[hal]

In my opinion, the following things have to be present:

A) wealth The original world that wants to dominate any region, will have to have sufficient resources available, to maintain its expansion by any means. By that, I include economic expansion via trade, wars of conquest via the military, etc.

B) Sufficient population. If you don't have a need for resources, then there is no need to expand outwards. If you lack wealth - you lack the means to project your will elsewhere. If you don't have the manpower to staff your trade system or staff your military system - you won't be able to build an empire

C) Opportunity. If you have all the basics required to start building an empire, the question becomes one of whether or not you have the means to build one. If you can't fly to the next planet within the system, you can't have colony settlements or outpost settlements. If there are no worlds within your limited reach, then you don't expand. Expansion however, is going to be based on the final thing...

D) Desire. Let's face it. We in theory could place settlements on the Moon - we could have done so in the years 1970 onwards. We lacked the desire to do so. Was it a cultural thing? Was it simple mathematics where "Hey, why spend 1 billion dollars to build a settlement on the Moon when we could spend the same Billion dollars to inhabit sections of Earth that are largely under populated? Why go to a harsh world when we can remain in a garden world environment?

For me? The "Dark ages" that came into being after the fall of the First Imperium (I really don't consider the Second Imperium to be distinctly different from the first - just new masters for an old empire) is going to be similar to that we saw happen with the Fall of Rome (and may see with the fall of the United States someday).

Unity of Governmental principles backed by the power of a Sovereign government interested in projecting its culture and/or power and/or wealth harvesting capabilities over vast stretches of territory.

When we talk of say, TWILIGHT 2000 or say CYBERPUNK 2020 - the United States tends to devolve into multiple governmental structures holding sway over smaller amounts of territory. When Rome faltered, we saw the withdrawing of Roman Legions from England, and the abandonment of rule/administration of entire territories.

My "gut" instinct is this: Many of the worlds that could or would eventually become "home world" like as far as population, infrastructure, and cultural unity - had to lose that or they would have become the nucleus of proto-empire builders. Marc Miller would eventually coin a term for those proto-empire builders...

Pocket Empires.

Heavily settled "sectors" would have had zillions of potential pocket empires, but ultimately, in the span of multiple centuries, would have gone empire building much sooner than Sylea ends up doing. Question is - why didn't they?

My guess is that they lacked two of the four ingredients necessary. Any of the three combined should have been enough to start a pocket Empire, and once that was started, the four elements would have eventually been present. Populations that are well fed, have a stable government, etc - tend to expand. With that expansion comes the need for resources. With that need, comes the expansion outward from the main world. With that expansion also comes the need to administer law and collect taxes, regulate business, and even protect them from criminals.

Why 17 centuries of dark ages in light of how modern technology seems to accelerate things?

Picture this:

One world fears outsiders because the outsiders tries to rape their world (ala Viking style raids). Another world fought wars against an enemy who damaged their ecosphere (hence tainted atmosphers still showing evidence of enemy bombardments centuries later). Yet another world had its infrastructure bombed into the stone age.

For some, the withdrawal of the First/Second Imperium culture resulted in a massive orgy of destruction both of social and economic infrastructures. For others - the withdrawal resulted in a slow decline as they battled against the alien environments relentless war on invaders who couldn't exist on said world without subsidized infrastructure support (ie life support equipment, luxuries, foodstuffs etc).

In the end? Without being able to detail every world, without using something like Pocket Empires as a system - any work detailing the dark ages will rely strictly upon narratives.

:(