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Doughnut-Shaped Time Machine
A new class of time machines that are toroidal, or doughnut-shaped, has been proposed. This model for time travel does not require exotic or improbable forms of matter; it consists of a toroidal vacuum embedded in a sphere of normal matter.
(In case you can't visualize a doughnut)
In his submission to Physical Review Letters, Amos Ori, physicist at the Israel Institute of Technology, provides this abstract:
We present a class of curved-spacetime vacuum solutions which develop closed timelike curves at some particular moment. We then use these vacuum solutions to construct a time-machine model. The causality violation occurs inside an empty torus, which constitutes the time-machine core. The matter field surrounding this empty torus satisfies the weak, dominant, and strong energy conditions. The model is regular, asymptotically flat, and topologically trivial. Stability remains the main open question.
According to Ori, the mathematics show that every period of time after the time machine was created would be somewhere in the vacuum inside the doughnut. The hard part is figuring out how to get there.
It should be possible to travel back to any point in time after the time machine was built. Exactly how to generate a gravitational doughnut is not covered in the paper, but Ori has suggestions. "It's wild speculation, but you may need to move large masses rapidly in a circular motion," Ori says.
Other physicists are interested in Ori's submission. "The paper is a welcome addition to the subject, and it does look like an improvement on the previous models," says Paul Davies, a theoretical physicist at Macquarie University in Sydney, Australia, and author of How to Build a Time Machine.
Science fiction fans all remember H.G. Well's classic 1895 novel The Time Machine, about an exotic device described here by the Time Traveller:
`This little affair,' said the Time Traveller, resting his elbows upon the table and pressing his hands together above the apparatus, `is only a model. It is my plan for a machine to travel through time. You will notice that it looks singularly askew, and that there is an odd twinkling appearance about this bar, as though it was in some way unreal...'
(Read more about H.G. Well's time machine)
Read more at A new class of time machine, Physical Review Letters and Gravity doughnut promises time machine. Thanks to an alert reader for writing in with this item.
Scroll down for more stories in the same category. (Story submitted 7/28/2005)
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