Backwards time travel might be possible, a scientist has claimed - if we can harness the power of wormholes.
Known technically as Einstein-Rosen bridges, wormholes were predicted in 1916 shortly after Einstein's general theory of relativity was published.
But until now they have never been detected - despite growing hopes that astronomers might be able to pin them down in future.
According to a report by LiveScience, Eric W. Davis, of the EarthTech International Institute for Advanced Studies at Austin, argues that these passageways through space-time might be passable.
"You can go into the future or into the past using traversable wormholes," Davis told LiveScience.
Physics "is infested with time machines whereby there are numerous space-time geometry solutions that exhibit time travel and/or have the properties of time machines" he adds.
But Davis also admits that the idea of sending humans forwards in time is almost certainly science-fiction for the foreseeable future.
Davis recently published a paper in the AIAA journal which reviews the areas of physics that might be provide space for a time-travel mechanism. Wormholes are chief among them because by linking two areas of space directly, they would allow a craft to travel between two points faster than light without actually travelling faster than light:
"Time machines are unavoidable in our physical dimensional space-time," David writes.
"Traversable wormholes imply time machines, and [the prediction of wormholes] spawned a number of follow-on research efforts on time machines."
However other scientists remain unconvinced. HuffPost US reports that Robert Owned at Oberlin College in Ohio thinks that the laws of physics "when fully understood, will rule it out entirely".