University of Minnesota
School of Physics & Astronomy

General News

Opening a new world--not ending this one


Professor Joseph Kapusta offers his professional opinion on the controversey surrounding the Large Hadron Collider at CERN. The LHC will run its first beam collisions on September 10th, 2008.

Opening a new world--not ending this one

We are naturally inquisitive. Witness people’s need to explore new lands, to figure out how things work, to ponder where we came from.
Soon, more than 2,000 scientists from around the world will embark on a journey of exploration into the unknown. They have converged at the European Center for Nuclear Research (CERN) in Switzerland, where they have constructed the largest instruments in history to explore how things work at the most fundamental level. This mammoth set of instruments is called the Large Hadron Collider (LHC).

With the LHC, researchers will measure what happens when protons, traveling in beams, collide at extremely high energies. The LHC is ready to make observations soon after the first beams are generated on Sept. 10.

This experiment will bring physicists closer to answering two burning questions in physics: What is the origin of mass, a property intimately connected with gravity, a force considered an outsider to all other forces? And, are there are more fundamental building blocks of matter than the ones we know about? Many physicists have theorized that to make logical sense out of what we already know, there must be more than four dimensions of space and time. It would be astonishing, perhaps even disturbing, to discover that there are hidden dimensions into which ghostly objects come and go.

Some informed individuals, though not practicing physicists, are concerned that mini black holes or chunks of strange matter called strangelets might be produced by the LHC, and that these would absorb matter and grow so large as to eventually destroy the Earth. Several have even filed a lawsuit to halt the experiments. There was a flurry of news stories in the media last spring in which these fears were discussed. The LHC was even referred to as a possible doomsday machine.

For those who know the history of high-energy physics, this is a case of déjà vu. A similar but somewhat smaller accelerator called RHIC (Relativistic Heavy Ion Collider) has been running for nearly 10 years at Brookhaven National Laboratory on Long Island. Following an article in the Scientific American just before RHIC was to begin operation, several individuals wrote letters expressing their concern.
One person wrote, “I am concerned that physicists are boldly going where it may be unsafe to go ... What if they somehow alter the underlying nature of things such that it cannot be restored?” Another individual expressed his concern that mini black holes might be produced, with disastrous consequences.

The magazine sought the advice of a prominent theoretical physicist, who dismissed as “incredible” the mini black hole scenario, but admitted to a small but respectable possibility that strangelets might be produced.

“But strangelets, if they exist at all, are not very aggressive, and they will start out very, very small,” he said. This could hardly be comforting to the nonscientist.

Another group of physicists estimated that the laws of nature were such that the chance of RHIC destroying the Earth was less than one in 5 million. That sounds like a very small probability, but consider that every day people buy lottery tickets with hopes of winning at much poorer odds. But there is a difference. In a lottery someone is guaranteed to win eventually. The RHIC and LHC accelerators could run forever without catastrophe because the laws of nature just don’t work that way.

RHIC was not even the first. An accelerator called the Bevalac operated from 1974 to 1993 at Lawrence Berkeley National Laboratory in California. There were concerns that the Bevalac might produce a new form of matter, called density isomers, which would fall to the center of the Earth and quickly consume it. Nobody took it too seriously, although a lab committee considered the possibilities and concluded that the experiments should go forward.

In 1993, at my urging, two of my colleagues wrote an article for Physics Today to summarize what was learned at the Bevalac. They were subsequently placed on the FBI Unabomber watch list, and their mail was checked for suspicious packages, because of what they wrote about experiments possibly causing the end of the world.

I know of no professional physicist who is truly worried that experiments at the LHC could go so disastrously wrong that they would cause the destruction of the Earth. The first collisions between particles in the LHC will occur sometime this fall. Let us wish bon voyage for the thousands of scientists going on a journey of exploration of a lifetime.

--Joseph Kapusta