In the year 2021 AD, the first "Astral Gate" is built in orbit around the Moon; a hyperspace gateway meant to expedite space colonization by making travel between planets a matter of days instead of months or years. This gate is destroyed in an incident that comes to be known as the "Gate Accident"; an explosion that shattered a massive piece of the Moon. Lunar debris began to fall upon the Earth with the same frequency as rain, devastating the planet's surface and killing 4.7 billion people. Fifty years later the human race numbers only 1.5 billion, but has colonized the entire Solar System through the use of perfected Gates.