According to *Science Alert*, physicists claim that while the materials needed to create a machine capable of travelling back and forth in time have yet to be discovered, time travel is mathematically possible using the curvature of space-time in the Universe to bend time into a circle. The mathematical model is called Traversable Acausal Retrograde Domain in Space-time. Who loves their *Dr. Who*?

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.

That allows us to consider the possibility of a space-time continuum, where different directions in space and time are all connected within the curved fabric of the Universe.