A weird elephantine noise appears, the wind sweeps around your feet, and a small, old-fashioned, blue British police box appears before you. A curiously dressed person steps out of it through the creaky front doors and says: “So – all of time and space, everything that ever happened or ever will – where do you want to start?”
The idea of traveling through time (and space) with the man (or woman) from Gallifrey is a magical idea, and one that currently remains in the realm of science fiction and fantasy. However, a new study in the journal Classical and Quantum Gravity has highlighted, once again, that it’s certainly mathematically possible.
“In this paper,” it begins, “we present geometry which has been designed to fit a layperson's description of a ‘time machine’. It is a box which allows those within it to travel backwards and forwards through time and space, as interpreted by an external observer.”
This paper mathematically describes a TARDIS. Doctor Who via YouTube
That certainly sounds like a time machine to us – and fans of Doctor Who will notice that the study’s title, “Traversable acausal retrograde domains in spacetime” can be acronymized to TARDIS, the very name of the Time Lord’s own time machine. How wonderfully geeky.
So what do the pair of mathematicians from the Universities of British Columbia and Maryland propose, then? Well, as has been suggested before, time machines will need to be able to warp the fabric of spacetime itself. In this sense, it’s best to think of spacetime as a unifying point for all three physical dimensions (width, height, depth) and time.
Special Relativity in a nutshell. Doctor Who via YouTube
Time only appears to go forwards to us thanks to a quirk of the decidedly pesky second law of thermodynamics. However, the warping of spacetime does appear to do some rather curious things to time. If you place a huge mass on it, it forms a huge gravitational well, and time does slow down considerably within this well.
Time still ticks forever onwards though – it won’t go backwards. For that to happen, you need to invoke a little bit of the theories of special and general relativity.