Doomsday predictions surrounding the start-up of Europe's Large Hadron Collider - a giant particle-smasher designed to explore the origins of the universe - come as little surprise to physicists.
The world's largest particle-collider has yet to begin experiments, but its trial run on Wednesday was accompanied by worries that it might spawn black holes with enough gravitational pull to swallow up the earth.
Edward "Rocky" Kolb, chairman of the department of Astronomy and Astrophysics at the University of Chicago, says such fears come with the territory.
"This is an experiment at the frontier of our knowledge of nature. It is opening the door into uncharted territory," he said in a telephone interview. But Dr Kolb feels awe, not fear.
"Rather than creating a black hole that destroys the universe, we expect to discover new laws of nature," he said. A group calling itself the Citizens Against The Large Hadron Collider filed a lawsuit trying to halt the project.
"The doomsday prophets would say they haven't had any collisions. They would say we are not out of the woods yet," said Dr Kolb, who spent a year working at the European Centre for Nuclear Research, or Cern.
"The reason I'm not concerned is that nature has already done this experiment. It was done in the early universe," he said.
"Cosmic rays have hit the moon with more energy and have not produced a black hole that has swallowed up the moon," he said. "The universe doesn't go around popping off huge black holes."
Dr Kolb and others said people made similar doomsday predictions before the opening of the Relativistic Heavy Ion Collider at Brookhaven National Laboratory in 1999.
Other physics experiments have engendered fear as well.
When Enrico Fermi was testing the first nuclear reactor in a squash court at the University of Chicago in 1943, some scientists worried that it could generate an explosion that might blow up the Chicago neighbourhood of Hyde Park.
"Dr Fermi had sort of a wicked sense of humour. He was taking bets at the test site about whether the world would end or not," Dr Kolb said.
The Big Bang
Recreating the Big Bang:
• The final tests involved pumping a single bunch of energy particles from the project's accelerator into the 27-kilometre beam pipe of the collider and steering them counter-clockwise around it for about three kilometres.
• The collider aims to simulate conditions milliseconds after the "Big Bang" which created the universe around 13.7 billion years ago.
• The collisions, in which both particle clusters travelled at the speed of light, were monitored on computers at Cern and laboratories around the world by scientists looking for, among other things, a particle that made life possible.
• The elusive particle, which has been dubbed the "Higgs Boson" after Scottish physicist Peter Higgs who first postulated nearly 50 years ago that it must exist, is thought to be the mysterious factor that holds matter together.
What is the Big Bang?
• Recreating a "Big Bang," which most scientists believe is the only explanation of an expanding universe, ought to show how stars and planets came together out of the primeval chaos that followed, the Cern team believes.
• Its essential feature is the emergence of the universe from a tiny speck about the size of a coin but in a state of extremely high temperature and density.
• The name "Big Bang" was coined in 1949 by British scientist Fred Hoyle to disparage a then emerging theory about origins that countered his own "steady state" view: That the universe had always existed and was evolving but not expanding.
• According to the Big-Bang model, the universe expanded rapidly from a highly compressed primordial state, which resulted in a significant decrease in density and temperature. Soon afterward, the dominance of matter over antimatter (as observed today) may have been established by processes that also predict proton decay. During this stage many types of elementary particles may have been present. After a few seconds, the universe cooled enough to allow the formation of certain nuclei.
• The theory predicts that definite amounts of hydrogen, helium, and lithium were produced. Their abundances agree with what is observed today. About 1,000,000 years later the universe was sufficiently cool for atoms to form.
What is Cern?
• Cern, the European Organisation for Nuclear Research, is one of the world's largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works.
• Founded in 1954, the Cern Laboratory sits astride the Franco-Swiss border near Geneva. It was one of Europe's first joint ventures and now has 20 member states, plus six actively participant observers including the US and Russia.