I know we would have no way to theorize how Timelord technology works, but is there ever any explanation given in Doctor Who about how Timelords create buildings or containers that are bigger on the inside than on the outside?

  • 5
    You'll have to ask Hermione.
    – Kevin
    Feb 1, 2012 at 4:36
  • 1
    He explained it to Leela once, and it made perfect sense.
    – Beta
    Feb 7, 2012 at 21:15
  • Transcendental engineering.
    – ewanm89
    Dec 26, 2013 at 16:49
  • It’s all a bit spacey-wacey. Oct 25, 2015 at 19:58

4 Answers 4


The interior of a TARDIS is actually in a different dimension than the exterior. That other dimension's contents are maintained by the TARDIS' energy. If the TARDIS is low on energy, it can delete rooms from the interior to free up energy (The Doctor's Wife).

The construction of a TARDIS isn't actually a process of building, it's a process of growing. It's unclear if this means the TARDISes are actually biological in nature, or if the technology Timelords employ when making TARDISes simply mimics biological growth (The Impossible Planet). The specifics of how the Timelords manage this feat hasn't been revealed.

  • 1
    Referring to the deletion of rooms to free up energy -- is it possible, if the device runs out of energy, for the interior to become detached from the exterior?
    – Tango
    Feb 1, 2012 at 5:00
  • @TangoOversway Unknown, but the TARDISes have built-in safeties to prevent harming occupants, so it's likely that there's a mechanism to prevent the TARDIS from breaking when low on energy. Perhaps there are emergency power generators in the current control room to ensure that when low on energy at least that one room can be maintained.
    – user1027
    Feb 1, 2012 at 5:05
  • 1
    One way to think of it is that the dimension is defined by it's contents (think of it as a bubble that can just barely hold the Tardis interior); it takes energy to 'grow' the rooms, but once they have been created, they don't require energy to sustain. The INTERFACE (i.e., the door) requires a bit of energy, but it's basically held in place by tension imposed during construction, and the act of opening it is enough to re-trigger it from an inactive state. IMHO, tho, so not cannon. Just seems to fit.
    – K-H-W
    Feb 1, 2012 at 6:10
  • 1
    The Interior was sort of detached in "Father's Day". I forget why. Feb 1, 2012 at 10:20
  • @TangoOversway Doctor who wiki if you search for the word "jettisoned" within the page you will find that several rooms have been ejected, for example a "Zero Room" (no clue) and a swimming pool. Not sure if this is for power or for other nefarious purposes.
    – erdiede
    Feb 1, 2012 at 13:56

From "The Robots of Death" (1977)...

LEELA: So, explain to me how this Tardis is larger on the inside than the out.

DOCTOR: Hmm? All right, I'll show you. It's because insides and outsides are not in the same dimension.

(The Doctor gets two boxes from on top of a cupboard. One box is larger than the other.)

DOCTOR: Which box is larger?

LEELA: (pointing to the larger box) That one.

(The Doctor places it on the time console then walks over to Leela with the other, smaller box.)

DOCTOR: Now which one is larger?

LEELA: (pointing to the larger box) That one!

DOCTOR: But it looks smaller.

LEELA: Well, that's because it's further away.

DOCTOR: Exactly. If you could keep that exactly that distance away and have it here, the large one would fit inside the small one.

LEELA: (beat) That's silly.

DOCTOR: That's transdimensional engineering, a key Time Lord discovery.


Whenever the Doctor is asked this, he always says: "It's dimensionally transcendent." And asked what this means, he replies: "It means it's bigger on the inside than the outside."


There actually is a way to plausibly explain, using modern human physics.

We know, through quantum theory, that the universe consists of more than just the 3 dimensions (or 4, depending on how you count Time) that we are able to directly experience. Some branches of quantum theory postulate thousands of additional dimensional axes or even higher. From our perspective, locked inside these 3 particular dimensions, those look like they're curled up at the individual points, but I'd imagine that if we looked at them outside of this context, they would just be additional axes on the grid.

Now imagine that you've found technology enabling you to shift matter from these dimensional axes to those. You could create a portal of sorts that you could walk through and be "rotated" into a separate 3 dimensional space. It's still 3 dimensions, just 3 different dimensions. Once in that separate space, you're no longer constrained by the matter in these 3 dimensions. The walls you were inside of here don't necessarily exist there. You could build a huge open space with everything you need, with this little blue box as the entrance. The TARDIS, as depicted, apparently does this so seamlessly and consistently that even light goes right through unaffected, allowing you to view directly in or out of the doorway. Time Lord technology is amazing, isn't it?

That would also explain the appearing and disappearing blue box, as well as the chameleon circuit. Since they (we assume) have the technology to "rotate" matter to and from those other dimensions, the disappearing is just the ship pulling in the gangplank, as it were. That blue box is ultimately just a solid illusion, and thus could be modified in its appearance. Once you have that first piece, the rest falls right into place.

So how do you power such a beast? Well, with so much room to play with, you could have some massive battery stores and generators. You could also have energy scoops that could be extended ("rotated") straight into the heart of a sun or other energy source to recharge the ship. Heck, you could have a star itself at the core of the ship. Plenty of power for billions of years.

But what would you use to build it? You could harvest material from those other dimensions just like you could from here (but with a bit of extra effort of course). Modern physics asserts that those are just as likely to contain matter as our own.

And as an added bonus... Since time is just another dimension, if you can move about in these extra dimensions, time travel would be a piece of cake, just like walking up the road. You just have to maintain fixed points to avoid any serious paradoxes, and Bob's your uncle. As I said, once you have that first piece, the rest is relatively simple.

  • Only a star? Look up eye of harmony, there is the Tardis power source right there, a star suspended at the moment of collapse into a black hole.
    – ewanm89
    Dec 26, 2013 at 17:22
  • True. It could be any energy source. Star, black hole, or some artificial singularity. Once you break through that first barrier, other limits fall away.
    – Indomitus
    Dec 26, 2013 at 17:29
  • If you can rotate matter through higher-order dimensions, you can create anti-matter virtually for free (this only requires rotating it correctly so that it ends up reversed back in the original dimensions). This basically allows for direct matter-to-energy conversion (very near 100% efficiency).
    – John O
    Dec 27, 2013 at 1:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.