Safety of high-energy particle collision experiments

The claimed dangers included the production of stable micro black holes and the creation of hypothetical particles called strangelets,[1] and these questions were explored in the media, on the Internet and at times through the courts.

Their operation involves directed beams of particles accelerated to very high kinetic energy and allowed to collide; analysis of the byproducts of these collisions gives scientists good evidence of the structure of the subatomic world and the laws of nature governing it.

[12] Similar concerns had previously also been raised in the context of the Relativistic Heavy Ion Collider, with Frank Close, professor of physics at the University of Oxford, to comment at the time that "the chance of [strangelet creation] is like you winning the major prize on the lottery 3 weeks in succession; the problem is that people believe it is possible to win the lottery 3 weeks in succession.

[14][15][16][17] After detailed studies, scientists reached such conclusions as "beyond reasonable doubt, heavy-ion experiments at RHIC will not endanger our planet"[18] and that there is "powerful empirical evidence against the possibility of dangerous strangelet production.

Physicists are unable to demonstrate experimental and astrophysical constraints of zero probability of catastrophic events, nor that tomorrow Earth will be struck with a "doomsday" cosmic ray (they can only calculate an upper limit for the likelihood).

"[13] After detailed studies, scientists reached such conclusions as "beyond reasonable doubt, heavy-ion experiments at RHIC will not endanger our planet"[18] and that there is "powerful empirical evidence against the possibility of dangerous strangelet production.

[26] The controversy mostly ended with the report of a committee convened by the director of Brookhaven National Laboratory, J. H. Marburger, ostensibly ruling out the catastrophic scenarios depicted.

Wagner tried subsequently to stop full energy collision at RHIC by filing Federal lawsuits in San Francisco and New York City, but without success.

[32][33][34][35][36] These opponents assert that the LHC experiments have the potential to create low velocity micro black holes that could grow in mass or release dangerous radiation leading to doomsday scenarios, such as the destruction of the Earth.

[1][37] Based on such safety concerns, US federal judge Richard Posner,[38] Future of Humanity Institute research associate Toby Ord[39] and others[40][41][42][43] have argued that the LHC experiments are too risky to undertake.

[45] On 9 September 2008, Romania's Conservative Party held a protest before the European Commission mission to Bucharest, demanding that the experiment be halted because it feared that the LHC could create dangerous black holes.

[52] Among other media sources, CNN mentioned that "Some have expressed fears that the project could lead to the Earth's demise,"[53] but it assured its readers with comments from scientists like John Huth, who said that it was "baloney".

[55] Brian Greene in the New York Times reassured readers by saying, "If a black hole is produced under Geneva, might it swallow Switzerland and continue on a ravenous rampage until the Earth is devoured?

"[56] On 10 September 2008, a 16-year-old girl from Sarangpur, Madhya Pradesh, India committed suicide, having become distressed about predictions of an impending "doomsday" made on an Indian news channel (Aaj Tak) covering the LHC.

[57] After the dismissal of the federal lawsuit, The Daily Show's correspondent John Oliver interviewed Walter L. Wagner, who declared that he believed the chance of the LHC destroying the Earth to be 50%, since it will either happen or it won't.

[65] The LHC Safety Assessment Group (LSAG) indicates that "there is broad consensus among physicists on the reality of Hawking radiation, but so far no experiment has had the sensitivity required to find direct evidence for it.

They would also have been produced by cosmic rays and have stopped in neutron stars and white dwarfs, and the stability of these astronomical bodies means that they cannot be dangerous:[3][66] Stable black holes could be either electrically charged or neutral.

[3] Otto Rössler, a German chemistry professor at the University of Tübingen, argues that micro black holes created in the LHC could grow exponentially.

"[74] On 1 August 2008, a group of German physicists, the Committee for Elementary Particle Physics (KET),[75] published an open letter further dismissing Rössler's concerns and carrying assurances that the LHC is safe.

[1][85] On 19 January 2009 Roberto Casadio, Sergio Fabi and Benjamin Harms posted on the arXiv a paper, later published on Physical Review D, ruling out the catastrophic growth of black holes in the scenario considered by Plaga.

One argument raised against doomsday fears was that collisions at energies equivalent to and higher than those of the LHC have been happening in nature for billions of years apparently without hazardous effects, as ultra-high-energy cosmic rays impact Earth's atmosphere and other bodies in the universe.

[4] On 20 June 2008, in light of new experimental data and theoretical understanding, the LSAG issued a report updating the 2003 safety review, in which they reaffirmed and extended its conclusions that "LHC collisions present no danger and that there are no reasons for concern".

[5][35][87] The report was reviewed and endorsed by a panel of five independent scientists, Peter Braun-Munzinger, Matteo Cavalli-Sforza, Gerard 't Hooft, Bryan Webber and Fabio Zwirner, and their conclusions were unanimously approved by the full 20 members of the SPC.

[6] On 1 August 2008, a group of German quantum physicists, the Committee for Elementary Particle Physics (KET),[75] published an open letter further dismissing concerns about the LHC experiments and carrying assurances that they are safe based on the LSAG safety review.

[69] The suit, which was summarily rejected on the same day, alleged that the Large Hadron Collider posed grave risks for the safety of the 27 member states of the European Union and their citizens.

[101] In February 2010, the German Constitutional Court (Bundesverfassungsgericht) rejected an injunction petition to halt the LHC's operation as unfounded, without hearing the case, stating that the opponents had failed to produce plausible evidence for their theories.