A group of researchers from the Massachusetts Institute of Technology led by Seth Lloyd analyzed the role of some of the paradoxes and features of real time travel, writes Wired magazine.
In science fiction movies and books, time travel may require you to accelerate a car to a certain speed or turn a magic clock. But from a physics standpoint, this journey is about more than just designing the right device.
Any theory of time travel has to deal with the destructive "grandfather paradox" in which the time traveler kills one of his ancestors, which makes his own existence impossible, which makes the murder impossible, and so on.
According to one model developed in the early 1990s by the English theoretical physicist David Deutsch, there may be a discrepancy between the past that the traveler remembers and the past that he experiences. Thus, one can remember the murder of his grandfather, whom he never committed.
"These are some mysterious features that are completely at odds with what we think is time travel," commented Dr. Lloyd.
In a new study, MIT researchers described a temporary travel model that explicitly prohibits such inconsistencies. The theory suggests that situations in which the time traveler can prevent his own birth do not occur.
“In our version of time travel, paradoxical situations are simply impossible,” the scientist explained.
True, this position in relation to paradoxical events may lead to the fact that possible, but unlikely events, on the contrary, will begin to occur more often.
“If you make small changes to the initial conditions, then the paradox will not happen. It looks tempting, but it also means that the closer you get to a paradoxical state, the more such changes will begin to occur,”explained an employee at the IBM Research Center in New York.
For example, if a traveler in the past tries to kill his grandfather with a gun, it is much more likely that the bullet manufacturer will make defective bullets, or the gun will not fire at the last moment, or "some quantum fluctuations will take the bullet aside at the last moment," Dr. Lloyd.
“This distorted probability when approaching a paradoxical situation seems strange. But the point is, when we change the familiar laws of physics, weird things end up happening. This is inevitable: you are dealing with time travel, don't you think this is strange in itself? - said an employee of the Institute of the City of Waterloo in Canada, physicist Daniel Gottesman.
In previous work, Dr. Lloyd's team tried to demonstrate this model using photons. Although they failed to send photons back into the past, the scientists created quantum situations similar to those that a time traveler might face.
At the same time, as we approached the paradoxical states with less and less frequency, it was possible to create the conditions necessary for the paradox. Based on this, physicists concluded that similar processes can occur with true time travel.