51: Chapter 51 A Loose Screw

On the fifty-third day, Jiang Lin solved part of the vector potential problem.

That afternoon, the sky of the Wasteland was pressed very low by thick grayish-yellow clouds, and even the wind carried a trace of rust.

He had just finished filing the practice piece numbered 008, and his right arm was so sore he could barely lift it.

After resting for a while, he wiped the powder off the surface of piece 008 with a cloth, then picked up the 90-degree knife-edge square and leaned it against the light of the camping lamp.

The light gap became extremely microscopic.

He took out the feeler gauge and probed bit by bit.

The 0.01 mm blade could not go in.

Strictly speaking, under his current conditions, if the 0.01 mm feeler gauge could not enter, it could only mean that the light gap was less than 0.01 mm.

It might be 0.009, or it might be 0.006, or even perhaps just an illusion created jointly by the knife-edge of the square, the oil film on the workpiece surface, and the lighting angle.

Therefore, he changed the square to three different angles, rechecked it three times in succession, and turned the workpiece around to lean the square against it again. After confirming that it was not a misjudgment caused by his hand being crooked or the lighting angle, he wrote in his logbook:

"Sample No. 008: The middle bulge is less than 0.01 mm under the current conditions of square light transmission and rough feeler gauge inspection. Achieved this set target for the first time."

After writing this line, he placed piece No. 008 side by side with piece No. 007 completed a few days ago.

The advantage of No. 007 was that the left-right direction error was well controlled, but the problem of the middle bulge had not yet been completely suppressed.

The middle bulge of No. 008 had indeed been suppressed within the 0.01 mm red line of the current rough inspection system, but when he checked it with oblique light just now, he keenly discovered that in a certain area on the edge of the workpiece, a file mark had a darker color.

This file mark was nothing at all in the eyes of an ordinary person.

But in the microscopic world of a bench worker, this was an alarm signal.

It showed that in the second half of the push-filing, the wrist pressure transfer was too fast, and the teeth tips bit away an extra shred of metal at that position in an instant.

Press down one end and the other pops up.

In order to suppress the middle bulge, the wrist movement deformed in another direction again.

After reflecting on it in his mind, he rested for a while, took out his phone, and clicked on the theoretical course video to be advanced today.

The content was electromagnetic induction, the law of Faraday.

The old professor on the screen held a half piece of chalk and deduced unhurriedly on the blackboard.

As the magnetic flux changed with time, it would stimulate an induced electromotive force in space.

When general college Physics was taught here, it often ended by drawing a coil and applying a formula.

But this was Electrodynamics.

In his blackboard writing, the professor began to write the real electric field in space as a combination of scalar potential and vector potential.

Jiang Lin took the handwriting tablet and followed step by step to deduce downward.

In an electrostatic field, the electric field was simply the negative gradient of the electric potential.

Things were very simple.

The electric potential was like a slope, and the electric field was like the slope gradient.

But in a time-varying electromagnetic field, everything changed.

According to the differential form of the law of electromagnetic induction by Faraday, combined with the fact that the magnetic field could be written as the curl of the vector potential, the partial derivative of vector potential A with respect to time grandly squeezed into the electric field expression.

E = - ∇ φ - ∂ A / ∂ t

The ghost variable A, it was back again.

This time, it no longer hid behind the scenes merely as a convenient tool for calculating the magnetic field B.

It jumped directly from behind the scenes to the front stage, openly entering the electric field expression that determined the force on charged particles.

Jiang Lin held his pen and stared at that term on the paper for a full half-minute.

The video was still playing.

The professor began to explain the core logic of gauge transformation.

The scalar potential and vector potential could change hand in hand simultaneously; you add the gradient of a certain scalar function to A, and at the same time make corresponding time-term corrections to the electric potential. As long as the transformation rules matched, the final calculated real electric field E and real magnetic field B remained unchanged.

Physics laws were immune under gauge transformation.

Jiang Lin reached out his finger and tapped pause on the screen.

The old professor was frozen in front of the blackboard.

In the Stone House, only the faint current sound emitted by the old inverter in the corner remained.

He turned around, rummaged through the desktop, and pulled out the draft paper full of confusion from a few days ago.

On it strikingly was written his past obsession.

"If A is not unique, is it ultimately a physical entity?"

When he wrote this sentence at that time, it was followed by several big question marks below.

Now, those question marks were still there.

But their positions had changed.

No longer a mess blocking his chest, they had turned into a certain question with a sense of direction.

He reopened his logbook, picked up his pen, and began to sort things out.

"Fact One: The value of vector potential A is not unique, and a gauge degree of freedom exists."

"Fact Two: The truly measurable electric field E and magnetic field B do not change with gauge transformation."

"Fact Three: In the classical macroscopic Physics world, what instruments directly measure are E and B, rather than A under a certain gauge."

"Old problem criticism: I have always asked which A is truly real before. This question itself was asked incorrectly. The Physics world does not care which gauge I choose."

"New problem establishment: The correct question should be — within this gauge framework that can change expressions, what structure remains unchanged?"

When writing about what structure remains unchanged, the somewhat hunched back of Jiang Lin involuntarily straightened up a bit.

This phrasing was much clearer than his previous entanglement over whether it was real or illusory.

The floodgates of memory were pushed open by a crack.

In those unbearable years of the fourth Wasteland, when he was hard-chewing through advanced parts of Quantum Mechanics, he had once seen a bizarre experimental phenomenon in a textbook.

The Aharonov-Bohm effect.

At that time, he had only roughly seen this term.

In his mind, there was roughly an image of an electron beam bypassing an energized solenoid and producing shifting interference fringes, but he had never systematically learned the mathematical derivation behind it.

Jiang Lin at that time was being tortured to death by angular momentum commutation relations, spin matrices, symmetry of identical particles, and complex scattering theory.

When seeing the A-B effect, he only numbly wrote a sentence on the edge of his concept notebook.

"Too convoluted, I will look at it later."

Now, it wound back from the path of Electrodynamics, blocking the mandatory path of his cognitive upgrade.

Jiang Lin exited the video and opened the supplementary lecture notes folder downloaded in advance on his phone.

He found the paragraph about the A-B effect and read it word by word.

The description in the lecture notes was ruthless and shocking.

In a special experimental setup, the energized solenoid was shielded.

The electron beam was divided into two paths, bypassing the magnetic-field-free region outside the solenoid, and then recombining.

In the region passed by the electrons, the magnetic field B could be strictly zero.

There was no magnetic field force to pull on them.

But the interference fringes shifted.

The electrons seemed to know that there was magnetic flux in that shielded region in the middle.

The reason was related to the vector potential.

Outside the solenoid, B was zero, but A was non-zero.

Jiang Lin looked at the lecture notes, and his breathing became slightly heavier.

But what the lecture notes said next was like a basin of cold water extinguishing the fanaticism that had just risen in him.

Even in the A-B effect, it was not that A under a certain specific gauge was directly read out by instruments.

Nor was it to say that a certain A chosen artificially by you suddenly possessed independent material entity significance.

What the experiment actually observed was the phase shift of the electron interference fringes.

And this phase difference was proportional to the vector potential circulation along the closed path.

According to the theorem of Stokes, this closed-path circulation was related to the magnetic flux within the region enclosed by the path.

What was truly observable was not the specific value of A under a certain gauge.

Instead, it was the phase difference that did not change no matter how you changed the gauge, the gauge invariant, and the magnetic flux structure enclosed by the closed path.

Jiang Lin stared at the screen for a long time.

Then he picked up the red marker, turned to yesterday's log page, and vigorously crossed out a false deduction that had flashed through his mind and been written down.

That sentence was: "At the quantum level, particles can truly feel A itself, so A is real matter."

Now he knew that this sentence was too crude, even dangerous.

A indeed entered the Schrödinger equation of Quantum Mechanics and would change the phase structure of the electron wave function.

However, A itself was still affected by gauge selection.

It was still a masked ghost.

You could not directly treat something deformable in mathematical expression as a tangible reality in the Physics world.

In the Stone House, the slightly warm-yellow light of the camping lamp quietly fell on the paper covered with handwriting.

Because the phone screen had not been touched for a long time, its brightness dimmed and it entered power-saving mode.

Jiang Lin leaned over the stone table, feeling the subtle changes of something in his brain.

When some hard ice in cognition loosened, it was not like what was played in movies, accompanied by the protagonist's roar, and then all puzzles were solved instantly, with the light of truth illuminating the earth.

Jiang Lin picked up his pen and wrote at the end of the summary.

"Vector potential problem assessment: Find a new underlying entrance."

"Classical side perspective: A is an advanced potential function describing B and E, with innate gauge degrees of freedom."

"Quantum side perspective: A participates in the wave function phase structure, but the bottom line of physical observability must fall on the gauge invariant."

"Self-level positioning: Currently only understood the entrance of the grand concept. Cannot claim to master gauge field theory. Subsequently, in the advanced stage of Quantum Mechanics, must systematically re-deduce the full mathematical picture of the A-B effect."

The sentence "cannot claim to master gauge field theory" was very important to him.

Many people, including Jiang Lin in the past, when flipping through advanced theoretical books, would accidentally see an esoteric term, such as gauge invariance, covariant derivative, or fiber bundle, and generate an illusory sense of superiority, thinking they had touched the door of advanced theory.

And even taking a walk behind the door.

But in fact, not at all.

You had only walked to the end of a dead end and saw where the door carved with the name was.

You did not even know that behind the door was a long corridor full of complex mathematics and counter-intuitive Physics phenomena, and everywhere in the corridor were traps that could tear your cognition apart.

Recognizing personal position and not impersonating a genius was the first rule of survival in the Wasteland.

In the following days, life passed like a river without ripples.

Progress was steady, so steady as to be somewhat boring.

In terms of benchwork skills, the practice pieces No. 009 and No. 010 unexpectedly did not continue to refresh the score of No. 008.

Not only did they not refresh it, but regression even appeared.

The left-right directional error of piece No. 009 swaggeringly rose back up from around the excellent 0.01 mm of piece No. 007 previously.

The middle bulge problem of piece No. 010 also reared its head again.

The 0.01 mm feeler gauge could probe down into the light gap again at certain angles, and when the square was leaned against it, that bright line became dazzling again.

If one only looked at the data of these two individual pieces, this was simply like a painful step backward.

As if the muscle memory of the past few days had all been fed to dogs, and the hand feel had disappeared without a trace overnight.

If it were an apprentice with a violent temper, they might have already slammed the file onto the workbench.

But Jiang Lin did not smash his tools, nor did he delete the ugly records and pretend they did not exist.

He neatly lined up the four steel pieces 007, 008, 009, and 010 on one side of the workbench, like reviewing a team of defeated soldiers.

Then, in his logbook, he used a ruler to draw a crude but data-detailed table.

"Recent Sample Fluctuation Record Table"

"No. 007: Left-right direction well controlled, current rough inspection close to 0.01 mm; middle bulge still exists. State: Highly concentrated state of mind."

"No. 008: Middle bulge less than 0.01 mm; edge file marks slightly deep. State: Started trying pressure transfer."

"No. 009: Both indicators rose back up. State evaluation: Afternoon processing, physical overdraft after high-intensity land-turning, fatigue compensation appeared in shoulder and back muscle groups, movement deformation."

"No. 010: Middle bulge reared its head again. State evaluation: Impetuous mindset, suspected unstable control of downward pressure in the late stage of push-filing, eager for quick success leading to wasted prior efforts."

After writing the cause troubleshooting, he wrote the conclusion below the table:

"Qualitative analysis: This is not a complete retrogression of craftsmanship, but a normal state fluctuation of the human body as a biological machine."

"Principle: To evaluate whether a manual skill is stably established, one cannot just look at an occasional extraordinary performance. Trends require continuous observation of a sample group of at least ten pieces or more in order to filter out the noise brought by physical strength, mindset, and environment. Continue filing."

In terms of theoretical study, he logically advanced into the deep-water zone of electromagnetism — time-varying fields.

The complete form of Maxwells Equations finally made a grand debut in the textbook.

That displacement current term supplemented by Maxwell re-entered his field of vision, stitching the originally fragmented electric field and magnetic field into a truly closed structure.

Immediately after, the wave equation of electromagnetic waves in vacuum was neatly deduced from the curl operation of the equations.

This grand mathematical derivation had already been deduced by him in the early years of the fourth Wasteland using countless draft notebooks.

Now, walking through it again with a reset, young and clear brain, the calculation speed was indeed much faster.

Those vector differential identities that once made him scratch his ears and cheeks were now as natural as the multiplication table carved on his hands.

But fast speed did not mean the process was easy.

Sometimes when his state was good, he could follow the waterfall of formula logic and deduce a full three pages of formulas in one breath.

Sometimes, why an inconspicuous minus sign was there, what a curl equation ultimately meant under a specific coordinate system, or the choice of boundary conditions whether to take the normal or tangential direction when encountering a medium boundary, would also make him stop his pen and fall silent for half an hour.

The current Jiang Lin was no longer irritated by this kind of pause.

He had become like an experienced hunter.

Knowing that feeling blocked in a formula derivation chart usually indicated that under the ground of that knowledge point, something truly valuable was buried.

Days thus slipped to the seventieth day amidst the monotonous filing sounds and page-turning sounds.

On this day, Jiang Lin felt a massive and real exhaustion for the first time.

It was not simply fatigue at the bodily level.

Bodily fatigue was something Jiang Lin was too familiar with, one could even say it was an old friend.

The soreness of the waist muscles when turning over hard and dry farmland, the strap marks on his shoulders when transporting and filtering stones from a turbid riverbed a kilometer away, and the swelling pain in his forearms when drawing water bucket by bucket to irrigate crops.

Those sufferings were all concrete.

They have definite weight, sore spots, and solutions as well.

Eat another roasted potato, drink another sip of hot water, sleep in a sleeping bag for twelve hours, or cut the workload in half the next day.

As long as the calories keep up, a young body can always slowly repair itself.

But the fatigue of the seventieth day was completely unlike this.

This was a deep, systematic crash.

That afternoon, he sat in front of the crude desk as usual.

The phone screen was playing advanced applications of electromagnetic wave equations in time-varying fields.

The professor in the video was not lecturing poorly; the logic was clear, and the blackboard writing was still that reassuring regular script.

But Jiang Lin listened stubbornly for twenty minutes, and suddenly felt a wave of palpitation.

He found that surprisingly nothing was left in his brain.

The auditory nerves in his ears were indeed working, and the professor's voice truly reached his eardrums.

The retinas in his eyes were indeed receiving photons, and the formulas on the blackboard were crystal clear.

However, his brain had turned into a funnel with a hole at the bottom.

The previous Physics concept was just poured in, and before the next sentence was spoken, the previous one had already leaked completely through that hole.

He looked at E and B on the screen, feeling they were like two unfamiliar alien bugs, completely unable to connect them to electric and magnetic fields.

Jiang Lin irritably rubbed his face and reached out to pause the video.

The old professor's voice stopped abruptly.

The Stone House instantly quieted down.

Once the house quieted down, the sound of the wind outside became extremely clear.

The wind on the Wasteland had never stopped.

But when people were focused, the brain would automatically filter out this white noise.

Now, that sound of the wind seemed to be coming straight for him.

Following the imperfectly sealed gaps on the stone walls, it made a whistling sound like a whistle, desperately drilling into the room.

This sound of the wind seemed to be reminding him of a deliberately forgotten fact.

This was not a campus, but the Wasteland.

He was a lonely ghost who could only gain something by relying on time differences.

Jiang Lin closed his eyes and began to examine this state where his brain couldn't retain things like a bystander.

The last time this funnel state of completely losing learning ability occurred was when he was stubbornly tackling Quantum Mechanics.

That time, amidst fear and helplessness, by stopping to turn the soil and repair ditches, he fortuitously survived that hurdle.

And this time, on the seventieth day of the fifth Wasteland, relying on residual experience, he perceived the red alert of system overload in advance.

Decisively putting down the phone, he went out.

Outside was the long and desolate afternoon of the Wasteland.

The dark red skylight penetrated the thick clouds, obliquely splashing onto the vast and boundless earth, pulling Jiang Lin's lonely shadow extremely long, extending all the way into the distant ruins.

He wandered around without a destination.

Unconsciously, he walked to the edge of the farmland behind the house.

He squatted down, reached out his calloused and scratched hand, and grabbed a handful of mud.

As he continuously filled in domestic waste, plant ash, and treated compost, the organic matter in the soil was slowly accumulating.

The color also changed bit by bit from a lifeless yellowish-brown to a dark color.

Jiang Lin looked at the loose soil in his palm, knowing very well in his heart.

This plot of land didn't become better naturally through the Wasteland's mercy.

This was a vitality he forcibly snatched from nature with sweat, deep plowing after deep plowing, composting after composting, retaining seeds on the brink of crop failure after crop failure, and facing withered failure after failure.

Like the steel materials on the workbench, it was ground out through physical actions.

He patted off the mud on his hands, stood up, and slowly walked a circle along the ridges of the field.

He checked whether the furrows were filled by wind and sand, and looked at those few native plants transplanted back from the riverbed a while ago.

Those plants that were originally half-dead had already straightened their stems under his care, and tender buds with the greenness of life sprouted from the tips.

A moment later, he returned to the house, picked up the engineering shovel, and walked to the east side of the farmland to turn the soil and reclaim Wasteland.

Doing so until his sweat soaked his back and he was exhausted, the distant sun pressed close to the horizon like a big fireball about to go out.

On the seventy-first day, everything started anew.

When Jiang Lin sat in front of the desk again, turned on his phone, and clicked on the textbook, that sense of recovery arrived as scheduled.

The old professor in the video talking about the change in magnetic flux of time-varying fields turned back into clear Physics logic, flowing smoothly into his thinking.

The calculus derivation on the draft paper at hand could also keep up with the rhythm of the lecture notes.

Even in certain steps, he could anticipate the professor's next transformation in advance.

Yesterday's desperate state like a funnel where nothing could be held receded like a nightmare after a low fever.

This derivation started from the complete Maxwells Equations.

Under the assumption that there were no free charges and conduction currents in space, taking the curl on both sides of Faraday's Law simultaneously.

Using classical vector calculus identities, the first-order curl equation was transformed into a second-order partial differential wave equation describing the propagation of electric and magnetic fields in space.

This road had been walked by Jiang Lin before.

But walking it again this time, his footing was obviously steadier.

The formulas turned into physical language describing the oscillation and propagation of fields in space.

The derivation was exceptionally smooth.

However, when the course progressed to the energy propagation of electromagnetic waves, his pen hovered in mid-air again.

Several important Physics quantities appeared in the video.

Poynting vector, energy flux density, electromagnetic field energy density.

These expressions could be written down casually by Jiang Lin.

Electric field energy density, magnetic field energy density, electromagnetic waves in vacuum carry energy and momentum, propagating in space.

He was also clear about a counter-intuitive Physics proposition.

In many engineering situations, energy transmission is definitely not like a water flow, obediently flowing from the power source to the load along the inside of the wire.

That crude water pipe model could simply not explain high-frequency electromagnetism phenomena.

What truly carries energy is the invisible and untouchable spatial electromagnetic field around the wire.

In the fourth Wasteland, he even wrote a sentence he was very satisfied with at the time.

"The noon sunlight crosses 150 million kilometers to fall on the surface of the solar panel, and that massive energy is propagated silently in the vacuum electromagnetic field; photons excite charges, and the charges are separated in the depletion layer of the semiconductor PN junction; finally, those currents trickle along the rough copper lines into the storage battery, lighting up the dark night of this Wasteland."

From the perspective of classical Physics, this sentence is still correct even now.

But today, when Jiang Lin faced these energy formulas on the screen again, he suddenly discovered that deep inside his heart, a certain strong dissatisfaction arose toward this description.

On the phone screen, the professor was deriving the law of conservation of electromagnetic field energy, which was Poynting's theorem.

Starting from Maxwells Equations, the professor dot-multiplied the equation representing the electric field by the electric field, and dot-multiplied the equation representing the magnetic field by the magnetic field. Through tedious but rigorous vector algebra arrangement, he finally derived a beautiful local energy conservation equation.

This equation revealed the change in electromagnetic field energy density within the local space, plus the energy flux divergence flowing out of that region, corresponding to the work done by the electromagnetic field on the charged particles within the region.

This was a perfect expression of energy conservation.

Jiang Lin followed the professor, deriving step by step without a single error to the end.

Then, the pen tip stopped at those last few words.

"Field energy density."

He knew how to calculate and use them, and also knew that these formulas were extremely useful in engineering calculations.

But in his head, he frantically wanted to ask a question that was even somewhat nitpicking.

In what physical form was this energy stored in that seemingly empty vacuum after all?

Jiang Lin knew there was a risk in asking such a question.

When unsupported by experimental data, questioning in Physics could easily make one's feet slip, tumbling into empty ancient philosophical sophistry.

Therefore, he forcibly split this big question into several specific comparison groups.

"Case One: Spring potential energy. Energy is stored in the stretched spring because the spring undergoes macroscopic geometric deformation; the essence is the change in the interatomic interaction potential inside the metal lattice. The carrier is specific."

"Case Two: Capacitor energy storage. It can be calculated from charging and doing work by an external power source, or written as an integral of the space electric field energy density between the two plates."

"Case Three: Inductor coil energy storage. It can be calculated from the work required for the power source to resist self-induced electromotive force to establish current, or written as an integral of the space magnetic field energy."

"Case Four: Poynting's theorem. It is directly derived from Maxwells Equations and is the inevitable form of local energy conservation."

Writing up to here, Jiang Lin suddenly stopped.

If there was a question on the final exam paper asking about capacitor energy conversion, he could calculate it.

Asking about the energy flux density of electromagnetic waves emitted by an antenna, he could also calculate it.

Even asking about an ordinary wire with resistance, how the surrounding energy seeps into the interior of the wire from space to become Joule heat, he could also derive it clearly using the direction of the Poynting vector.

But what got stuck in his heart was not these surface calculation skills.

But another matter.

Fields were not springs.

In the empty vacuum universe, no visible and touchable steel wire was elongated, and no lattice deformed.

Then, is the so-called field storing energy a real attribute in the structure of the universe?

Or is it an extremely exquisite mathematical bookkeeping method written by physicists to maintain energy conservation, turning the fact that electromagnetic waves can transmit across vacuum and do work into equations?

Inside the classical Electrodynamics system, a self-consistent answer had already been given.

Fields carry energy and momentum.

But Jiang Lin faintly felt that this was not the end.

If he continued digging along field ontology, its veins would lead to relativistic field theory, to vacuum fluctuations, to creation and annihilation operators, and to quantum field theory.

And those behemoths were definitely not domains that the present him could touch relying on a few undergraduate textbooks.

Jiang Lin took a deep breath, forcibly suppressing the fanaticism of wanting to get to the bottom of it.

In information islands like the Wasteland that severely lacked external calibration, the easiest mistake to make was that a basic concept suddenly loosened, generating inspiration.

Thus acquiring a false sense of omnipotence, thinking that he could take advantage of the momentum to advance triumphantly and rush directly into a deeper and more grand ultimate theory.

Without a solid mathematical map, rigorous academic training, and high-precision experimental data to calibrate the direction, rushing in rashly would most likely result in only one outcome.

Not only would you fail to find the truth, but you would also get lost in abstract dimensions, and in the end, you wouldn't even be able to tighten the most basic screws in the Real World well.

Time passed like the wind and sand of the Wasteland.

In the blink of an eye, the calendar turned to the ninetieth day.

Manual fitting training finally welcomed a new node in this long and boring tug-of-war.

That morning, Jiang Lin had just finished filing the practice piece numbered 012.

This piece of steel had been tortured on the bench vise for a full three days.

After taking it down, as usual, he began that cumbersome inspection process bordering on obsessive-compulsive disorder.

First, using an oil-stained square, he repeatedly pressed it against the horizontal, vertical, and diagonal directions to check for light leakage.

Next, using a vernier caliper at the four corners and the center position, he rechecked whether the overall thickness decreased in parallel.

Finally, lifting the workpiece, facing the dimly slanting skylight, he squinted to check the direction and depth of the surface filing marks.

He no longer wrote 0.008, nor did he write 0.007.

Those pretty numbers had no meaning under the current tool conditions.

The only thing he could confirm was that in the current crude set of square light transmission and feeler gauge inspection systems, the left-right directional error of part No. 012 no longer allowed the 0.01 mm feeler gauge to smoothly probe in.

The surface shape error of the bulge in the middle was also pressed within this red line.

This was the first time.

Two core indicators that had always constrained each other were, for the first time on the same piece of steel, simultaneously pressed to within 0.01 mm of the current rough inspection system.

Of course, Jiang Lin knew as clearly as a mirror in his heart that this was not any industrial-grade strict flatness.

It was merely an estimated value of local light transmission.

If a dial indicator swept around it, this piece No. 012 that made him proud would most likely still expose a bunch of potholed microscopic fluctuations.

He picked up part No. 012 and placed it at the very back of the previous eleven practice pieces.

Looking at these twelve pieces of iron, Jiang Lin felt an unprecedented sense of down-to-earth stability in his heart.

This was the most authentic phased achievement in Wasteland survival.

It was ten thousand times more real and ten thousand times more powerful than the empty phrase "I finally understand the mysteries of Electrodynamics".

Because these twelve pieces of iron were placed right here, the error data could be rechecked, and the light gaps could be re-inspected.

Physical facts were indisputable.

That night, the sound of the wind outside diminished a little.

Sitting under the low-voltage lamp, Jiang Lin made a general conclusion of all today's records and wrote them into that thick general Wasteland survival log.

At the end of the diary, he put forward two core questions for himself for the next stage.

"Core dilemma of the next stage:"

"In the hands: How to turn a single piece occasionally meeting the standard into continuous samples stably meeting the standard?"

"On paper: How to turn the smoothly derived electromagnetic wave equations in a vacuum into real electromagnetic field tools capable of handling complex media, rough boundaries, and non-ideal structures in the Wasteland reality?"

One question grew on both hands, and one question was printed on the draft paper.

Seemingly unrelated.

But at the lowest level, these two difficult problems actually looked the same.

Solving them did not rely on a flash of insight one night or knowing a final standard answer to end the battle.

They both required the same cruel quality.

You must endure your temper amidst the realistic constraints full of noise, friction, fatigue, and non-ideal states, starting over time and time again, and calibrating the sights leading to correctness amidst failures over and over again.

Closing the logbook, Jiang Lin turned off the camping lamp.

In the dark Stone House, listening to the desolate sound of the wind outside, he calmly closed his eyes.

Tomorrow the sun would rise as usual.

And his file would continue to push forward.