Abnormal crossing

Chapter 2: The Delinquent Youth
"3000 meters?"

When Gu Wei heard the number coming out of Sister Huang's mouth, he was stunned when he was about to screw the bottle cap back on.

Although his academic field is astrophysics, as an amateur writer, Gu Wei has some knowledge of some strange and bizarre knowledge.

If he remembered correctly, the deepest natural cave known on Earth was called Krubera Cave, located in the Arabika Mountains in the Gagra District of the Republic of Abkhazia, Georgia, which could be used as a test of your Mandarin proficiency.

The cave was discovered in 1960 and its deepest point was measured at 2012 meters in 2197. It is currently the only natural cave in the world that is over 2000 meters deep.

And if what Sister Huang said is true, then the title of the deepest natural cave on Earth will probably be given to this black pit.

How can I describe this feeling? It seems a little... casual?

After all, he is the world's number one.

Then Gu Wei glanced at the deep pit again and asked Sister Huang, "Sister Huang, is the 3000-meter data reliable? Is there any error caused by external factors?"

"It's at least 3000 meters." Sister Huang shook her head and corrected Gu Wei's statement: "It's actually quite strange. Other pits and holes are more or less curved, but the internal structure of this pit is almost straight down. It looks like a hollow cylinder."

"The stationmaster and his team first used a 905μm portable rangefinder to measure the depth. They couldn't receive any reflected signals when the laser was vertically aligned. However, when the angle was slightly offset so that the laser hit the pit wall, the data they received was over meters - any deeper would exceed the range of the rangefinder."

Gu Wei listened quietly and nodded thoughtfully: "So that's it."

Laser rangefinders are generally divided into pulse method and phase method. The measurable distance of the phase method is determined by the wavelength of the modulated light. It is generally shorter but very accurate. Even civilian products can be accurate to about half a millimeter.

The pulse law, in contrast, can measure objects at long distances, but with relatively limited accuracy.

The pulse rangefinder brought by Gu Wei and his team this time uses a non-civilian standard wavelength of 3270μm. The detection device is an APD, which is much more advanced than a photodiode. It is a component of a high-resolution terahertz photoacoustic imaging module and has a maximum theoretical measurement distance of more than 30 kilometers.

Glancing at the people tinkering with the equipment in the back, Gu Wei roughly guessed what Xia Shaoxing was thinking:
The Delingha Observatory has limited equipment for radio sources, and it is difficult to detect spectra. In this case, we might as well just measure the more common physical data such as the depth of the hole first, and then deal with the rest after the subsequent reinforcements arrive.

There is nothing wrong with the plan, otherwise it would be unreasonable if I didn't even know how deep the pit was when reporting to my superiors.

More than ten minutes later.

The debugged pulse rangefinder was moved to the edge of the cave entrance. Xia Shaoxing looked around and casually said to Gu Wei: "Xiao Gu, Xiao Tian, you two come and help, just hold the two ends of the pole."

The laser transmitter of the rangefinder is a silver rectangle that looks like a supermarket surveillance camera. Since it needs to detect vertically downward, Xia Shaoxing and others fixed it in the middle of a stick more than three meters long.

This way, the transmitter can measure directly downward from the center by simply placing the stick across the hole.

There were professionals in charge of the rangefinder's operating table, and the others also had their own tasks, so Gu Wei and Tian Ye each held one side of the pole and acted as tools.

The launcher is very light and the pole position is fixed in less than a minute.

Xia Shaoxing turned around and talked to the technician at the operating table for a few words, then turned to Gu Wei and said, "Xiao Gu, you stay there for now. We may have to change positions later. Xiao Tian, come over and move another piece of equipment."

Tian Ye rolled up his sleeves and walked back: "Okay!"

Once everything is ready, the device starts up quickly.

call out--

A detection laser shot out quickly from the front end of the transmitter and fell straight towards the pit.

A few seconds passed.

The technician at the operating table suddenly exclaimed: "Huh? This is impossible?"

Xia Shaoxing came to him quickly: "Xiao Zhang, what's wrong?"

The technician named Xiao Zhang looked up at him and pointed at the screen and said, "Look at this."

Xia Shaoxing turned his head and saw that at this moment, the operation screen displayed an English message:
infinity.

The word literally means infinite, but in the context of distance measurement, it has another meaning:
The target's distance exceeds the detection limit.

But you have to know that the theoretical maximum value of this rangefinder is as high as 30 kilometers!

The deepest hole dug by humans on the surface so far is the Kola Superdeep Borehole, which is only 12262 meters deep.

12262 m.

30km+.

These two numbers are no longer in the same range, the difference is three times!
Then Xia Shaoxing suddenly thought of something and asked quickly, "Could it be the air or dust that caused the effect? You know, the distribution of atmospheric refractive index in vertical space is extremely uneven. Would it affect the optical path? - For example, the laser was blocked by dust a few hundred meters underground, but because there was no reflection, we don't know?"

Xiao Zhang shook his head with a bitter look on his face, pointed to another slightly smaller page and said, "Stationmaster, take a look at this - this is the ranging interface of the secondary transmitter. It has a dynamic angle with the primary transmitter, that is, when the laser of the primary transmitter is pointing vertically downward, the light of the secondary transmitter is offset and will reflect off the pit wall at a certain position, and then feed the information back to the receiver."

"According to the detection results of the secondary transmitter, the reflection point is approximately ."

"22 kilometers."

After Xiao Zhang finished speaking, one could hear a pin drop.

A pit that emits pulse signals and is more than 30 kilometers deep.
How horrifying.

另外
With such a straight internal structure, is it really formed naturally?

However, the silence did not last long. It was broken by the operator of another device not far away: "Stationmaster, there is a situation! The reading of the gravity gradiometer is abnormal! - There are some changes at the bottom of the pit!"

Xia Shaoxing frowned, walked a few steps to the operating table of the gravity gradient instrument, and said in a more serious tone than before: "What's the situation?"

The AGRVC atomic gravimeter is the most sophisticated equipment in the observatory. It works with ultra-cold chain rubidium atoms and can be used to detect short waves, that is, fast-changing gravity fields in space.

This device has been monitoring the conditions in the pit since yesterday, and the readings have always been stable - it should be said that in today's fixed surface area, this thing cannot be unstable.

However, at this moment, this device, which should theoretically be the most "dead" in the entire scene, actually showed an abnormality?

The operator typed on the keyboard a few times, his forehead covered with sweat. "The vertical △Φ curve is rising, and there is a 170E gradient signal jumping back and forth around meters. It looks like..."

"Like what?"

Gulu.

The operator swallowed hard. "Like... a whirlpool."

The voice just fell.

Not far from the pit.

The ground near the pit mouth suddenly began to shake violently.

Gu Wei, who was closest to the pit entrance, reacted quickly and subconsciously wanted to escape from the area.

However, just as he turned around, he felt a huge suction force under his feet, pulling him to the bottom of the pit.

As the world spun around, Gu Wei used all his strength to pull the dirt at the mouth of the pit, and instinctively yelled out a sentence, and then he fell to the bottom of the pit:

"Lao Tian, tell my brother to take good care of my parents, and also--"

“Smashed my computer and tablet!!!”

(End of this chapter)