As soon as Neil got out of bed, a green light lit on the wall of the dormitory, and two female staff members politely knocked on the door and took him to wash and eat.

Neil first met the female Drowgins, who were also tall, graceful, and very beautiful.

After the meal, a small spaceship takes Neil to another underground building, and the crew takes Neil into a room full of machines and equipment, where Schimer is already waiting.

When he saw Neil, he waved warmly, and said with concern and humor: "Child, I don't know if you sleep well, you know, one day and night we have here is more than twenty days on the earth, and time passes very slowly, I'm afraid you have to adjust to the jet lag." Neil smiled politely and told Schimer that he slept well.

"Neil, the last time you asked me what happened to my ancestors after they fled to Earth, I would like to tell you those stories. However, the events that have occurred since that are too significant to have your worldview upended. I know that you humans have an idiom called hearing is false, seeing is believing, and it just so happens that we Zolkin people now have some small technology that can take you to the past and the future, I don't know if you are interested in going back in time with me and experiencing for yourself what happened on Earth in those days? Schimmer looked at Neil with a groan, and Neil's heart immediately became ecstatic like a sail blown by the wind.

Time travel! Something that only exists in legends! Not to mention being an astronaut, even as an ordinary human being, it is also a dream experience!

Before Neil could answer, his eyes had already revealed his inner thoughts. Schimmer looked at Neil and smiled, "Your reaction is the same as I expected, so let's not talk much." He reached out and took the two sets of silver-white clothes handed to him by the staff, handed one of the small ones to Neil, and said, "Put it on, and get ready to go." Neil took the suit and found that it was a metallic outfit with a certain weight, thinner and softer than his previous spacesuit.

Neil expertly dressed and looked up to see that Schimer had also finished changing. The lights in the room cast a long shadow of Schimer on the ground, and his tall body was shrouded in a silver light.

"Alright, Neil, get ready for an extraordinary trip." I'm going to take you back to Earth more than 6,000 years ago, and there will be many things you wouldn't have imagined. A staff member worked on the dashboard on the desktop for a while, then turned back and nodded to Schimer.

Schimer raised his left hand and adjusted some scales on one of the dials he was wearing on his wrist, and after a few seconds, a small vortex of air slowly appeared about five meters in front of him, and with a crackling sound of electricity, the vortex became larger and larger, and rotated more and more violently, and at the same time a strong suction force hit the other side.

Neil was surprised when Schimer's big hand grabbed him and led him into the vortex. Neil felt the room he was in disappear in an instant.

In a trance, some fragmentary scenes appeared in front of his eyes: he saw himself and Buzz and Michael still sitting in a spaceship to the moon...... He is on a docking mission outside the Gemini 8 spacecraft...... Self in a spacesuit at NASA Flight Center in training...... The plane piloted by himself on the battlefield in North Korea was hit by an artillery shell...... These images flashed in front of his eyes like a slide, until they finally turned into a halo of white flowers.

By the time the halo had faded, Neil found himself standing with Schimer in the interior of a pipe-like space that grew from wide to narrow to the width of two or three people.

The inner wall of the pipe was an undercurrent of silvery-white air, mixed with countless faint arc-like flashes, and those beautiful lights and shadows continued to retreat behind Schimer and Neil.

Unlike the intense tear felt when the moon first fell to the ground, this time the journey was unusually smooth.

Schimer held Neil's arm firmly until a few minutes later, when the two of them had stabilized.

Schimer and Neil stood in the pipe, silent, and the atmosphere was slightly awkward. Schimer chuckled softly and said, "Neil, this trip, we won't be arriving soon, the journey is lonely, why don't we take this time to talk about time travel?" Neil said yes, looking forward to what he had to say.

"Neil, before we talk about time travel, I'd like to ask you to tell us what time you have in mind. Neil didn't expect the other party to ask such a question, he thought about it for a while, and replied: "In my opinion, time is a coordinate axis that began to arise at the beginning of the universe and extended infinitely to record the changes of everything in the universe. Schimer shook his head and said, "Your statement is roughly correct, but it is not rigorous. The human beings on your earth, because they are bound by space, the time that you observe from your eyes is like flowing water evenly and slowly, from ancient times to the present, without interruption. But if you have the opportunity to go out of the confines of Earth and go to the vastness of outer space, you will find that time is not a ubiquitous element in the universe. Time is unevenly distributed in cosmic space, and it is a bit like a giant earthworm, intermittently existing between the birth and death of each cosmic unit. In the case of the universe as a whole, there is no time before the beginning of the universe, and on the day the universe ends, time also ends; Specific to each star in the vast universe, when the star explodes and is born, time has just been born for this star, and when the star collapses and dies, the time of this star also dies. In other words, if the sun explodes tomorrow, time will come to an abrupt end for you, me, and every life in the solar system. But at the same time, for life beyond the solar system, time continues. Therefore, although you can think of time as a universal coordinate axis in the universe, this axis belongs to different regions of different cosmic space, they are different in length, and they are also in different directions, some are still continuing, some are finished, and different times belonging to different regions are not related to each other in normal conditions, and only when they intersect can they be defined as the same unit, and they can be reduced to the same sense. Neil listened attentively to what Schimer had said, and though he did not fully understand what he said, he felt that he was generally right: for the earth and the moon, the time must be different in their eyes; And for the Drow Venus, which has been destroyed, the concept of time no longer exists.

Schimer continued, "This statement may confuse you, because your current human knowledge system is not structured this way. You usually say that the universe was born 13.8 billion years ago, the solar system was born 4.6 billion years ago, and so on, but I tell you, this is a paradoxical statement in itself. The universe is too vast, and as an intelligent creature on Earth, before it can travel to the target location, it can only define the time of the Earth, and is not qualified to judge the time of other cosmic regions or even the entire universe. In the same way, if you are still on Earth, the time before the birth of the Earth and after its destruction is as meaningless to you as a number with a denominator of zero. If you have to define the time when a universe was born, then you can only assume that you are looking at the universe from the perspective of the God who created the whole universe, and not just from the perspective of a small earthling or a small Dorgin in the solar system. To be more specific, for you, Neil, when your life ends, so does your time. Other people's time doesn't mean anything to you. Neil's head swirled to Schimer's words, a thoughtful look on his face.

Schimer smiled: "Isn't it a little confused? It doesn't matter, Neil, you just need to remember an axiom that you humans will soon discover: time only makes sense for living individuals, or more accurately, time is created and exists only in the conscious brain. This is equivalent to saying that what you see and perceive is time: you open your eyes and time will pass before your eyes, and if you close your eyes, time will not disappear in your life, because your eyes will open again and your mind will still work; But when your brain stops working, your eyes are permanently closed, and you no longer have any sense, time is over for you. This leads to a key definition of time: observation, thinking, and these elements related to intelligent beings are decisive for the existence of time. Neil had just felt a little clearer of his mind being confused again.

Schimer looked at him with a smile and said, "Okay, Neil, I'll talk about something that's relatively easy to understand." Let's talk about time travel. In layman's terms, time travel means going back in time or going to the future. Through the minds of the geniuses of the beginning of this century on your planet, you have also glimpsed the way to this end. In a simple four-dimensional space, time travel is a by-product of space travel, and time travel needs to rely on space travel to achieve it. What you earthlings are currently able to achieve with technology is only space travel, and space travel is limited to the human life cycle. Your journey from the Americas on Earth to Europe is a space travel, and time hardly changes; When you travel from Earth to the Moon, it is also space travel, and time changes by a few microseconds, which is negligible relative to human life. You understand why, it's because the speed at which you travel is too low and too low, and the small speed is nothing to the behemoth of time, and it can't make any difference in it, or in the least of it. At present, it will take more than 70,000 years for you humans to reach Proxima Centauri, the star of Satan, in your fastest spacecraft, and the physical body has not yet arrived, and life has long since ended, and even if you reach it, there is no point. But you know, as you get faster, the longer you can travel in a short lifetime in a spacecraft? As you continue to accelerate, the giant palm of time captures you and it becomes harder and harder to control you; When your speed reaches the speed of light, time can no longer dominate your life, and you can already keep up with it; And when you are fast enough to exceed the speed of light, time can no longer control you, and you can break through its boundaries to the past or the future. ”

"But", Neil couldn't help but interject,

"According to the theory of mass-energy equivalence, the speed of light is the maximum speed in the universe, because even the tiniest particle will become very massive when it is close to the speed of light, and if it reaches the speed of light, its mass will be infinite, so it is impossible for an object to exist beyond the speed of light."

"Yes, Neil, you're right. This law is perfectly applicable to any cosmic existence with mass. You and I both have quality, so time travel, on the one hand, does require you to run ahead of the light, and on the other hand, you can't race against the light to achieve it. Neil began to be confused again.

Schimer then explained to him, "Have you ever heard of wormholes? At present, we Dzorkin people rely on wormholes for time travel. Although we have found other possible ways to achieve time travel in the lab, and wormhole travel has its limitations, it is still the most effective method at present. Neil nodded and said, "I have heard of the concept of wormholes, which was put forward by Einstein and Nathan Rosen in the 30s, so we also call wormholes Einstein-Rosen bridges." However, this is only a hypothesis put forward by theoretical physicists, and no one in the real world has ever discovered the existence of wormholes. Schimer shook his head and said, "Just because something hasn't been discovered doesn't mean it's not real, and that's just in terms of the current level of technology of your human race. What I'm telling you is that wormholes are real, and there are many of them. There are countless wormholes near the center of the Milky Way, but they are so far away that they don't really mean much. There are also some wormholes around the perimeter of our solar system, but they have been obscured by dark matter, so they are difficult to detect. The difficulty of time travel is not how to find the wormhole, but how to 'make' it properly. A wormhole is created because it must be accompanied by a black hole nearby. It is precisely because of the combination of black holes and wormholes that time travel becomes possible.

"As for the black hole, it is a cosmic existence with a supermassive mass and a super-strong gravitational force, and objects that are too close to it will be ruthlessly devoured by it, including light; However, if you are at a distance from it, you will only be pulled away by its slightly weakened gravitational pull, which also includes the trajectory of light. You can imagine a model of a track and field arena where you're running a 200-meter sprint race against light, and you both of you should take a straight route based on the shortest straight-line distance between two points, but there's a guy named Black Hole sitting in the bunker in the center of the field, and it's distorting the space around it so badly that you're only racing on a circumferential curved surface along the track that has been drawn at the edge of the field. Okay, now the starting gun goes off and the game begins. Hikari honestly runs on a semi-circular track, but because you are brave and resourceful enough, you find a shortcut through the playground from the edge of the bunker, and when you pass by the bunker, you are not attracted to the bunker by the black hole sitting inside, and as a result, even if you are much slower than Hikari, you can still reach the end before it. Next, you have another race with Hikari, this time at a distance of 399 meters, and when the starting gun sounds, Hikari begins to run hard in a circle, but without professional ethics, you only take a small step backwards and reach the finish line. In this way, although your speed is much slower than the light, you still run ahead of the light. Like you humans, our understanding of black holes was initially limited to theory and did not make much progress in practice. Fortunately, after cracking the secret about dark matter, the process was greatly accelerated. Today, tens of billions of black holes have been discovered in the inner galaxy alone, and there are also a small number of them around the solar system, which makes time travel possible. At 17 o'clock right ascension at the declination of 0 degrees and right ascension, which is what you humans call Ophiuchus, we have detected a medium-sized black hole that is about 0.07 light-years away from the Sun, and we are currently traveling through this black hole.

"You already know very well how travel works. Depending on the distance to be reached, we only need to create wormholes of different arcs in the four-dimensional space near the black hole, which has been deflected, and then travel through it. Of course, the premise is that we can't be swallowed up by a black hole with a strong gravitational pull. Neil thought for a moment and said, "Okay, regardless of whether or not the way to pass through the edge of the black hole is feasible, I can basically understand this means of going beyond the speed of light." But high priest, why does being faster than the speed of light mean being able to go beyond time? "Neil, imagine a scenario where planets A and C are one light years apart, and when you and your companions observe planet C with a telescope on planet A, and you happen to see a giant walking on the surface of planet C, then for you who are observing, you are seeing the scene on planet C a year ago, because it took a year for the light to be projected from the giant into your eyes; If you leave immediately and arrive on planet C in a magical spacecraft, then your companion who remains on planet A at this moment can see that you have gone to the giant and walked with him, then for your companion, you have gone back to a year ago.

"Again, suppose the giant you are watching doesn't notice you, but he suddenly stops walking, and travels from planet C to planet A in a spacecraft and appears in front of you, and now it seems to you that he has come from the world a year ago to you a year later, in other words, the giant has gone to the future. But you have to note that all this kind of time-traveling behavior can only occur when your worlds intersect, and as I said to you earlier, if you are in two separate cosmic spaces that are not connected to each other, then each other's time is meaningless to each other. Neil's head was a little dizzy, and before he could properly appreciate Schimer's words, he suddenly noticed that the pipes around him began to widen slowly, and all kinds of strange buildings flashed in front of his eyes, and groups of strange-looking people in bright clothes with wide robes and large sleeves swept past him very quickly, and then a hole of light appeared in front of him for no reason, and the light grew bigger and bigger, and before his brain could react, his body had already left the pipe he was in before and entered the real world.