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Large Hadron Collider (LHC) Dangers?

  1. Feb 28, 2008 #1
    The highest energy particle collisions ever attempted will begin at LHC at CERN near Geneva later this year. Are there any possible risks, even at an extremely low probability, from these experiments? Could we accidently trigger something like fusion? Could micro-black holes fuse and become a macro-black hole? Could strangelets or monopoles begin some as yet undefined chain reaction with matter that can't be controlled?
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  3. Feb 28, 2008 #2


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    Many of the things you mention have been raised as possibilities, though they are very remote. One reassurance is that no matter how much energy we can accelerate particles to, nature does far better all the time. The cosmic rays that bombard the Earth routinely have energies greater than the LHC will get to, and they don't cause the Universe to spontaneously disintegrate!
  4. Feb 29, 2008 #3
    Thanks Wallace. Not that I'm losing sleep over this or anything. I read somewhere that the energies are so high in the collider that they will be reproducing, to a microscopic degree, conditions in the early universe, such as immediately after the BB. Are you saying that every time a cosmic ray comes along, that reproduces conditions in the early universe?
  5. Feb 29, 2008 #4
    We don't really know, since we can't contain and examine what happens. All we know is that these cosmic particles come in with MUCH more speed than we can give something, so they hit much harder, and we haven't seen anything bad happen yet.

    Also, you have to define what you mean by "conditions of the early universe". Basically everything was really close together right after the BB, which leads to a bunch of interesting things, but getting particles really close together and seeing what happens is one way to tell what it was like.
  6. Mar 1, 2008 #5


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    The point remains, cosmic ray collisions in the earth's upper atmosphere - far more energetic than the LHC can ever hope to achieve - have naturally occured for billions of years without triggering a catastrophe. If a mini black hole were produced in the LHC, it would immediately decay [according to science as usual] spewing a zoo of exotic particles. If, for some unknown reason, it did not decay it would sink to the center of the earth and consume our entire planet - in about a gazillion years.
  7. Mar 9, 2008 #6
    I'll be visiting CERN sometime nexy year! Can't wait!
  8. Mar 9, 2008 #7

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    Even that's unlikely, since the black hole is probably traveling in excess of escape velocity.
  9. Mar 24, 2008 #8
    If you're interested in more details about these high energy cosmic rays that everyone's talking about, this a very cool experiment measuring them. http://www.auger.org/
  10. Mar 24, 2008 #9
    I have lately thought of another way to answer the recurrent
    Yes there are. In fact, quantum mechanics marked a major epistemic revolution : the end of certitudes. Everything must be evaluated in terms of probability. The world is not a perfect clockwork anymore.

    Now for instance, let us say an event has a "negligibly small probability", if by definition there is less than one in a billion for it to occur during the age of the universe, in a volume equivalent to the size of the visible universe. It can safely be disregarded and should not prevent us from sleeping. There are probably more relevant questions to turn one's attention to. :smile:

    It has just recently occured to me that answering "those probabilities are negligeable" is just not convincing enough. One should stress the more interesting point as to why we must talk in terms of probabilities in the first place. And give concrete orders of magnitudes only later. It reminds me of the fear to fly an airplane while driving a car on a daily basis. The more technology advances, the more fears become irrational.
  11. Mar 24, 2008 #10
    Good luck trying to stifle/educate the media/pop-sci crew that loves to convert
    "there is a supremely small possibility" to "Physicists agree, LHC COULD DESTROY MANKIND!"

  12. Mar 25, 2008 #11
    Not necessarily, right? AUGER sees a handful of events in the 10^12 GeV range (if I did the conversion from their eev unit correctly), but there should also be cosmic rays of intermediate energies as well, so that some events (more than at the high energies) occur at energies comparable to the LHC. So if there are black holes being produced in the upper atmosphere, some of them are moving very fast and some of them are moving very slow.
  13. Mar 25, 2008 #12

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    I don't understand why Auger gets into it. My point was that it's very unlikely that a black hole produced at the LHC is traveling less than 25,000 miles per hour.
  14. Mar 25, 2008 #13
    But I'm saying that not all of the high energy cosmic rays are coming in with the same energy. This means that there are some collisions in the atmosphere with energies comparable to LHC energies.

    I could be wrong, but I don't understand how you can say that all of the black holes produced would have velocities far in excess of escape velocity, when not all of the collisions happen at the same energy.
  15. Mar 25, 2008 #14
    Because, in order to "produce a black hole", you need a lot of center of mass energy (not the fixed energy of the hadron system, the energy of the partons) and once it has been produced, it will all go away in the hole mass (in the center of mass) thus velocity (in the lab).

    What about holes with large angular momenta ? They will decay even faster (because of their larger surface) ?
  16. Mar 25, 2008 #15

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    Read what I wrote. I did not say that all of the black holes produced would have velocities far in excess of escape velocity. I said that it was very unlikely that a black hole would be produced with velocities below 25,000 mph.

    Most objects produced in these collisions, even heavy ones, are moving at a significant fraction of the speed of light - which is much,much faster than escape velocity.
  17. Mar 25, 2008 #16
    Ehhh...sorry if I'm being dense, but it is conceivable that there are some collisions in the atmosphere with COM energies near the threshold for black hole production---that is, collisions with just enough energy to produce a black hole nearly at rest.

    However UNlikely this is, it must be that (given the fact that the Earth has been around for four billion years or so) at least a few black holes would have been produced in the atmosphere? Not to mention in, say, Jupiter or the sun where the escape velocity would be much higher?
  18. Mar 25, 2008 #17
    Think of all the high energy cosmic rays intersecting the sun, other stars, nebulae, and so on. There must be quite a lot of continuous black hole production all over the place. It would be a rare one at rest near another celestial object but it seems lots of them should be zipping around if they don't evaporate first......? Has this ever been quantified, in theory at least?
  19. Mar 25, 2008 #18
    Well...that's the point. IF they CAN be produced in the LHC, and they DON'T decay like everyone thinks they should, then they SHOULD be a whole lot more common around the solar system.

    But aparently there's something I'm missing.
  20. Mar 25, 2008 #19


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    Ben, thats fine. Except the probability is obviously considerably larger that they scatter with much higher energies, which is all I think that the others are saying.

    The whole discussion is stupid frankly, Hawking radiation is pretty much a certainty if these things even exist in the first place (which is likely not true at the energies we are discussing), so some sort of monstrous blackhole gobbling up the earth is precluded ad initio with a high degree of confidence.
  21. Mar 26, 2008 #20
    I agree. But it would be nice to have a sort of magic bullet to stop these threads before they get to...oh...20 posts :)
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