The following is a quote lifted from Charlie Stross’s blog and is pretty much In Full.
…We. Are. Not. Going. To. Die. On. Wednesday.
The maximum energy the particles generated by the LHC (7TeV) get up to is many orders of magnitude below the maximum energy of cosmic rays that hit the Earth’s upper atmosphere from space every fricking day. None of them have created black holes and gobbled up the planet, or turned us all into strange matter. Nor have they done ditto to any cosmic bodies we can see, such as planets or stars. Therefore the world isn’t going end when they switch on the LHC on Wednesday.