The sun has been setting for a long time.

The old cat and Tang Yue sat on the roof of the car, with the star catalog spread out on their knees, looking up at the sky.

But tonight's weather was gloomy, no longer the bright starry sky of the past, the atmosphere exuded a turbid pale red shimmer, the starry sky seemed to be covered by a layer of thin veil, Tang Yue squinted his eyes, "There are many fewer stars tonight than yesterday, probably only a few hundred." ”

"Because the weather is bad, it's not always clear on Mars." The old cat stretched out its eyelids with its hallux and index toe, and a round cat's eye swept around.

"Can you see them?"

"Absolutely." The old cat turned his head, "The average person can distinguish the brightness of a fifth-magnitude star at the very least, even if your eyesight is stronger than a normal person, the resolution limit will not be lower than the sixth-magnitude, this is your physiological limitation, the diameter of the human pupil is no more than five millimeters, and at most twenty square millimeters of light can be allowed to pass through, but I am different, I am a cat." ”

The old cat's pupils dilated suddenly, like the lens of a video camera.

"The mammalian eye is structurally no different from a camera telescope, but of course the larger the aperture, the more powerful the telescope."

The old cat was quite proud.

"What kind of mammal are you?" Tang Yue muttered.

The old cat's ears are pricked up.

"Why am I not a mammal anymore?" The old cat corrected, "My place in animal taxonomy is that of the Vertebrate phylum Mammalian Carnivorous Feline of the genus Robotic Cat species. ”

Lao Mao and Tang Yue judge their own longitude according to the position of the two satellites of Forbos and Demos, Phobos Forbos is quite conspicuous in the clear night sky, it is a small spot of light, about one-sixth the size of the moon, in fact, the diameter of Phobos is far less than the moon, the diameter of Forbos is only twenty-six kilometers, the reason why it looks so big is because the orbit is too low, Forbos is only six thousand kilometers from the ground, almost flying close to the surface of Mars, and can orbit Mars three times a day.

Deimos, on the other hand, looks like a normal star, a dimly lit dot that would not even be found if it weren't known in advance.

The energy carried by the comet Tom-Tang-Mai is amazing, even if it is only a slight scratch, and the small Chery QQ of Demos has also been thrown away, and the near-circular orbit that was originally 23,000 kilometers above the ground has now become a large ellipse.

"Forbos is going up." The old cat counts the time and points to the west.

Tang Yue looked in the direction it was pointing at, and under the dark red canopy, the blurred spot of light had risen to the horizon.

Forbos doesn't have the obvious edge of the moon, it's just a large rock with a diameter of more than 20 kilometers, the surface is covered with craters, in the words of the old cat, "it's a potato eaten by a mouse", and the reflection of sunlight is actually very low.

"Forbos is also bleak." Tang Yue said, "This ghost weather is like haze. ”

"The reason for atmospheric activity, I once told you that the structure of the Martian atmosphere is very different from that of Earth, and there is a troposphere tens of kilometers high." The old cat looked up at the sky, "The wind can roll dust and sand particles high into the air, and then flow around the world forty kilometers above us, carrying them to every corner of the planet." ”

"How?" Tang Yue asked, "Are we on the right path?" ”

"A little bit off." The old cat replied.

"How much worse?"

"Five arc points, as I expected." The old cat straightened his forearms, then shifted slightly to the left, "When we leave tomorrow morning, we should go a little to the east." ”

"You navigate, you have the final say." Tang Yue fell down lazily, "As long as you can reach your destination accurately, I don't care if it's left or right, do you think I'm very open-minded?" ”

"How do I know if you're hot." The old cat shrugged, "If you come by yourself, I think you can deviate to the North Pole." ”

"Open-minded!" Tang Yue lay beside the old cat and turned his head to shout at it.

The old cat put the star catalog on his face, and also lay down on his back, pillowed the back of his head, and lifted Erlang's legs.

The ears of the two cats moved, and the star catalog was rhythmically cocked - the old cat was humming, but it did not shake its legs, it shook its ears.

"There are still thirty kilometers tomorrow, and thirty kilometers the day after tomorrow." Tang Yue said, "The third day should come, these days are really like a year." ”

"But God knows exactly what will be waiting for us on the third day." The old cat turned his head under the table, and his burning gaze came through the gap in the white paper, "You may know what is tomorrow, and you can know what is the day after tomorrow, but you will not know what will be on the third day, and on that night after three days, you may be in the same place, or you may be at the end of the universe." ”

Tang Yue was stunned for a moment, and it took a few seconds to understand what the old cat meant.

He can't see the future through time, three days is actually tantamount to an infinitely distant future, where will he be in three days?

At the destination?

At Kunlun Station?

On Earth?

Or in some cantilever in the Milky Way, in a galaxy beyond the river, or even beyond the observable universe?

Except for the first one, which has the highest probability, he may be in every corner of the universe.

No.

Is the first one really the most probable?

The probability that he would be in any corner of the universe is probably equal.

Tang Yue thought silently.

"What do you want to say?" Tang Yue asked, "What is really unknowable is the future?" ”

"The real unknowable is the future."

Tang Yue was silent for a moment, took out a pen from his pocket, and held it up in the air, "But we can actually predict the future, just like this pen, if I let go of my hand now, then it will fall immediately, and we can accurately predict its speed and state at any time and any position according to Newton's laws of motion." ”

"Then you let go of it, and it will fall on you?" The old cat asked.

"Of course." Tang Yue replied.

"Then you let go of it."

Tang Yue glanced at it, he didn't know what to do in this experiment, normal people could see that if he let go, the pencil would fall under gravity.

He let go of his hand.

But the pencil did not fall on Tang Yue.

Because the old cat stretched out his paws and grabbed it.

"We can only predict the future within a particular system in a limited way, and we can't calculate the unknown influencing factors outside the system, just like you can't predict with Newton's laws of motion that I will suddenly reach out." The old cat shook the pencil, "Prediction requires conditions, the condition is to draw a line, since the line is drawn, then there will be inside and outside the line, there will always be unknown factors outside the system in this universe, it may interfere with you, or it may not interfere with you - the most extreme interference is that a super civilization spaceship landed in front of us in the next second, tied you up, and then reached the other side of the galaxy through the wormhole." ”

"You're sophistry." Tang Yue didn't know how to refute the old cat.

"But it's logical." The old cat hummed.

Tang Yue stared at the dark red night sky, not knowing what he was thinking, his eyesight limit could see the thin clouds at a height of twenty kilometers at the peak, twenty kilometers above the clouds, the atmosphere was flowing slowly and silently, carrying hundreds of millions of tons of dust and gravel, covering the entire Martian continent little by little.