"Fundamentally, the goal of stealth is always the same. Firstly, any particle or field that passes into the region of the object being stealthed must appear on the other side identical to if it had passed through vacuum or air or whatever the medium of relevance may be. Secondly, the object being stealthed must not emit any additional particles or fields of its own."

"All of this is, of course, far more easily said than done. Any ship traveling through space, for instance, will obviously have a strong need to "see" its surroundings—but even passive sensors must absorb something from the environment, and active sensors are of course much worse. It is theoretically possible to absorb the particle, perform your measurements, then reemit a similar particle out the other end, but this is of course an immense technical challenge, and not completely solved. Further, in certain cases it may be impossible to safely absorb the particle without being detected—numerous stealth detection schemes exist that use quantumly correlated particles as part of the detection framework."

"Further, it is easy to get lost in a discussion of particles and fields, and forget that within star systems starships encounter a much higher density of stellar material, including micrometeorites that may contain a macroscopic number of atoms. Clearly absorption and reemission is out of the question in this case, and the watchful enemy observer may notice the subtle realignment of stellar material. Enemies performing active detection may of course simulate a similar effect with the deployment of vast numbers of microdrones, which serve a similar purpose."

"Even avoiding the spontaneous emission of radiation or material is a severe technical challenge. Every stray internal EM transmission must be brought under control, heat emissions from the engines and passengers must be somehow stored, radiation from decayed exotic matter must be dealt with, and so forth. Further, acceleration of any kind must be very carefully done—conservation of momentum ensures that something must be left behind altered, regardless of the propulsion system used, so extreme care must be taken about accelerating in the presence of a watchful enemy."

"All of this must be added to the simple fact that it is impossible to maintain stealth if your ship must pass through a large piece of solid matter or a forcefield. The best fixed defenses will make liberal use of such devices to construct as much of a wall as possible, presenting an obstacle course difficult for even the best stealth ship."

—Excerpt, "Stealth Technology", article from Military Science for the Precocious Child, online magazine