Physicists have come up with a plan to build a real-life time machine that they say is mathematically consistent with known physics. And here's the best part: they've named the machine a "Traversable Acausal Retrograde Domain in Space-time," the acronym for which is actually TARDIS.
For those who aren't fans of the long-running British science-fiction television show "Doctor Who," the TARDIS is the fictional time-traveling spacecraft of the Doctor himself. (Although in the show, TARDIS stands for "Time And Relative Dimensions In Space.")
The real-life machine imagined by physicists is, like the fictional TARDIS, shaped like a box that's capable of carrying passengers backwards and forwards through time and space. All that's needed to build it, say physicists, are the materials.
"People think of time travel as something as fiction. And we tend to think it's not possible because we don't actually do it," said Ben Tippett of the University of British Columbia, mastermind behind the contrivance, to Phys.org. "But, mathematically, it is possible."
Tippett and colleague David Tsang from the University of Maryland have used Einstein's theory of general relativity to come up with their mathematical model for time travel. They claim that the division of space into three dimensions, with time in a separate dimension by itself, is incorrect. Their model instead conceptualizes space-time as a continuum, whereby different directions are connected within the curved fabric of the universe.
Tippett reminds us that time is curved in the same way that space is: "The time direction of the space-time surface also shows curvature. There is evidence showing the closer to a black hole we get, time moves slower. My model of a time machine uses the curved space-time — to bend time into a circle for the passengers, not in a straight line. That circle takes us back in time."
It's all very exciting to think about, but it's another thing to imagine a machine that can feasibly (and safely) carry passengers through time. If the box-shaped contraption envisioned by Tippett and Tsang were to actually work, it would need to be built with some extremely exotic materials ... and that's the rub. Such materials are so exotic that they haven't been discovered yet.
So although building a TARDIS is mathematically possible, the materials with the necessary properties to open up a hole through space-time and also withstand a jump through it are merely theoretical. That doesn't mean that such materials couldn't one day be produced, but it's not clear at this time how to do that.
Of course, there are also the various paradoxes of time travel that we'd have to contend with, such as the grandfather paradox (if you could travel back in time and kill your grandfather, would you ever have been born in the first place?). So maybe time travel isn't something we really want to mess with, even if it is possible.
Then again, could you resist the temptation if a TARDIS suddenly appeared in your neighborhood?