|A simulation shows the particle tracks that scientists
think could be given off by the decay of a black hole
in the Large Hadron Collider's ATLAS detector.
Europe's CERN particle-physics lab has issued its long-awaited report on safety issues surrounding the Large Hadron Collider, the world's biggest and most expensive atom-smasher. Some have feared that when the collider reaches full power, sometime next year, it might create microscopic black holes or other exotic phenomena that could endanger Earth. The new report, like earlier safety studies, rules out the possibility of global danger.
The report's argument follows the basic line used in past reports: Even the most energetic collisions planned for the LHC are far less powerful than cosmic-ray collisions that have been going on for billions of years.
"Nature has already generated on Earth as many collisions as about a million LHC experiments – and the planet still exists," CERN said in its lay-language summary of the report. "Astronomers observe an enormous number of larger astronomical bodies throughout the universe, all of which are also struck by cosmic rays. The universe as a whole conducts more than 10 million million LHC-like experiments per second. The possibility of any dangerous consequences contradicts what astronomers see - stars and galaxies still exist."
The report also delves into the theoretical implications even if it turns out that microscopic black holes may hang around longer than most scientists think, and still ends up ruling out the catastrophic risk. In the stable-black-hole scenario, physicists do not expect the black holes to gobble up matter and grow to a monster size. Instead, they would interact - or not interact - with the particles they came across.
CERN discussed the safety report in a news release today, issued after this week's meeting of the CERN Council. Here's the text:
"At its 147th meeting in Geneva today, the CERN Council heard news on progress towards start-up of the laboratory's flagship research facility, the Large Hadron Collider (LHC). Commissioning of the 27-kilometre LHC began in January 2007 when the first cooldown of one of the machine's eight sectors began. Today, five sectors are at or close to their operating temperature of 1.9 degrees above absolute zero and the remaining three are approaching that temperature. Once all sectors are cold, electrical testing will be concluded in readiness for first beams, currently scheduled for August.
"'The accelerator, detectors and computing are all on course,' said CERN Director General Robert Aymar, 'and we are looking forward to the earliest possible LHC start-up.'
"When the LHC starts up this summer, its proton beams will collide at higher energies than have ever been produced in a particle accelerator. The collision energy of the LHC, however, is modest compared to the energies of the cosmic ray protons that have been striking the Earth's atmosphere for billions of years.
"'The LHC is the highest-energy particle accelerator on Earth,' said Dr. Aymar, 'but the universe has far more powerful ones. The LHC will enable us to study in detail under laboratory conditions what nature is doing already.'
"The LHC is subject to numerous audits covering all aspects of safety and environmental impact. The latest of these, addressing the question of whether there is any danger related to the production of new particles at the LHC, was presented to Council at this meeting. Updating a 2003 paper, this new report incorporates recent experimental and observational data.
"It confirms and strengthens the conclusion of the 2003 report that there is no cause for concern. The report was prepared by a group of scientists at CERN, the University of California, Santa Barbara, and the Institute for Nuclear Research of the Russian Academy of Sciences.
"'With this report, the Laboratory has fulfilled every safety and environmental evaluation necessary to ensure safe operation of this exciting new research facility,' said Dr. Aymar.
"The new report has been reviewed by the Scientific Policy Committee (SPC), a body that advises the CERN Council on scientific matters. A panel of five independent scientists, including one Nobel laureate, reviewed and endorsed the authors' approach of basing their arguments on irrefutable observational evidence to conclude that new particles produced at the LHC will pose no danger. The panel presented its conclusions to this week's meeting of the full 20 members of the SPC, who unanimously approved this conclusion.
"'It was right for the Director General of CERN to commission a formal assessment of safety issues, examining even the most unlikely of scenarios,' said Council President Torsten Åkesson. 'This new report concludes that there is no basis for any concern, a position endorsed by the 20 independent experts who form the SPC.'
The news release confirms that researchers will start sending beams through the LHC in August rather than July - but the startup procedure is expected to take months, with actual collisions coming later, and collisions at full power coming later still.
We've been following this issue for a while, and once you've looked over the report, I'm sure you'll want to weigh in with your comments below.