The sun had set for a long time.
Old Cat and Tang Yue sat on the roof of the car with the star chart open on their knees, looking up at the sky.
However, the weather tonight was gloomy, and the sky was no longer as bright as before. The atmosphere exuded a turbid light red glow, and the sky seemed to be covered by a layer of gauze. Tang Yue squinted. "There are a lot fewer stars tonight than yesterday, probably only a few hundred."
"Because the weather is bad, the sky on Mars is not always clear." Old Cat used its thumb and index toe to open its eyelids, and a round cat eye swept around.
"You can see them?"
"Of course."
Old Cat turned its head. "The average person can at least distinguish the brightness of a fifth-class star. Even if your eyesight is better than that of a normal person, the limit of your discrimination won't be lower than sixth-class. This is your physiological limitation. The diameter of a human pupil is no more than five millimeters, and at most, it can only allow light of twenty square millimeters to pass through. But I'm different, I'm a cat."
Old Cat's pupils suddenly dilated, like a camera lens.
"The structure of a mammal's eye is no different from a camera telescope. Of course, the larger the aperture, the more powerful the telescope."
Old Cat was quite proud.
"What kind of mammal are you?" Tang Yue muttered.
Old Cat's ears perked up.
"How am I not a mammal?"
Tomcat corrected him. "In terms of animal taxonomy, I'm a United Nations subspecies of the Carnivorous Cats of the Vertebrate Phylum."
Old Cat and Tang Yue determined their own longitude based on the positions of the two satellites, Phobos and Deimos. Phobos was quite conspicuous in the clear night sky. It was a small spot of light, about one-sixth the size of the moon. In fact, the diameter of Phobos was far smaller than the moon. Phobos' diameter was only twenty-six kilometers. The reason it looked so big was because its orbit was too low. Phobos was only six thousand kilometers above the ground, almost flying close to the surface of Mars, and could orbit Mars three times a day.
Phobos, on the other hand, looked no different from an ordinary star. It was a dim little dot. If one didn't know its location in advance, most people wouldn't even be able to find it.
Deimos had deviated from its original orbit due to the collision accident not long ago. The energy carried by Comet Tom-Tang-Mai I was astonishing. Even though it was only a slight scratch, Deimos's small Chery QQ had been flung out. The originally nearly circular orbit of 23,000 kilometers above the ground had now become a large ellipse.
"Phobos is about to rise." Old Cat calculated the time and pointed west.
Tang Yue looked in the direction its paw was pointing at. Under the dark red sky, the blurry spot of light had already risen to the horizon.
Phobos didn't have clear edges like the moon. It was just a large rock with a diameter of more than twenty kilometers, and its surface was covered in craters. In Old Cat's words, "It's like a potato that a mouse had gnawed on." Such a thing's reflectivity to sunlight was actually very low.
"Phobos is also very dim," Tang Yue said. "This damn weather is like a haze."
"It's because of atmospheric activity. I once told you that the structure of Mars' atmosphere is completely different from Earth's. There's a troposphere dozens of kilometers high here."
Old Cat looked up at the sky. "The wind can sweep dust and sand high into the sky, then move them around the world at a height of forty kilometers above our heads, transporting them to every corner of the planet."
"How is it?" Tang Yue asked. "Are we on the right track?"
"There's a slight deviation," Tomcat replied.
"How much off?"
"Five points. It's within my expectations."
Old Cat straightened its forearm, then moved slightly to the left. "When we set off tomorrow morning, we should go a little east."
"You're in charge of navigation."
Tang Yue lay down lazily. "As long as we can reach our destination accurately, I don't care if we go left or right. Don't you think I'm very optimistic?"
"How do I know if you're angry or not?"
Old Cat shrugged. "If you're angry, you can do it yourself. I think you can deviate all the way to the North Pole."
"Optimistic!" Tang Yue lay beside Old Cat and turned its head to shout at it.
Old Cat covered its face with the star chart and lay down on its back. It rested its head on the back of its head and crossed its legs.
The two cat ears twitched, and the star chart bounced up and down rhythmically. Old Cat was humming, but it didn't shake its legs. It shook its ears.
"There's another thirty kilometers tomorrow, and another thirty kilometers the day after tomorrow," Tang Yue said. "We should be there on the third day. These past few days have been like years."
"But God knows what will be waiting for us on the third day."
Old Cat turned its head under the chart, and its eyes shone through the gaps of the white paper. "You may know what will happen tomorrow, and you may know what will happen the day after tomorrow, but you won't know what will happen on the third day. On the night after three days, you may be still in the same place, or you may be at the end of the universe."
Tang Yue was stunned for a moment, and it took him a few seconds to understand what Old Cat meant.
He couldn't see the future through time. Three days was no different from an infinitely distant future. Where would he be after three days?
At his destination?
At Kunlun Station?
On Earth?
Or in a cantilever of the Milky Way, in a galaxy outside the Milky Way, or even outside the observable universe?
Except for the first option, which had the highest probability, he could be in any corner of the universe.
No.
Was the first option really the most probable?
The probability of him being in any corner of the universe was probably the same.
Tang Yue thought silently.
"What are you trying to say?" Tang Yue asked. "The real unknown is the future?"
"The real unknown is the future."
Tang Yue was silent for a moment, took out a pen from his pocket, and raised it in the air. "But we can actually predict the future. Just like this pen, if I let go now, it will fall immediately. We can accurately predict its speed and state at any time and position according to Newton's law of motion."
"So if you let go of it, it will fall on you?" Old Cat asked.
"Of course," Tang Yue replied.
"Then let go of it."
Tang Yue glanced at it, not knowing what was so good about this experiment. Any normal person could see that if he let go, the pencil would fall under the effect of gravity.
He let go.
But the pencil didn't fall on Tang Yue.
Because Old Cat reached out and grabbed it.
"We can only predict the future of a specific system in a limited way. We can't calculate the unknown factors outside the system, just like you can't predict that I will suddenly reach out with my hand using Newton's law of motion."
Old Cat shook the pencil. "Prediction requires conditions, and conditions are drawing 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. They may or may not interfere with you. The most extreme interference is when a super civilization's spaceship lands in front of us in the next second, ties you up, and then arrives at the other end of the Milky Way through a wormhole."
"That's sophistry." Tang Yue didn't know how to refute Old Cat.
"But it's logical." Old Cat snorted.
Tang Yue stared at the dark red night sky, thinking about something. The limit of his vision was at most 20 kilometers high, and 20 kilometers above the clouds, the atmosphere was moving slowly and silently, carrying hundreds of millions of tons of dust and sand, covering the entire Martian continent bit by bit.