I didn't die. What a let down...

tbh there was a small chance and they shouldnt have taken the risk it wont help us at all really will it?

Not directly or immediately, but it will prove certain things that will further our knowledge of the universe. I also believe that it would allow certain more quantifiable technological developments within the next few decades.

Personally, I wouldn't have allowed it if it were up to me. Considering what might possibly have been at stake if certain things that weren't expected actually did happen.

But, the first steps have happened and we haven't died so I'm waiting to learn about the direct implications of their findings.

They won't be colliding at full power till the late spring 2009.
BTW: the same theory that predicts that black holes could be formed also says
that they'll evaporate. So if the theory is right we've got nothing to worry about,
if it's wrong then we've also got nothing to worry about.
check this out: http://cosmicvariance.com/2008/08/04/what-will-the-lhc-find/

Like Y2K bug, this was another example of the media creating a story where one didn't exist. All the experts knew that the LHC was perfectly safe and that there was virtually no chance of destroying the universe.

I'm a theoretical physicist working in a related field and have plenty of colleagues working directly in the LHC project (specifically the ALICE project which is the largest of the detector experiments in LHC). abgemacht is correct with respect to the media-hype being totally off the mark and this is just another one of countless instances in which 1) journalists don't understand a first thing of what they're reporting and 2) the scientific community don't understand a first thing about how to talk to ignorant, sensation-hungry journalists. One of my colleagues and friends works with a project dealing specifically with black hole formation within ALICE and it's not really an issue of whether or not there will be generated black holes in the collisions, because in all likelihood they will. But as sceptic_ka says, they will be extremely tiny and will consequently evaporate again (mainly through Hawking radiation, I'm told) in a matter of nano- or mili-seconds. The interesting perspective is that if it is possible to observe these tiny black holes during their extremely short lifetime (a very difficult task, by the way) it may indirectly demonstrate the existence of extra dimensions, something that string theorists have been suggesting for years without ever having been able to attach experimental evidence to their claims. So in short: black holes are almost guaranteed to form in LHC but they cannot and will not present any danger whatsoever as they will evaporate into nothingness extremely quickly. The risk that someone will accidentally ignite the Earth's atmosphere when they light a cigarette is infinitely larger than LHC creating an Earth-swallowing black hole, so if the paranoid public needs something to worry about, there it is ;)

I believe I've heard a number of leading scientists state that they don't know what would happen - and not ruling out a massive explosion that would destroy the earth :P

I don't think anyone really took it seriously but there was that 0.0000000000001% chance that something completely unthinkable would happen. Most people thought of that possibility as amusing rather than a threat. I personally haven't been watching it closely - the little I know comes from that guy who appeared on the Colbert Report a month or two ago and some stuff on BBC World. I did watch the countdown to the first experiment 5 or 6 hours ago though.

Ferinz - thank you, that's the first time I've heard or read something which I actually understand about the LHC! Perhaps you should move into communications instead?

I also say thanks. The effort is appreciated.

Thank you Ferinz. I have been following the LHC stories for months and probably read about 50-60 articles. i was just finally starting to put together all the pieces of information together to understand what was really going on. You did it with a paragraph. Well done

i'm not a theoretical physicist like Fenriz, but i would like to point out one thing, even if a black hole is formed, it will have the same amount of gravitational attraction as the mass used to form it.

Which is of course the same attraction as the mass had before it becamse a super dense black hole.

If you compress an apple into a black hole it will have the same attractive force as an apple, that is to say not very much.

So the fact that it will not last long at such densities (due to evaporation by hawking radiation) means it will not have time to suck in more matter and increase in size.

What if I feed one and keep it as a pet?

Wow, what a response! You're all very welcome, just happy to help clarify things as much as I can :)

Orathaic is absolutely correct (my compliments, few non-physicists actually grasp this point about black holes), and in principle Chrispminis would be able to keep his pet black hole alive if he kept feeding it. In time he might even build up a black hole big enough to swallow the Earth ('in time' here would probably mean several million years if he had to use terrestrial density matter...). But that would require an extremely rapid feeding mechanism, at least in the beginning, as you only have a few nanoseconds before the black hole evaporates. If you figure out a way to do it, I'm sure my friend working with extra dimensions in LHC would be very interested, though... ;)

Archonix is basically right, there's always an element of the unknown, and I think any scientist would be bad at his job if he or she claimed to know exactly what would happen when testing something that hasn't been tested before (after all, if EVERYTHING was known in advance, what would be the point, then, to test it?). One should never completely rule out any eventualities, however, eventualities which are absolutely negligible (I consider 10 to the minus 25th, or whatever Sean Carroll sets it to, negligible) should be downplayed since the press seems to be attracted to extravagant drama rather than dry facts, no matter how unlikely that drama is. I think the whole problem emerges because journalists will hook onto the single extravagant detail that they do understand when they don't really get the rest of what is being said. In short, they hear a lot of (to them) nonsensical chatter from which they need to write a story and steadily panic starts to set it... but THEN comes the mentioning of the exotic possibility of a black hole forming and in the journalist's mind the picture of a roaring, supermassive interstellar black hole appears in his mind. The result: a completely off-the-point, biased story about scientists building a Doomsday device beneath the Swiss Alps. I'm being a bit rough here, I know, but you get the picture. Let me put it another way: I think the possibility that LHC spontaneously creates a pink elephant during a collision is about as big as the risk of it creating an Earth-swallowing black hole. But so far, I haven't read any stories examining what to do if the accelerator tube in LHC suddenly clogs up due to the spontaneous appearance of a pink elephant...

I should say that I'm not trying to pick on journalists in general, and if any of you guys work in that field I hope you will not take offense. I think most journalists are probably conscientious professionals doing their job to the best of their ability (others are certainly not, but let's keep them out of the discussion). But modern particle physics is a subject that requires years of study to comprehend and most journalists simply do not have that kind of time. I know, since I once had a journalist girlfriend ;)

Fenriz, your explanation was very good (perhaps the most concise and easily digestable explanation I have ever read) and I agree with your view that the media tend to exaggerate things. That is what sells newspapers after all...

I just have one tiny correction to make, and I hope you won't mind. ALICE was actually an experiment on the LEP collider, which is a predecessor to the LHC. The LHC uses the same tunnels as LEP. However, LEP collided electrons with positrons together. The LHC is a proton-proton collider. Both types of colliders have their advantages and disadvantages. If anybody is interested, I will try to explain - let me know.

I think you just had a slip-of-the-tongue when you said ALICE. I think you meant ATLAS. However, it would be unfair to say that ATLAS is the largest experiment at the LHC. CMS is comparable in size, and both ATLAS and CMS are the big general purpose experiments at the LHC.

Everything else you said was perfect - I wish I was as good as you are with such explanations. Actually, I wish you lectured me in theoretical physics - it would have made my job a lot easier!

Hi mps247. Thanks for your comments and your nice words :) Actually, I believe ATLAS and ALICE are both experiments in the current configuration of LHC (check out the LHC wiki-article: http://en.wikipedia.org/wiki/Large_Hadron_Collider and the official webpage: http://lhc.web.cern.ch/lhc/). I may, however, have mixed up the sizes of the experiments, and looking at the wiki-article it sounds like ATLAS is actually the big one, not ALICE. ATLAS and CMS are the instruments looking for the Higgs boson, arguably the most important task of LHC. So in that context, CMS and ATLAS could be considered the 'largest', in the scientific sense at least... but anyway, we all know that size doesn't matter... ;)

Being a theoretical astrophysicist and therefore slightly outside the specific field of collider physics, I would very much like to know more about the differences between LEP and LHC, besides the obvious energy level difference (proton-proton collisions clearly generates larger energies than proton-positron collisions, due to the difference in total mass), if you can spare the time to explain it. Thanks again!

Orathaic, Ferinz, mps247 - thank you once again. Not only do I begin to grasp some of the conceptions you talk about, but you talk about it in a highly amusing way! I have been chuckling away to myself for the last ten minutes, much to the confusion of my girlfriend. Usually when I'm on this website, all that comes out of my mouth is a string of curses as my best laid plans lie in ruins!

I nominate this thread as five star!

For further clarification:

http://xkcd.com/474/

Does that mean the Loc Ness Monster, Big Foot, and flying soucers are not real also? I'm crushed!

but even if it happens there's no better way to die, right? death from a black hole sounds exciting

we've finally found what detremines L in the drake equation.
(no wonder contact is so improbable...) :/

There is the serious suggestion apparently that if you enter a black hole you wouldn't actually "notice" any change, whilst an observer (from outside the 'hole) would witness a horrid death. Appeared in the New Scientist.

One beam today... Black holes tomorrow... Negotiate* like crazy while you still have the chance!!!!!!!!!!!!!!!!!!

*Or something else more end of the World-y!

I thought getting to near a black hole caused spaghettification.
I haven't done the math so depending upon its size this might not happen till you're inside the Schwarzschild radius (point of no return for light), where if I remyember correctly an outsider would see you boil up or something.
Black holes are cool.
@Any Physicists: BTW, how would you contain a tiny black hole, since it's so small wouldn't it just pass through normal matter and sort of fall into the
center of the earth?

Archonix, you were missing two zeros.

Sceptic: Spaghettification increases once you get near a black hole as the gravitational acceleration (G.A.) increases greatly with the inverse distance to the Schwarzschild radius, actually becoming infinite at the radius, thus creating tidal effect (aka spaghettification). But since the

Hi Fenriz - I'm sorry, you were correct! It was I who got confused between ALICE (a LHC experiment) and ALEPH (a LEP experiment)! The names are too similar. However, as you rightly state, ALICE (and LHCb for that matter) is a relatively small experiment. The main two general purpose experiments are ATLAS and CMS. You can call them competitors really - they've been trying to outdo each other for years, even before the beams started. Each of these big experiments has around 2000-2500 particle physicists. When they will publish anything, the author list will be about as long as most papers!

I will try to explain the difference between electron-positron and proton-proton colliders. Please ask me if anything doesn't make sense. Firstly the principles behind colliders. When we fire one particle into another, they collide at a certain energy, annihilating one another. This energy must go somewhere, and can result in other particles being produced. As energy must be conserved (you cannot take out more than you put in), the maximum energies of the produced particles cannot exceed the energy of the collision. How can mass and energy be compared in this way. Well, in particle physics we use natural units (electronvolts - our energy scales are gigaelectronvolts, or GeV for short), hence we are able to compare mass and energy. This is a very simple explanation, and there are many things I have left out. I'm just not sure how to explain it before I start to confuse everybody... and myself... just assume mass = energy, which isn't true, but for all intents and purposes it is - otherwise I will have to talk about momentum, and I might as well send a copy of my PhD thesis to all of you...

As the electron and positron are fundamental particles (ie. they cannot be broken down into smaller pieces), the products of their collisions are very easy to deal with. This is because if you fire an electron beam of energy 50 GeV against a positron beam of energy 50 GeV, the centre-of-mass energy (energy at collision) is 50 + 50 = 100 GeV. Every collision will be of this energy. Therefore, the particles produced in this collision cannot exceed a total mass of 100 GeV.

However, electrons and positrons (positrons are the antimatter particles of electrons) lose energy through bremsstrahlung radiation losses when they follow a curved path. The 27 km circumference accelerator ring, like the one at CERN, is such a circular path. As you put more energy in, the radiation losses get worse, until you reach the point of diminishing returns. The LEP collider was run at the maximum energies possible for a ring of its size - I think 200 GeV centre-of-mass energy - for the last period of its life.

Enter protons! Protons don't suffer such losses as they are more massive. Therefore, the highest energy possible at collision is 14 TeV at the LHC (14 TeV = 14000 GeV). However, they are not fundamental particles - they are made up of quarks. It is the quarks that collide, and as the total proton energy is shared among the quarks, the actual collision energy could be anything below 14 TeV - there is a wide range of possible energies. This makes the analysis more complicated.

Another problem is the fact that quarks, outside the bound state of proton, are unstable. Hence, if two quarks collide, the protons are destroyed, and the other quarks that were not involved in the collision "decay", creating more particles. These particles are not part of the collision, and must be removed, adding another complication to the analysis.

Therefore, higher energies are possible with proton-proton collisions, so we can detect particles of greater mass. However, electron-positron collisions are easier to analyse, allowing for more accurate estimations of particle properties, such as mass. They compliment each other - proton-proton colliders give you an idea of where to look for a new particle, and electron-positron colliders allow you to study that particle in more depth.

Was that really complicated? I tried really hard to explain that in an easy way, but I don't think I've done a very good job. Please tell me if there is anything that you don't understand.

...(ups little miss click there)... G.A. becomes infinite due to the math of the Schwarzschild solution to the Einstein Field Equation you are in your full right (i think at least) to be a bit sceptic about the hole thing. (Or am i wrong Fenriz... this really must be your area!?)

On the question of LHC experiments there are 4 major experiments and a few smaller ones (not at all small just smaller!). The 4 big ones are ATLAS, CMS, ALICE and LHCb. Now it is true that both ATLAS and CMS are general particle detectors but i think it is worth to notice that in volume ATLAS is 6 times larger than CMS. As I recall it has to do with the lack of a muon spectrometer at CMS that is isn't bigger (still something like 20m*15m*15m). Though due to its very very heavy crystal calorimeter the weight of CMS is just less than twice the weight of ATLAS. ALICE is about the same size as CMS in both dimesions and weight (a bit bigger but a bit lighter also). LHCb is the smaller of the 4 but still in the same league in both size and weight. I know ATLAS is at 7000 tonnes and both ALICE and LHCb are a bit less.

Hi Fly - I don't know too much about black holes, but as you say, Fenriz is likely to know a lot more. I can talk about the LHC though. I don't know if it will help.

Yes, ATLAS and CMS are the largest experiments, as in they have the most manpower purely because they are general purpose. LHCb and ALICE have very specific roles, which are equally important, but do not require the same resources.

Yes, I believe that CMS doesn't have a muon spectrometer, so it could very well be smaller. I'm afraid that most of the people I know work on ATLAS (I work on something related, but not at a big collider - my research area is more small scale). Is a muon spectrometer necessary - depends on who you ask. I don't doubt that they may add one at a later date should they require it. It is the last detector to go on, on the outside, so it is not a difficult task (yes, it's actually very difficult, but imagine trying to add an extra detector somewhere inside your detector instead - you would have to redesign everything outside).

For further clarification:

http://www.youtube.com/watch?v=j50ZssEojtM

Theoretical Astrophysicist? Is there any other kind?

mps247 - yes that was complicated, but very well explained. I mean it's nuclear freakin physics after all, it's supposed to be complicated.

Thanks philcore - I'm glad it made some sense. It makes me feel a lot better.

Chrispminis - I saw that earlier today. Posting it on this board didn't even occur to me. Thanks, that was a very good idea.

Some people say that once humans figure out all the secrets of the universe, it will be spontaneously destroyed and then replaced by a more complicated version of itself ... others say that this has already happened once!

Pretty sure Iread that in a Feynman book, but I don't think he took credit for it, he was quoting someone else.

Speaking of Feynman, for the physics geeks on the forumn, who is your favorite physicist? Feynman would definitely be on top of my list.

Dirac. He was the Man.

To mps247: Thanks a million for your excellent explanation. I hadn't considered the (actually rather obvious) fact that colliding hadrons is more complicated that colliding leptons but you've made me aware of this, thanks! Can I ask what area you work in? It sounds interesting.

To Fly: as far as I recall (and I admit it is some years since I looked it up, so there may be some imprecisions in the following; corrections are welcome!) the Schwarzchild radius is the critical distance as seen from an outside observer, i.e. observing the black hole at a certain (presumably safe) distance. No information can escape from within this radius, which is therefore also called the event horizon. An outside observer observing a person falling into the black hole will see the person's velocity decrease asymptotically as the falling person nears the event horizon. So, to the outside observer, the falling person will never actually reach the black hole, he will be forever falling slower and slower until at infinite time, he will be infinitely close to (but still outside) the event horizon, moving infinitely slow. The falling person, however, will not notice passing the event horizon and his velocity will increase asymptotically as he gets closer to the actual black hole singularity. He will, as has been mentioned, eventually experience tidal effects, due to the fact the gravitational pull on the part of his body closest to the black hole will be many orders of magnitudes stronger than the pull on the part of his body which is furthest from the singularity. Eventually, this tidal effect will tear him apart, limb by limb, molecule by molecule, atom by atom, lepton by lepton, and quark by quark, until he finally reaches the singularity and is absorbed within the black hole. There are a number of different ways to describe this, all of them specific solutions to the Einstein field equations of General Relativity. The most common transformations are the Schwarzchild, Kruskal and Reisner-Nordstrøm solutions, and they give slightly different results, all depending on the position of the observer, the rotation and charge of the black hole and so on. I'll spare you the details, as it is somewhat mathematically involved ;) But I encourage you to look these up if you're interested in the subject.

To philcore: yes, there are experimental (or observational, whichever you prefer) astrophysicists as well. Some might simply consider these people astronomers, the boundary is not clearly demarcated :) To answer your question, my favourite physicist is good ol' Albert Einstein. But Steven Weinberg also scores high on my chart, not least from the fact that he's a brilliant physicist AND an outspoken atheist.

... oh, and Niels Bohr, of course. But that's primarily because he was Danish (as am I ;)

To Fenriz: thank you, I'm glad it made sense. Until recently I was involved in the search for dark matter. However, I recently started working on the BELLE upgrade (BELLE is a detector at another collider in Japan). So, I'm an experimentalist through and through. What are your main research interests?

To philcore: Michael Faraday.

To mps247: all right, that explains how you know so much about collider physics then. Never heard of BELLE, but I'll definitely look into it now that you've mentioned it. Good luck with your work.

My main areas are astrophysics and cosmology, more specifically the Cosmic Microwave Background (CMB) radiation and relic gravitational waves. But I've dealt with elementary particle physics a bit in the past as well, although on a purely theoretical level (I'm a theoretician through and through). I guess I just don't have the patience to do experimental work, and anyway experiments just seem to malfunction catastrophically whenever I'm around. Come to think of it, maybe it was a good thing I wasn't anywhere near CERN yesterday, otherwise we might actually have had to deal with the planet-eating black hole! ;)

It is frustrating to be nearing the end of a physics bsc while the work being done now is out of reach :-(

Thanks mps & Fenriz for the interesting posts though, it's /such/ a breath of fresh air to hear informed opinions in an LHC discussion.
Compared to another forum some apparently genuinely worried people were quoting news articles with "doom machine" in the headline, others saying "Hawking bets that the LHC will produce nothing", that the LHC may disprove the big bang, etc.

This stuff is widespread and it is truly depressing, almost as much as if all people talked about during the moon landing was "oh no, what if the moon is knocked out of orbit?!" Very sad, I just hope the focus shifts once has started up

To Fenriz: I liked your comment about experiments malfunctioning whenever you are around. I know quite a lot of theorists (and some experimentalists) who feel that way! I like the challenge of getting your equipment to work, and it is just so satisfying when it does. I have trouble getting my head around a lot of the theory behind my work, purely because my mind doesn't think in that way. If I can't see the way something works, I find it almost impossible to understand it. I remember writing about the CMB in my thesis (I was involved in dark matter research), but this was a few pages where I had to outline the evidence for dark matter particles. I'm sure you are familiar with WMAP, and gravitational wave experiments such as LIGO. Please excuse my ignorance when I ask this, but do you work with simulations?

To kestas: I remember that after my BSc, and I'm sure that Fenriz will agree with me, I was nowhere near ready to do a PhD. It took at least two years of research (one year at MSc, and the first year of my PhD) before I could even grasp the subject and start research. At undergraduate level, there isn't enough time for you to focus on it because you are learning about other fields. As you may have guessed from Fenriz's and my replies, we know a little bit about each other's fields, but we are unable to swap places with each other. So don't get disheartened - the stuff you are learning now are the basics that we use everyday, so it is very important. You need to specialise in order to do research, but after your BSc you know enough to start specialising.

To Kestas: you're very welcome, just happy to help :) And I agree with you on the point that there's a lot of ignorance concerning what LHC actually does. Actually, that goes for advanced science in general, but I think scientists bear at least some of the responsibility for this. We should be better at explaining to the public what it is that we do and why. The funny thing is that CERN is actually one of the few scientific institutions that really prioritise public relations work (in Europe, at least, I imagine that American institutions are slightly better at it). For some reason that has not really worked as planned this time...

To mps247: it's a curse that has followed me since basic school, my experiments always went awry (that's how I remember it, at least ;) and consequently I function exactly opposite of you: I need to grasp the theory before the experiment makes sense to me (at least if it's a more complicated setup than simple Newtonian mechanics experiments). Actually, I've worked quite a bit with WMAP and currently I'm involved in the PLANCK satellite project. Launch day is in a matter of months and we're all very excited about it! I've dealt a bit with LIGO, but only on a very general level. I'm primarily interested in cosmology, and LIGO is not directly relevant to this field, since it will never be able to detect relic gravitational waves (GWs), i.e. gravitational waves arising from parametrical amplification of quantum fluctuations in the gravitational field during cosmic inflation, very early in the Big Bang. What LIGO will be able to detect are 'astrophysical' (as opposed to relic or cosmological) GW-emissions from nearer sources, such as inspiraling/colliding binary neutron stars or black holes, and these observations will provide better distance measurements, and thereby better constraints on basic cosmological parameters such as the curvature and general topology of the Universe. So in that light, LIGO is of course interesting from a cosmological point of view. However, it may still be some years before LIGO detects anything and once they do, they will need to do quite a lot of measurements before that can be correlated with cosmological models. So for that reason, my work has primarily revolved around detecting relic GWs in certain statistical imprints in the CMB.

Hmm, the last paragraph got a little longer than I had anticipated, sorry. I hope you've managed to stay awake this far ;)

I couldn't have slept even if I had tried. Thanks Fenriz - I found out quite a lot of very interesting things that I didn't know. Yes, it is a shame that we scientists are quite poor in public relations on this side of the Atlantic.

"Some people say that once humans figure out all the secrets of the universe, it will be spontaneously destroyed and then replaced by a more complicated version of itself ... others say that this has already happened once!"

This is Douglas Adams, in his Hitchhiker's Guide series. It's not the exact wording but similar idea.