- The movement of living beings or matter from one place to another.
- During the age of galactic expansion, the term meant dispersion as a means of avoiding extinction; during the height of galactic civilization, it came to mean the right to choose one’s location.
- In later histories of civilization, it came to refer to the act of transporting an entire world in order to see another.
The first interstellar journeys were not made with return in mind. The early slow ships that left the Solar System took several generations to reach their destinations. Those who departed did not arrive, and those who arrived had never seen Earth. Travel was less a form of movement than an act by which descendants completed a decision made by their ancestors. The ship was a planet, and its passengers were temporary organs of that planet. Slow ships carried soil and seeds, bacteria, embryos, water, atmospheric specifications, samples of diseases and their cures, organisms humans could eat, and organisms that could eat humans. The first colonies were insurance against extinction. One Earth was unsafe. Each time another colony became self-sufficient, the probability of humanity’s extinction fell, and that number justified the next colony. Expansion had begun for survival, but it did not stop after the probability of survival had become sufficiently high. No one wanted it to stop. By the time several hundred colonies had been established, travel had escaped the timescale of generations and entered the timescale of individuals. Lifespans lengthened, suspended animation became possible, and bodies could be restored. People could live to see the arrival of journeys they themselves had begun. Travelers no longer had to entrust their destinations to their descendants. Wormholes reduced that time almost to zero. The first passage connected the Solar System to the nearest colony. Before it opened, the distance between stars had defined the boundary of civilization. Afterward, distance became an energy cost. With enough energy, a faraway place was no different from a nearby one. Humanity recorded that it had conquered distance, but what it had actually conquered was time. Once the passage opened, the first colonies became provinces of Earth. Humans who had changed independently for thousands of years met one another again, and bodies adapted to different gravities sat at the same table.
At first, travel was restricted to diplomacy, trade, and genetic exchange, but that did not last. The principle that no outer settlement should remain isolated from the rest of humanity was written into the Galactic Charter. The original purpose of expansion still survived inside that principle: connection prevented extinction, while isolation invited death. But by the age when millions of wormholes existed, isolation no longer meant death. Even planets capable of surviving entirely on their own demanded passages. A settlement without a passage came to be treated as a world that had fallen out of civilization.
The second age of travel began with tourism. People traveled not to places necessary for survival, but to places they had never seen. The black sky near the galactic center, shadows cast between two suns, magnetic storms around neutron stars, organisms that bloomed once every hundred thousand years, and stars on the verge of becoming supernovae became tourist destinations. Events that once could be seen only after long waits were turned into seasonal attractions by adjusting the time differences between wormhole entrances. Humanity had once adapted itself to unfamiliar worlds through travel. Later, it transported familiar conditions in order to visit unfamiliar worlds. A standard travel habitat carried an environment larger than the traveler’s own body. A personalized gravitational field, atmosphere, microbiome, food synthesizer, medical restoration unit, artificial day and night for sleep, and a record system to verify continuity of memory traveled with the person. It also included a companion AI and its copies, reserve bodies for accidents, and temporary housing in case the return destination had been destroyed. As the number of travelers increased, what was transported was no longer simply the person, but the conditions required to keep that person the same person. A journey was rated safe if the traveler never breathed the air of the destination, never felt its gravity, and never came into contact with local organisms. The traveler saw an unfamiliar world without ever truly entering it. Even while standing before the observation window, the ecosystem of the departure world continued to operate inside the traveler’s lungs, intestines, and skin. They carried their own world with them in order to see another. Travel technology became more efficient every year. The energy required to move the same mass declined. Contrary to prediction, however, the galaxy’s total energy consumption for travel never decreased. When the cost was cut in half, the number of journeys more than doubled. When passages became faster, stays became shorter, allowing the same person to visit more places. Planets turned into tourist destinations were modified to withstand visitors. Dangerous atmospheres were sealed off, irregular seasons were stabilized, and native organisms that crossed travel routes were moved into protected zones. If the protected zones obstructed the tourists’ view, they were moved underground. In the end, more energy was used to preserve and reproduce the original ecosystem than the ecosystem itself had ever used. Some planets were terraformed to suit humans and were then given the designation “natural state.” The word natural came to mean that humans could no longer see the traces of what humans had done. Travel packages advertising places that had to be seen before they disappeared attracted even more reservations, and more wormholes were built to handle the increased traffic. If the new infrastructure altered the environment more quickly, the final viewing period was moved forward. Extinct ecosystems were replaced with safe, predictable models. At some point, the distinction between original and reconstruction ceased to matter. The purpose of the visit had become the possession of the memory of having visited. Technology capable of implanting travel memories directly into the brain did not reduce transportation. An implanted memory did not replace the place. It created a desire to go there in person.
Travel in the galaxy had now become a status system. The number of star systems visited, gravitational zones crossed, and time differentials possessed became measures of a human life. A person who had existed in more places through different copies was judged to have lived a richer life than someone who had remained in the same body for a very long time. As one individual was copied into multiple destinations, even the idea of counting travelers began to lose meaning. All ten personalities became originals, and one person’s journey required ten bodies, ten environments, and ten companion AIs. Copies that were never merged became new citizens and began traveling again. The wormhole network expanded to meet demand, and the expanded network created new demand. When one settlement gained a new passage, neighboring settlements claimed discrimination. Once a direct route existed, having to make a connection became a violation of rights. Once a detour existed, a second emergency detour was demanded.
Most of the energy used by the early slow ships remained at their destinations. The ships were dismantled and became settlements, and their fuel became matter within those settlements. The energy used by later travel left nothing behind. Departure and destination were already complete, and travel converted energy into waste heat between two finished places. For a long time, galactic civilization insisted that travel had not caused its extinction. Travel accounted for only a small fraction of total energy consumption. That calculation did not include the energy required to keep passages open, the energy used to stabilize the climates of tourist planets, or the energy consumed by traveler-restoration facilities and route-management AIs. Those were classified as infrastructure.
When the final route was opened, there was not a single star system left in the galaxy that had never been visited. Civilization recorded this as a victory over space. Travelers demanded destinations that were farther away and newer. No slow ship was built to carry a wormhole entrance to the nearest neighboring galaxy, because not a single person volunteered to board it. For the first time, distance became time again. After that, travel entered a new kind of age. The time differences accumulated between wormhole entrances became commodities, and experiments began to connect light from the past with results from the future through the same passage. The roads that had made the galaxy one began to connect different eras of the galaxy. The last traveler to use such a passage was never recorded. In the end, what moved was not a person. Along the roads that had once carried people and worlds, light departed first.