By 2099, Earth's axis had shifted causing it to rotate at a 90% angle to the equator of the 20th century. This led to a series of natural disasters that lasted for three years and wiped out the entire population of ten billion. However, two million colonists survived on the moon. After a period of tranquility, some of the survivors returned to Earth, establishing seven new cities to begin repopulation. Nevertheless, the remaining moon colonists were concerned that their previous neighbors could potentially pose a threat, leading them to construct a defensive ring of satellites to keep them trapped on their newly repopulated homeworld.