TARDIS
General characteristics
Apart from the ability to travel in space and time (and on occasion, to other dimensions), the most remarkable characteristic of a TARDIS is that its interior is much larger than it appears from the outside. The explanation is that a TARDIS is "dimensionally transcendental", meaning that its exterior and interior exist in separate dimensions. In The Robots of Death (1977), the Fourth Doctor tried to explain this to his companion Leela, using the analogy of how a larger cube can appear to be able to fit inside a smaller one if the larger cube is farther away, yet immediately accessible at the same time (see Tesseract). According to the Doctor, transdimensional engineering was "a key Time Lord discovery". To those unfamiliar with this aspect of a TARDIS, stepping inside the ship for the first time usually results in a reaction of shocked disbelief as they see the interior dimensions ("It's bigger on the inside!"). The Eleventh Doctor is particularly fond of this reaction, and is surprised and confused when Clara Oswald (in "The Snowmen", 2012) inverts the usual response by saying "It's smaller on the outside."
TARDIS-14