A team of researchers from the Massachusetts Institute of Technology (MIT) led by Seth Lloyd has analyzed the role of some of the paradoxes and characteristics of real time travel, says the magazine Wired.
In science fiction movies and books time travel may be possible by using a time machine or a magic clock. But from the standpoint of physics, such a journey is more than just the development of a suitable device.
Any time travel theory has to deal with the distressing “grandfather paradox” in which a time traveler kills one of his ancestors, which makes impossible his own existence, which in its turn makes the murder impossible, and so on.
According to a model, developed in the early 1990s by British physicist David Deutsch, there may exist a discrepancy between the past a traveler remembers and the past he is experiencing. Thus, he may remember the murder of his grandfather, which was never committed. “These are some mysterious features that are completely inconsistent with what we think is a journey through time“, said Dr. Lloyd.
In their new study, the experts from MIT described a model of time travel, which imposes a direct prohibition on such inconsistencies. This theory suggests that situations in which a time traveler could prevent his own birth do not occur. “In our version of time travel these paradoxical situations are impossible“, said the scientist.
However, this position with regard to the paradoxical events can make possible, but unlikely events occur more frequently. “If you make a small change in the initial conditions, the paradox is not going to happen. It looks tempting, but it also means that the closer you come to a paradoxical condition, the more these changes will happen“, said Charles Bennett of the IBM Research Center in New York.
For example, if in the past a time traveler tries to kill his grandfather with a gun, it will be much more likely for a bullet maker to produce defective bullets, or for the gun to break, or for the bullet to bounce away at the last moment, says Dr. Lloyd.
“This distortion of the probability of approaching the paradoxical situation seems odd. But the fact is that when we change the laws of physics, it makes strange things happen. It is inevitable: don’t you think that dealing with time travel itself is strange?” Said the Canadian physicist Daniel Gottesman.
In a previous research the Dr. Lloyd’s team tried to demonstrate this model by means of photons. Although the scientists did not manage to send photons in the past, they created a series of quantum situations similar to those that might be experienced by a time traveler. As the photons were approaching to the paradoxical conditions, the frequency of the experiment success was decreasing. On the basis of this, the scientists concluded that the real time travel might occur by similar processes.