Temporal radiation is an exotic form of energy first encountered by the crew of the Enterprise NX-01 in 2152. It had disorienting time-distortion effects which caused those in close proximity to a time pod from the 31st century, which the crew had discovered adrift in space. The radiation caused individuals affected by it to experience a kind of “time loop,” in which the same moment repeated over and over again, while time outside the radiation’s influence proceeded at a normal pace.
Commander Charles Tucker and Lieutenant Malcolm Reed were the first to become exposed to the radiation after removing a panel from the time pod. As a result, they began reliving the same moment repeatedly. Although the particle density was too low to allow any lasting effects, Archer sealed off the launch bay where the pod was being held to prevent further exposure.
Later, Reed and Archer would go through the same experience of deja vu while attempting to load a warhead from a spatial torpedo onto the pod with the intention of destroying it before it could fall into Tholian hands. Although the Tholians were able to disarm the warhead, the pod itself would disappear after Tucker activated its temporal beacon. (ENT: "Future Tense")