What is the timeline?
In the past, 24-year-old Shen Hui said this to Shen Yue:
"The timeline is just one line. When you look at it from afar, it's a straight line, but if you look closely, you'll find that the line is uneven, thick and thin in places.
The thick areas are where time has been overwritten. This means someone used retrospective in that segment of the timeline and generated new time that overwrote the original timeline, causing that segment of the timeline to thicken.
And the more times it's overwritten, the thicker the timeline becomes.
In theory, if the timeline could be visually observed, then you could judge whether a period of this world has experienced retrospective and how many times it was overwritten based on the thickness of the timeline.
But in reality, the timeline in the three-dimensional space that humans currently inhabit can only be cognized, not observed.
This also means that once the timeline is restarted, aside from the one person who restarts the timeline and overwrites it, retaining memory of all that time, no one else can perceive it."
"Xiao Yue, do you feel like you've only lived this one life?"
"But in fact, this is already your 26th timeline. Isn't that interesting?"
Shen Yue had never been interested in Shen Hui's research. After all, Shen Hui was far smarter than her. Shen Hui researched things every day that Shen Yue couldn't even understand, so she had never asked about Shen Hui's research.
But this time, Shen Yue asked Shen Hui a question. "If the timeline can't be observed, how do you know this is the 26th timeline?"
Shen Yue knew that as long as it was a question she asked, Shen Hui would definitely answer it. So she rarely asked Shen Hui questions—she was afraid of knowing things she shouldn't, which would deprive her of the last warmth she got from being by Shen Hui's side.
But now, there was one thing she especially wanted to know, so she asked, "If this is the 26th timeline, were we also like this in the previous timelines?"
"No," Shen Hui answered. "This is the first time I've met you. In the previous 25 timelines, I never managed to escape before age 25 or return to the Shen family."
Hearing this answer, Shen Yue felt relieved in her heart. She hoped that her and Shen Hui's encounter belonged to the shared memories of both people, rather than one person endlessly bearing the pain of memory while the other knew nothing about it all.
Possessing beautiful memories alone would be too cruel for the one who remembers.
"Sister, doesn't this seem like fate?"
"Yeah, it does a bit."
"It's as if you overwrote time 25 times just for our meeting this time around. Hmm...a bit cheesy..."
"It does really seem like the theory of destined fate, but the one who overwrote the timeline 25 times isn't me—it's someone else." When Shen Hui mentioned the other person, her expression was very complicated, an expression Shen Yue had never seen on Shen Hui's face before.
She became even more curious.
"Sister, you just said timelines can't be observed. If you aren't the one who overwrote them, how do you know we're on the 26th timeline now?"
After Shen Yue asked this question, Shen Hui told her about the theory of time retrospection...
It was a bit complex, but Shen Hui explained it very carefully without using any advanced theories. She used established facts as examples, which also allowed Shen Yue to understand what this so-called time travel was all about.
According to the special theory of relativity, the faster a material object moves, the higher its total energy.
Just like relativistic momentum—as a particle's velocity soars exponentially closer and closer to the speed of light, its relativistic energy increases exponentially, approaching infinity.
This leads to the conclusion that for a particle with mass to accelerate to the speed of light c, infinite energy must support it, which is clearly impossible.
But about 100 years ago, a scientist discovered a kind of substance and accidentally found that this substance could carry mental energy. Using this medium-like substance allowed mental energy to accelerate beyond the speed of light.
This is the space-time medium Shen Hui currently uses.
When a person dies, they emit tremendous mental energy. The space-time medium allows this mental energy to be transmitted to the past and future.
But transmitting mental energy to the future is meaningless, because in the instant of death, the future no longer has a container capable of receiving mental energy. Going to the future has only two possible outcomes: either merging into another person's body and being suppressed by the mental energy originally in that body, or dissipating directly.
Transmitting to the past can serve as a prompt for one's past self.
And mental energy can also be called memory information. Transmitting it to the past has limitations—the limitations of a person's brain capacity.
A person's brain capacity differs at different periods. If the brain capacity during a certain period is insufficient to receive mental energy, side effects will occur in the body at that time, such as drowsiness, absentmindedness, mental dissociation, memory confusion, etc.
These side effects often appear when overwriting a timeframe of over 10 years. This kind of overwrite is called linear overwrite.
Apart from linear overwrites, there are also dot overwrites.
"The advantage of dot overwrites is that they only transmit very short bursts of information, such as 1 minute or half an hour. Such short bursts of mental energy won't burden the brain too much, so they can be performed repeatedly many times."
"You asked earlier how I know we're on the 26th timeline now even though worldlines can't be observed. This is related to the theory I just explained.
Timelines don't disappear, they're just overwritten. Ordinary people can't feel timelines being overwritten because they never possessed memories of other timelines to begin with. To them, their current memories are their only memories, their only timeline.
But I'm different. I performed retrospection at different points on different timelines, so as soon as I reach one of those points, I can recall conducting retrospection on the timeline before, and extrapolate from there.
When I was 12, the worldlines were the 2nd, 3rd and 4th. When I was 13, the timeline became the 5th and 6th. When I was 15 the timelines were the 10th and 11th. Up till the day we met, when I was 20, the timeline was the 26th, and it still is now.
For people like you who have only ever lived on one timeline, you can also judge whether someone has overwritten a timeline. Take me for example—if I suddenly change behavior in a way that completely defies previous logical progression, it means I've received information from the future and am about to overwrite the timeline."
Shen Yue asked again, "Could there be more than 26 timelines now? Maybe in a few years you'll find out this is actually the 27th?"
Shen Hui firmly shook her head. "No. Because the person who overwrote entire timelines, his brain capacity has maxed out. Every time he goes back, the point he returns to gets closer and closer. The 26th time was his last. He no longer has the medium to go back and make changes now."
Shen Yue seemed to semi-understand. "Why?"
"Because the medium is still in my hands right now."
