The aroma of crucian carp and tofu soup at home had not yet dissipated. Lin Chaoxi returned to her room. It was late at night and there were still review materials for the teacher's exam on her desk.

After Lao Lin fell ill, he became no different from a charlatan.

Sometimes he suddenly recalled the past, sometimes he made chicken soup, and sometimes he suddenly tortured his soul. Lin Chaoxi tried his best not to think about Lao Lin's last few words, but how could he not think about it?

As the daughter of a former mathematician, her mathematical foundation is indeed not bad.

When she was young, not only was Lao Lin's mathematical enlightenment to her incredible, she herself was also very interested in mathematics. She was even very happy every time she attended the Olympiad classes.

If she had persisted on the path she had taken as a teenager, she might not have become as capable as Pei Zhi, but she would not have felt inferior due to her ignorance when faced with that question.

But she didn't know when she started to stop going to classes and stopped reading any math-related books in the library.

She was afraid of mathematics and felt terrified and disgusted by it. She firmly believed that it was the realm of genius and beyond the reach of ordinary people.

Thinking of that time, Lin Chaoxi felt a chill all over his body and tried to stop his thoughts from running wild.

My life path went astray a long time ago, so let it be. The most important thing now is Comrade Lao Lin.

Lin Chaoxi rubbed his face quickly, turned on the computer, found the content about setting up the living environment for Alzheimer's patients, and prepared to do something that would not easily cause his mind to wander.

Alzheimer's disease manifests itself as short-term memory loss, but long-term memory can be recalled.

So, you can put things that make them feel comfortable and happy in a prominent place at home, such as nostalgic photos, favorite plants...

Alzheimer's patients often have trouble telling which door is their own, so special markings can be made on the door to help them identify it.

Lin Chaoxi tore off a piece of note and wrote down the precautions.

Something that can make Lao Lin feel comfortable and happy requires nostalgia?

Is she going to find a proof of Fermat's Last Theorem to hang on the wall?

It’s quite exciting to think that in the future my house might be covered with mathematical theorems and formulas.

Lin Chaoxi read through a bunch of materials and summarized the key points. The primary problem is that Lao Lin often forgets to bring his keys. If he doesn't have a key, he can change to a fingerprint lock.

But the new village they live in now is a large old-style residential area with hundreds of buildings, each with a small courtyard under the building. If Lao Lin comes back from a trip and sees these courtyards that look exactly the same, he will easily be confused.

We need to work on the doors and walls...

She put the note in her pocket, changed her shoes and went out.

It was late at night, and the street lights in the old residential area were sparse. Apart from the rustling of wild cats, there was no other sound.

She walked across the patio, pushed aside the aster flowers leaning against the doorframe, and stood outside the courtyard wall.

At her feet was a whole box of chalk.

She tilted her head back slightly and looked at the entire wall.

When they were young, they lived in a small bungalow in the city center. Although the house leaked, it had a small patio. Lao Lin worked during the day and served dishes in a restaurant at night.

At nine o'clock in the evening, she would sit at the door of her house waiting for Lao Lin.

The starlight on summer nights is beautiful, and Lao Lin always brings back snacks and never looks tired.

They sat under the loofah vines in the patio and ate snacks together. Lao Lin would always fight with her for the snacks, being extremely shameless.

While eating, Lao Lin would tell all sorts of random scientific stories, such as Pasteur's discovery of the hidden asymmetry of hydrochloric acid crystals, Franklin and the lightning rod...

Children from nearby would also come to listen, after all, Lao Lin’s stories were really interesting.

There was only one time that was particularly fun.

When Lao Lin was telling a story, he was confronted by the son of a nearby professor.

The middle school kids are more terrifying than the middle school boys. The kids say that what Lao Lin said is useless, the real science is extremely profound, and Lao Lin is just fooling them with stupid stories.

Actually, that’s not wrong…

But the kid started reciting Newton's three laws of motion and the Pythagorean theorem on the spot, which was quite scary.

Old Lin didn't say anything at first, just listened with a smile. When the kid finished reciting a series of formulas, Old Lin stood up and did something that Lin Chaoxi now thinks is very childish.

He held the child's hand and walked out of the door. He picked up a small piece of red brick from the roadside and wrote a formula on the wall under the light of the street lamp.

E=MC2 (square)

Lao Lin: “Do you know what this is?”

"Einstein's!" the little boy said proudly, "Theory of Relativity!"

Lao Lin did not comment. He picked up a small brick and wrote another more complicated formula on the wall. He asked, "What about this one?"

The second formula begins with R and has superscripts and subscripts.

Lin Chaoxi was stunned and the little boy was speechless.

But if he stopped at this point, he wouldn't be Lao Lin anymore. He continued writing. The third one was an expression, something expanded with parentheses...

Anyway, Lin Chaoxi couldn’t understand it either.

After writing this, Lao Lin did not stop. The formulas, theorems and equations that followed were beyond description in words.

As Lao Lin waved the bricks in his hand, formula after formula gradually emerged under the dim light of the street lamps. They spread out until they covered the entire courtyard wall.

Finally, Lao Lin threw away the red brick with only a few scraps of writing left and said to the little boy, "You continue to read it?"

Lao Lin looked like a middle school student, very proud.

The little boy's face turned red and he was unable to speak.

After a while, Lao Lin slowly walked to the second equation starting with R that he had written, but his tone was unexpectedly calm.

“These are the field equations from the general theory of relativity,” he said.

"This is an expression of narrow relativism."

“This is the Dirac equation.”

"This is the Chen-Gauss-Bonnet theorem."

"It's the Lorenz equation."

“…”

"This is the Maxwell equations"

Finally, Lao Lin slowly returned to E=MC2 (squared) and said, "This is not relativity, it is Einstein's mass-energy equation."

At this point, the little boy finally burst into tears. The other children looked up at the wall full of formulas, not knowing what to do.

At that time, Lao Lin squatted down, wiped the boy's tears with the back of his dirty hand, and asked: "Why are you crying?"

The child was so angry that he couldn't say anything except crying.

Lao Lin said to himself: "Do you feel embarrassed that I, an adult, am bullying you? Do you feel embarrassed in front of a child? Or do you feel frustrated that these formulas are too difficult?"

Lao Lin: "But you just did the same thing as me in front of other kids."

"Isn't it annoying when people show off their good memory?"

The little boy cried even louder. Lin Chaoxi looked around, fearing that the boy's family would rush out and beat him up.

But it would be strange if Lao Lin cared about these things.

"There will always be someone with a better memory than you," said Lao Lin.

"When you only remember the formula at face value, anyone who memorizes more than you will make you heartbroken."

"Why? Because you actually know nothing."

"You can recite the formula, but all you see are those few broken characters and the compliments from others. But actually, these..." Lao Lin poked the entire wall and pointed to the starry sky above their heads, "It's that."

"Star?"

Lin Chaoxi muttered to himself, and then received a slap from his father.

"Call it the Universe."

"oh."

If the children then asked what the universe was, the story would go on and on. It was obvious that at nearly nine o'clock in the evening, most children had no patience to listen to a trembling young man talking about the cosmic truth behind every formula.

So when Lao Lin talked about the Pythagoras theorem, most people had left.

Lao Lin was speaking excitedly, but when he came to his senses, the only person left in front of him was the crying little boy.

Lin Chaoxi squatted at the door, looked at them, and yawned.

Lao Lin then threw the brick away and began to summarize his speech: "In summary, it is meaningless to just recite formulas. At your age, you are still unable to understand the true meaning behind them, so what's wrong with me telling you some interesting science stories?"

Lin Zhaoxi: “…”

Little boy: "I...my dad said...I need to memorize it."

"What your father said is not as right as what her father said."

At that time, she was already staggering with sleepiness, but she vaguely remembered that Lao Lin pointed at her and said proudly.

In short, in her memory, this was a rather bizarre story.

Lao Lin is full of vigor and energy and would grab the children to give them brainwashing science education.

She is still very young, and she has a long and full of possibilities in front of her.

Unlike now...

Not at all.

Lin Chaoxi came to his senses when his cell phone vibrated.

She turned on the screen and saw a WeChat message on it.

Xiao Liu——[My father knows the director of the Department of Neurology at the Sixth Hospital. Let’s have dinner together tomorrow. I will introduce him to you.]

Holding the phone tightly, she raised her curtains and took a deep breath.

In front of her was a wooden door panel. She bent down, picked up the chalk on the ground, took a step forward, and wrote down the first formula that Lao Lin had casually written on the wall that year.

E=MC2 (square)