Gateway
After centuries of development Earth is a bustling world full of grand cities and carefully maintained parks. Gleaming arcologies rise a mile into the sky and their basements burrow deep into the ground. Carefully managed aquafarms provide food for the teeming billions, and robotic factories provide for all their material needs. All this is powered by solar power beamed from space and massive fusion plants on the ground.
Corporations have grown larger and stronger, but they have not supplanted national governments. Those governments in turn still squabble among themselves for power and prestige, but a global war has been avoided for a century. And overall life is good for the majority of the world's citizens.
That is until disaster strikes. Over a period of some years the moon begins to slowly shake itself apart. Scientists were at a loss to discover the cause, but the results are easy to discern as an increasing number of lunar fragments begin impacting the Earth.
Under intermittent bombardment the underground systems of foundations and utility tunnels were strengthened and improved to house as many survivors as possible. Huge quantities of food and supplies were stored, but without the global aqua farms there was simply not enough for even that fraction of the population that managed to squeeze in. The underground enclaves were wracked by infighting, starvation, and strained life support equipment as the lunar bombardment reached its peak.
Years later the surface and is a cratered ruin and the few surviving enclaves maintain a tenuous existence in their deep shelters. The remaining information networks of the old world link them to each other intermittently, but physical travel is nearly impossible. The world is ruined and things look bleak, but one ray of hope remains.
Shortly before the lunar catastrophe leading physicists had discovered the math proving the existence of countless parallel dimensions, and experimental quantum portals had been opened to them. Now the survivors have managed to scale up that technology. Their most hardened survivors have been given the best remaining equipment and are ready to be sent out. Their mission is to find an inhabitable world and new home for humanity.
