Once Upon in Nanjing-Chapter 20 - 7 Tritium Tube

What's a half-life?

The half-life is the time it takes for half of the atomic nuclei of a radioactive element to decay. Using the half-life of the radioactive isotope carbon-14 to determine historical ages is a common research method in archaeology—just by measuring the decay content of the radioactive elements, one can figure out the age of the target object.

It sounds pretty high-end and seems to have no connection to the everyday life of ordinary people, let alone to Bai Yang, an ordinary high school student. We common folks live our lives honestly—what relationship could we possibly have with radioactive isotopes? And what connection could we have with half-life?

Actually, you can. Please raise your left hand.

Roll up your sleeve.

Look at the dial of your watch in the dark—if you're an old lech... gentleman, owning an old-fashioned luminescent watch, then its dial is coated with a common radioactive isotope.

Tritium.

Bai Yang isn't even sleeping anymore; he immediately gets up from the bed and takes out his phone to open Taobao.

With the almighty Taobao, there's nothing you can't buy.

Tritium tubes!

Tritium tubes are a common type of luminescent tube, completely sealed in glass, small ones a few millimeters long, large ones a couple of centimeters. The inner wall of the glass is coated with phosphorescent powder, and the tube is filled with the radioactive isotope of hydrogen, tritium. The rarefied tritium gas is weakly radioactive, exciting the phosphorescent powder to glow. This substance is commonly used in luminescent watches, military compasses, and the sights of firearms, and sometimes even fishing enthusiasts in the air force use it for float indicators.

The half-life of tritium is twelve years, meaning a clump of tritium will half die off in twelve years, the brightness of a tritium tube will decrease by half in twelve years, and approach extinguishing after twenty-four years.

The timing is just right!

It's perfect to use tritium tubes as time markers.

Bai Yang plans to buy two brand-new tritium tubes on Taobao, then find one that has been used for five years and one that has been used for ten years on Xianyu, two new and two old—but because none have reached their half-life, all four tritium tubes are still glowing, and to the naked eye, there isn't too much of a difference.

This is his plan:

Stick all four tritium tubes in a transparent plastic box with UV glue, arranged in the order of new, five-year, ten-year, new. When BG4MSR digs out the time capsule later, Bai Yang will have her find the time markers inside the capsule and ask her about the glowing condition of the tritium tubes—if all four tubes are glowing normally, with no difference from when he buried them, then it means the other party is talking nonsense.

All that talk of apocalypse and the year 2040, all crap.

If all four tritium tubes are nearly not glowing in the dark, then it proves the girl is telling the truth, and at least twenty years have indeed passed.

If the five-year or ten-year-old tritium tubes have extinguished, but the new tritium tubes are still glowing, then it would prove that BG4MSR is indeed living in the future, but she inaccurately estimated her own era.

Bai Yang believes there is no more solid and reliable evidence than this, this is so-called brute force over finesse, grasping the essence, directly seeking the truth, not getting into all those needlessly complicated and elaborate twists and turns. Even if the person were James Bond, 007, The Great Thief, with a thousand methods to stealthily dig out the time capsule from underground and see what's hidden inside before burying it back without anyone noticing, it could not change the glowing result of the tritium tubes.

And as long as he does not reveal ahead of time that it's a time-marker, does not reveal that they're tritium tubes, the other party will not possibly know what they are, let alone lie and deceive him.

Utilizing forces beyond human reach to verify, that's how all falsehoods and lies are precluded.

This is Bai Yang's method.

I've buried the tritium tubes here, bring it on!

No matter what tricks you use, no matter how you manipulate things, as soon as you open the lid and take a look, I will definitely know whether what you've said is true or false.

Place the order!

Thirty yuan each, I spent sixty yuan on two.

It's going to hurt so much again.

But Bai Yang is eager to try; as a high school student who has always followed a conventional route and studied hard, he seldom has the chance to do something so bold, absurd, and rebellious, yet Bai Yang is increasingly excited. His mundane life, bland as boiled water, was finally infiltrated by a hint of a different color. In novels and movies, this often marks the beginning of a grand adventure. He stayed awake until 3 a.m., his mind full of his plans, resulting in him oversleeping the next morning.

Ban Xia put down her headphones and hand mic, slowly lying face down on the desk.

What did he mean by that?

Can he provide me with evidence? Prove to me that this year is 2040?

But didn't he claim to live in 2019?

How could a person living twenty years in the past help me?

With her cheek pressed against the cold wooden desktop, her right elbow propped on the table, and an amulet hanging from her index finger swinging gently like a pendulum—that was the coin left by her teacher, with a hole punched through it and threaded with a red string, normally worn around her neck. Ban Xia's gaze followed the swaying coin back and forth, utterly baffled.

The chubby plastic desk lamp beside Ban Xia's head was the only source of light in the room. The girl's face was illuminated by the lamp, while her body sat in darkness. She liked to sit in the dark to think; the serene night allowing her brain to stay cool enough.

How could he cross twenty years to provide me with evidence?

Bury it? Hide it? And then wait for twenty years?

Ban Xia quickly thought of this possibility—the other party lived twenty years ago—assuming he really did live in the past (which Ban Xia herself did not believe, but she had no other choice), then he could dig a hole in that era, bury what he wanted to send in the soil, and inform her via radio, so she could dig it up.

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If she could find it, it would prove that all this was real.

He would know that she lives in 2040.

She could be sure that he lives in 2019.

It sounds wonderful.

Ban Xia stared at the red string and coin hanging from her finger. The coin gradually lost its kinetic energy from friction, its swinging amplitude decreasing more and more until it came to a stop and slowly spun around the hanging string, twisting it into a double helix.

This sounds reasonable, but her teacher once said that hearing and seeing are not the same, and seeing and doing are again different. To judge whether something is feasible, it's not enough to just use your ears; you must engage your ears, eyes, hands, and brain.

The girl's eyebrows slowly furrowed, and she felt slightly worried.

If the other party really intends to do this—to purposefully send something across the long span of twenty years into her hands, then it's probably not a simple task.

Once purpose is involved, obstacles naturally follow. The world always leads you inadvertently to a destination you don't want to reach while setting up multiple obstacles before the goal you aim for.

It's definitely—definitely—not as easy as imagined.