Although Service Vehicle Zorglube had been orbiting the Anomaly for a century or more, it had no answer to the question. It was far easier to say what the Anomaly wasn't. It didn't have mass. It didn't emit particles, including those of light. It did have an extent and this was only discernible because where the Anomaly was present there was no light visible from the other side. And this was so from any direction from which it was observed. It was much longer than it was wide. That length could now be measured in tens of thousands of kilometres although its width had never increased beyond a kilometre. The Anomaly's fuzzy and indistinct boundary was as elusive as its mass. It could be defined only as the point at which light no longer passed through space, but that was a range that constantly changed. Sometimes the boundary flickered open to the extent that it simply swallowed up particles that not long earlier were beyond the boundary and now by chance no longer were. And when that happened, the particles simply ceased to be measurable. They had essentially vanished.
The period of time during which a particle vanished was as fuzzily defined as the boundary that defined the Anomaly's extent. When those particles happened to belong to a Sirius vehicle then its demise was exactly as indistinct and undefined as everything else consumed by the Anomaly. There was no prior indication from the transmission that anything untoward was about to happen. The last few signals were no different to those before the vehicle's communication systems flickered out of reach. And then it unhurriedly receded out of sight in a curiously foreshortened event horizon. The vehicle was gone and that was the end of it.
The Anomaly was a crowded place, even though this was wholly invisible to human civilisation from its viewpoint in the ecliptic plane. Several thousand space vehicles from the Sirius system were hovering about or orbiting in its immediate neighbourhood, but few were detectable by the technology available to the other stellar robot civilisations in the vicinity. There were several hundred Proxima Centauri space craft which were as visible to Sirius sensors as they were to each other, but were as totally invisible to human observers as the Sirius fleet was. The only robots visible to human observers and their sensors were the crude probes that the Interplanetary Union had sent to the Anomaly over the last century or so. They were woefully inadequate for the task and mostly ignored by the more sentient robots they were unable to see. They had attempted countless inconclusive experiments in the vicinity, but in general they were just orbiting the Anomaly and getting in everyone else's way.
Besides space craft from the Solar System, Proxima Centauri and Sirius, there was a more modest number of space vehicles from other neighbouring star systems but these were really hardly any better at the task of observation and research than the space probes sent by humans. Proxima Centauri and Sirius were the two robot civilisations with the greatest interest in the Anomaly and they kept their intentions—along with all other communication—very much to themselves. Neither knew about the objectives of the other and both asserted that their presence so far beyond the comet clouds of their own stellar systems was purely for reasons of scientific research.
A small fire was burning half a million kilometres away. This was again impossible given the fact that there was no combustible material in this region of deep space and certainly no oxygen to maintain it. Inside the fire was a bird the size of a large chicken that appeared to be regenerated rather than consumed by the flames. This was an event that couldn't happen even on Earth where there was plenty of oxygen in the atmosphere. The apparition then vanished and again left no indication that it had ever existed.
Service Vehicle Zorglube knew that, although these apparitions appeared to be illusory, if they came into contact with any other object during the period of time they existed the interaction was as actual and physical as it would be with a corporeal object. On several occasions, these apparitions occurred in a region of space where a space craft was located. Usually this was nothing worse than a mere oddity. A man with huge outspread wings flew directly into an invisible space craft and rebounded in pain from the unexpected impact. A rowing boat in which an owl and a cat were sitting momentarily spun out of control in the vortex of gravitational flux surrounding an invisible force field. Sometimes the result was rather less benign. A diplodocus materialised within the confines of a vehicle that was too small to accommodate it and the deadly outcome of this encounter was a sudden explosion of blood and burst intestines. However, every single blood splatter and freely floating internal organ vanished simultaneously with those parts of the animal that remained intact. On another occasion a vehicle exploded from the impact with an internal object whose presence could only be fleetingly glimpsed in the flying fragments of the previously invisible space craft.
It seemed that the only possible way to find out more about the Anomaly was by penetrating its boundary, but for external observers such a suicidal endeavour was pointless in the pursuit of useful knowledge. The first observation of a space vehicle disappearing without trace within the Anomaly was undoubtedly a significant event, but as a growing number of increasingly sophisticated space vehicles disappeared and revealed no more information than the first loss such an adventure was now viewed as nothing more than an expensive waste of resources. The effort required to design a vehicle, build it, and then transport it over eight light years of empty space was a drain that couldn't be supported when there were no useful observations or results.
There would be little to worry about if the Anomaly were to simply remain as it was. There were countless other currently inexplicable phenomena in the vast expanse of time and space which were also of general academic interest. As they were mostly a huge number of light years distant and stayed stable over a long period of time there was no urgency associated with such research. The Anomaly, however, was in the local stellar neighbourhood and its extent was increasing at an alarming rate. Its length was extending by several hundred kilometres a year and this rate of growth was actually accelerating. It didn't take much arithmetic to calculate the threat posited when a significantly large region within the star cluster was growing at an increasing rate and whose only observable effect was to swallow up without trace whatever it came into contact with. If the Anomaly spread as far as the ecliptic plane then the entire Solar System would be at best destabilised and at worst totally consumed.
