The clock is ticking.

At 3:30 a.m. EDT Wednesday, scientists on the Franco-Swiss border will flip the switch on the Large Hadron Collider, a 17-mile underground ring where subatomic particles will be accelerated to astonishing speeds and then smashed into each other.

It'll be months before any usable data comes out from the experiments, but the so-called "Big Bang machine" already has physicists salivating at the prospect of unlocking the mysteries of the universe — and many other people worried it'll create a black hole or strange self-replicating particle that will gobble up the Earth.