One of the most iconic images from BBC's Doctor Who franchise is the famous TARDIS Police Box, which carries the Doctor and their various companions throughout time and space. The name is actually an acronym for "Time And Relative Dimension In Space," and the vessel operates as both a time machine and a spacecraft, allowing the Doctor to travel literally anywhere and anytime. It's a very convenient method for travel and is inconspicuous to humans, as it appears as a standard British Police Box. But one of the biggest mysteries surrounding the TARDIS is its size - it's a heck of a lot bigger on the inside, causing surprise and confusion for all of the Doctor's companions. Here are the reasons behind its incredible interior size.

The standard response from the Doctor is that the TARDIS is "dimensionally transcendental," meaning that the interior and exterior of the ship exist in completely different dimensions. While that may seem like a bunch of science mumbo-jumbo, it helps to know that a dimension is simply considered a direction one can travel in. This essentially means that the exterior of the TARDIS can exist in one time and place, like in 2009 London, England, while the interior is existing in a completely different time and place.

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The next question becomes how are the interior and exterior connected. Science gives sway to two main possibilities: either a wormhole or a tesseract. A wormhole connects two points in space and time, which could easily connect the two parts of the TARDIS. Perhaps the Doctor has a sustained wormhole that adjusts as they travel, constantly keeping the inside and outside connected no matter how far apart they are. So even if the exterior of the TARDIS stays in the United Kingdom, the inside can move around at will and still sustain the connection via the wormhole.

The second scientific possibility is the use of a tesseract. A tesseract is the four-dimensional reading of a cube, allowing for the fourth dimension to come into play as opposed to the typical three that most people are familiar with. The fourth dimension, while often considered to be time, is actually just another dimension of space in which something can travel. To sum it up, a tesseract allows for more space to exist within a particular shape, like the TARDIS. From the outside, it looks like a three-dimensional object. But once one steps inside, the dimensions increase, allowing the space to expand and encompass more surface area than the exterior suggests. While the science of a tesseract can be complicated, it can easily explain how the TARDIS can operate as it does.

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While the definitive explanation for the TARDIS's interior size is still up for debate, it's a given in Doctor Who canon that the TARDIS is a versatile, surprising vehicle. Not only can it change its positions in time, space and dimension, but it can also change its own exterior appearance, like becoming invisible to the naked eye. In addition, the interior is endless. The audience knows that it's big, but there are no clear boundaries to its interior. It has countless rooms, corridors and areas - the Doctor even says at one point that it is "infinite in size." Ultimately, the TARDIS has absolutely everything the Doctor needs to survive as an inter-dimensional traveler, from hospital rooms to squash courts.

The TARDIS is an enigma that baffles even the most intelligent people in the galaxy, vut it has called itself home to the Doctor and their companions over the millennia. It continues to surprise viewers with its ever-evolving innards and has been the most constant aspect of Doctor Who since the very beginning. It's an iconic image that is directly tied to the Doctor Who franchise, and for good reason. Without it, the entire concept of Doctor Who might crumble to dust. The Time Lord needs it in order to have their adventures and to travel from place to place, from time to time. The Doctor even considers the TARDIS to be a living, breathing entity. One could argue that it's the most consistent companion the Doctor has ever had. So while it's bigger on the inside than the outside, it's biggest in the heart of the Doctor and the fellow beings that temporarily call it home.

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