The Answer-Man is In…
Got a letter on Sunday asking me our Question of the Day: How much does the TARDIS weigh? The question was in relationship to an image of the TARDIS being carried by the Doctor’s former companion, Clara Oswald in an episode called “Flatline“. (Series 8, Episode 9, Story #250)
The quick and dirty answer is: It depends on where you measure it. On any backwater planet in the Universe, it will only weigh enough to be able to crane it into the back of a truck and carry it away. It’s “apparent mass” doesn’t seem to be very high. It has been carried by a large number of men, even without vehicles, so it’s apparent mass is pretty light.
On the other hand, if we were to be able to bring all of the TARDIS into our dimension, it would be enormous. It’s “absolute weight” the weight of the entirety of the dimensional spaces and anything contained within those spaces which comprise a TARDIS, plus the hidden sun powering the thing means you could never leave a TARDIS in its “absolute mass mode” on any planet you want to go back to.
Despite its humble appearance, a TARDIS can weight more than our Sun!
Surprised? I was too. I even had a hard time trying to visualize this until I found a graphic online which tried to explain the “dimensional engineering” of the Time Lords.
What is a TARDIS?
A TARDIS — sometimes styled Tardis, but also called a TT Capsule or just a timeship — was the primary space-time vehicle used by the Time Lords of Gallifrey. These were the vehicles and sometimes weapons used by the Gallifreyans, a long-lived, humanoid species believed to be one of the earliest developers of artificial means of traveling through time.
The Doctor’s TARDIS was an older, obsolete model, which is why the two of them were able to escape the Time Lords at all. A Type 40, Mark III TARDIS was considered far past its prime, having no military capacity whatsoever. The Doctor’s TARDIS also has a broken “chameleon circuit” meaning it’s lost the ability to disguise itself and always appears as a London police box (see above).
We won’t get into the mechanics of their time travel, only that the Timelords were able to, utilizing these machines and an exotic interface, cross the temporal dimension as easily as you and I could cross a room. With their connection to the Eye of Harmony, a TARDIS, properly piloted could travel from the beginning to the end of time.
A TARDIS was designed to have six pilots but the Doctor has been flying his rather badly for centuries by himself. The suspicion is he is a poor pilot and the TARDIS, which is self-aware, does most of the heavy lifting, taking the Doctor to places in time she deems in need of his particular skills. Yes, the TARDIS is alive, grown using the super-science of the Gallifreyans and is self-aware. She considers herself the Doctor’s first Companion.
What interests us today, is the condition of the TARDIS having more dimensions inside than out. In fact, the doorway and the outer construction (the police box) is just a construct of the technology. The TARDIS is shielded, quite durably. The aperture (the front door) is resistant to even the most sophisticated technologies. It doesn’t mean the TARDIS can’t be harmed but she is quite stout under most circumstances.
The dimensional technology of the TARDIS means there is more space inside than out. How much space has never been official mentioned, but designs of the theoretical space of the TARDIS can be found on the Internet, and some are quite good. Here’s one of my favorites:
According to this image and from information revealed by the series, the inside of a TARDIS may be as large as the asteroid Ceres with containment areas whose sub-dimensional spaces may still be even larger. One of those areas is reputed to hold a heavy mass star on the cusp of becoming a singularity. It is frozen in time, where this energy can be harnessed when needed for time travel.
This means, a TARDIS, if it were to materialize over a planet, could be the size of a moon and have sufficient mass to crush that planet under the weight of its trans-dimensional spaces. Thankfully, the TARDIS does not have this kind of mass in our Universe. The bulk of its mass, is outside or “dimensionally transcendental” our Universe. We know the TARDIS does not exist completely within our Universe. It is a vast but finite pocket dimension/universe that intersects at the doorway to the TARDIS. This doorway is an interface or bridge between the pocket universe of the TARDIS and the Universe of 11 dimensions we exist in.
We have seen the TARDIS carried off multiple times, in something small as a flatbed truck. In the aforementioned episode Flatland, when the TARDIS was losing “dimensional energy” the outer representation (and that is all the shell of the TARDIS is; a representation of a portal to the smaller pocket dimension/universe within) the TARDIS lost dimensions and grew smaller to the point where it was portable and could be carried around in Clara’s purse. Neither did it appear to lose any of its internal dimensional spaces as it has in previous episodes, though the Doctor trapped within could no longer exit the aperture due to its reduction in apparent size.
From Wikipedia’s TARDIS Entry:
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, trans-dimensional 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!”).
Given what we know about just one room on the TARDIS makes the weight of the TARDIS vast, but calculable, if it were able to materialize completely within our Universe. This single room is called the Eye of Harmony Chamber.
We see the chamber housing the Eye of Harmony in the episode Journey to the Centre of the TARDIS (Series 7, Episode 10, Story #236) and this is one of the most extensive views of the hidden interior of the TARDIS ever recorded. The interior of the TARDIS has had multiple representations and they have varied wildly in the different versions of the series, but this one thing remains true.
No matter its size, the Eye of Harmony produces artron energy allowing the TARDIS the capacity to travel through time. Given the history of the Gallifreyans, the true nature of the Eye of Harmony has been revealed multiple times, each laying claim to something different.
What we know for certain is the Eye of Harmony is a star on the verge of collapsing into a Black Hole. It is this state of collapse which allows the TARDIS to harness artron energy necessary to travel through time. This star is held within a sliver of Time so that it can be harnessed for its chronal energy as the star collapses in perpetuity.
While this collapsing star is not equal in size or power to the original Eye of Harmony in scope or scale (the original Eye of Harmony was said to power remotely all active TARDIS being used by the Gallifreyans as long as they remained in our Universe) it is still a star massive enough to be collapsing into a black hole. This means it is a star whose mass is two and a half to ten times greater than our sun because only stars with that kind of mass can become black holes at all!
The TARDIS is designed to not completely manifest within our Universe, as a safety feature, since the mass of a star held in collapse would also be part of that mass. Note that even in siege mode where the TARDIS is running out of energy, it grew smaller, closing the aperture between our Universe and its pocket dimension in Flatline. When the TARDIS is in this precarious state of not having enough energy to maintain the portal between our Universe and its pocket space, it enters siege mode and shrinks until it can be restored with sufficient energy to return the aperture to normal size.
The Doctor’s inconsistent where the TARDIS is concerned…
While the Doctor said the weight of the TARDIS would fracture the Earth, I think he was underestimating it so that he wouldn’t alarm Clara. Clara was quite clever and probably suspects the true nature of the TARDIS already, but like most Humans, vast numbers and galactic scales simply don’t truly make sense to our mortal minds.
Note the size of the TARDIS as it collapses into Siege Mode. The portal grew smaller and I suspect if the TARDIS continued to lose dimensional energy, the portal would eventually shrink out of existence protecting anything, say, like a planet in our Universe from the terrible mass of a suddenly completely materialized TARDIS.
From the novelizations when a TARDIS is lamenting its bonded partner, they often commit suicide by throwing themselves into a star. Or materialize onto a planet destroying it (we assume the planet would be empty…)
From what I have read in the novelizations of the TARDIS, when we see the Doctor in the episode “The Name of the Doctor” (Series 7, Episode 13, Story #239, nominated for a Hugo in 2014) near the end of his life, the giant-sized TARDIS while appearing ancient is still utilizing its powers to maintain its existence in our Universe. This was not an accident. My suspicion is the TARDIS was trying to rescue the Doctor even as he and it lay dying.
We have barely scratched the surface of the TARDIS …
Given what we know of the internal dimensional shifting and manipulations of space within the TARDIS: Its mass is not infinite, if it was, it would be greater than the Universe and thus unusual given there were thousands of TARDIS in existence at any one time. We are told they are created outside of our Universe, presumably to deal with the paradox of their nature, but it would seem unlikely they are infinite inside.
But if we assume a finite mass, existing albeit in a pocket dimension, as a reasonable assumption and given we know the mass of at least part of the TARDIS, we can safely assume the TARDIS must have at least THAT much mass if not more.
The mass of a single super-dense star (necessary to create a black hole and power the Eye of Harmony within the TARDIS) would indeed be sufficient to fracture and ultimately destroy all life on Earth should the TARDIS’ inner pocket Universe suddenly coincide with our own.
Here’s an infographic revealing the basic care and feeding of your friendly TARDIS:
An early version of this essay first appeared on the SciFiStackExchange.