Even though I doubt this is real, I'll still warn everyone that this is a spoiler/theory about what One Piece actually is, meaning the end. It's floating on the web, I find it pretty suspect because there are holes in it ( many ) but w/e.
Here it is.
CRAZY SPOILER ALERT ABOUT THE ENDING OF SERIES YOU HAVE BEEN WARNED DO NOT READ ON IF YOU DONT WANT ENTIRE SERIES SPOILED A korean friend of mind has found an obscure web blog that he was kind enough to translate for me that basically outlines the entire ending of onepiece. Be warned that this is a major spoiler. I have cross referencing a lot of the information and it seems to be dead on
THIS IS THE LAST WARNING SPOLIERS AHEAD
Once there was a kingdom on the moon that had advance science technology and it's name was birka(idk if it's spelled right for the english ver. of onepiece but its how it's pernounced in korean). The people of beerka could make robots and dials(the things that they use in sky...pia). However, they migrate to the blue planet because they run out of resources.(the blue planet is earth, and if you see the comic cuts with enel in it when he goes to the moon, you can see wrtings that say people of birka migrated to the blue planet because of lack of resources.) The ship schematic that the people of beerka used to migrate is probably the one that Tom(franky's dad) had.
When the people from the moon(birka) came down to earth, they accepted everyone to join and use their technology in peace and soon developed into a huge kingdom. However, a secret organization wanted to take the power and authority of the ...birka for themselves and started a war. So the birka developed two weapons to win the war.
The weapons are named pluton and poseidon.(idk if the english ver. uses the same names for the weapons but these two weapons are mentioned several times during the comic) Pluton runs underneath the ocean floor to change the tides of the sea to make a shield against enemy ships. Later on, the trace of pluton's drilling underground builds up due to undersea volcano eruptions and becomes the "red line". Furthermore, the cambelt and the grandlne are formed which devided the ocean into four.
Poseidon is a cannon made from fairy bass.(sand from the moon) The sand from the moon has a tendency of coagulating sea water and the solid form of sea water made from the moon sand was used as the cannon ball. Later on, the cannon balls that were used during the war sank into the ocean floor and became ores called seastones.(the stones that devil fruit users are weak against)
even with these extraordinary weapons, the people from the moon lose the war after 100 years of fighting. They conceal the two weapons(pluton and poseidon) so the secret organization can't use it for themselves. The survivers of the people of the moon hide away from the secret organization and take the shape of a half moon 'D' to use as their middle name.(explains Monkey 'D' Luffy, Portgas 'D' Ace, Gol 'D' Roger and so on.)
The secret organization that betrayed and destroyed the people of the moon name themselves "World Government" and start a project to hide their wrongdoings. 1. They erase the 100 years of history of the War.(the 100 years of history that Robin wants to find) 2. They send 20 soldiers to the moon to erase any trace or evidence of the people of the moon.(The 20 soldiers that were sent to the moon are later called World Nobles and their offspring are treated like Kings. This also explains why World Nobles always wear space suits.)
The Survivors of the people of the moon make a small island called rapeutel so that the secret organization can't find them. 'One Piece' is in this iseland and Gol 'D' Roger was the only person to find the Iseland. The reason that Luffy, Ace, Roger, and Blackbeard are not on the Island even when they're all D's is because the people of the moon wanted the world to know the evil deeds done by the World Government. They made Poneglyph's(bits and parts of the 100 years of history) and placed it all around the world and sent out a selected number of their own people(D's) to find it and let the world know the truth. The Birka's(people of the moon) make one final secret weapon while they are on the island of Rapeutel. This weapon's ability is to take the four seperate seas that were devided by Pluton, and turn it back in to one Huge ocean(aka. all blue(the ocean sanji always dreams of)). Because it's ability is to turn four sea's in to one, the weapon is called "One Piece".