Tachyon

In Solar Storms, tachyons are not particles, or at least, not particles in the conventional sense, having no momentum despite the ability to cause noticeable interference in matter. Their effects are many and varied, but the essential difference between them and a normal particle is that while a normal particle exists for a certain length of time and have limited space, tachyons exist across a certain length of space and have limited time. Although this can simply be interpreted as having a half life shorter than any other known particle, the line-effect of the particle is undeniable.

When initially discovered in the 22nd century, these effects were not believed to be of any use for superluminal communications, as there was initially no means of generating them, even in theory, without modifying the entire length of spacetime in which the tachyon was to inhabit anyway - making it a bit of a moot point.

The dawn of the 23rd century brought exomatter and the mobius patterns. Suddenly, energy could be focussed in ways never thought possible before. Within a few short years, Ouranos Prime, the first satmet, was constructed.

Relativity

Causality is inviolate. When sending a message instantly between two points moving at different velocities from each other, the effect is to find a common frame of reference for those two points. This doesn't reveal a common frame for the entire Universe - just the points that are communicating. Using the Lorentz and Poincare transformations in such situations merely leads one into silly places - or at least risks such.

Effects

When a tachyon 'fires', the specific kind of particle has a set effect, either while it remains in existence or after it decays. The exact strength and of these effects can vary based on the relative acceleration of the 'firing ship' and the 'target', as well as gravitational wells. This difference is most frequently noticed when moving through stargates, though other situations can occur, such as proximity to a neutron star. Most notably, patterns completely suppress tachyons within their area of influence - though wraiths and cerevates are fully capable of noticing and even analyzing them. Lesser patterns, such as infusions, can also be made to recognize tachyon signals and attacks.

When communicating, an effect is usually chosen based on the desired range. Most often the line of effect simply decays into a photon burst - meaning such a system can effectively be used as a multi-parsec radio station. Other, less instantly obvious means of communication decay into neutrons or other slow-moving particles instead.

Attacks are a bit different. Even communications attempts draw immense amounts of energy - actually focusing tachyons into an attack medium requires a truly phenomenal power source. Initially, humans used things such as megafusors and a significant portion of Sol's light to destroy single starships. Current designs are directly linked to a Klein tap, and thus some could, in theory, focus enough energy to crack a planet.

Of course, a tap of sufficient potency could do that anyway - but with tachyons, there is no chance of warning.

Such devices are often mounted on a turret that, when firing, appears as if it recoils or projects suddenly at high speeds. This isn't recoil, or some weird factor caused by the tachyon itself. Instead, it's an acceleration adjustment so the 'right kind' of tachyon effect with strike the target. The first such 'right kind', during the Jovian Massacre, turned roughly 40% of the target ship mass into antimatter.

When not somehow adjusted to cover a very tight, specific range distant from the firing vessel, attacks that generate light always appear to originate at the point closest to the viewer. This can be a confusing phenomenon to those not aware of what is going on - see the Kennedy Station incident.

Alternatives

The discovery of halons would soon eclipse the original satmet array concept, at least after contact has been made with other civilizations, when the point of hiding from potentially hostile civilizations was shown to be moot given the destruction of Kennedy Station. Simpler devices still remain in use, however, as they are far more secure, as well as a reliable means of transmitting to and from the Milky Way's halo.