Back to the future, via a donut-shaped vacuum?

Could all our blunders be reversed, our failings eliminated? Perhaps so, if an Israeli scientist's research is to be believed. With the help of Prof. Amos Ori, we might just be able to go back and stop the screw-ups from happening in the first place.

Ori, a physicist from the Technion-Israel Institute of Technology in Haifa, has come up with what he says are practical solutions to overcome the hindrances that experts have long regarded as stopping us from traveling back in time.

In a paper published in the latest issue of the Physical Review journal, the scientist offers a theoretical model, based on mathematical equations describing conditions that, if established, could help lead to the development of a time machine of sorts. But rather than building an actual device, Ori explains that "the machine is space-time itself."

Time travel research is based on bending space-time so far that the time lines actually warp back on themselves to form a loop.

"We know that bending does happen all the time, but we want the bending to be strong enough and to take a special form where the lines of time make closed loops," explains Ori. "We are trying to find out if it is possible to manipulate space-time to develop in such a way."

While the possibility of time travel has never been ruled out, scientists have identified a number of physical challenges, including a perceived need for some form of exotic matter to create the necessary warp and get the wheels of time to turn back. Such matter is predicted by the quantum field theory to exist, although only in quantities too small for the construction of an actual time machine.

But Ori puts forth a different approach eliminating the need for exotic matter.

"If the proper initial conditions were achieved, the time machine would evolve on its own without any further intervention," he asserts. "It can be likened to shooting a ship with a cannon. Once the cannon is aimed properly and fired, the cannonball hits the ship on its own, driven solely by the laws of physics. The machine is space time itself. If we were to create an area with a warp like this in space that would enable time lines to close on themselves, it might enable future generations to return to visit our time."

But don't pack your bags and get ready to go dinosaur-hunting yet. "We, however," he cautions, "could not return to previous ages because our predecessors did not create this infrastructure for us."

The details of Ori's research are so complicated as to be baffling: In a 2004 paper, Ori outlined a set of conditions that would allow for the creation of a time loop without the need for exotic matter. According to that theory, the time loop would form as a donut-shaped vacuum, inside which time would curve back on itself, so that a person traveling around the loop might be able to go further back in time with each lap. A sphere containing a non-exotic - but unidentified - matter would in turn surround the loop.

But Ori's latest work eliminates the need even for that unidentified matter. His new calculations show that the envelope can in fact be packed with dust, a simple modeling of which is used regularly in theoretical physics, while still allowing for the evolution of a time machine.

Although Ori is certainly not alone in theorizing on time travel - previous theories are well-grounded in Einstein's General Relativity theory - he, like many other scientists, says serious questions remain about the overall stability of a time machine.

His own calculations - done in collaboration with doctoral student Dana Levanony, with those of other physicists, suggest that the evolution of a time machine would be dependent on a very narrow range of initial conditions that might be difficult or even impossible to reach, but he is working to show ways such a configuration could be achieved.

Original here