After changing into clean clothes, Yan Xiuze casually had breakfast in the villa under Ou Cheng's name, and then set off for the headquarters of the Alliance of Liberals, which was built on the outskirts of Reykjavík.

However, he had not come here to meet his friends who belonged to the Alliance of the Liberals, but to be another guest.

"Scan Start ......"

Yan Xiuze stood in front of an electronic door and honestly accepted the scan.

After a while, an electronic voice sounded again without any emotional fluctuations: "Identity confirmed, Supreme Authority." ”

"Welcome, Mr. Yan Xiuze."

The electronic door slowly opened, Yan Xiuze didn't stop too long, and walked in directly.

And there was already a person waiting in the door early, who was holding his hands behind his back at this time, leaving only Yan Xiuze with a back.

The person who was originally staying indoors also seemed to be aware of Yan Xiuze's arrival, subconsciously stroked a strand of red rope tied to the back of his head, and slowly turned around: "Earlier than I expected, your body's conditioning ability is unexpectedly good......"

"Instructor......" Yan Xiuze looked at the old man in front of him who had wrinkles on his face and was no longer young, and said softly.

"What? It looks like your super physique is a lot stronger than when you crossed over before...... Is it the changes that occur when you traverse the wormhole, or do you have another adventure in that parallel world? The instructor was obviously very interested in Yan Xiuze's physical changes and asked.

"Well...... It's a long story, but it has nothing to do with crossing a wormhole. Yan Xiuze said helplessly.

"But I guess since you asked me to meet here early, it should have a lot to do with the wormhole crossing, right?" The instructor quipped.

"Hmm...... It's really ......" Yan Xiuze couldn't help but glance at the red rope tied to the horsetail on the back of the instructor's head, and hesitated: "I really have doubts about this, I want to ask you." ”

"But...... Should I continue to call you 'Instructor', or should I call you Professor Zhou Jianping? ”

"Name, just a code name." The instructor suddenly looked a little lonely, and waved his hand: "Just pick your mouth and call it...... Zhou Jianping, heh, no one has called me by this name for many years. ”

"But now that you know my real name, you must have seen 'me' in the other world, right?"

"Well, that's right, it's really thanks to that 'Professor Zhou' that I was able to come back this time."

The instructor opened his mouth, as if to ask something, but in the end he swallowed the question he had already raised in his throat and did not speak.

"Okay, without further ado, you can ask me whatever you want." After a while, the instructor said slowly: "But I said it in advance, I have actually been distracted by a large part of my martial arts for so many years, so ...... When it comes to physical standards, it may not be as good as another person in a parallel world. ”

"I can't answer your question, but it's not necessarily."

"No, it's not a complicated problem, it's really about physics." Yan Xiuze scratched his head and asked, "That, instructor...... Do you think that the universe we live in has boundaries? ”

The instructor narrowed his eyes and looked at Yan Xiuze in front of him with a scrutinizing gaze.

Yan Xiuze was a little furious by his gaze, and hurriedly said, "Can you stop staring at me like this?" ”

"I'm sorry, I'm just a little suspicious of your identity right now." The instructor tugged at the corners of his mouth and teased: "I remember teaching you similar knowledge twenty years ago, why, it's only been a few months for you, and all the little knowledge you learned before has been returned to me?" ”

"That's not it, I just want to check with you again." Yan Xiuze smiled bitterly.

"Well, although I don't know what kind of medicine is sold in your gourd...... It's just a review of your homework. The instructor cleared his throat and said, "Although the jury has not yet been made whether the universe is infinite or not, there is a more mainstream view, and one that I support more, that is, 'finite and unbounded'. ”

"Limited Unbounded......" Yan Xiuze nodded silently, which was basically consistent with his previous conjecture.

"The so-called finite and unbounded is actually very simple to explain." The instructor continued: "We believe that the universe is not actually infinite, but it has no boundaries...... In other words, with the technology of the three-dimensional world alone, there is no way to reach its boundaries at all. ”

As he spoke, the instructor's palm suddenly emitted a faint milky white light, and he used the holographic projection technology in the room to unfold a translucent "white paper".

"It might be hard to understand this, I'll explain it to you with a projection." The instructor's other hand dotted a few times in the air, and dotted a few small black dots on the white paper suspended in mid-air: "Suppose that we now land in a dimension and imagine our world as a two-dimensional world. ”

"Then, we three-dimensional creatures will become two-dimensional paper people."

As the instructor spoke, the small black dots that fell on the white paper turned into vivid "black villains".

"Let's say we're these little black people, trying to find the boundaries of our world." As he spoke, the instructor manipulated the little black figures to move towards the edge.

And when the black figure moves to the "border" of the white paper, it can no longer move forward.

"See? We have now reached the boundary of the world, and it is impossible to move one step further, because this two-dimensional paper world is so big. The instructor said lightly: "But what if this piece of paper world has no boundaries?" ”

As he spoke, the blank piece of paper in the instructor's palm began to expand rapidly, eventually filling the entire room.

"But that's 'infinite.'" Yan Xiuze shrugged.

"It seems that I still remember the knowledge of the year very well!" The instructor laughed, put away the "white paper" that spread out the entire room, and let it regain its original size: "You are right, in this way, this paper world is infinite, and it obviously does not support my previous view of 'finite and unbounded'. ”

"In fact, this is what ordinary people think, who often think that the universe we live in is an expanding 'sphere', or simply an infinite space, but in fact it is very likely that this is not the case."

The instructor put away his smile, and the white paper in his palm began to "roll" together, and after a while, it became a round "sphere" without any edges and corners.

"Continuing with the previous assumption, what if the 'paper world' we live in is not tiled, but the 'sphere' of a sphere?"