Earth is also the origin of the Muah, a highly advanced people which is said to have existed on the Mu continent, located in the middle of the Pacific Ocean since the Pangaean era over 12,000 years ago. Legend says the continent sunk into the sea over the course of a single night. It is later revealed that a meteor struck, destroying their homeland and opening a vortex which transported the Muah themselves across the galaxy.
Thousands of years later, the Muah, or rather their genes, would play a vital role in humanity's attempts to create humans capable of surviving the harsh environment after the disastrous nuclear effects of World War III.
Whilst this plan resulted in 'limited success', which could be described as a failure, since it only produced three surviving subjects. However, where ever one's perspective may reside, it no doubt in the created events which would change the course of history in the universe.
It is explained that the environment of the Earth was severely damaged, caused by the unchecked destruction of World War III and its resulting aftermath. Major cities and countrysides alike lay barren, complete and utter wastelands. The remaining population could not survive and retreated to the underground, if the situation deteriorated as such, humanity would be wiped from existence. This in turn prompted mankind to unite, turning to space exploration, in hopes to find planets that could support life. Two years after these attempts, the Terran Alliance is formed. There the scenes imply the Earth is being restored, so it can be assumed the Terran government gave up on colonization of planets, in light of the UP3, but this remains up for debate.
The crew of the SRF-003 Calnus are accidentally sent to an alternate dimension Earth while on route to En II. This Earth is currently in the year 1957. Although, the only area that is able to be explored is a desert area, this marks the first time in the series that the planet Earth is visited outside a cutscene. In this alternate dimension, Reimi is kidnapped by members of the US Army and taken to Area 51, Nevada, where Edge saves her with the help of Klaus Bachtein, along with Meracle Chamlotte. This alternate Earth is ultimately destroyed in a massive explosion, when Milla Bachtein's irresponsible (or irrational) handling of a highly experimental antimatter engine, and the Calnus's exalithium crystal, creates a Pair Annihilation in an uncontrolled environment, an unwanted event that happened due to Edge's delivery of the technology. The group is able to escape and return to their own dimension, but because of his part in this Earth's destruction, Edge was sent into a state of despair, unable to take command of the Calnus while the group repaired the ship on planet Roak. Reimi assumes acting command until Edge recovers.
(While Edge, in fact, may have been responsible for saving more lives than he ultimately led to the deaths of, as his rescue of Meracle prevented Milla from getting her hands on an even more powerful exalithium crystal, this fact is never called into question.)
In the first Star Ocean, Ronyx and Ilia take Roddick and Millie to Earth after the Lezonian bio-weapon is released on Roak. There, they encounter Lezonian emissaries and discuss the status on Roak, only to discover that the host of the released virus deceased 300 years ago. Later, Ronyx plans their journey 300 years into the past.
After returning to SD 346 Earth, it was revealed to the heroes that Jie Revorse and the planet Fargettwas the third party described in the initial war between Lezonia and the Terran Alliance, all in an attempt to conquer Earth. Fortunately, this diabolical plot was foiled.
The Earth plays a pivotal role yet again, now in SD 772, a technological wonder housing the ever expansive Pangalatic Federation, whom has been at war with the Aldian Empire for over sixty years. Cities of the pre-SD era are still active, such as New York City, Paris, and Tokyo. In some cases, historic landmarks have either been preserved or replicated. In a often lesser discussed topic that has roots in the first Star Ocean, it is implied that in the current age robotics are used to stimulate the natural environment (such as oceans), to such a level that inhabitants opt to vacation on resort planets such as Hyda III & IV. Even wildlife in nature are implied to be a rarity, often replicated through robotic or holographic means. Explanations tend to venture into the aftereffects of the Third World War and the course of development due to space exploration and Earth's role within the galaxy.
During the Executioner attacks, the Federation assembles an armada of battleships, attempting to halt the advance at the final line. Unfortunately, the Executioners prove too powerful of an enemy, destroying most the defense fleet in a single attack alone. With nothing hindering them, they then proceeded to launch several devastating symbological attacks on Earth itself. The planetary shields, despite raised to full power, are no match for these attacks and Earth's cities are enveloped and destroyed in horrific, electromagnetic crimson rays. It is assumed that millions, perhaps even billions of the inhabitants were annihilated out, but there is evidence of evacuations to other planets such as Roak.
However, it is not known how many Earthlings were evacuated nor how many remain in the galaxy.
Ilia notes that Earth is very polluted and the atmosphere is dirty, and that Roak should stay an undeveloped planet so as to not end up like Earth, this is expanded on in Star Ocean The Second Story/Star Ocean Second Evolution, as Claude states that the atmosphere of Expel is very fresh and smells nice, saying that where he grew up the air was very filthy.