A mathematics and physics professor has come up with a mathematical model for a Traversable Acausal Retrograde Domain in Space-time, or TARDIS. This is a time machine of sorts that can go back and forth in time and space.
Of course, the obvious thing that might spring to mind is the Doctor's own time machine, which also has the same name (though the acronym stands for something else). However, this isn't an episode of Doctor Who, and there won't be a police box zooming in between dimensions (unfortunately).
Professor Ben Tippet's time machine is purely theoretical at this point. Tippet studies black holes and Einstein's theory of relativity for a living, but he's also a fan of science fiction. Time travel as we know it is of course purely fictional. It may be fun to entertain the possibility of going back and forth through time, but it seems unlikely to be possible in real life. This, however, hasn't stopped Tippet from taking the fiction out of science fiction.
Tippet claims that time travel is mathematically possible. He says that we shouldn't envision time as a fourth dimension separate from the three dimensions of space. Instead, we should consider all four dimensions as a curved space-time continuum.
The curvature of space-time is an important detail. According to Einstein's theory, this curvature is the reason for the circular orbits of planets. Massive stars cause space-time geometry in their vicinity to curve. “Flat” space-time will make celestial bodies move in a straight line. When these bodies are in the vicinity of a massive star, their trajectories curve into an orbit around the star.
Thus, Tippet's mathematical model relies on this curve in space-time. Note that time only moves forward, much like how celestial bodies only move forward outside the vicinity of a massive star. The curve in space-time will be able to take passengers in the theoretical time machine back in time, instead of inexorably forward.
Tippet's TARDIS isn't a retro police box. Instead, it's a “bubble of space-time geometry” that traverses time through a circular path. To move back in time, the bubble would have to travel faster than the speed of light.
H.G. Wells, a prolific science fiction author, was responsible for coining the term “time machine”. Wells also published a novel, The Time Machine, that explored what time travel could be like. He was also responsible for the concept that we need a machine or vehicle of some sort in order to travel through time.
However, is building an actual time machine possible? Not just yet, says Tippet. Building a TARDIS is mathematically feasible, but the feasibility ends there. Or course, we can't just build a machine that bends time and space out of ordinary materials. Tippet says that we need things called “exotic matter” to build a time machine. The problem, however, is that we haven't discovered actual exotic matter yet.
Scientists, philosophers, writers, and movie makers have long been toying with the possibility of traveling back and forth through time. Tippet's research gives a new perspective into how we could go about traveling through the space-time continuum. Now, if we could just find a source of exotic matter, we'd be all set.
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