A small furry animal today took on the largest atom smasher ever made, and won. According to internal documents at CERN, the Large Hadron Collider was knocked out of commission at about 5:30 am CEDT when a weasel caused a "severe electrical perturbation" when it stepped on the bare connections of a 66,000 volt transformer. This not only proved instantly fatal to the weasel, but it also short circuited the power system, causing the LHC to execute a fast abort as the sudden power loss created a series of anomalies.

According to CERN, the weasel wasn't in the accelerator itself, but in transformers at the power substations on the surface that relay electricity to the giant machine. The sudden loss of power affected all the accelerators and shut down all the beams used to study subatomic particles. Most of the magnets powered down correctly, though some did not, the cryogenic system used to supercool the accelerator went offline, and air leaks developed that compromised the vacuum in the beam chambers.

In a slide presentation of the supercollider's status, the event was referred to as "not the best week for LHC." Speaking to the BBC, a CERN spokesman said that it will take a few days to bring the LHC back online.

This is not the first time that the LHC has been shut down by wildlife. In 2009, a bird dropped a piece of bread into the electrical system, which briefly disabled the collider.

Source: CERN (PDF)