Background radiation
Mrs Wormwood identified the artron energy accumulated by Sarah Jane Smith's travels through the Time Vortex as background radiation. (TV: Invasion of the Bane [+]Loading...["Invasion of the Bane (TV story)"])
Rose Tyler became aware that, by travelling in the Doctor's TARDIS, she had "soak[ed] up" background radiation, which the Daleks evolved to use as a power supply in the Last Great Time War; (TV: Doomsday [+]Loading...["Doomsday (TV story)"]) by making physical contact with Rose and thus extrapolating her biomass, the "Metaltron" was able to restore itself. (TV: Dalek [+]Loading...["Dalek (TV story)"]) By travelling across parallel universes through the Void, one would accumulate Void stuff, which the Tenth Doctor identified as another form of background radiation. (TV: Doomsday [+]Loading...["Doomsday (TV story)"])
