Chapter 859: The Secret of King Qin's Bone-Reflecting Mirror

"Linear algebra?" Zhao Ruizhi furrowed his brow, too preoccupied to be angry. He was wondering what kind of divine secret manual this was and why he had never heard of it.

Not just him, even Mi Li, who had read all the books in the Qin Royal Library, was completely bewildered. "What in the world is linear algebra? Why don't I know about it?" she wondered.

Only Bi Linglong seemed thoughtful. She recalled her previous investigations into Zu'an; wasn't he an arithmetic teacher at Bright Moon Academy? And when he had visited the National Academy, even those normally haughty teachers from the back mountain had been deeply impressed by his profound knowledge. It seemed likely that this "linear algebra" was just one more of his many abilities.

Zu'an confirmed the inscription with Zhao Ruizhi again, muttering to himself, "'Dark clouds facing the heavenly gate' describes our ascent to the island earlier..."

However, the subsequent phrases involved ancient astrology, which Zu'an wasn't too familiar with. Fortunately, he had a living encyclopedia by his side.

He quickly asked Mi Li, who then roughly explained the secret within the inscription.

The Heavenly Gate referred to the Horn Constellation (Jiao Su), one of the Twenty-Eight Mansions. "Heavenly Sun" naturally meant the sun. Historically, "Golden Palace" generally referred to the celestial palace where gods resided, and in ancient astrology, the Purple Forbidden Enclosure corresponded to the dwelling of the heavens.

Ancient astrology divided the sky into Three Enclosures and Twenty-Eight Mansions. The Three Enclosures were three vast star fields directly overhead, each containing numerous constellations and stars, known as the Purple Forbidden Enclosure, the Supreme Palace Enclosure, and the Heavenly Market Enclosure.

The constellations near the ecliptic were then divided into twenty-eight regions, called the Twenty-Eight Mansions. These mansions were grouped into fours, with seven mansions in each group, corresponding to the Four Symbols: Azure Dragon (East), Vermilion Bird (South), White Tiger (West), and Black Tortoise (North).

"Southern Star" likely referred to the Southern Dipper, the Dipper Mansion among the northern seven mansions. "Jade Weight" probably meant the Yuheng star of the Big Dipper. For the Southern Star to revolve around the Big Dipper was astronomically impossible under normal circumstances, which was why the emperor had been so desperate. However, since this stone slab array corresponded to the starry sky, they only needed to align the respective symbols; there was no need to actually manipulate the stars.

"Canopy aligning with Purple" meant the Canopy Star of the Purple Forbidden Enclosure, and "Purple" referred to the Ziwei Emperor Star.

"Elegant Sound entering Zheng." In ancient times, "Elegant Sound" referred to the Xia sound, and as the Xia people were descendants of Xuanyuan, it likely indicated the Xuanyuan Star among the mansions. "Zheng," on the other hand, referred to the Zheng Star in the Heavenly Market Enclosure.

With Mi Li's help, Zu'an quickly deciphered the secrets within the inscription. All that remained was to align the corresponding constellations.

This mechanism, where moving one pillar affected several others, could be brute-forced if it were simple. However, with the complex correlations described in the inscription, random attempts would clearly be futile.

Although these ancient mechanisms were intricate, they should not be difficult for someone with a university education; it was essentially an applied linear algebra problem.

He first ordered each pillar. When the first pillar was rotated, he recorded how many times the other corresponding pillars turned. For example, if the second pillar didn't turn, it was recorded as 0; if the third turned once, it was 1; if the fourth turned twice, it was 2, and so on. This could be represented as d1 = [1, 0, 1, 2...]ᵀ.

Then, if the first pillar was rotated X1 times, the state of the pillars would become X1 * d1.

If the second pillar was rotated X2 times, its state would become X2 * d2.

Following this pattern, the final state of the pillars would be X1 * d1 + X2 * d2 + X3 * d3 + ... = b.

Here, 'b' was a definite constant, as the initial inscription information determined which patterns corresponded, allowing him to ascertain how many rotations each pillar had completed compared to its starting position.

This was equivalent to solving a non-homogeneous system of linear equations to find X1, X2, X3..., which would indicate how many times each corresponding pillar needed to be rotated to achieve the state described in the inscription.

Zhao Ruizhi watched Zu'an drawing symbols on the ground that he had never seen before; it was completely incomprehensible to him, like reading a celestial script.

He couldn't help but secretly glance at the others, and seeing the bewildered, almost idiotic expressions on Bi Linglong, He Li, and the rest, his exploding frustration immediately calmed considerably.

A moment later, He Li, standing nearby, also couldn't resist a covert look at Zhao Ruizhi. He saw Zhao Ruizhi nodding slightly and continuously as he watched Zu'an draw those "ghostly scribbles," seemingly engrossed. He couldn't help but admire him, thinking, "The Emperor truly lives up to his title; he can even understand this!"

After a while, Zu'an finally stood up. "All done!" he announced.

He then approached the array of stone slabs, recalling the answers he had just calculated, and rotated the corresponding pillars a few times each.

Sure enough, after he rotated them in that sequence, all the patterns aligned perfectly!

Immediately, a rumbling sound emanated from below; clearly, the mechanism had begun to operate.

The entire stone slab array suddenly emitted a glow. The light swiftly ascended, and all the luminous pearls previously placed in the holes lit up.

A beam of light passed between the luminous pearls, finally striking a specific spot on the stone slab, a section that was noticeably tilted.

Yet, after a moment, nothing happened. Zhao Ruizhi frowned. "What's going on?"

He wasn't quick to assign blame, as previous indications suggested Zu'an's solution was correct. Was something still missing?

After thinking for a long time without any clue, he simply looked at Zu'an. As emperor, of course, he didn't need to handle everything himself; troublesome matters could be left to his subordinates.

Zu'an was also perplexed. Everything had gone smoothly, so why hadn't anything appeared?

At that moment, Mi Li's voice suddenly rang out: "Do you remember the last line of the stone tablet we found?"

"'The moon, as a noble person, enters the center...'" Zu'an murmured the phrase, noticing a slightly recessed groove on the stone slab where the light beam shone. The shape of the groove seemed to resemble a mirror.

His heart stirred. He pulled out the Qin King's Soul-Illuminating Mirror, which he had found earlier in the Azure Moon Dragon's treasure hoard. Sure enough, its shape matched perfectly.

After acquiring this mirror, Zu'an had tried various methods to activate it, but it had remained completely inert, like a lifeless object.

But at this very moment, as the beam of light struck the mirror, the long-dormant object suddenly flared with brilliant light, like a miniature sun, making it impossible to look at directly.

A bright beam of light shot out from the mirror's surface, soaring skyward and hitting an unknown spot on the third immortal island.

Then, something astonishing occurred: a bright yellow beam, over a zhang wide, slowly unrolled from the third immortal island.

Yes, it unrolled like a carpet, and before long, the light reached the second immortal island.

Immediately, another bright yellow beam unrolled from the second immortal island, directly towards their position, quickly embedding itself near the stone slab array and forming a transparent light bridge between the two islands.

Once the light bridge was formed, the bright glow from the luminous pearls on the stone slab slowly faded, and the Qin King's Soul-Illuminating Mirror also returned to its normal state.

Zu'an quickly put it away. This was clearly a treasure, and he couldn't bear to leave it there.

Zhao Ruizhi glanced at him, clearly realizing the mirror was extraordinary. He was about to snatch it and then eliminate Zu'an, but he immediately recalled what Zu'an had just said and witnessed his bizarre problem-solving skills. Thinking that this fellow was indeed adept at deciphering these mechanisms, he decided to wait. There might still be times when he would need Zu'an's help later.

Suppressing his murderous intent, he was the first to step onto the light bridge.

At first, he was cautious, but he soon discovered that although the light bridge looked transparent and daunting, it felt solid underfoot, with no risk of falling.

"Is this the method of immortals?" Zhao Ruizhi's gaze grew more fervent as he looked towards the distant palaces. He moved like a blur and quickly ascended to the second island.

Seeing this, He Li and the others hastily followed. After all, there might be immortal blessings ahead, and who wouldn't want a share?

Zu'an, however, inwardly lamented. He had just tried to close the light bridge to make the emperor fall to his death, but unfortunately, neither the pearls nor the pillars could be moved anymore; they seemed to be welded in place.

"Never mind, I'll find another opportunity later," Zu'an thought, then led Bi Linglong onto the light bridge.

Bi Linglong was utterly astonished throughout the journey, excitedly looking all around the light bridge.

Having seen such scenes countless times in various wuxia and xianxia TV shows and games in his previous life, Zu'an found nothing new in it.

He quietly pulled out the Qin King's Soul-Illuminating Mirror. It seemed to have been activated just now, but he wondered what its functions were.

Unfortunately, after examining it for half a day, it still looked ordinary, with no discernible difference.

"Was it just my imagination?" Zu'an frowned.

Just as he was about to put the mirror away, Bi Linglong suddenly came up to him. "What are you looking at?" she asked.

Zu'an was holding the mirror, and Bi Linglong stood behind it, looking at him quizzically.

Zu'an lowered his gaze to the mirror's surface, and two streams of nosebleed instantly gushed out.