Most of us know what the TARDIS is, but for those who don’t, here is a quick recap. The TARDIS is the time machine from the long-running sci-fi series “Doctor Who”. It is a blue police phone box that is bigger on the inside than the outside and can travel through time and space. It is flown by the Doctor,  a 900 year old alien who loves to travel through time. While time travel and the like may seem like pure fiction, this is science fiction, so let’s take a look at the physics of the TARDIS.

My first possible theory is that the exterior of the TARDIS is an Einstein-Rosen Bridge (better known as a wormhole). An Einstein-Rosen Bridge is a “shortcut across time and space” and is supported by general relativity. However, Einstein-Rosen Bridges soon collapse on themselves, and controlling them would be, difficult. Luckily, it would seem that our time lord friend the Doctor has the fortune of coming from a race advanced enough to create and manipulate Einstein-Rosen Bridges. So, we know the TARDIS uses wormholes to travel through time, but what about the size paradox? Well, believe it or not, the wormhole theory solves that too.

   If the TARDIS used an Einstein-Rosen Bridge to travel, or, as it were, is an Einstein-Rosen Bridge, it could be that the exterior of the TARDIS is truly only a mouth of a wormhole disguised as a phone box. Then, the mouth of the bridge just moves wherever the Doctor wants it to be, and he can exit from a remote location (the TARDIS Interior) through the other mouth of the wormhole. With his advanced alien technology, the Doctor surely could manipulate the Einstein-Rosen Bridge based on where he wanted to be. So, the TARDIS is just an illusion, a gateway to some far-off place the Doctor calls home. When he wants to travel to London to meet some new people, he just moves the Einstein-Rosen Bridge to the corresponding place in space and time, and he is there. All he needs to do is step out the doors across the universe onto the London streets, all in an instant. It looks like the TARDIS and time travel aren’t so complicated after all, are they?