After a year's delay, scientists at the world's biggest accelerator have restarted an experiment to recreate "Big Bang" conditions that had sparked suggestions the earth would be sucked in by millions of black holes.

Scientists at the European Organisation for Nuclear Research have established circulating particle beams in both directions in the underground Large Hadron Collider, a step which is already beyond where the experiment stalled during a first attempt in September 2008, CERN spokesman James Gillies said.

The high-profile experiment, through which tiny particles are smashed in a bid to learn more about the birth of the universe, had failed just nine days after it was launched due to a technical problem that it took longer-than-expected to fix.

"The Large Hadron Collider is a far better understood machine than a year ago," said CERN's Director for Accelerators Steve Myers.

CERN, a 55-year-old organisation that counts 10,000 scientists and technicians worldwide working on its research projects, has vigorously rebuffed any suggestion the ground-breaking experiment would cause the world to end.

"There is no foundation to these stories," Gillies said.

CERN's Director General Rolf Heuer said getting the experiment re-started at the 10 billion Swiss franc ($9.82 billion) collider under the French-Swiss border had been an "herculean effort".

"We've still got some way to go before physics can begin, but with this milestone we're well on the way," he added.

The experiment will be fully under way when the particle beams will be smashed at energy levels higher than those so far tested in such type of collisions. This will most likely happen in January, Gillies said.

The next important step in the ongoing experiment will be low-energy collisions, expected in about a week for now, CERN said.

The experiment can be followed step-by-step on http://twitter.com/cern.