Talk:Safety of high-energy particle collision experiments

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

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)

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)

/* Legal challenges */ Present Johnson's "allowed in the courtroom" quote.

I have expanded the legal 'Legal challenges' section a bit to quote Johnson's appalling statement on p. 874 of his paper, that "Given such a state, it is not clear that any particle-physics testimony should be allowed in the courtroom", which I think deserves thought and attention.

Taken seriously, it really might arrest the whole LHC project, and also seems to have the potential to stop any kind of future technical investigation demanding great specialized knowledge, if challenged by some allegedly serious danger. Yet his argument does not seem quite ridiculous, given the realities of the human world—much as I (biased as I am) wish it could be dismissed out of hand. Wwheaton (talk) 18:55, 30 December 2014 (UTC)

I fail to see how an opinion of one attorney makes a case precedent or case law. It is an opinion only and a not highly valid one, as one can easily explain in a court of law that higher energy particles are measured striking the upper atmosphere of the Earth each and every day than what the LHC can produce. There are Constitutional issues as well, for prohibiting a scientist from testifying at a trial then removed that scientist's due process rights.Wzrd1 (talk) 22:11, 30 December 2014 (UTC)

First it is published in an academic, university law journal. It is not case law, but it could be argued in court, and might conceivably be upheld. It even has some internal logic (experts in particle theory are certainly mostly committed to the subject), though I agree the implications (only the ignorant can be qualified to testify) are ridiculous. Wwheaton (talk) 03:28, 9 December 2015 (UTC)

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)