  Recently, black hole and brane production at CERN's Large Hadron Collider
(LHC) has been widely discussed. We suggest that there is a possibility to test
causality at the LHC. We argue that if the scale of quantum gravity is of the
order of few TeVs, proton-proton collisions at the LHC could lead to the
formation of time machines (spacetime regions with closed timelike curves)
which violate causality. One model for the time machine is a traversable
wormhole. We argue that the traversable wormhole production cross section at
the LHC is of the same order as the cross section for the black hole
production. Traversable wormholes assume violation of the null energy condition
(NEC) and an exotic matter similar to the dark energy is required. Decay of the
wormholes/time machines and signatures of time machine events at the LHC are
discussed.
