the safety argument. Your usage of the term normal is arbitrary and misleading, as if the cosmic rays with energies higher than 10^10 eV were somehow abnormal. Note BTW that 10^17 eV is not considered ultra-high energy.

3) most importantly, if you understand the cosmic ray argument it should be clear to you that the "density of collision" is irrelevant to it. Therefore, the difference between the flux of cosmic rays from the sky and the luminosity of the LHC has no place in the article, because it is not a safety issue . If you can find a reliable (=academic and peer-reviewed) source that claims otherwise we can talk about it. Otherwise, you are just trying to push your personal inferences into the article.

Cheers, Ptrslv72 (talk) 12:11, 14 January 2011 (UTC)

Ptrslv72, I would be more than happy to stop questioning the LHC if you could refer me an article where it is explained that density of collisions is not a safety issue and irrelevant. Kind regards Michel_sharp (talk) 15:78, 14 january 2011 (UTC)

Sorry, I will not go again through the arguments of our earlier discussion. The important point here is the following: neither the Safety of the LHC article nor this talk page are the right place for you or me to "question the LHC". The article is meant to report on the debate on the safety of the LHC that took place in the scientific literature, in the mainstream media and in courts. The purpose of this talk page is strictly limited to discussions on how to improve on the reporting. You can go discuss your personal misgivings about the LHC in physics forums, there are plenty out there but this page is not one of them. I, however, have neither the time nor the inclination to give you an introductory course in particle physics. Cheers Ptrslv72 (talk) 15:08, 14 January 2011 (UTC)

Sorry Micheal, I agree with Ptrslv above, and regarding your statement for him to show it's not a safety issue, I'm afraid the burden of proof lies with you. You have to demonstrate that it is a safety issue, using reliable and verifiable third party sources, such as peer reviewed journals, or published papers to show this and not through your synthesis of data. Regards ^Khukri 17:58, 14 January 2011 (UTC)

Mmhh, I've started a topic at www.physicsforums.com but no one wants to go deeper into the subject and you are quickly considered as a Crackpot, here is the topic if you want to check it: Density LHC vs Cosmic Rays. Anyway I also contacted the guy from that Spanish website that Ptrslv72 gave and he was very friendly and came up with the idea of getting some info from String Theorists although they'll probably also don't want to touch the subject. I'll come back if I get some more references, best wishes Michel_sharp (talk) 23:00, 15 january 2011 (UTC)

Michel, you seem to think that quantity (density) of collisions means that some event, which has already been repeatedly stated as utterly impossible, is more likely to occur. Yet, you reject the sheer number of said interactions that have occurred with those few per year high energy particle collisions with the atmosphere of the Earth of the 4.5 billion year history of the planet. You also fail to consider the million fold higher interactions of the sun, over the 4.5 billion years of ITS existence, yet it is not a singularity, it is not being "eaten" by a singularity and it isn't a large, large, large bucket of strangelets. Indeed, to be blunt, when in full possession of theory, facts and events, as you even provided some accurate numbers, you have given great evidence of being a crackpot. Planets have been found still orbiting the remnant of stars after a supernova, no singularity created. By your candle, every planet in a star system should be loaded not with planets that were thoroughly cooked, but instead, all singularities, which would NOT be detected.Wzrd1 (talk) 00:14, 15 February 2012 (UTC)

Wzrd1, The LHC generates temperatures (pressure) more than 100.000 times hotter than the heart of the Sun, concentrated within a minuscule space. Hence that's why the protons do break apart, there and not in the core of the sun. There's a difference.

And I said in my previous comment, its a matter of frequency an density, because super high energy cosmic rays only come flying in a couple of times per year over the whole surface of the Earth or the Sun, in the LHC the frequency is in the billions for an area that is a few cubic centimeters.

Here are some numbers:

In nature there are about a thousand Cosmic-ray collisions of a few GeV’s (1 GeV= 10^9 electron Volt) per second per m^2. In LHC it are about one 1 billion per second per cm^2. That’s 1.000.000 times more for an area which is 10.000 smaller, it is a density & frequency difference of 10 billion and unique in the Universe.

At the end of last year we humans have even generated collisions on this planet, that were an other 1000 times more intense, with energies of 8 TeV (1 TeV= 10^12 eV). These collisions are in nature of course less frequent per m^2 while the density & frequency at the LHC of 10 billion per cm^2 was maintained.

... and just like a match that's lighted isn't just one single *spark* but millions as you rub it, or just like in a combustion engine, its the high frequency that lights it all up and makes the difference. best wishes Michel_sharp (talk) 21:30, 25 oktober 2013 (UTC)

The Flux of Cosmic Rays versus LHC

There is no clear overview in the article of what the Flux differences are between the LHC and Cosmic Rays. Therefor I would like to add this topic: The Flux of Cosmic rays versus those in the LHC

This graph shows the cosmic ray flux as a function of energy:

source: [[1]]

The first plot on the right shows a graph of flux, measured in number of particles per square meter per second per steradian per GeV (10^9 eV), on the vertical axis, versus particle energy, in electron volts, on the horizontal axis. You will see that the largest flux is at low energy (about 10^9 eV), where the flux is about 1000 particles/m^2-s-sr-GeV . So in one square meter, looking over the whole upper half of the sky (2 pi = 6.2 sr), in a bandwidth of 1 GeV, one sees 1000 particles every second. That is very small compared to the luminosity of the LHC, which is somewhere around 10^30 collisions per square centimeter per second, the difference is 10^27.

The protons in the LHC have an energy of around 3.5 x 10^12 eV (3.5 TeV). The cosmic ray plot shows that the flux of particles with energies around 10^12 eV is much lower, around 10^-3, that is, 0.001 particle/m^2-s-sr-GeV, or about 3 particles per square meter per steradian per GeV per *hour*.

For the number of particles created in cosmic ray showers the general trend is that higher energy cosmic rays produce more secondary particles. So while cosmic rays with energies of a few GeV may produce a handful of particles, the highest energy cosmic rays, around 10^19 eV, produce showers containing billions of particles. A somewhat technical overview on cosmic ray showers can be found here: http://pdg.lbl.gov/2007/reviews/cosmicrayrpp.pdf

The flux of cosmic ray shower particles versus particle type can be seen in Figure 24.3. The horizontal axis this time is atmospheric depth, which is zero at the highest altitudes, and about 1000 grams per square centimeter near sea level. Near sea level the cosmic ray secondary particles are mostly neutrinos and muons (about 100 particles per square meter per second per steradian), with smaller amounts of protons, neutrons, electrons, positrons, and pions.

Michel_sharp (talk) 20:08, 11 januari 2011 (UTC)

I hyperlinked cosmic rays in the article, so the interested reader can access the plot. I don't see the need to add the plot directly in the article about the safety of LHC. Cheers, Ptrslv72 (talk) 15:18, 13 January 2011 (UTC)

I made a diagram that compares the number of collisions due to cosmic rays and experiments next to earth Compare Collision Rate Of Cosmic Rays With Colliders. See also the paper behind the diagram Comparison of the rate of cosmic ray and collider experiments. The result is in the order of the value given by Ellis et al. in the LHC safety report of 2008 (CERN-PH-TH/2008-136). They just formulate it different "...This means [6] that Nature has already conducted the equivalent of about a hundred thousand LHC experimental programmes on Earth already...". With the 4 billion as the age of the earth and a planned run time of LHC of 10 years this is equivalent of saying that the LHC produces in each year while it runs as planned 4000 times as much high energy collisions as occur naturally on earth.

--Malanoqa (talk) 13:49, 24 November 2013 (UTC)

The diagram shows the integral over space angle (Half full sphere) and energy (From the given energy to infinity). The integral to infinity makes sense, as the flux vanishes very fast with higher energies. The diagram is not really precise regarding the values for the colliders. It would be more correct to draw a line that begins with energy zero, at the energy of the collider it would drop very fast to zero.--Malanoqa (talk) 15:06, 20 December 2013 (UTC)

The image posted here by Malanoqa is imo wrong so I'm adding a corrected version based on a reference from the IceCube Collaboration [[2]], and want to add this to the page as a reference of the Flux difference between Cosmic Rays in nature and High Energy Collision experiments in Particle Accelerators. Michel_sharp - (talk) 14:14, 20 december 2013 (UTC)

Cosmic-ray spectrum with LHC luminosity

Slight misrepresentation of the Ord paper

The mention of the position of Toby Ord and the rest of us co-authors of the arXiv:0810.5515 paper is slightly wrong: we are criticising the risk assessment rather than arguing that there is a relevant risk. Basically, for very low-probability risks the probability of an error in arguments trying to bound the risk overshadows the risk itself, requiring a more robust assessment procedure than has been used in the past (especially since we are talking about a potential existential risk). Since I am a co-author of the paper I will refrain from tampering with that part of the text, but it should be updated since the reading is not correct. Anders Sandberg (talk) 19:45, 15 April 2015 (UTC)

"ultra high energy cosmic rays"

This article fails to explain how it is possible to have ultra high energy particles hit the earth at speeds even close to the LHC due to the basic fact that universal expansion inherently slows them down by the red shift that occurs naturally as they travel to us. Jeff Carr (talk) 19:41, 28 August 2015 (UTC)

Particles don't red shift, they are slowed by interaction with magnetic fields, matter and the cosmic background radiation when traveling extraordinarily long distances (intergalactic or greater distances). Still, we've measured a 50 J particle impacting the Earth's atmosphere, which is a lot more than anything we could ever attempt to engineer at our current technological level.Wzrd1 (talk) 15:51, 29 August 2015 (UTC)

The speed of particles absolutely "red shift". That is, they slow down relative to earth. "50 J particle impacts" are likely clusters of many particles. Jeff Carr (talk) 19:54, 7 September 2015 (UTC)

Actually, approaching the Earth, they'd be blue shifted and at relativistic velocities, have a higher relative mass while still traveling, then bremmelstrung emissions would occur as the particle interacts with the atmosphere.20.137.7.64 (talk) 22:24, 7 September 2015 (UTC)