"Dialect classmates, do you know anything about dimensional space?" Professor Lin Lao helped his reading glasses and said, this is a professor of physics in Jinghua University, who is deeply loved by the students of Jinghua University.

"Professor, I used to have a certain understanding of the theories in this area, but I found that these theories were very vague, and there were some problems that could not be solved at all."

He has been insomnia for two days after reading the news of Cao Cao's tomb, and he has been to the library and collected information on the Internet, but he found that he alone cannot explain the problem from a scientific point of view.

"Dialect students, although you study well, you still have to pay attention to rest." Professor Lin looked at Fang Yan's deep-set eyes and admonished,

"I'll first explain to you the concept of dimensional space as we know it now, and if you have any doubts, let me know."

"Hmm." Fang Yan replied to Professor Lin.

"The scientific theory is that zero-dimensionality is a point." Professor Lin took out a blank piece of paper, tapped it with a pen, and marked an o on it.

"There are no three concepts of time, length, width and height at this point. If we let this point move, it becomes a line. Professor Lin took the pen and extended a straight line from that point, marked with an x.

"This is a one-dimensional world, with only length, no width and no height."

Professor Lin glanced at the dialect he was pondering carefully, nodded, and continued without hurry:

"If we fork a straight line y at any point of the line, we become a two-dimensional world, a plane, with the concepts of length and width.

"Then we're adding a concept of height to this two-dimensional space. This constitutes the three-dimensional space in which we live. ”

Professor Lin drew a straight line Z with a perpendicular xoy plane at point O, picked up the tea on the table, took a sip, and continued:

"And the next four dimensions are to add a timeline on the basis of this three-dimensional, in short, it is the collection of the past, present, and future of our world." Professor Lin redraws a straight line on the paper, marking the past, present, and future on the straight line.

"Now we're sitting in our office, at this point in this timeline, and that's a three-dimensional space. Dialect students, can you understand? ”

"Speaking of the five-dimensional space, let me ask you a question, what did you eat last night?" Seeing that Fang Yan nodded, Professor Lin paused and asked.

"Stir-fried pork." Fang Yan replied quickly.

"And what if you had a fast food in the cafeteria last night?" Professor Lin smiled and continued,

"You see, at this point in time, one you go to eat fried meat, and the other you go to eat fast food, so that at this point in time when you have dinner, if there is a disagreement, a new timeline will be extended."

"And there may be countless bifurcation points on a timeline, extending countless time and space. We call this set a five-dimensional space, like this, like a treemap. ”

After Professor Lin finished drawing, he handed the drawing to the past, and looked at Fang Yan quietly, he knew that this student already had questions at this time.

Fang Yan looked at Professor Lin, thought about his first time traveling, and asked, "Professor, if a person goes back to ancient times, does not come into contact with people, and only stays there for a period of time, or even leaves any traces, then how will the development of this parallel time and space change. ”

"If we assume that a person goes back to antiquity and then immediately returns to modern times, staying infinitely close to Planck time (the smallest interval between time quanta), then his influence on this new bifurcated space-time is infinitely small."

"As far as I am concerned, the development and changes of this parallel space-time are basically the same as the universe before him, and they can be regarded as two timelines that are approximately parallel." Professor Lin thought for a moment and answered the question of dialects.

"Professor, if a person goes back to ancient times and kills Qin Shi Huang when he was a child, will he return to the time and space without Qin Shi Huang when he returns to modern times?" Fang Yan then asked the question that he was most concerned about.

"Let me briefly tell you about the grandmother paradox, if a person goes back in time and kills his maternal grandmother, then his mother will not be born, if you think about it, will he return to the time and space without his own mother?" Professor Lin asked rhetorically.

"Probably not."

"But if a person A in a three-dimensional space has the ability of a six-dimensional space, A travels to the past and kills his grandmother, and then finds the space-time without his mother in many four-dimensional spaces, and uses his six-dimensional ability to replace himself with another person in this three-dimensional world, B, then A has returned to the original space-time? Or have you gone to a changed plane? Professor Lin continued to ask.

"Our understanding of the future of three-dimensional space is just a theory based on existing scientific thought, and this universe has too many unknowns and wonders that we cannot explain now." Professor Lin sighed.

"Can you go to the library and borrow Stephen? William? Professor Hawking's "A Brief History of Time", after carefully studying it, come to my office and tell me what you think. ”

Fang Yan was silent for a moment, bowed to the professor, and left the office with the drawings.

——————

There is nothing that cannot be solved after experiencing one crossing, and if there is, then go through it twice, let alone go through the dialect three times......

There are three bags of compressed biscuits left uneaten, all of which are there; There is no mineral water left, 6 power banks, clothes for each season, 3 books, quilts......

Fang Yan turned over the notebook in his hand, opened his backpack from time to time, carefully checked what he had left, and crossed out an item with a pen whenever he finished checking it.

"That's it!" Fang Yan stood up, shook his sore legs, and looked at the time, there were still 4 hours before his return.

After packing the tent, cleaning up the remains of the fire in the cave, and then carefully searching in the cave to make sure that nothing with a modern atmosphere was left, Fang Yan put on his backpack and came to the mountain forest outside the cave, sat down, and looked at the clear sky in a daze.

Existence is reasonable, everything that exists has a reason for its existence, and everything that exists can find its reason for existence. Suddenly, the dialect thought of Hegel's words.

So, what is my raison d'être? What is the purpose of my existence?

I'm just an ordinary person, and I just want an ordinary life.

Gradually, the sky began to flush, Fang Yan stood up, took a deep breath of the air without PM2.5, and finally took a look at the lush forest around him, and closed his eyes.

consciousness begins to fade away......