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Time travel is still somewhat possible in the eyes of the world, and although it is not realistic, it is getting closer and closer to the desired future, so people are still keen to discuss and deliberate about time travel.
In fact, according to the existing physical theories and scientific experiments, time travel is impossible to achieve, because time is a basic factor of the universe and a natural regulation of human beings, not something that can be used by random people to play.
But because of this, there are many brain-burning paradoxes about time travel, which make people doubt not only the timeline and cause and effect, but also the laws of physics that we are familiar with, and even the search for new cosmology to replace our existing one.
The four time travel paradoxes are the grandchildren paradox, the strong corrective principle, the weak corrective principle, the fatalistic paradox, and the Joseph Poczynski paradox.
1. The grandfather and grandson paradox.
The grandparents paradox can also be called the causal cycle paradox, which shows that when something happens, it is actually a circle from the time it happens to the end.
It's like the story of the grandson who went back to the past to save the grandfather after the grandfather died, but in fact, the grandfather can live until the grandson returns to the past to save his old man, so that there can be a chance for the grandson to go back to the past, otherwise the grandfather would have died a long time ago, and the grandson would not have the slightest chance to come here to save the grandfather.
This is obviously seriously inconsistent with causality and linear time, and secondly, with the causal cycle of relativity.
In the causal cycle, the time of the event should not just go forward along the arrow of time, but the time centered on this event has come to this point, a bit like the time is squeezed to this point after the event until the event is completed, and then in the time after this point, the causal relationship is established step by step according to the linear time trend, a bit like the cards in the pile when shuffling, but the cards are arranged in order.
Some people may be unwilling, according to various scientific calculations, as long as the grandson goes back to the past to save the grandfather, the grandfather will not die, according to the logic of the timeline, the grandson will not go back to the past to save the grandfather, and there will be no paradox, is this paradox will break.
Actually, this is not the case, and there is a prerequisite for this paradox, that is, the timeline cannot have branches.
If you take a pen and cut it in half, then it will only be half, that is, if you take the original half of the pen and throw it back to it, it will not be able to become a complete pen again, and the original complete pen will only be half left, this is also because of the law of time and space, the original pen only has one chance to become a complete pen.
In the same way, even if the grandson goes back in time and prevents the grandfather and grandmother from meeting, it will only make the grandson disappear, because it is impossible for the grandson to change his birth and make the linear timeline of cause and effect branch.
Because this destroys the structure of the entire timeline, so that not only can you save grandpa and rule time, but the human universe becomes a personal virtual world that can be controlled, which is too boring.
So no matter how the grandson tosses, as long as he can go back to the past, then his grandfather will inevitably meet his grandmother, because this is a rule that grandma is going to meet grandpa.
Second, the principle of strong correction and the principle of weak correction.
The principle of strong correction and the principle of weak correction are actually two statements that the timeline and causality cannot be tampered with.
The principle of strong correction states that the time traveler cannot interfere with his ancestors, because this is likely to destroy the timeline and cause the timeline to be unable to be rebuilt, so the time traveler will definitely encounter various interference situations, such as steel and other debris falling from the sky, or something around him will not work properly in time.
The weak correction principle says that the appearance of the time traveler has already interfered, because regardless of whether the time traveler interferes or not, only he appears in that era, so he cannot interfere with the correction timeline.
It's like a time traveler who went back to the 70s and sold an iPod on the street, although the iPod was not born at this time, but because of the time traveler's appearance, Apple engineers were inspired by his iPod, and then invented the iPod.
Similarly, if the time traveler had met his parents in the 80s, he would have tried to prevent them from becoming lovers, but then due to the separation of his parents, a new time traveler would eventually appear, and he would have to sit idly by for the sake of the timeline.
In fact, both the principle of strong correction and the principle of weak correction are preaching a kind of "where it is placed there is the best arrangement", and the same parents are together with a fixed number, so the grandson will definitely go back to the past, and it is impossible for the parents to get rid of the fixed number of encounters, just like even a shovel cannot withstand the power of a fixed number.
The weak correction principle also has a consequence, that is, it makes people doubt their own free will, after all, it is their own fixed number, everything they do is like themselves, no matter how hard they try, they will eventually be corrected by the timeline, which is meaningless, isn't this fate, and it will be beaten again.
But in fact, there is no contradiction between the weak corrective principle and free will, but free will is activated by the weak corrective principle, although your own fixed number is love, but you can't just say that you don't work hard to pursue a better self, after all, there is nothing wrong with working hard, and if you don't work hard, it's not you.
3. The paradox of fate.
The paradox of fate is also a causal cycle, which is based on the premise that there is a single cycle in the timeline, and in this cycle, past events affect future events, which in turn affect past events.
The simplest example of the paradox of fate can be illustrated by the fact that a rat kills a devil.
According to the rat's method of killing the devil, the devil has to jump into the flame of the door after the rat has opened a door, and then he can go back in time and prevent himself from entering the door, and after he enters the door, he must wait many years before he can go back in time and stop himself.
This constitutes a cycle, but there may be slight changes between each process, just like a mouse killing a devil, each process will change with the devil's experience and memory, so the mouse that kills the devil will become more skilled after each cycle of killing the devil for the second and third times.
This constitutes a time causal loop, where past events affect future development, and conversely, future developments affect past events, so you will find that after each cycle, the result will change, as long as it is a time loop, it is definitely not this one result.
4. The Joseph Poczynski paradox.
The paradox is like this, imagine a billiard, this billiards can shuttle back and forth in the wormhole, and the trajectory of the billiards is also very simple, that is, after the first shuttle is completed, it will return to the beginning and start shuttle.
And there is a person, he saw this billiards and wanted to go back to the past, so he crossed in front of the trajectory of this billiards, trying to make this billiards turn back, but this billiards will definitely return to the original trajectory, just like the person who came to witness at the beginning, so the timeline will still go on looping.
But when this billiards ball returns to the original trajectory, the person who witnesses it will not become a person who returns to the original trajectory of this billiards, but he will not come again, so the timeline creates a new billiards trajectory, so what about the people who don't come?
Didn't the emergence of this new billiards trajectory make this person come again, but he didn't let this billiards return to the original trajectory, so it went on in a loop?
epilogue
The paradox of time travel undoubtedly makes us re-examine time and causality, providing a new view of the universe that raises us with a myriad of new questions.
Although the time travel paradox is an almost impossible scientific study of time travel, it is undoubtedly an innovation for the scientific community.
This innovation also extends the human exploration of free will and fate, and poses a new challenge to the meaning of human existence, which is a very meaningful discussion.