The eagerly awaited start-up of the Large Hadron Collider (LHC), the world's largest particle accelerator, has been put off—again. The LHC was shut down in September, just days after being switched on for the first time, when an electrical malfunction caused a helium leak in the collider's tunnel. The repairs, which had been expected to last until spring, will now keep the LHC off-line into early summer, according to published statements from a spokesman for the accelerator's operator.

"If we can do it sooner, all well and good," James Gillies, head of communications for CERN, the European laboratory for particle physics, said. "But I think we can do it realistically [in] early summer." (His remarks were quoted by the Associated Press, among other news agencies.)

When the LHC does come back online, it is expected to provide clues to a number of unanswered questions in physics, possibly revealing entirely new elementary particles and allowing scientists a better view of the universe as it looked in the moments after the big bang.

CREDIT: Maximilien Brice/CERN