Day 6: A stitch in time takes a long, long time

In a universe unexpectedly separated by vast gulfs of time, the relics of a forgotten age clash with humanity's new beginnings.

Humanity's spread to the stars was perhaps inevitable. Within generations of its initial, clumsy explorations of the Moon, it had established in-orbit outposts, and then permanent (if fragile) extraplanetary colonies. Within a few centuries, bustling cities dotted Mars and the Moon; outposts housed thousands near the other planets, where residents studied and mined the worlds and their moons.

Eventually, near-light-speed travel was developed. Self-sufficient colony ships scattered to the near stars; not only would those ships travel for centuries, the time dilation caused by moving at such speeds meant that many didn't establish their bases for upwards of 1500 or 2000 years, from the point of view of Earth, from when they left.

In that timeframe, Earth's scientists continued to refine travel and communication. The single largest breakthrough came in the form of sub-space movement. With it, scientists found they could "tunnel" through the universe, creating two points that matter could pass between. From an outside observer's point of view, matter moving through the tunnel would immediately pass from point A to point B, as if it teleported; within the tunnel, however, matter would not experience either a shortening of either space or time. In essence, researchers had discovered how to invert time dilation, creating a sub-space tunnel through which near-light-speed movement could be maintained, without the drawback of time dilation. The same technology was used to create nearly instantaneous communication.

Humanity's far-flung colonies were reunited and a second Golden Age of exploration was inaugurated. While cryogenic technology was still required to move explorers from point to point, it was perfected; humans were able to be kept in such conditions for tens of thousands of years, if necessary. Many ships, especially cargo-carriers, were entirely automated.

However, something happened. Whatever it was, it was swift and thorough. Humanity lost the ability to maintain the sub-space tunnels. The outside equipment necessary to maintain them simultaneously failed, across the cosmos. Interstellar communication was cut off; whole colonies were set adrift in regions that could not harbor human life without extensive terraforming using outside materials.

Many colonies were fortunate enough to have been established on worlds that were similar to Earth. While most required some degree of terraforming, most were able to support a stable, post-petroleum technological environment.

The bulk of worlds with human presence, however, lacked the material support for such endeavors. Many were lifeless before humanity and lacked petroleum reserves. Within a few hundred years, their supplies exhausted, these colonies reverted to hardscrabble pastoral communities, locked forever in a pre-industrial environment. For many of these worlds, the fabulous history that brought them to their homes has become the stuff of myths.

However, something new is on the horizon for these worlds. The ships that once plied the sub-space tunnels have returned.

When the sub-space tunnels collapsed, they vomited their contents into roughly analogous real space. These ships continued along, carrying their sleeping passengers and cargo, headed for destinations that were simultaneously decaying into a form of barbarism.