Ohara is known as the Island of History and the Island of Knowledge, boasting an endless collection of books, though the former name is more famous. The island's scholars are predominantly historians.
Sig had initially wondered why Oden went to Ohara. Ohara might have been good for deciphering Ancient Script, but that didn't compare to Oden's legacy.
However, it now seems that they went to Ohara not for historical knowledge, but for... astronomical knowledge!
Due to "strange refraction," the three islands seen from the moon are not their actual geographical locations.
Not to mention that Bilca is a moving Sky Island, and its location can only be indicated when its position is within three points and the "Hiyori" phenomenon is also present.
In summary, this is an "astronomical problem," and with sufficient astronomical knowledge, it should be possible to calculate it.
Although the Hiyori usually occurs every one or two years, Roger clearly wouldn't be able to wait for the next one, and even if he did, he wouldn't be able to see "Skypiea's Lights." He could only determine the final location through astronomical calculations...
On the high seas, Ohara is known as the "Demon Island," and the general public only knows that scholars there conducted research against the World Government.
Only a small minority understood that they were destroyed by the World Government, which feared the exposure of the "Void Century," because they were pursuing history.
However, Sig is now beginning to wonder if it really is because of "history"...
The one who directly issued the Buster Call was that fool Spandine; the order he received was to forbid Ohara from having any further contact with history.
Searching for the Void Century is naturally considered one of the original sins by World Government.
However, just like in the original work, Spandam, CP9, and even CP0 always believed that the reason for hunting Robin was "Pluton," without knowing that what the World Government actually feared was her ability to decipher the Poneglyph...
Could the destruction of Ohara because of its historical research be merely a superficial excuse?
What the World Government actually fears more is that Roger once used the astronomical knowledge there to calculate some kind of result?
After all, the Ohara Incident occurred less than a year after Roger's execution...
In this way, what Sig needed became clearer—the astronomical data of Ohara!
The image that Sig simulated in his dream was just his imagination. In reality, the angle that can be seen from the moon, the cycle of "Hiyori" and the overlap with the cycle of "Bilca appearing within the reflection of the three points" all require more astronomical knowledge to calculate.
I wonder if this knowledge is also in Robin's mind...
Sig could only hope that Robin was an "all-around genius," since after the Buster Call, Robin's memories were of the last Ohara.
You don't even need to actually remember her; just having seen her before is enough. Once Sig becomes Sequence 5 "Dreamwalker," you can try to awaken Robin's memories in her dreams.
However, if he didn't watch it at all, there's nothing Sig can do.
"It seems we still need to find the survivors of Ohara..." Sig snapped his fingers, and the dream vanished.
"Yawn... Not bad, you still have some adventures to take. Don't look so reluctant, I'd like to switch with you." Yamato a yawn.
Sig rolled his eyes; he would have preferred someone to "spoil" the plot for him.
However, Sig now even doubts whether anyone knows Laugh Tale's exact location— Bilca is moving, so does it mean that the two coincide at the same position every time there's a "Hiyori," or that Laugh Tale is also moving, Bilca is tracking it across half of Earth?
Roger's crew was quite large, and despite their frivolous nature, when they encountered the protagonist, they would ask, "Do you want me to tell you where Laugh Tale is?" one day and tease him the next with, "Laugh Tale? Actually, it's right here..." However, no matter what they said, the location of Laugh Tale was never revealed!
"It's not just Nico Robin... After that, let Inuarashi and Nekomamushi leave first. I'll stay in Wano Country and try to make contact with someone!" Sig said, a thoughtful look on his face, but he finally made his decision.
If it's confirmed to be related to "astronomy" and the moon, Sig will have other clues.
Firstly, there's the weather island of "Visalia," which has many meteorologists. At first glance, "weather" might seem unrelated to astronomy, but it's actually closely related to "atmospheric refraction." If we can decipher this aspect, Sig can simulate things more realistically.
Secondly, there's the option of going directly to the moon. Roger only needed to use his knowledge to deduce the truth because he didn't have enough lifespan left; otherwise, the "Hiyori" phenomenon would occur every year or so. Going directly to the Moon and observing it would allow them to locate the "lightless" Bilca, which would be the most effective way to decipher the mystery.
Thirdly... that is, the descendant of the lunar visitors that Sig wanted to find afterward, and unlike the Sky Island Sky Island person who lost their civilization, he inherited the special characteristics of the Moon person, and may know some secrets... Jhin!
King is a descendant of the Lunarian who was rescued from prison when Kaido was being studied by the World Government, and was also used as research material.
This race once lived on the Red Line Continent and were called "gods"—they are highly likely to have come from the moon.
Now that we understand that we might need to look from the Moon, Sig should go find Ember first; it's never a bad idea.
The only thing to consider is...
King is very loyal to Kaido and might even turn against Sig and fight him!
Sig didn't intend to involve Yamato Wano Country either, and Jin really didn't want to reveal anything; he could simply run away if necessary.
The first two clues, the one about the weather island of Visalia, may not be useful, but it is relatively easy to find. It's like a clue lying around, so there's no reason not to take a look.
Going to the moon would definitely be useful, and unlike Sig and Roger, they weren't in a rush and could Hiyori and the cycle.
Judging from Oden's Wife's strong urging of Oden to go to Laugh Tale with Roger, "finding Laugh Tale" and "the prophecy of destroying the World Government after eight hundred years" should not be completed simultaneously. The former should be earlier than the latter, or even a directional preliminary action.
So the most optimistic estimate is that we can see the results every Hiyori and cycle. The most pessimistic estimate is that it will definitely not take eight hundred years. The only two things that need to be worried about are how to get to the moon, and... how to make Bilca shine so that it can be seen!
This is the normal way to solve the mystery of Laugh Tale; there are no shortcuts, and there's no need to worry about wasting effort.
Sig plans to try King first, then Savile, and if that doesn't work, he'll try Nico Robin. If he can't find her, or if Robin doesn't understand astronomy, then he'll have to honestly try to get to the moon— Enel in the original work was able to get to the moon, Sig isn't without options...