Ygsium is an exotic material essential for the functioning of much of the faster-than-light technology. When charged and discharged like a capacitor, two identical pieces of solid ygsium instantly teleport surrounding matter from the vicinity of one piece to the vicinity of the other. Ygsium is not produced naturally, and no civilisation from the First Galactic Senate era onwards is capable of generating it by artificial means; all existing deposits being left over from Empire of Arckas as well as the Omni who discovered how to refine a lower quality variant of the substance. Atomic ygsium is comprised of a single ygson orbited by a single electron; as a solid it is a metallic reflective room-temperature superconductor; liquid ygsium is black; ygsium gas is colourless. The material is far denser than any conventional substance, but far less dense than other high-density exotic materials such as neutronium.
The most important properties of ygsium concern its exceptional ability to instantaneously teleport nearby objects from one location to another, which can only occur under specific circumstances. The process requires two identical pieces of solid ygsium of high purity; they must be the same shape and size, and ideally the same temperature. To trigger teleportation, one is charged with a negative electric charge while the other is charged positively at exactly the same rate. When the charge passes a certain threshold, the two pieces discharge into one another, despite no current passing through the intervening space. In the process, a certain amount of surrounding mass is teleports from the vicinity of the negatively charged piece (ygsium-) to the vicinity of the positively charged piece (ygsium+); the larger the mass of ygsium used, and the smaller the distance between the two pieces, the more mass is teleported. The charge threshold which triggers teleportation rises with the mass of ygsium used and can be lowered by exposing the ygsium to a powerful electric field (though this will reduce the amount of mass teleported).
Though the science behind the properties of ygsium is not fully understood, millennia of experimentation has established the basic rules of the teleportation process. Ygsium- always teleports the closest mass available. The mass reappears after zero time in exactly the same configuration relative to the original location of the ygsium+ as it was around the ygsium-. For the process to succeed, the vicinity of the ygsium+ must be a vacuum or near-vacuum; if there is an obstruction, the corresponding chunk of teleported mass will simply remain in its original location, even if this means separating it from anything which teleports successfully. It has been determined that ygsium- always tries to teleport itself along with the mass around it but is never able to because its destination is perfectly obstructed by the identically shaped ygsium+. An object does not act as an obstruction if it itself is teleported away in the same process, so objects will successfully teleport over small distances even if the original and teleported object overlap.
Point-to-point teleportation is the most obvious application of ygsium, though such systems are rare due to their great expense. The amount of ygsium required to teleport a given mass rises dramatically with distance; the ygsium expense even for a modest cross-city teleporter makes such systems economically unviable apart from in the most exceptional circumstances. The power requirements for each teleportation are similarly overwhelming.
Where they can be found, ygsium teleporters usually consist of two large identical pieces of ygsium, each with an internal cavity - while ygsium teleports the closest mass, it has been found to favour the mass within a cavity above all else. Cargo (or passengers) are placed in one cavity, while the other cavity is converted to a vacuum. Teleportation can then take place. Ygsium teleporters have a certain maximum mass which can be teleported, which can be lowered to the mass of the cargo by exposing the ygsium to a strong electric field. As with all instances of ygsium teleportation, it is important that the teleporter is calibrated carefully. If the teleportation mass is set too high, mass around the device will also be teleported. If the teleportation mass is set too low, not all of the cargo will be teleported; usually this means the teleporter will favour the closest available mass; but within a cavity, the teleporter favours a random selection of particles, with undesirable results.
The cheapest application of ygsium is in faster-than-light communication. This relies on three properties of ygsium:
- The larger the teleportation distance, the more ygsium is required to teleport a given amount of mass.
- The less mass is being teleported, the less ygsium is required to teleport it.
- Smaller amounts of ygsium require less electric charge to trigger a teleportation.
While the amount of ygsium required to trigger a teleportation rises dramatically with distance, ansibles counter this by teleporting something with insignificant mass - a signal. Ansibles use a miniscule amount of ygsium shaped into a hollow cavity, usually encased in some form of electrical component. Millions of times every second, a signal packet is sent into the cavity and teleported to a corresponding cavity somewhere else in the universe. Because of the equivalence of energy and matter, signals technically have a tiny mass, so the signal strength is made as weak as possible to minimise any issues this causes. Due to the small size of the cavity, ansibles tend to use short-wavelength signals such as microwaves. A modern ansible can transmit anywhere in the galaxy and beyond with zero delay; older or low-grade models may have range issues over extremely long distances.
Thanks to standardisation by the Galactic Senate, there are trillions of identical ansible cavities across the galaxy, all with the potential to link with each other. As with any other system involving ygsium teleportation, ansible cavities must be charged in perfect synchronicity in order for them to link (otherwise, no teleportation will occur). To ensure that two given cavities link with each other and not something else (by malicious intent or otherwise), ansible cavities are charged in a complex fluctuating pattern defined by a pre-agreed 'key'. Any break from this pattern on either side will result in a link being severed. The protocols used to set these keys are the backbone of galactic mass communication.
- Main article: FTL Drive
The FTL drive is perhaps the most well-known use of ygsium in the galaxy. FTL drives work thanks to three important properties of ygsium teleportation:
- The ygsium- always tries to teleport itself but is obstructed by the ygsium+.
- Teleportation is successful if potential obstructions are teleported away in the same process.
- The destination is defined by the original location of the ygsium+, even if the ygsium+ moves during teleportation.
As a result of these two properties, if the two pieces of ygsium are placed close enough together that the ygsium+ is within the range of the ygsium-, the ygsium+ will teleport in line with everything else, allowing the ygsium- to teleport unobstructed into the original location of the ygsium+. In effect, the whole configuration, including the ygsium, jumps forward in no time. As the ygsium- takes the place of the ygsium+, the distance they both move forward is exactly the same as the distance between the two. A single such teleportation is not very useful for faster-than-light travel.
FTL drives work by performing billions of such short-range teleportations every second. Since each of these teleportations takes no time, the rate at which an FTL drive can move is not limited by the speed of light, nor does it involve any feelings of acceleration. Such a rapid succession of teleportations is usually achieved by wiring the two pieces of ygsium (referred to as 'ygsium cores') to a powerful waveform generator. The speed of an FTL drive is calculated as the frequency of the waveform generator multiplied by the distance between the two ygsium cores. For example, a ship with a drive displacement of 30 feet running at 1 billion Hertz would travel at a speed of 30 billion feet per second, or 30 times lightspeed.
- Main article: Jumpgate
The amount of ygsium required to teleport a given mass rises logarithmically with distance - it increases dramatically over relatively small distances but starts to level off over galactic distances. A civilisation with access to vast quantities of ygsium can therefore build teleporters which send objects across the galaxy almost as easily as they send objects to nearby star systems. While no present civilisation has the ability to build such devices, previous civilisations have done so, and the galactic network of jumpgates (or 'stone rings') is used to this day.
A jumpgate consists of a vast torus of ygsium; placing mass within the torus guarantees it to be favoured for teleportation over mass on the outside. Every jumpgate has its own independent power source to provide the incredible amounts of energy required; depending on the size of this power source and the size of the object to be teleported, it may take some time for a jumpgate to reach the charge threshold which triggers a teleportation. As long as their ygsium toruses are the same shape and size, any two jump gates can be linked if directed to do so from both sides; the vast majority of the jumpgates across the galaxy are of the same specification and can therefore be linked.
An atom of ygsium consists of a single electron orbiting an exotic particle known as an ygson. The ygson is a highly massive particle not known to occur naturally - it must be synthesised under conditions which do not exist in nature. Due to the high mass of the ygson, this process requires energy densities which can only be achieved in particle accelerators on the scale of star systems. No present civilisation is capable of reliably synthesising ygsium though many have tried.
All known ygsium in the galaxy originated in either Arckasian or Omni particle accelerators long ago. Arckasian ygsium is often nicknamed "perfect ygsium" as it exhibits far more refined properties such as greater fuel efficiency than that created by the Omni.
Most of the galaxy's ygsium consumption is satisfied by the recycling of old components. The ygsium cores of most FTL drives are standardised to certain specifications, so they can be easily removed from decommissioned ships to be installed in new ones; waste disposal companies painstakingly extract the tiny pieces of ygsium from electronic components; despite their great expense, every major civilisation runs at least one ultra-high temperature ygsium furnace to melt down old components and cast them into new ones. Recycling represents the bulk of the galaxy's ygsium economy, but it cannot satisfy all needs. No recycling process has a 100% recovery rate, and civilisations hoping to expand their use of ygsium technology must draw a surplus from other sources.
The widespread use of ygsium by previous civilisations has left deposits scattered across the galaxy. Apart from recycling, the excavation of these deposits is the only source of ygsium for modern civilisations, making prospecting a lucrative business. The highest-grade deposits are in excavated ruins, but due to the passage of time there are also lower-grade deposits imbued in the lithospheres of some planets and asteroids. While jump gates technically represent the largest deposits of ygsium, they are rarely dismantled for their resources as they are far more valuable for their role in galactic travel. An irreparable jump gate, however, could be dismantled to supply an entire civilisation with ygsium for a long time.
Ygsium is not evenly distributed across the galaxy. The highest concentrations can be found on the footprint of the Empire of Arckas civilisation, as well as the footprints of the Omni, Taroran and Buyuk civilisations which also extracted and utilised large amounts of ygsium in their time. Though there are many exceptions (notably the high number of ygsium deposits in Greenwater), in general the concentration of ygsium increases toward the galactic centre.