A Mathematical Model For Time Travel?

From Science Alert:

"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 theoretical physicist and mathematician, Ben Tippett, from the University of British Columbia in Canada. "But, mathematically, it is possible."

Together with David Tsang, an astrophysicist at the University of Maryland, Tippett used Einstein's theory of general relativity to come up with a mathematical model of what they're calling a Traversable Acausal Retrograde Domain in Space-time (yep, the acronym is literally TARDIS). But before we get into the madness of legit time travel, let's put this into perspective real quick - the researchers aren't claiming to have a blueprint for a Doctor Who-style time machine that can be built tomorrow. They say the materials we'd need to build this thing are so exotic, we haven't even discovered them yet... but we'll get to that in a minute.

Firstly, let's talk about what Tippett and Tsang are actually proposing. The model is based on the idea that instead of looking at the Universe in three spatial dimensions, with the fourth dimension (time) separated, we should be imagining those four dimensions simultaneously. (Read more.)