The Large Hadron Collider (LHC): Why we are still at risk
Editors: J. Jones and R.D. Jones
The LHC has been switched on and Earth has not been destroyed.
Does that mean that there is no danger?
The first switch-on on 10 September was only a test and we must not be misled into thinking that this unremarkable start-up proved that we are not at risk.
The first LHC collisions will now commence in Spring 2009, although the full power of the collider will not be used to begin with. However, as the months pass the power and thus the energy of particle collisions will be increased. This and the long duration of these experiments will boost the statistical risk of producing dangerous particles or other unknown and unexpected effects.
There will always be a risk as long as we experiment using the technique of opposite speed collisions.
The main defence by CERN is that cosmic rays with high energy have beeen colliding with Earth for millions of years and yet Earth is still here.
The failing of this argument is that:
Although heavy particles with little reactivity that are created by cosmic rays will retain great speed and so will pass through the Earth and be loosed into space, the same particles created by opposite speed collisions will have a very low speed and could be captured by Earth’s gravity.
Our study indicates that some categories of unexpected particles or phenomena present a risk for Earth.
Significant financial and human efforts have been invested in building the LHC and great hopes for new knowledge are now tied in to it.
Various safety studies have been produced by CERN, with a more complete evaluation in 2008 [Ref.1, Ref.2 and Ref.3]. The possible creation of stable micro black holes, strangelets, vacuum bubbles and magnetic monopoles has been studied.
Safety studies are important because new phenomena may be expected and if any of these are dangerous the whole planet could be involved.
The conclusions of CERN studies are reassuring but an important safety problem linked to the possibility of unexpected phenomena has not been adequately treated in these studies.
The CERN studies evaluate the possibility of dangerous phenomena in the context of our current theories, but these theories are not complete and unexpected phenomena could occur.
We do not have a complete theory of physics (the “Theory of Everything”) and numerous factors are not understood (dark energy, dark matter, etc.).
I ** No guarantee of safety from the behaviour of cosmic rays
The CERN 2008 study advances as the principal argument in favour of safety the fact that cosmic rays that have been colliding with Earth and stars for millions of years with energies far more significant than those reached in the LHC.
At the same time, these studies accept the fact that opposing collisions in the LHC will produce particles with speeds far lower than those produced by cosmic rays which means that the cosmic ray model cannot strictly be applied to the LHC [Ref.1].
Experiments using the technique of colliding high-energy particles with opposing speeds create conditions on Earth different from natural collisions due to cosmic rays.
Starting from this notion of the slow speed of heavy particles produced by colliders, we will study the possibility of specific dangers from these colliders.
Special relativity indicates that in the case of a proton-proton collision between a cosmic ray with a speed of 299,999.9 km/sec and terrestrial matter, a heavy particle of mass 1 TeV created thereby would have a speed of 299,700 km/sec. If such a particle is not very reactive it will “always” cross planets or stars and disappear into space.
The Standard Model is unsatisfactory. Many other theories have been proposed but at this moment in time we still do not have a complete and final theory of physics.
An enormous part of the matter composing the Universe (90%), is unknown to us (dark matter, dark energy).
Maybe it is just a hole in our theories that could, in the future, be explained by, for example, the MOND theory, which proposes a change in gravitational equations over large distances, or perhaps by other theories.
We should reflect on the limits of our knowledge and admit that, without a complete theory of physics, we cannot discount the possibility that high energies in colliders may create unexpected heavy particles (or other unexpected phenomena).
We can be certain that such particles could present a much higher risk of being captured by the Earth’s gravity than is the case with particles produced by cosmic rays.
As our theories are incomplete and the particles are unknown, if such an event was to occur, the significance of the danger to Earth would be difficult to evaluate.
III **Classification of potentially dangerous particles:
We suggest studying the possibility of danger with a classification of particles in relation to their reactivity with terrestrial matter, their time of decay, the possibility of absorption of other particles etc.. A first attempt at such a classification is proposed here:
******Classification by particle effect:
A/ Heavy particles that can absorb matter (same effect as a black hole as an example)
B/ Heavy particles that could transform ordinary matter (same as strangelets)
C/ Heavy particles that could destroy ordinary matter (same as monopoles)
D/ Heavy particles dangerous for other reasons
*******Classification by reactivity with ordinary matter.
Such particles could only present danger if the safety cosmic ray model cannot be used:
A/ In case of little reactivity with ordinary matter.
Danger levels will depend on the rate of decay and on the degree of reactivity.
In the case of a long decay time, if such particles are created by cosmic rays they will retain significant speed, pass through the Earth, and become lost in space.
If they are produced with opposite speed collisions as in the LHC, some of these particles could present a serious danger because their slow speed could mean capture by terrestrial gravitation.
This could be the case with an absorbing particle which is not very reactive.
B/ Heavy particles reactive only at very slow speeds.
Danger levels here will also depend on the decay time and on the degree of reactivity.
These particles could present a danger because of their slow speed, resulting from the use of opposing speed collisions as in the LHC or RHIC.
This could be the case with particles that transform or absorb at slow speeds.
C/ Heavy particles that are non reactive with ordinary matter present no danger.
D / Heavy particles reactive with ordinary matter.
Such particles theoretically do not present any danger because the cosmic ray model is valid in this case; they would always be captured by terrestrial matter.
IV **Some examples of possible danger:
1/ *****A small unexpected phenomenon could have grave consequences
Recently, the RHIC succeeded in producing a plasma of quarks-gluons [Ref.5] (the last step before creating black holes with even higher energies).
The physicists were amazed to see that this plasma was much denser than expected, acting like a “drop of liquid” and not like a “gas” as predicted by theory.
This quark-gluon plasma reduces the speed of and retains the particles created in the collision (“particle beam suppression”) and as this plasma, moreover, also produces « strange quarks », we can conceive that it could slow their speeds and create, given prolonged use of the RHIC accelerator, the famous strangelet considered so dangerous to the planet.
Arguments suggest that in the LHC the strangelet danger will be less significant than in the RHIC but it is notable that the LHC will be producing a greater number of these decelerating plasmas.
In this example, we cannot confirm absolutely that the decelerating plasmas present a real danger but we want to point out that simple unexpected phenomena could be the source of significant danger.
2/ *****Another example linked to the rapid development of theories:
In the RHIC safety study, [Ref.4] the number of dimensions for evaluation was only 4.
At that time, they did not imagine that there could be the possibility of a larger number of dimensions that could facilitate the creation of heavy particles.
If a larger number of dimensions exist, the creation of black holes could be easier than predicted and in this case the evaluation of danger by the RHIC would have been false or incomplete.
The rapid rate of evolution of theories shows the need for prudence and theories or risk-evaluations could be obsolete within a few years or even a few months.
3/ ***** Possible mistakes in evaluation.
In the first CERN safety studies for the LHC, the physicists had not considered the possibility of non-evaporation of micro black holes and their possible capture by Earth because Hawking evaporation seemed to be fact. For similar reasons, any safety study could be revealed to be incomplete or invalid because of human error.
V ** Risk evaluation:
Risk evaluation for unexpected phenomena is always subjective and depends for the evaluation on knowledge that we do not yet have.
Yet risk evaluation is of crucial importance, because the safety of the entire Earth is involved.
A reasonable minimum estimate of unexpected phenomena or the creation of unexpected particles in the LHC could, as an example, be evaluated as between 1% and 10% and the possibility that they present a danger could be evaluated between 0,1% to 1%.
Such a risk to the Earth is not acceptable.
VI ** Conclusion:
We do not have a complete theory of physics and we must acknowledge that high energies could create unexpected heavy particles (or other unexpected phenomena).
CERN safety studies evaluate the possibilities of dangerous phenomena in the context of our current theories, but that does not means that completely unexpected phenomena could not occur and mean danger for Earth.
This study seems to indicate that some categories of unexpected particles or phenomena could present a risk.
Previous accelerators, less powerful, have never yet produced a catastrophic event and it is easy to imagine that this will always be the case; but this could be an illusion.
If we accept that the behaviour of cosmic rays can no longer be considered as a proof of safety for the use of opposing high-energy collisions we must acknowledge that:
The more powerful the accelerator becomes, the more unpredicted and dangerous events may occur.
As noted above, a reasonable minimal estimation of unexpected phenomena or unexpected particles could, as an example, be from 1% to 10% and the possibility that they present a danger could be from 0,1% to 1%.
It is suggested that the risk that could be accepted is equivalent to the exceptional and very small risk of a heavy meteor colliding with the Earth, or the risk of a close supernova destroying all life on Earth.
Earth is our most precious treasure and we cannot permit any dangerous risks, just for the satisfaction of our scientific knowledge.
A 0,1% or a 1% risk for Earth cannot be accepted.
We propose obtaining data safely from astronomical sources or from accelerators not using opposite speed particle collisions.
As an example the satellite Planck (launch is scheduled for the end of 2008) or the neutrino detector KATRIN in 2009 could bring answers about the possible MOND theory.
In addition, the use of particle detectors to study cosmic rays over many years could give data as significant as that from colliders.
The best calculations, the best theories could prove to be wrong when tested.
Since it concerns a risk that could threaten the security of the planet, the decision taken must transcend all personal interest and if we have the least doubt, the LHC must not be activated.
As long as we do not have a satisfactory and complete theory of physics and are ignorant of the composition of 90% of the matter of the Universe it would seem wise to defer activation of the LHC
In this current age when we need to preserve and develop our planet the ‘precautionary principle’* or ‘safety first principle’ indicates that we should wait for more precise data coming from Astronomy before proceeding with any experiments with high energy opposite speed particle collisions.
1.. Review of the Safety of LHC Collisions. LHC Safety Assessment Group.2008.
John Ellis, Gian Giudice, Michelangelo Mangano, Igor Tkachev(**) and Urs
Astrophysical implications of hypothetical stable TeV-scale black holes
Steven B. Giddingsa,1 and Michelangelo L. Manganob,2
3..Review of the Safety of LHC Collisions. Addendum on strangelets
4.. Review of speculative disaster scenarios at RHIC
W.Busza, R.L. Jaffe, J.Sandweiss and F.Wilczek
5.. BBC New