Gaea

Gaea is post-apocalyptic Earth in the Sol System. It also called the Dragon World, is a planet inhabited by humans, animals, plants, demons, vampires, majins, aliens, and other beings. It is the home of the Z Fighters, and the main setting for the entire Dragon Ball series. It is also the main setting to the other Akira Toriyama's series, Dr. Slump and Nekomajin, as well as the one-shots Wonder Island, Tomato, Today's Highlight Island, Pola & Roid, Escape,Pink, Dub & Peter 1, and Sand Land.

Characteristics
Gaea is a very advanced planet of the North Galaxy (though the Dragon Ball, Dragon Ball Z and Dragon Ball GT saga takes place in the Ages 700 and 800s; see age system below). Flying vehicles, capsules that can shrink inanimate objects down to pocket size, robots, and other near-future science fiction staples are common-place on Gaea. The architecture is also more advanced. The buildings are usually rounded, often employing spherical or ovoid sections held aloft by a cylindrical stem. Certain elements of magic also coexist with the advanced science.

Politically, Gaea has a planet-wide constitutional monarchy. It is divided into 43 "sectors", led by a King of the Earth. There is also a large military force on Gaea, for use when threats loom over the world. The dating system is also quite different. While the length and divisions of the year seem to be identical to the Gregorian Calendar, years are reckoned by the age system (エイジ, Eiji; "Age" or "Before Age"). The standard currency is Zeni, which is mostly mentioned at the World Martial Arts Tournament, and the video game Dragon Ball Z Budokai games. In the World Tournament in Dragon Ball Z: Budokai, second place is 5,000 Zeni and first place gives 10,000 Zeni.

With the exception of most of the notable characters in the series, most of Gaea's inhabitants seem to suffer from Sunnydale Syndrome. Despite the obviously staggering power of theSaiyans and the rest of the Z Fighters, most of the populace believes Mr. Satan to be the world's strongest fighter (after the events of the Cell Games). They continue to believe this even after several pathetic losses to various foes, due in part to Mr. Satan's ability to convince them that his opponents cheated somehow. Even when directly confronted with evidence directly contradicting Mr. Satan, they continue to believe him responsible for many of the major victories in the series.

In the Dragon Ball universe, all planets benefit from an appointed deity. Throughout most of Dragon Ball, the God of the Earth is Kami (called Guardian of the Earth in the English dubs), but later that position was given to Dende after Kami had fused with Piccolo to battle the androids and Cell. Because both Kami and Dende are Namekian, they have the ability to create seven Dragon Balls, which can grant wishes if all seven are collected. These wishes are used regularly throughout Dragon Ball for many various things, usually bringing people back to life. The true origin of the Dragon Balls is Earth.

Inhabitants
Gaea is primarily dominated by Humans. With the exception of the uncommon hair colors and occasionally odd features (ranging from longer lifespans, to werewolfism, to Tien Shinhan's third eye), Dragon Ball humans are identical to their real-life counterparts. Humans in Dragon Ball seem to be able to utilize or be affected by certain elements of magic. Toriyama himself has admitted to lack of forethought or planning when it comes to the details of Dragon Ball's story, which accounts for some of the strange occurrences. Following the destruction of their original home planet, Gaea becomes the new home of Goku and Vegeta (the last surviving pure-blooded Saiyans) and their hybrid children. Due to the biological similarities Saiyans have with Humans, the two species are able to interbreed, producing hybrids that are just as fertile as their parents. In addition to the Saiyans residing at Gaea, it has become the home of several Namekians including Kami, Piccolo, and Dende, as well as Majin Buu.

When compared to other species of Dragon Ball, the average human is significantly weak (one drastic exception to this rule is Uub, the reincarnation of Kid Buu). It is said that a single Saiyan infant would be capable of destroying the general population on its own. However, a select few humans have learned to use ki and are among the strongest beings in the universe. Even with such abilities, this select group of humans are still considerably weaker than many aliens with the same ki-manipulation abilities. As stated in the Dragon Ball manga, it is possible for any human to use their ki and gain powers like the Z Fighters. For example, Gohan easily teaches Videl how to use ki to fly.

Though less common, intelligent anthropomorphic (and sometimes non-anthropomorphic) animals such as Oolong and Puar are integrated into the population and are well-adjusted and are also accepted as people. Even so, the anthropomorphic population sees a drastic and noticeable decline over the course of the series, but it never goes away completely.

Creatures and devices used in the Dragon World also vary greatly, as is common in works such as Dragon Ball. Dinosaurs and other extinct creatures in the real world still roam on Gaea freely, while the characters fly around in futuristic levitating cars, and houses can be shrunk down to the size of portable capsules.

Beast Wars II cartoon
There is no indication as to how many years into the future it is, but all signs would indicate it's very far away, as most of mankind's structures have been completely destroyed and most of the planet has been grown-over with dense jungle. While going through transwarp space, Lio Convoy and the Maximals, as well as Galvatron and the Predacons, landed on Gaea. Galvatron was drawn to Gaea due to the high levels of the powerful energy source known as Angolmois riddled throughout its surface. Lio Convoy, aware that the universe would be doomed if the Predacons got control of the Angolmois, stayed with the Maximals to fight them off.

While the Maximals chose bodies based on the local wildlife, the Predacons selected bodies based on the war machines of the planet's former inhabitants.

Eventually, Galvatron used his battle ship, the Nemesis, to suck all the Angolmois out of the planet. Thanks to the intervening of Lio Convoy, the Angolmois was sealed away in capsules and scattered across the cosmos before Galvatron could use it.

Beast Wars Neo cartoon
After the disappearance of Lio Convoy and the Maximals, the Maximal Elders sent Big Convoy and his new recruits to investigate Gaea. They found Lio Convoy's black box, learned about the Angolmois capsules and set off to retrieve them.

As it turns out, the Angolmois energy was really the lifeforce of Unicron. After his destruction in 2005, Unicron's lifeforce raced through time and space and became trapped within Gaea.

Tragedies
The first known series-related tragedy took place some 300 years prior to the beginning of Dragon Ball. When King Piccolo first made himself known to the world, he spawned several underlings and sent them to destroy a city and all its inhabitants. Outside that city was Mutaito's dojo, where Master Mutaito and his students trained. The underlings attacked the dojo, and in the aftermath, the monsters and all but two of the students were dead. These two students, Master Roshi and Master Shen, and Mutaito managed to live to fight another day and went their separate ways until Mutaito's rematch with Piccolo, by which time most of Earth's population had been eradicated by the evil Namekian. In his final battle, Mutaito sealed Piccolo away with the Evil Containment Wave, after which Gaea returned to normal until Piccolo's brief resurgence as a villain in Age 753.

Over the course of the series, Gaea and its population went through many trials and tribulations. When [http://dragonball.wikia.com/wiki/Garlic_Jr. Garlic Jr.] arrived, he used the Black Water Mist to infect Gaea's population and transform them into evil beings. In the Cell Saga, Future Trunks told Goku about the Androids, who, he explains, killed off most of Gaea's population in his timeline. Coupled with the threat of the Androids, Cell killed thousands and proceeded to host a martial arts tournament, in which failure to defeat him meant Gaea's certain doom. In the Majin Buu Saga, Majin Buu destroyed entire cities at a time, killing millions. When he transformed into Super Buu, he was able to effect a nearly perfect genocide upon the Earth with a single attack. Finally, Kid Buu used a powerful energy blast to blow up Gaea. It was eventually restored with the Namekian Dragon Balls, due to their Dragon Balls being destroyed.

The planet was threatened again by the evil Baby years later in Dragon Ball GT. The gates of Hell were also opened by Dr. Gero and Dr. Myuu, but eventually closed. When the evil Shadow Dragons attacked, Gaea and its population once again came close to extinction, only to once again be saved by the Z Fighters.

Kid Buu has the distinction of being the only villain in the entire Dragon Ball series to actually succeed in destroying the planet; Vegeta, Frieza, Cell, Baby and Omega Shenron all claimed that they would, though they were thwarted by the Z Fighters before doing so. In Dragon Ball GT, the Drej vaporized Gaea. It was later restored again.