"Do you understand the language of the dragon clan?" The old man did not directly answer Jiang Fei's question.

"Understand." Jiang Fei replied. He had worked hard in this area before.

"That's good, it's hard for me to express it clearly in human language..." The old man changed to using the dragon language to communicate with Jiang Fei.

Because Jiang Fei studied the Dragon Clan language hard for a period of time, he could completely transform the words said by the old man into his own language and understand them.

"What do you understand about space?" the old man asked. The dragon language he spoke was automatically translated by Jiang Fei into a vocabulary that he could easily understand.

"Space? I know that we live in three-dimensional space, and perhaps there may be creatures living in higher dimensions than us." Jiang Fei said, but in his heart, it is no longer possible that there will be creatures in higher dimensions, because those guys have invaded this universe!

"By the way, senior, is the fourth dimension of the four-dimensional space time?" Jiang Fei suddenly thought of a question.

"Of course not!" The old man shook his head and said to Jiang Fei: "Time is a special vector. There is time in one-dimensional space, and there is time in two-dimensional space. There is time in every dimension of space! Time and space are two different concepts!"

"That's it!" Jiang Fei nodded.

"Okay, the relationship between time and space has been explained. So can you tell me the relationship between various spatial dimensions?" The old man nodded, and then continued to ask Jiang Fei in the language of the dragon clan.

"Relationship?" Jiang Fei was stunned. He didn't understand what the old man meant when he asked this.

"Okay, let me tell you from the beginning." The old man sighed, and then said to Jiang Fei: "The so-called one-dimensional space is a straight line. If there are creatures on this straight line, then from its perspective, there is only one point in front and back, and it can only move forward or backward."

"And countless straight lines form a plane, which is the so-called two-dimensional space. The creatures here are no longer limited to straight lines, but can move freely up, down, left and right." The old man continued.

"Well!? That's true!" Jiang Fei nodded. The old man's description coincided with the knowledge he had in the world of science and technology. Although the dragon language's name for spatial dimensions is different from that of the outside world, it also has the same meaning when it corresponds to each other.

"The three-dimensional world we live in is actually composed of countless planes. After layered two-dimensional worlds are superimposed, they form the three-dimensional world we live in." The old man said this and looked at Jiang Fei, then continued: "So you can imagine that the four-dimensional space is actually formed by superimposing countless three-dimensional spaces."

"What is that four-dimensional space like?" Jiang Fei asked curiously.

"To talk about this issue, we have to start with our understanding of space." The old man said here and paused for a moment, and then continued: "I don't know if you have discovered it. Our observation of the world is actually done through dimensionality reduction."

"What does it mean?" Jiang Fei was stunned.

"Give an example." The old man stretched out his hand and a ray of light appeared in the air.

"This is a straight line, which represents a one-dimensional space. If a creature lives here, then in his eyes, there is only a point in front and a point in the back. This means that the creature living in a one-dimensional space can only see points." After the old man said that, he waved his hand, and the light in the air disappeared, replaced by a light wall.

"Look, this is a plane, which represents a two-dimensional space." Then the old man waved his hand and many patterns appeared on the light wall, including squares and circles.

"If it is a creature living on this plane, from his perspective, he can't see these squares or circles. All he can see is a line facing him." After saying that, the old man waved his hand again, and the light wall disappeared, but replaced by a solid wall.

"We live in a three-dimensional world. Now, from your perspective, what is ahead of you?" the old man asked Jiang Fei.

"A wall!" Jiang Fei said naturally.

"Well! That's right! But this is also a plane! You can't see what's behind the plane at all, because you are a person in the three-dimensional world, so you can only see the level of the two-dimensional world." The old man said.

"No! I can see three-dimensional objects, such as this ball!" Jiang Fei said and took out a ball from the ring space.

"Haha, that's just the answer you have learned from your subconscious based on a lot of relevant knowledge..." The old man said as he took the ball from Jiang Fei's hand. Then he waved his hand, and the light around him instantly became dim. At this moment, in Jiang Fei's eyes, there was only a faint round shadow left on the ball.

"Look, after losing the contrast between light and dark, your brain can no longer calculate, and the real image you see in your eyes is just a circle." The old man smiled.

"So that's it..." Jiang Fei nodded. It turned out that the three-dimensional world in his eyes was just the result of the supplementary calculations based on knowledge such as light and dark contrast and distance.

"So, a person in a dimensional space can only perceive the space he is in through dimensionality reduction, and he cannot see the true face of the space he is in!" The old man finally gave the conclusion.

"So that's it!" Jiang Fei nodded. No matter how charming the scenery in the picture is, all creatures in the two-dimensional space can see are straight lines, and the colorful three-dimensional world is just a splicing of pictures in people's eyes. Although this answer made Jiang Fei a little disappointed, it was the fact.

"So you understand." The old man smiled and continued: "The so-called four-dimensional space is the product of countless three-dimensional spaces stacked. Of course, this stacking is not a simple stack like a brick building. The accumulated one is still a three-dimensional world. This stacking is built together in a way that we cannot understand. People there can see through our world like we see through the essence of the two-dimensional world; the world in their eyes is composed of real three-dimensional images, and because we cannot observe the real three-dimensional world, we cannot describe their world."

"Can't even imagine the four-dimensional world we people in three-dimensional worlds imagine what they look like?" Jiang Fei asked.

"No!" the old man shook his head and said, "But I discovered something interesting, which may help you solve some doubts."

"What interesting thing?" Jiang Fei asked immediately.
Chapter completed!