Big Bang simulation shows time travel is impossible
Scientists have replicated the physics of the Big Bang by observing the way light moves through a special 'metamaterial,' with surprising results.
Wed, Apr 13, 2011 at 07:20 AM
Physicists from the University of Maryland have created a specialized kind of material, called a "metamaterial," that mimics the mathematics of the Big Bang when light is beamed through it, reports Wired.
The breakthrough invention is a simulated glance at how the universe expands, and also gives invaluable clues about the nature of time. For instance, the results have already provided a better understanding for why time only moves in one direction and that time travel into the past may be impossible.
"What we have done, with simple experimental geometry, is reconstruct the way that space-time expands," said Igor Smolyaninov, one of the lead researchers on the project.
Smolyaninov and his colleague, Yu-Ju Hung, utilized exotic substances called "metamaterials," which are specialized materials capable of twisting light in unusual ways. The researchers modeled their metamaterials so the mathematics of the metamaterials' electromagnetic spaces were analogous to the mathematics of general relativity in a Big Bang-like scenario.
Thus, by illuminating the metamaterials with a laser and observing the way that light spread through the substrate, the researchers were able to simulate the expansion of the universe following the Big Bang.
One of the primary experimental objectives of the researchers' incredible toy cosmos was to study the thermodynamic arrow of time, a long-standing problem in physics.
The thermodynamic arrow of time is essentially the expansion of time according to the Second Law of Thermodynamics, a law that says as a system advances through time, it becomes more disordered.
Most physical laws work just as well whether time moves forward or backward, but not so with the Second Law of Thermodynamics. The reason is that a system moving backward through time should actually increase in order, rather than decrease. This would therefore be a violation of the Second Law.
The University of Maryland researchers were able to simulate the thermodynamic arrow of time in their model by making the metamaterial imperfect. Imperfections would thus distort the light rays and cause them to cross paths, and weaken.
"It’s reasonably good and interesting model of time," Smolyaninov said.
It wasn't long before the researchers realized their novel model of time could also be used to test for the possibility of time travel, since the metamaterial could be manipulated to refract the light in circles. Light moving in one direction could therefore be redirected back to its starting point, which would be analogous to a particle returning to a previous point in time via a closed timelike curve.
When the experiment was attempted, however, the results were not what science fiction fanatics might have hoped for. It turns out that for all light that behaves like a particle, circular orbits proved impossible. In other words, time travel as we all imagine it to be would be impossible.
Of course, the metamaterial isn't a perfect model for the actual universe, so although these results are not encouraging, its always possible that time travel could survive future experiments.
"It will never give you the real final answer about the real Big Bang and real time," said Smolyaninov. "But if you study it, you may discover something, and you may be able to ask more intelligent questions."
Interestingly, the light-twisting capabilities of metamaterials used in these experiments have prompted some researchers to suggest they could be used to build invisibility cloaks, since they can potentially bend light around objects and render them invisible. There's hope for science-fiction fans yet!