In *Logopolis*, the final hour for Tom Baker’s fourth incarnation of Doctor Who, the chanting mathematicians of that distant world have a natty little phrase. They are holding the death of the Universe at bay with their calculations and declare that “the essence of matter is structure, and the essence of structure is mathematics.”

So what do you think script editor and computer guru Christopher H Bidmead would have made of this? A mathematics and physics instructor at the University of British Columbia Benjamin K Tippett and his colleague David Tsang have formulated a mathematical model that arguably offers a viable time machine. Hopefully without the gravity and dimension crunching effects that afflict the Doctor in *Logopolis*?

Their model is revealed in a paper called *A Traversable Acausal Retrograde Domain in Space-time*. Those initials seem familiar. The paper is published on *IOP* S*cience Journal* along with others that might be useful if interstellar travel is an ambition.

Tippett and Tsang describe their model as a bubble of space-time geometry which carries its contents backward and forwards through space and time over a large circular path. The bubble moves at speeds greater than the speed of light allowing it to move backward in time.

“Studying space-time is both fascinating and problematic. And it’s also a fun way to use math and physics,” Tippett told

Science Daily. “Experts in my field have been exploring the possibility of mathematical time machines since 1949. And my research presents a new method for doing it.”

### Traversable acausal retrograde domains in spacetime

http://iopscience.iop.org/article/10.1088/1361-6382/aa6549/meta

### Fundamental limitations on ‘warp drive’ spacetimes

http://iopscience.iop.org/article/10.1088/0264-9381/21/24/011

### Warp drive with zero expansion

http://iopscience.iop.org/article/10.1088/0264-9381/19/6/308

https://www.sciencedaily.com/releases/2017/04/170427091717.htm