Role of Imagination
Time travel theories have always been one of the most intriguing discourse for physicists, cosmologists and even sci-fi enthusiasts. Not every hypothesis is a proven theory but every proven theory was once a hypothesis. In science, imagination plays a pivotal role from postulation of a scientific phenomenon to its actual discovery. Professor Stephen Hawking extrapolated tendencies of blackhole 5 decades ago, Christopher Nolan conjectured and visualized the external appearance of the blackhole in “Interstellar” in 2014 and finally in 2019 Event Horizon Telescope (EHT) an international network of radio telescopes managed to capture the image of M87 blackhole. It became possible because of Katie Bouman an American computer scientist, successfully developing the algorithm that generated the first ever image of the blackhole. In conclusion if one intends to explore all possibilities of time travel then his line of action should consist of unbound imagination, precise extrapolations and exhaustive hypothesis. These factors are essential to predict the unknown phenomena which later on can be proven through empirical experiments and veridical evidences.
Postulated Physics of Time Travel
Einstein’s theory of general relativity gives us a plausible reason to believe that time travel might be possible. Theories like twin paradox, bootstrap paradox or the grandfather paradox put forth logical conundrums if time travel ever became a reality. Professor hawking made a supposition that there can be a possibility that time can be reversed in a contracting universe au contraire to the ever expanding one. That is to say when Eddington’s thermodynamic arrow of time would be reversed. Although, later on professor hawking rectified that “disorder would in fact continue to increase during the contraction and the thermodynamic and psychological arrow of time would not reverse when the universe begins to recontract or inside the black holes.”
According to Feynman’s theory of antimatter, a positron is an electron moving back in time. This phenomenon of an antiparticle moving forward in time is considered as a particle travelling backwards in time. Conjectures have been made considering the aforementioned theory of particle physics as a pragmatically reasonable model for time travel. Central idea of Nolan’s “Tenet” has proximity to Feynman’s theory, where he kind of reverse engineered the idea of entropy and time as they are interlinked supposing that inverting the entropy of an object would invert the arrow of time for that particular object. Now let’s consider even If one manages to warp the spacetime, maintaining the energy density negative and generates a wormhole from Casimir effect to go back in time keeping the thermodynamic, cosmological and quantum mechanical implications aside for a while. There are other indispensable conditions one needs to take into consideration.
Reversal of Psychological Arrow of Time
Reversal of psychological arrow of time would give rise to some of the most fundamental problems of time travel. I intend to delve into investigating the reversal of psychological arrow time and its possible ramifications. If one considers there can be a slightest possibility of travelling back in time in a contracting universe where the second law of thermodynamics is violated due to recollapsing of universe into singularity and direction of time arrow is reversed still, it won’t reverse the psychological time arrow as for that to happen ONE’S KNOWN PAST HAS TO BE HIS UNKNOWN/FORGOTTEN FUTURE AND HIS UNKOWN FUTURE HAS TO BE HIS KNOWN PAST. This very prerequisite of inverted psychological time arrow which demands oblivious past and enlightened future, creates a paradox which I would like to term as The River Lethe Paradox.
Etymology of The River Lethe
The word Lethe emanates from Greek mythology. Lethe is daughter of Eris (goddess of discord and strife) she’s personification of oblivion. Lethe is also name of a river in orphism. It is believed that any newly dead who would drink from the River Lethe would lose all of his memory from past experiences.
The River Lethe Paradox
In a normal world when psychological arrow of time is moving forward, a person living in present has a past that is known to him and a future that is unknown to him. Refer to fig. (1) one can be certain that knowledge of the past (historical existence) and unawareness of the future are two indispensable features of one’s past and future. If either one of these features are missing then his present is dubious that is to say if his historical existence is missing then he was never born and if the possibility of having a future is missing then he no more exists (dead in the present).
Now keeping the antiparticle model of time travel in front of us if we consider one enters in an inverted time zone where the psychological arrow of time is reversed, a person in his present (in an inverted time zone) while moving forward is actually moving backwards in time. This is where the River Lethe Paradox (RLP) comes into picture. According to the RLP, in a reversed psychological time arrow one’s entire psyche including the direction of his consciousness must be reversed that is to say one cannot be aware of his past because in that time zone that past has to act as his future. If one is aware of that future, it cannot be said as his future in a true sense or it would simply mean that person has acquired supernatural faculty of clairvoyance. On the other hand, his future (of a normal world or non-inverted time zone) must act as his past and he must ultimately have ken of that past. So technically, he should be having knowledge of a past, which is actually a future that he never lived or witnessed and as it is established before the indispensable feature of a person’s past is that, it is known to him. Refer to fig. (2) This series of complicated contradictions is the River Lethe Paradox.
The crux of the matter is unless we don’t develop technology of erasing memories somewhat similar to the memory erasing gizmo in Men in Black along with faculty of prognostication like Dr. Strange reversing the psychological time arrow is out of question. One might say if according to RLP, having an erased memory is a prerequisite for travelling back in time then may be a person with Dementia or Alzheimer (suffering from memory loss) can travel back in time? No, as along with oblivious past that person is required to have complete awareness of his future which he actually never lived or witnessed.
Generally, while discussing theories of time travel one considers the complex phenomena of particle physics and quantum mechanics but fails to comprehend the effects of travelling back in time upon us as primates with limited physical endurance or capabilities. One can say it is as uncertain as Heisenberg’s uncertainty principle. For instance, one cannot predict what effect reversed psychological time arrow will have upon our anterior prefrontal cortex, dorsolateral prefrontal right cortex and other complex parts of our brain controlling perception of time and reality. As per RLP, in a reversed psychological time arrow one’s functioning conscious cannot operate in a conventional manner unlike when arrow of time is moving forward. Why? Because reversal of thermodynamic, cosmological and psychological arrows of time (reversed entropy) is a prerequisite in an antiparticle model of time travel. If all three arrows of time are not absolutely reversed then it would go against the very principle of theory of antimatter and negate the possibility of travelling back in time. So, for now I can conclude it’s not practically possible for one to survive in reversing time or having an inverted psychological arrow of time due to its intricate complexities. Nolan has considered one of such complexities in Tenet where protagonist has to wear an oxygen mask in an inverted time zone as air in that time zone is also required to be inverted. One can’t afford to bog down fulfilling all the lacunae of scientific implications arising from time travel as that would defeat the purpose of science-fiction and thus one has to take refuge in fictional liberty.
While discussing the River Lethe Paradox one can take reference of Professor Hawking’s Chronology Protection Conjecture which explicates that the laws of physics conspire to prevent macroscopic bodies from carrying information into past. This Chronology Protection Agency makes it impossible for macroscopic bodies to travel back in time, ultimately preventing all the time paradoxes.
To Sum Up
According to the antiparticle model of time travel in order to travel back in time one needs to be in a reversed psychological arrow of time i.e., have an oblivious past and comprehensive knowledge of future along with reversed thermodynamic and cosmological time arrow. The River Lethe paradox negates the possibility for one to travel back in time with a conventional psyche (forward psychological arrow of time) as it is not only contradictory to the very principle of time travel but also not feasible due to its complex contradictory nature. Professor hawking’s chronology protection conjecture corroborates this argument.
Check this out: “The EPR Paradox“
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