TARDIS

The TARDIS is a fictional time travelling machine in the British television programme Doctor Who.

The word is an acronym for Time And Relative Dimensions In Space. The Doctor's TARDIS is an obsolescent "type 40" that he borrowed "unofficially" when he departed his home planet of Gallifrey - all the other type 40s have long since been decommissioned and replaced by new improved models.

Although it is supposed to blend inconspicuously into whatever time or environment it turns up in, it invariably shows up as a (British circa 1950s) blue police box. (This was probably a ploy by the BBC to save time and money in props, but became an in-joke genre convention in its own right, particularly since there have been very few police boxes left in Britain for some considerable time.) The rationalisation for this was given quite early in the series as a failure in a mechanism (the Chameleon Circuit) which was responsible for making the outside of the machine change to fit in with its environment. Despite his considerable ingenuity in other fields, and his ownership of a sonic screwdriver, The Doctor has been entirely unable to fix this problem. Ironically the exterior appearance of the TARDIS has become the only completely unchanging feature of the show over the course of its run.

Although it is only as big as a telephone box on the outside, the TARDIS is huge inside. The Doctor explains that it does this in the same way that large objects that are far away look small to the eye, and describes the TARDIS as being "dimensionally transcendental." meaning that its exterior and interior dimensions exist in separate dimensions. Suspension of disbelief becomes a more important dramatic element when budgets are tight!

Because the Doctor's TARDIS is so old it is inclined to break down, and the Doctor has often had to give it "percussive maintenance" to get it to start working properly. We also often saw him with his head stuck in a panel carrying out maintenance of some kind or another. (This gives us the amusing paradox of a space-time machine which is considerably more advanced than anything in the Star Trek universe, but which is at the same time an obsolete and unreliable piece of junk.)

The Master, a re-appearing nemesis of the Doctor and fellow Time Lord, had his own TARDIS, a later model whose Chameleon Circuit was not broken. In one episode each Time Lord's TARDIS materialised within the other, which led to a very confusing state of affairs!

Other characters with TARDISes include the Meddling Monk, The Master and The Rani. Presumably all renegade Time Lords had TARDISes at one time or other.