After some serious number crunching, a researcher says that he has come up with a mathematical model for a viable time machine: a Traversable Acausal Retrograde Domain in Space-time (TARDIS). He ...

A while ago, we introduced the space time diagram. It's just a graph of position in space-- just one special dimension for simplicity-- versus position in time.

Scientists develop a means of creating 'hopfion' crystals, complex, knot-like patterns of light that repeat across both space and time.