The movie "Living Together in Time", as a tragic and joyful time-travel romance film, has become a phenomenon-level movie while "Avengers 3" dominates. In the movie, the young woman Gu Xiaojiao in 2018 and Lu Ming in 1999 met due to the overlap of time and space, and what is even better is that the two can bring each other to their own era through their own doors.
At the end of the plot, Lu Ming changed the past and changed the trajectory of his life in the future. So what problems will it bring if you "mess up" time? What do we need to do to change the past? The following is a systematic analysis for you.
Cross the big pit that the work does not want to step on
Crossing has always been a popular theme for the public, and the passage text that is usually considered by the public is to travel from one era to another era in ancient times or in the future. Published in 1895, "Time Machine" is a novella written by the British writer Herbert George Wells, and it uses a more rigorous science fiction writing method to set the tone for future science fiction cross-story.
However, most of the time spans of the cross-text are relatively large, and it is impossible to meet themselves in ancient times or in the future, not even their own ancestors. In "Living Together in Time", you can't meet at different times, otherwise the world will fall apart.
Why do so many cross-over works try to avoid encountering the past self or the future self? Crossing all the crossings, are you still afraid of being eaten by yourself at different times? This involves a big pit that authors are reluctant to step on — the paradox of space-time.
The Paradox of Time and Space – If I Kill My Grandmother
If only I could go back in time... If only the past could be changed...
"If I go back in time and kill my grandmother, then my mother will not be born, then who am I and where do I come from?"
This is the famous space-time paradox. This paradox has made many film screenwriters relish it, and has produced wonderful movies such as "Butterfly Effect", "Black Hole Frequency", "Journey to the West", "Terminator" and so on, and is also regarded by many writers as an insurmountable pit.
Later, physicist Hugh Everett proposed the theory of parallel universes (also known as multiple worlds), arguing that there are many parallel universes in the world, and that each different decision will produce a new parallel universe. That is, if you kill your grandmother, it will create a new parallel universe that your mother does not exist, and the original universe will not be affected.
Hugh Everett
Whether it can be confirmed or not, this theory seems to have gone beyond physics, because as early as the fourth and fifth centuries BC, the philosophers Democritus, Epicurus, and Gautama Siddhartha, among others, proposed similar concepts.
So what happened to my grandmother when I went back in time?
Many scientists want to use theoretical models to express the storyline of time travel.
In the early 1990s, David Deutsch, a physicist at the University of Oxford, devised a model that suggested that a person's crossing simply killed his ancestors in memory, and did not actually do so at all.
In July 2010, Professor Heath Royd of the Massachusetts Institute of Technology in the United States proposed a "post-selection model" in a research report, that is, after crossing, all operations that change history are prohibited, so there will be no paradoxes.
But there are also those who believe that there is a butterfly effect in time travel, and that any small change will superimpose into a big change in history. So Roedd and his assistants, who loved to study, developed a model that could be automatically corrected.
Andrei Lind, an expert on Russian-American inflationary cosmology, believes that even if there are parallel universes, they are in a very distant space-time and will never come into contact with our world.
A model of parallel universes in which each bubble represents a universe
Please click to enter a description of the image
Are these scientists really reliable? That has to go back in time to verify. But according to general relativity, time in space-time is one-way and irreversible, that is, time cannot be reversed. If you want to achieve space-time travel, you need to first find a theoretical model that is better in line with the observational facts than general relativity.
In fact, we can see the events of the past every day
At present, we have not found anything that can exceed the speed of light, but assuming that people can run faster than the speed of light, then they can catch up with the light emitted by the object before and see the scenes that have happened in the past, like upside down film. But it's just a matter of seeing that because the past has already happened, there's no way to make it change.
However, although we can't exceed the speed of light, we can rely on space to achieve similar effects. Some massive stars explode into supernovae at the end of their lives, but because the distance may be hundreds of light-years away, that is, it takes hundreds of years for light to reach Earth, we see supernova explosions in the night sky, which is exactly what happened hundreds of years ago. In fact, the stars we see in the night sky are what they were many years ago!
Black hole crossing? Wash and go to sleep
According to general relativity, space-time is distorted by gravity, and the greater the mass of the object, the greater the curvature of space-time near it. Who has the most mass in the universe? That has to be a supermassive black hole.
Physicists Rosen and Einstein once proposed the wormhole theory, arguing that inside a black hole is a special "bridge" called a wormhole that can quickly travel to another space. It is as if after bending a piece of paper, the two points at both ends of the paper have a "wormhole" such a short path. At the other end of the wormhole is a white hole, which is the opposite of the characteristics of a black hole, which can only erupt outward and does not absorb anything. After passing through the wormhole, time and space change.
But any object on Earth that is sucked into it by a black hole is torn into atomic-level slag by the enormous gravitational differences on different parts. Even if people really travel through time and space after entering the black hole, I am afraid that it will be difficult to come out alive to tell the story of crossing. In addition, wormholes and white holes are currently theoretical hypotheses and have not yet been observed by humans.