Originally Posted by bp2:
“That doesn't explain anything at all. If it was 4D the inside can't be bigger than the outside.”
If what was 4D?
People are hung up on this 'bigger on the inside' thing. That is a shorthand expression. I never assumed it was meant to be the literal explanation for the TARDIS.
Saying something is 'bigger' than something else is a purely relative, grammatical term. Something could have a larger surface area, but a lesser mass than another object. Which of these is 'bigger'? I would imagine the TARDIS will have a greater mass than most suns.
To get into theoretical physics you have to have imagination. Because the typical member of the population doesn't possess much (having been taught from a young age not to use it) it is typically not something employed as a plot device in mainstream media - even in supposed 'Science Fiction'.
"But that bit looks bigger than that bit but it's inside! That's silly!" Well actually, no. What things 'look like' is purely down to our perceptions, which are predicated upon our senses, which in fact can only tell us the barest amount of information about our surroundings. You know, that computer you are looking at now is actually a mass of tiny little atoms etc. All we 'see' of the world is just a by-product of our nervous system.
You could theoretically fit the entirety of a 2-dimensional universe on the surface of a piece of paper; you could probably fit the entirety of our universe inside a TARDIS. Who knows? What things 'look like' and what they are do not necessarily have any correlation, especially when you are talking about dimensional properties beyond the comprehension of our senses.
Originally Posted by doctor blue box:
“but surely that means the universe of the inside is indeed inside the phone box somehow, and the phone box isn't a gateway.
I know some people think this gateway theory, and fair enough if that's what they believe, but I've always thought it was an entire universe somehow fit inside the phone box, and the inside and outside are one and the same item. if this wasn't the case then it wouldn't make sense how they feel the effect's of what is happening to the outer part of the tardis when they are inside, or how the inner and outer tardis could cross to paralell worlds, or bubble universes etc together.
This being my opinion, I just assumed it was compression as it is the only way I could think it could happen.”
You're right; some things won't correlate properly, in the sense of being consistent with each other. That is because with the TARDIS, as with every other part of Doctor Who lore there has been no real consensus between different writers. For instance, some have implied that the TARDIS is exceptionally heavy (and could stay in place when the tide comes in and completely submerges it, for example), others have implied it's light enough to be carried around on the back of an old lady (near enough

). At the same time, it is supposedly near impregnable, and yet a little arrow can embed itself into its surface. Imagine what a huge arrow could do
So, at the end of the day if you want a consistent theory the onus is on the viewer to select the elements that seem most likely to them and ignore the others. In my opinion, the inhabitants of the TARDIS
shouldn't feel any effect from what is happening to the exterior of the TARDIS.
Compression: okay, but I haven't seen anything that implies it, only circumstantial evidence such as the Master's shrinking gun, which does imply
some level of compression technology; then again, who knows where in the Universe he got that. It's not necessarily Time Lord technology.
I would say: if the interior of the TARDIS is a compressed universe, where did all that matter come from in the first place?
I think the easier clue is in the title: Time and
Relative Dimension in Space. Apart from the awkward wording to make the acronym cool, it seems pretty straight-forward to me.