Is Time Travel Doable? It Depends on How You Go About It
Is time travel feasible?
The question was recently discussed by an astrophysicist contributor to Forbes.
Einstein’s special relativity theory provides the understanding that the experience of time is constant. However, the perception of the time being experienced by another person will vary based upon that person’s speed reference with respect to the person that he is observing. Faster moving objects will appear to the slower moving viewer to experience time slower, while the opposite holds for objects moving slower than the viewer.
By accelerating fast enough and returning to the same location, the traveler would arrive in the future, though experiencing no appreciable aging himself. This “twin paradox” is what underlies one understanding for how time travel into the future would be possible.
Traveling back in time, under this model would require that space loops back onto itself. Since in general relativity, space and time are part of the same substrate underlying the framework of our universe, in a system that loops back onto itself it would be possible to return back to the same space/time reference point by simply by traveling long enough in the same direction.
An interesting time travel proposal was offered by David Deutsch, a theoretical physicist from Oxford University, in 1991. A proponent of the parallel universes theory in quantum physics. Deutsch believes that it is possible to travel both directions in time, avoiding the obstacles encountered in Einstein’s relativity such as a problem that would occur from modifying the past to corrupt the chain of events leading up to the time traveler’s own birth, the grandfather paradox.
In Deutsch’s model, the time traveler simply re-enters one of the parallel universes that was created when the quantum system branched. Since quantum states are represented as possibilities, the time traveler has potentially infinite paths to both the past and the future.