A few years ago, there seemed to be a risk that the Large Hadron
Collider (LHC) at CERN would destroy Earth. The risk was based
on speculative, if serious, physics. The probability that Earth
would be destroyed seemed low because the theories that allowed
trouble were speculative. Nevertheless, even given a small
probability, destruction of Earth would have an enormous
negative expected value (probability times value, the
appropriate metric for decision theory). Collider advocates put
forth several reasons not to worry, but others found lacuna in
those reasons. CERN conducted two safety studies, the second
necessitated by flaws in the first. The final study was fairly
good, but was still subject to criticism. Despite all this, CERN
declared that the probability that the Earth would be destroyed
was zero and fired up the LHC in 2008. Despite a minor
industrial accident, the Earth was not destroyed. Much of the
risk that we can control is behind us. In most models
destruction of Earth takes a few years, but the