The Large Hadron Collider, at low power, accelerates particles such that much of the total energy provided goes towards increasing their kinetic energy and their masses increase to some extent as well, and so Newton's equations are valid for this situation. However, when it's turned onto high power, as the particles tend to the speed of light, any additional power provided by the accelerator increases mostly the masses of the particles and their kinetic energy increases only slightly. That is why these high energy particles can pack quite a punch. It's sort of like taking a car and propelling it such that it transforms into a massive freight train.

This is a very stupid question, but I bet I'll get some really remarkable answers. If the power output of the Large Hadron Collider were infinite (or at least a very big number), and notwithstanding a failure or limitation of the mechanical and engineering aspects of the machinery, would it eventually "explode" if the power is turned up too high?

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    $\begingroup$ Hi Michael, this question isn't really well defined as it is, and in addition you have some misconceptions about special relativity (according to the modern definition of "mass," it is a constant regardless of the speed of the object). $\endgroup$ – Rococo Mar 12 '17 at 18:34
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    $\begingroup$ However, I think you will find this interesting and relevant to your question: symmetrymagazine.org/article/december-2007/… . Note that the superconductor quench that they warn about in this article actually happened, about a year after it was written, and it did cause a significant explosion that shut down the accelerator for several months. $\endgroup$ – Rococo Mar 12 '17 at 18:36
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    $\begingroup$ Just to correct one point, the kinetic energy of the particles does increase as the mass increases, even though the speed is limited. That's why we bother building big accelerators $\endgroup$ – Martin Beckett Mar 12 '17 at 21:25
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    $\begingroup$ As @Rococo says, the LHC kind of did explode in 2008 $\endgroup$ – Ander Biguri Mar 13 '17 at 16:38
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    $\begingroup$ @MarcvanLeeuwen Modern usage is to use the term mass to refer exclusively to what you call "rest-mass." See this question: physics.stackexchange.com/questions/133376/… and also the blog link that Countto10 has given in his answer. $\endgroup$ – Rococo Mar 14 '17 at 3:23

In the case of the LHC, yes the beam can do quite a lot of damage.

At full power there is something like 350MJ stored in the beam - close to a freight train, or roughly the kinetic energy of a full jumbo jet at take-off. There is a very complex safety system to dump the beam safely eventually steering the beam energy into a large block of graphite inside a much larger cooled block of metal inside a very big block of concrete.

Without this any instability in the beam could allow it to hit the wall of the vacuum tube where it would slice through it and then through the magnets like a hot knife through butter, or indeed like a high intensity beam of relativistic protons through superconducting magnets which is more impressive and a lot more expensive.

edit: detail of the beam dump below, Sorry I was obviously half-remembering a talk on the quench protection heaters.


  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – rob Mar 14 '17 at 4:16
  • $\begingroup$ It should be noted that the beam dump is not just a safety mechanism but integral part of an experiment run: the used low luminosity beam is disposed of therein. $\endgroup$ – PlasmaHH Mar 14 '17 at 12:49
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    $\begingroup$ like a high-intensity beam of relativistic protons through a superconducting magnet is my new favourite simile. $\endgroup$ – Jules Mar 14 '17 at 19:38
  • $\begingroup$ All very true. But I feel unrelated to the actual question. Can you damage the LHC by turning it up to 11. Which I would say not. The limits of the LHC come from the synchrotron radation. Its like saying, "Could I create a tsunami by turning on the tap/facet too high?". The answer is, no. The water would leak away from your sink before you build up enough water for a tsunami. $\endgroup$ – Aron Mar 15 '17 at 4:43
  • $\begingroup$ @Aron I would say this answer directly addresses the question. MartinBeckett mentions that, yes, there is enough energy buildup in the LHC for measures to be put in place to mitigate damage which could be caused by a "runaway" particle beam -- in the form of a massive graphite-and-concrete block. This is meant to contain up to 350MJ of energy. A magnet failure in the main ring would likely deal heavy damage to the collider structure itself as well as its surroundings. $\endgroup$ – Jules Mar 15 '17 at 13:15

I take it the Large Hadron Collider works like this... At low power, the particles gain kinetic energy but do not increase in mass very much so Newton's equations are valid for this situation. However, when it's turned onto high power, as the particles tend to the speed of light, any additional power output of the collider increases mostly the mass of the particles and their kinetic energy doesn't increase at all (or very little). That is why these high energy particles can pack quite a punch. It's sort of like taking a car and propelling it such that it turns into a massive freight train.

As noted in the comments above, it's a misunderstanding that the mass increases at very high speeds, a better explanation​ that I can give you is a blog that I highly recommend you read, Relativistic Mass.

The energy of freight train idea is true, but the point here is this is only because of the concentration of energy in a tiny area, the cross section of the collision, which is extremely small. You can easily flatten a fly with your hand, but hitting an elephant with the same hand power will not hurt the elephant, if it even noticed it.

Any explosion is dramatic, to be pedantic, as is noted in the comments above, it is a failure of the cooling system that is the danger, not the power involved in the beam itself.

There is far more energy used in the magnets used to steer and control the beam than there is in colliding elementary particles together. So my answer is no, the beam by themselves won't cause an explosion, but yes a failure of the support systems might.

From LHC Power Consumption

It takes 120 MW to run the LCH - approximately the power consumption of all the Canton State of Geneva. Need a better comparison? 120 megawatt is equivalent to the energy used by 1,2 million 100 watt incadescent light bulb or 120,000 average California home. CERN turn the system off in winter, because of the power consumption involved.

enter image description here

Image source: LHC: Taking a closer look

This is where the beam ends up after an accelerator run. It's possibly counterintuitive, but a light, high melting point block of graphite is used to absorb the energy of the beam. If lead or another metal was used, it would melt, and a messy cleanup and replacement block would be required after each run. This block of graphite is intended to last the lifetime of the LHC.

  • $\begingroup$ And if you speed your hand close to c, is it going to hurt the elephant? $\endgroup$ – BЈовић Mar 14 '17 at 8:22
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    $\begingroup$ @BЈовић Well, even at normal hand speed, I personally would not annoy an elephant in any way. $\endgroup$ – user146020 Mar 14 '17 at 10:09

The only thing that could explode are the magnets. As mentioned by Countto10, there is a huge amount of energy stored in these magnets. Superconducting magnets are used, they are cooled using liquid helium. Due to a problem with the cooling, it can happen that part of a wire suddenly makes a transition from the superconducting state to the normal state. The huge current that moves through the wires will then get dissipated at that spot, generating an enormous amount of heat which will cause the liquid helium to exceptionally rapidly boil, expand in volume by a factor of ~800, heat the remaining helium, boil it, and therefore cause the whole magnet to essentially explode.

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    $\begingroup$ Note that while normally this eventuality is controlled by the so called Quench Protection System, the major LHC incident occurred in 2008 and leading to more than a year of delay, had this origin, for details see press.cern/press-releases/2008/10/… $\endgroup$ – DarioP Mar 13 '17 at 10:12
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    $\begingroup$ This would be what connoisseurs call a "BLEVE", or to use its full name, a boiling liquid expanding vapour explosion. And another, equally accurate resolution of that acronym is Blast Levelling Everything Very Efficiently. $\endgroup$ – biziclop Mar 15 '17 at 13:42

If the power output of the Large Hadron Collider were infinite [...] would it eventually "explode" if the power is turned up too high?

Yes - any hypothetical object capable of producing infinite power would "explode if the power is turned up too high," because an extremely high power output is pretty much exactly the colloquial definition of the word "explosion."

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    $\begingroup$ Just what I was going to answer as well. Of course, if you crank up the energy even more (while keeping the volume the same), it will eventually implode into a black hole. $\endgroup$ – Graipher Mar 14 '17 at 8:46

protected by Qmechanic Mar 12 '17 at 21:22

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