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It's been said many times that CERN is going to destroy the Universe and everybody in it, but most educated people know that this is absolute hocum. It seems being the biggest supercollider therefore increases the chances that it's going to break by a near infinite margin.

However, if something were to go catastrophically wrong, what would be the consequences of that happening? Could the Universe actually be destroyed?

Also, during the development of the supercollider, were there ever any accidents?

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    $\begingroup$ That link made me want to weep for humanity. It blows my mind that people like that get paid for their journalism. There's not even one citation to back up any claim (and more than a few misquotes of scientists). $\endgroup$ – thanby - reinstate Monica Sep 4 '15 at 19:28
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High energy physics experiments, like those done a CERN, don't have a limit as to "the worst thing that can happen." That bar is at least as high as your imagination.

CERN is basically saying "we have a model of how we think things work. We think its possible our model could be imperfect under conditions X and Y. Let's go build something that operates under conditions X and Y and gather data." They are intentionally probing regions we do not fully understand. As such, there is no saying what they could discover if they arrive at a set of conditions where some of our fundamental "laws" of physics prove to be modeling assumptions.

So yes, any number of bad things can happen. However, to be fair in such a statement, any number of unexpected things can happen when you walk out the door. In fact, one might argue that there is no "worst thing that could happen" at CERN which could not happen simply by you opening your front door tomorrow just wrong and creating just the right conditions to hit a corner case in the laws of physics that we never uncovered. And, of course, the same arguments apply if you asked "what's the best that could happen."

As for the black hole scare, its virtually impossible to disprove such things in the world of quantum physics, where scientists are always forced to talk about probabilities. However, from what I remember, the scientists were aware of the possibility of something going wrong, and they actually did some math to determine how likely their models claimed it would be. If I remember, the black hole, if created, was statistically likely to be so small that it would evaporate a few moments later, without sucking much of anything in.

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    $\begingroup$ +1 We don't know for sure that atoms will always stay stuck together the way they do currently, so at any moment the entire cosmos could just dissolve into subatomic particles and scientists would just shrug and say "Hey we told you it was just a theory." That could happen regardless of the LHC doing anything, and it's about as likely as the LHC being responsible for ending the universe due to other unknown physics (which is to say, not likely, or even predictable by current physics). $\endgroup$ – thanby - reinstate Monica Sep 4 '15 at 19:16
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However, if something were to go catastrophically wrong, what would be the consequences of that happening?

A big bang and a big hole in the ground. Less damage than the Japanese power plant accident...

Could the Universe actually be destroyed?

No if something happened with the powerplant or they collected enough anti-matter and had a containment failure they might blow up the entire facility, making a big crater where CERN used to be.

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  • $\begingroup$ "making a big creator", you saying we can make a God? o_O $\endgroup$ – Varrick Sep 4 '15 at 15:26
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    $\begingroup$ @Varrick Apparently I'm not awake yet... $\endgroup$ – bowlturner Sep 4 '15 at 15:26
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    $\begingroup$ Though they are trying to make the 'God' particle... $\endgroup$ – bowlturner Sep 4 '15 at 15:27
  • $\begingroup$ "No if something happened with the powerplant or they collected enough anti-matter" - there is no antimatter being collected neither in the Japanese powerplant nor at CERN, unless you consider those few antiprotons to be "collected". Antimatter does not even enter the question. $\endgroup$ – Radovan Garabík Sep 4 '15 at 18:32
  • $\begingroup$ I meant the a problem with the power plant at CERN. And I know they (CERN) 'create' anitprotons. They also don't have the ability to collect enough to truly be a danger. $\endgroup$ – bowlturner Sep 4 '15 at 18:44
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The answer is : not much due to the experiment.

The experiment is about making particles reach very high energy, and then smash it together. The highest energy reached in CERN, according to wikipedia is $13 \cdot 10^{12}$ eV (eV stands for electron-volt).

However, cosmic ray (energetic particle coming from the space) hit the earth constantly. Here is a little graph from wikiepedia which explain how much, relative to the energy of the particle :

Graph : flux of cosmic ray versus particle energy

(the flux of particle is graduated in what could look as a strange unit, but the label on the curve are way more informative, $1$ m$^{-2}$ s$^{-1}$ for example represents the level corresponding to 1 particle crossing an area of 1 meter squared each second)

You can see that around one particle with energy about $10^{19}$ eV pass through a surface (on earth) of one kilometer squared each year (1 km$^{-2}$ yr$^{-1}$ label). That is an energy one billion time hight than is CERN, and given the total surface of earth and its age, if something could have gone wrong with particle of this energy, it would most likely already have happened.

Note however that since in quantum mechanics is about probabilities, worst case scenario in CERN can not be excluded for sure, but it could as well happen inside my kitchen due to a nasty cosmic ray.

So the worst thing which could probably happen at the CERN is some kind of "regular" incident, like fire or leaks of supercooling liquids or gases (if you visit CERN they actually tell you what to do if it happens). Note that the link I gave, reports a leak of "approximately 6 tonnes of liquid helium".

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Stephen Hawking said there WAS a non-null probability for the LHC to create a black hole.

It's highly unlikely, and I can't find the numbers anymore. Plus, not all theoricians agree about these numbers.

But the worst ? This video made to frighten people against CERN

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    $\begingroup$ There's no s in Prof. Hawking's surname :P $\endgroup$ – Beta Decay Sep 4 '15 at 15:25
  • $\begingroup$ Damn. And I can't even blame my english for this one ! Thanks :) $\endgroup$ – Tyrabel Sep 4 '15 at 15:28
  • $\begingroup$ Haha no problem :) $\endgroup$ – Beta Decay Sep 4 '15 at 15:29
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    $\begingroup$ IIRC, he said it only had that potential at ridiculously high energy levels (as in not producable at all with current or near-future tech). There are endless articles quoting him out of context, though, like much science "journalism" likes to do. $\endgroup$ – Geobits Sep 4 '15 at 15:30
  • $\begingroup$ What I got from the answers to this question on black holes is that even if you create one, it has to be pretty big before causing any sort of catastrophic damage. $\endgroup$ – DaaaahWhoosh Sep 4 '15 at 15:45
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However, if something were to go catastrophically wrong, what would be the consequences of that happening? Could the Universe actually be destroyed?

The very absolute worst that could happen is that some kind of nuclear reaction can trigger false vacuum decay and thus destroy all the matter in the universe at the speed of light. However, as already mentioned before, the energies CERN operates at are many orders of magnitude lower than those e.g. unleashed during supernova explosions, so this would have already happened.

We might equally well say that there is a risk that the nuclear collisions might draw the attention and wrath of Loki...

(disclaimer: I graduated in nuclear physics, but I do not work in that field anymore since many years)

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