Wormholes were initially discovered not by some deep-space telescope but as an odd solution to Einstein's theory of general relativity. It wasn't until the 2050s that Japanese scientist Hirasaki Masuyo isolated one as it bubbled up from the quantum foam on Phobos. It was infinitesimally small, and it didn't lead anywhere exotic: Its two mouths were a mere Planck length apart.
But Hirasaki developed techniques to grab each mouth and keep them from winking out of existence. He learned how to incorporate mass and energy into the wormhole, widening it. Separating the mouths allowed him to connect two points as if they were right next to each other.
Japan's then-monopoly on solar power stations, asteroid mining and antimatter manufacturing allowed it to finance the grandest project of all: sending a wormhole mouth to Proxima Centauri, the nearest star to Earth. The first men and women transited the wormhole a little more than a decade after Hirasaki's discovery.
To open up new stars, nations employed big breeder ships to detect and capture wormholes before they evaporated. Once secured, tiny robotic wormhole transports called "Valkyries" relied on direct antimatter annihilation to achieve relativistic speeds. The antimatter fuel – far more than conventional ships used to spark their fusion drives – made them terribly expensive, but they could reach a star five light-years away in just under six years for the people waiting back home.
Once the distant Valkyrie entered orbit around the destination star, engineers at the origin would widen both mouths to the standard Jumpmax diameter of 40 meters and change; any larger required prohibitive amounts of energy. They would construct a solar array at both mouths, to provide the energy to maintain the opening, and a new star system was free for exploration.
It wasn't easy or cheap: Typically, about a quarter of Valkyries didn't survive the trip, lost to high-speed collisions with interstellar dust. And no nation had managed to build a Valkyrie that didn't break down after nine or ten light-years' travel, so reaching distant stars required accessing a series of lily pads, usually dim red dwarf systems without hope of habitable worlds.
Hirasaki and his successors also learned that wormholes were funny, fragile things, and they came with rules. It was as if the universe only grudgingly allowed them, and took every opportunity to attempt to make them go away. To prevent wormholes from collapsing, nations were forced to keep their wormholes in space and distant from one another.
For example, they could collapse if you only used them in one direction. Mass must be conserved on both sides, so a 10,000-ton freighter going from Sol to Sirius would eventually need to be balanced by an equal mass going in the other direction. Outside each mouth of a wormhole was a robot tug that pushed ballast – usually rocks mined from a nearby asteroid – into the guidance rings, which formed a weak electromagnetic catapult to propel it through. Typically, a single ship won't destabilize a balanced wormhole; however, a fleet in a hurry might if it doesn't stop for the tugs to take load-balancing measures. Occasionally, newer wormholes would temporarily prohibit transit while waiting for a delivery of new ballast mass on the far side. This was one reason to keep wormholes out in space: On a planetary surface, differences in air pressure, gravity and other factors at each mouth will draw stray matter from one side to the other, and, over time, crash it.
Many of the remaining restrictions on wormhole travel extend from what most believe is a universal law: "Thou shalt not travel back in time!" But that isn't quite accurate. The real law is more particular: "Thou shalt not be able to travel back in time to interfere with your own past."
Thanks to the time dilation effects of traveling at high velocities, a robot Valkyrie could conceivably reach a five-light-year-distant destination star in just three years in its own time frame, potentially opening up a new colony two years early! The wormhole-crossing colonists would leave their origin in 2105, but arrive in 2103. Wormhole theory said this should be fine, as long as they were unable to pass stock tips from the future to everyone else in 2103. Going back through the original wormhole would put them in 2105 again, so they would need a loop of other early-arriving wormholes to attempt to pass people or information to influence their own past.
However, the moment anyone tried to build such a loop, some or all of the wormholes collapsed, just as wormhole theory predicted. But what didn't mesh with the theory was the fact that every Valkyrie that had tried to take advantage of time dilation had lost its wormhole anyway, even when no offending loop was created! After the loss of several early Valkyries, everyone took care to set up a wormhole link using a synchrotron that kept the stay-at-home wormhole mouth at the same speed as its counterpart on the Valkyrie. They stayed in synch, neither ahead nor behind each other in time. But physicists struggled to explain why any and all out-of-synch wormholes still collapsed. Their chief theory involved infinitesimally small, primordial wormholes arrayed around the galaxy, which interfered with the manufactured wormholes. But no one had found any.
The mystery deepened in the 2120s when a malfunctioning Japanese Valkyrie deposited its wormhole at the red dwarf AT Microscopii B three months before its counterpart at the origin had fully decelerated. The wormhole pair should have crashed, and it ultimately did, but only a month later, after the Japanese breeder ship entered the system and tried launching another wormhole toward a nearby star with an existing European wormhole. It was several years until AT Microscopii B was reopened, this time with in-synch wormholes. The breeder ship was quickly located, as were the bodies of the crew. They had starved to death.
Mouths from different wormhole pairs were also territorial: They could destabilize if they passed within several million kilometers of each other, as even small differences in the velocities of close wormholes could create an out-of-synch loop and thus a time machine. This effect prevented you from sending a wormhole through a wormhole or mounting a wormhole on a regular ship. Earth's stellar nations kept their wormholes distant from one another, often at Lagrange and Trojan points where they could anchor mass for ballast.