Some extremely old wormholes in an advanced state of decay collapse in on themselves, leaving only a tiny corridor between different parts of the galaxy.
This article comes from Star Trek Magazine, v. 1, i. 12.
Most wormholes are unstable, and fluctuate wildly between many points in normal space; however, there are some rare examples of stable wormholes.
In 2371, on stardate 48579.4, the crew of the USS Voyager NCC-74656 discovered a stable wormhole. Because Voyager was lost in the Delta Quadrant, the wormhole offered the possibility of a much faster way back to the Alpha Quadrant. But this spatial singularity exhibited some properties not commonly associated with wormholes.
The wormhole appeared to be extremely ancient and in an advanced state of decay; it had most likely been collapsing in on itself for several centuries. It would best be described as a micro-wormhole, since it had mostly dissipated, leaving an extremely narrow passageway through subspace. In fact, the aperture of the wormhole was only about 30 centimeters in diameter, far too small for a vessel to traverse. The micro-
Although Voyager was unable to pass through the wormhole, Ensign Harry Kim managed to use the trapped microprobe as an amplifying relay station to send a signal.
The first transport involved a test cylinder, which had a varietal molecular matrix that simulated most organic and non-
Unfortunately for the crew of Voyager, it was discovered that the strange phase variance discovered earlier was a by-product of the fact that this micro-wormhole not only traversed space but time as well. The crew determined that the Alpha Quadrant terminus of the micro-wormhole was located 20 years in the past.
In 2376, Starfleet engineer Reginald Barclay, working on the Pathfinder project, managed to create a micro-wormhole by directing a 60-terawatt tachyon beam from the Mutara Inter-dimensional Deep Space Transponder Array (MIDAS) at a Class-B itinerant pulsar. The beam eventually produced a gravimetric surge that was powerful enough to generate a tiny wormhole.
Barclay was able to move the micro--wormhole and managed to briefly establish communication with Voyager, thousands of light years away from Earth.