Board Thread:Fiction Universe Discussion/@comment-47205-20160329150225/@comment-1073312-20160330000315

My science and technology input:
 * Because FTL technology is still quite limited in this new setting, I imagine STL methods of interstellar travel would still take precedence, especially with less advanced societies or the less advantaged parts of society. There are generally two kinds of STL travel, the slow kind that takes a whole generation or more to reach even nearby destinations, or a very fast kind of STL travel that utilises time dilation; that could permit an individual to explore the entire universe ship-time.  Obviously, the setting makes the very fast kind of travel hard.  However, there could be a meeting point that is no too fast, nor too slow.  For an interstellar civilisation, managing relativistic effects (and time delays) would be a monumental effort, but also a very interesting one to explore (for example, balancing real time and subjective time, which I once considered).
 * Despite the lack of FTL travel, it is possible for a civilisation to spread across the universe at slower than light speeds, using self-replicating spacecraft or by gradually building things on a stellar scale. I understand this will not be part of this setting, however that leaves a problem: it only has to happen once in the universe.  So we either need a great filter of some kind that stops a civilisation getting that far (and I never find these sorts of explanations good); an alternative mode of advancement or transcendence; or some other pre-existing canon element, like the Dawn Hunters from OA or Reapers from Mass Effect.  Go by luck of not encountering such aliens if you like, but then the density of civilisations in the new sector needs an explanation.  In main fiction universe we have the Xhodocto, the Grox, and likes of Zargoth to scourge and dominate the universe every few million years, as hinted at in The Great Expedition.
 * More considerations: One thing that might fix this problem is that we make this setting to be in the early universe, so that the civilisations are generally the first generation that evolved from the first habitable terrestrial planets.
 * Ghelae suggests an "extraphysics" realm. I actually suggest we go for a limited form of hyperspace travel.  Ghelae explained to me that wormholes are ruled out of many modern quantum gravity theories, and that warp requires some-kind of phantom energy that can be localised.  Neither look so likely any more; however there's a paper about M-theory that suggested some kind of tachyonic faster than light motions that involve hopping between braneworlds.  Or something like that.  And that kind of sounds like hyperspace.  The technology may use a lot of energy, or there may be something that interrupts this process only making short hops feasible.