"Critics have called for serious attention to the possibility that the collider might generate a subatomic object called a ‘strangelet,' which could, if certain assumptions are correct, start a chain reaction converting everything into ‘strange matter,'" they write. "The process would, according to Sir Martin Rees, Astronomer Royal of the United Kingdom, leave the planet ‘an inert hyperdense sphere about one hundred meters across.'"
An inert hyperdense sphere. That doesn't sound good. Doomsday never sounds good.
A strangelet is the speculative boogieman of particle physics. They are hypothetical post-collision particles that condense from the primordial matter to form an up, down and a strange quark which combine to make a strangelet. Although they have yet to be detected from any particle collision experiment, the risk posed by the potential existence of strangelets, argue Johnson and Baram, should be investigated. One theory suggests that should stranglets be created, a chain reaction with ordinary matter could rampage around the planet, reducing Earth to a hyperdense sphere.