"Theory of Planetary Mass Constancy?" Li Ping repeated, just listening to the tone, he knew that Li Ping had not heard this theory. In fact, this is normal, this is just a word that Liu Xuan suddenly thought of.

"Yes, the main idea is that the mass of the planet has formed the most perfect mass in the development of hundreds of millions of years, and once the mass changes, it will cause a chain reaction." It is not difficult to understand this point of view put forward by Liu Xuan, everything has a gravitational force, and the magnitude of gravity is determined by mass, and the change of gravity will inevitably lead to a series of changes.

"What do you mean......" Li Ping didn't finish speaking, it seemed that she had understood what Liu Xuan meant.

"It's too early to say that, and we can't stop it." Liu Xuan smiled, and said indifferently, the outcome of some things has been determined, how difficult it is to change the outcome of the future, Liu Xuan has no courage to change the future, so he can only retreat to the next best thing and keep the last glory of mankind.

"yes. It is often said that the truth is often in the hands of the few, and it is also the principle that the minority obeys the majority. This in itself is a fallacy. Li Ping was also very emotional about such a situation.

The two men fell silent again, and by this time they had walked out of the city, and the light of the artificial sun in front of them could already be seen, and this artificial sun had been silently shining on those who had died for the future of the planet with its insignificant brilliance. Liu Xuan didn't know the date when the artificial sun began to work, but from the time he first came to the city, this sun was spreading its own brilliance, and it had been more than a hundred years.

Those immortal souls sleep here, most of them are people from a hundred years ago, the dungeon at that time was a secret existence, their identity and name are also a secret existence to the outside world, and many people only have their own simple names on their tombstones.

Standing at the entrance of the cemetery, Liu Xuan bent down again, and a nearly ninety degree bend showed his high respect for them.

Li Ping walked in front, Liu Xuan followed, and the two of them walked step by step to Professor Ma's final foothold.

Professor Ma's tombstone is located at the edge of the entire cemetery, and fortunately, the light of the artificial sun is still so bright when it hits here. Professor Ma told Liu Xuan that what he fears most is the dark universe, and what he likes most is that little bit of starlight, and Professor Ma has not spent it in the dark in this hundred years.

Liu Xuan squatted next to the tombstone, carefully observing the tombstone, Professor Ma's appearance is still vivid, but he didn't expect Liu Xuan to say an accident, causing the two of them to miss a hundred years.

Just like Li Ping said, the tombstone was made by Professor Ma before his death, and I can't tell what the material is, there are only two ordinary big characters on it, Ma Xuan. Except for this character that looks a little weird, the others are very ordinary.

"What is this?" Liu Xuan pointed to the tombstone, a place that looked different from the material and asked.

"Looks like solar panels?" Li Ping glanced at it and said suspiciously, what is Professor Ma doing with solar panels on the tombstone?

"He loves light." Liu Xuan thought to no avail, so he had to say something like this.

The two of them were silent, Liu Xuan stroked the tombstone with his hand, endured his grief, said goodbye to Professor Ma, and walked straight in the direction of the research room.

Along the way, the two of them walked slowly like this, without goal or direction. If you really want to talk about it, they are all old people from a hundred years ago, and they don't understand some advanced physics knowledge, and when they reach the age of 30, they also lose the momentum to learn. Liu Xuan is okay, in the past 100 years, the aero engine has not made much progress, and his knowledge can still be used. However, Li Ping no longer has much contribution value to this era, whether she admits it or not, she is completely out of touch with the times, and her knowledge is no longer enough to cope with the current research.

The research room has not forgotten these two "centenarians", and Liu Xuan and Li Ping still have the permission to enter the research room.

After a familiar process, the two people smoothly entered the research room, and nothing changed in the research room except for the change of personnel, even the original computers were retained, but the interior of these computers was improved, but the appearance remained the same.

Standing at the entrance of this research room, both of them were full of emotion, and the researchers who came and went did not pay too much attention to these two strange people.

Liu Xuan walked to his position, there were no documents stacked, it seemed that no one occupied his place, the seat next to him was a hundred years ago, Professor Ma's seat, everything seemed to have not changed, but time had passed, and things had long been different.

Cruel!

This is the first time that Liu Xuan has such an understanding of time, time can erase everything, and time is the only measure in the universe.

"Hello, who are you? This is the location of the Lightspeed Engine, so please don't bother with our research if you don't have anything to do. A young man with eyes and a casual suit stood in front of Liu Xuan and said to him.

Liu Xuan glanced at Li Ping next to him, and casually asked a few questions to this young man, all of which were about the lightspeed engine.

The young people didn't think about these questions, and after Liu Xuan's question, they were directly confused and couldn't answer any of the questions.

"Hello, I was offended just now. My name is Mu Chen, I am an ordinary researcher, who are you? This time, this young man didn't dare to be arrogant, the questions just now were enough to show that the person in front of him, who seemed to be a few years older than himself, was much more accomplished than himself in the field of light-speed research.

"Hello, my name is Liu Xuan, and I am the chief designer of the nuclear fission engine." The small voice, the flat tone, and the simple title made the entire research room quiet. They know what the name means.

"Professor Li, Professor Liu, welcome back." A slightly old voice sounded behind Li Ping, Li Ping was startled, Liu Xuanke didn't introduce her just now, and it must be a contemporary who can recognize her.

"You're the observer back then!" Seeing the old man in front of him who was about sixty years old, Li Ping also said in surprise.

"yes, I didn't think you would recognize me like this. For the sake of the development of future observations, I was also placed in the freeze. It's just a few years later than you, and I woke up a few years earlier than you, and it's like this. The observer was also very happy to see the two old acquaintances.

After confirmation by observers, no one doubts the identities of Liu Xuan and Li Ping anymore. The whole research room sounded with a welcoming voice, all of which made Liu Xuan and Li Ping's hearts warm.