In anticipation of the upcoming first beam of the CERN Large Hadron Collider (LHC), scheduled for 10 September 2008.  According to the CERN website:

The Large Hadron Collider (LHC) is a gigantic scientific instrument near Geneva, where it spans the border between Switzerland and France about 100 m underground. It is a particle accelerator used by physicists to study the smallest known particles – the fundamental building blocks of all things. It will revolutionise our understanding, from the minuscule world deep within atoms to the vastness of the Universe.

Two beams of subatomic particles called ‘hadrons’ – either protons or lead ions – will travel in opposite directions inside the circular accelerator, gaining energy with every lap. Physicists will use the LHC to recreate the conditions just after the Big Bang, by colliding the two beams head-on at very high energy. Teams of physicists from around the world will analyse the particles created in the collisions using special detectors in a number of experiments dedicated to the LHC.

There are many theories as to what will result from these collisions, but what’s for sure is that a brave new world of physics will emerge from the new accelerator, as knowledge in particle physics goes on to describe the workings of the Universe. For decades, the Standard Model of particle physics has served physicists well as a means of understanding the fundamental laws of Nature, but it does not tell the whole story. Only experimental data using the higher energies reached by the LHC can push knowledge forward, challenging those who seek confirmation of established knowledge, and those who dare to dream beyond the paradigm.

Anyone paying attention to this upcoming event (which is actually scheduled for a few hours from the time of this post) has probably heard that numerous groups have tried their best to stop this “first beam,” from occurring, citing fears that the LHC will spell doomsday for the Earth.

To address these concerns, scientists and engineers of the LHC Safety Assessment Group submitted a paper for review to the prestigious Journal of Physics G: Nuclear and Particle Physics of the Institute of Physics (UK), which was subsequently published on 5 September 2008 after passing through the peer-review process.  The citation for this article is as follows:

• Ellis, J., Giudice, G., Mangano, M., Tkachev, I., and Wiedemann, U. (2008). “Review of the Safety of LHC Collisions.” Journal of Physics G: Nuclear and Particle Physics, Vol. 35, pp. 1-18. (doi:10.1088/0954-3899/35/11/115004). (available here for free).

The abstract from this paper is copied below:

The safety of collisions at the Large Hadron Collider (LHC) was studied in 2003 by the LHC Safety Study Group, who concluded that they presented no danger. Here we review their 2003 analysis in light of additional experimental results and theoretical understanding, which enable us to confirm, update and extend the conclusions of the LHC Safety Study Group. The LHC reproduces in the laboratory, under controlled conditions, collisions at centre-of-mass energies, less than those reached in the atmosphere by some of the cosmic rays that have been bombarding the Earth for billions of years. We recall the rates for the collisions of cosmic rays with the Earth, Sun, neutron stars, white dwarfs and other astronomical bodies at energies higher than the LHC. The stability of astronomical bodies indicates that such collisions cannot be dangerous. Specifically, we study the possible production at the LHC of hypothetical objects such as vacuum bubbles, magnetic monopoles, microscopic black holes and strangelets, and find no associated risks. Any microscopic black holes produced at the LHC are expected to decay by Hawking radiation before they reach the detector walls. If some microscopic black holes were stable, those produced by cosmic rays would be stopped inside the Earth or other astronomical bodies. The stability of astronomical bodies strongly constrains the possible rate of accretion by any such microscopic black holes, so that they present no conceivable danger. In the case of strangelets, the good agreement of measurements of particle production at RHIC with simple thermodynamic models severely constrains the production of strangelets in heavy-ion collisions at the LHC, which also present no danger.

As a risk study, this report is very cool.  It considers a variety of plausible events associated with use of the LHC that are not necessarily independent of one another.  These include, but are not limited to, the following:

• Nothing of note happens
• Production of vaccum bubbles (section 2)
• Production of magnetic monopoles (section 2)
• Production of microscopic black holes (section 4)
• Production of strangelets, that is, hypothetical pieces of matter analogous to conventional nuclei, but also containing many of the heavier strange quarks (section 5)

The interesting thing about this risk analysis is that almost the entire report is reasoned through from evidence and theory since, after all, the LHC is a unique object and there is nothing really comparable to it.  From what I can tell in my first pass through the report, the authors do a really good job at explaining what would happen (and likeliness) given the occurrence of the above mentioned events. And from what I can tell, this paper is very fair, that is, it considers (and refutes) alternative viewpoints.

But alas, since the focus of this paper seems to be on debunking myths, little attention is paid to whatever residual likeliness remains for really bad outcomes.  These bad outcomes are examples of either counterexpected (i.e., so low probability such that it is deemed practically impossible) or perhaps even potentially surprising (i.e., not even considered) events.

In the end, the authors state the following (which actually appears in the last paragraph of the introduction):

We conclude by reiterating the conclusion of the LHC Safety Group in 2003: there is no basis for any conceivable threat from the LHC.  Indeed, theoretical and experimental developments since 2003 have reinforced this conclusion.

Yet, in the conclusions section (Section 6), the authors state:

Having reviewed the theoretical and experimental developments since the previous safety report was published, we confirm its findings.  There is no basis for any concerns about the consequences of new particles or forms of matter that could possibly be produced by the LHC.

What if our understanding of the universe is incomplete (as I am sure it is), and unexpected “black swans” do occur?  If our knowledge is incomplete and there are things that can occur that reside outside our understanding, we still wouldn’t have anything to base our speculations on since having such a basis requires having the knowledge we lack.  Yet, we may still be at risk; we are just ignorant of what the risks are.

Now let’s look at this whole thing from the security engineers point of view.  What about the less sexy events associated with “classical physics,” such as faulty wiring leading to a very, VERY bad explosion at CERN.  Is this possible?  Where is the safety report that mentions what could happen in the event of catastrophic system failure, or worse, sabotage?  What about the failure modes, effects, and criticality analysis?  Maybe such studies exist, but they definitely wouldn’t be novel enough to go through the same peer-review process as one centered on theoretical concerns.  I, as a security risk analyst, am very interested in understanding and mitigating those non-theoretical events that have the potential to cause harm to people, prestigious scientists included.  Scientists are playing with a lot of energy here, and I really hope their systems engineering was done well enough to ensure this energy remains contained.

Since the authors are so certain of the LHC’s safety, I suppose we will know in a matter of a few hours whether they are wrong.  I trust we will be ok, because after all, no more Earth = no more science experiments (and physicists definitely would take the conservative route when confronted with a possibility of such a future).

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