The only thing that needs to be preserved is the desire to build more colonies. I'll grant even that's a stretch, but demanding 100% cultural fidelity is silly for discussing the Fermi paradox.

Terrorism, as you mention, might be possible (but again remember, no stealth) and claim jumping (where you displace another group that got there roughly when you did). But even in densely packed stellar neighborhoods the average star is surrounded by a moat several light years across. Once the locals are developed enough to mount a serious defense, they're probably immovable.

More generally, the point I'm raising is symbolized in entirety by the Spartan faction's ideology in that narrative environment.

Dropping asteroids on habitable worlds and causing ice ages to clear out the population _might_ still be faster/cheaper than terraforming a semi-hostile world.

Further starship drive capable of reaching a significant fraction of the speed of light make one hell of a weapon. But you still need to deal with space based assets that can dodge your initial bombardment and at a minimum are armed with powerful engines. So sure you can destroy planetary populations etc, but now your still out gunned 1,000:1 locally and pissed off a civilization capable of doing the same thing to you. Net result MAD.

A large technical advantage may make up for this, but that means the winner has better tech is much harder to take over a second time. On top of this the only thing worth shipping between stars is information at the speed of light. Making conquest largely pointless without FTL.

It could be worthwhile to beam energy out to interstellar distances (also at the speed of light). This is probably needed for interstellar travel anyway.

That's hard. I'd say harder than solving the physical problems of interstellar travel. Once a generation has learned to live with the limited resources of a starship, living with the limited resources of a planet is going to be a very attractive option. What's their incentive to colonize more from there?

If more technologically advanced aliens exist then our not sensing them is much more likely because they don't want to be sensed than some other consideration like them stopping to setup on some habitable planet. I'm horrified about war, and I'd hope they would be too, but it may be that aliens come to understand species or ecosystems in a more expansive way and may consider the process of ending war as a necessary one for the maturation of an ecosystem.

Or the great filter is true. We all end up killing ourselves because it's impossible to escape exponential technology growth and mismatched incentive problems, or something else like that.

That is, if we are talking about something comparable to current humans. Immortal super AIs might don't care about idling in the void for a few million years, just for the opportunity to re-sync those gained experiences to their decentralized knowledge a few million years down the line. I really like the single omnipotent AI scenario, since being immortal and not depending on others changes quite drastically what strategies can be successful - it won't be anything like human kings who need to keep their subjects at bay and working for them to support their power and limited life. But we shouldn't restrict our imagination, if we are talking about possibilities and galactic time-spans.

The important part is, as mentioned by GP, the desire to expand, since this is a dominant strategy. In comparison, not every living being on earth has the drive to participate in evolution by e.g. creating offspring. Those usually just drop out of the "game" and likely won't matter in the long term, at worst making it a bit harder for the others initially till their disappearance. What matters are those who have persistent impact... e.g. by colonizing/making offspring.

Further it seems much less likely the populace would be so willing to send aide to Britain during WWI if it weren’t for the cultural similarities. If instead Spain had colonized the US it seems very likely the country would have remained neutral as Spain did.

It's not just the US either. India was a profitable colony at the time but might turn out to be a major detriment to Britain overall, both as a source of cheap skilled labor and as a powerful nation of their own. Who knows what would have happened without the British. A lot of the borders in the Middle East are drawn by Britain as part of their WWI mandates/colonies, and the problems from how those borders were drawn spill over into Britain (yes, it's not the only problem in the Middle East by a long shot, but it's one of them).

I still think overall Britain came out ahead (just look at Hong Kong for what cultural influence can do), but it's not hard to imagine how colonization might be seen as a net negative if a few times things turned out even slightly worse.

https://commons.m.wikimedia.org/wiki/File:Imperios_Español_y...

It could have gone another way, there’s a reason we’re talking about Britain instead of England and Scotland, but I would say it has worked out brilliantly.

Also, a neighbor idea of the scientific progression in thousand years from now on doesn’t account for an artificial biology progression, like the same humans in 1k years would do unimaginable things. Would they be still individual humans? Personally I don’t think it is more than juvenile civilization’s tunnel vision illusions.

The number one attribute that needs to be preserved is the disinclination to blow each other to smithereens. I suspect self-destruction (to a level where technological progress is setback millenia) is a common enough occurrence that would occur well-before FTL becomes a possibility.

I also suspect (despite decades of reading SF and my own wishes to the contrary), that the kinds of attributes that encourage exploration, expansion and risk-taking, are also somehow linked to aggression and violence - "might makes right".

Any empire/political system/civilization needs some means of holding it together. Traditionally this is done through armies. As our transport technology has gotten better, our ability to move armies around the world has increased and with it the ability to control large economic systems without them breaking apart. Nowadays we have a globe-spanning economy. However, time scales of interstellar travel are so big that cultural change is much faster than the method to build a colony. By the time that nuclear bomb ship has arrived at the other planet, we might have changed our mind threefold.

In fact, already if you send a generational spaceship to a star 100 ly away to reach its destination in a thousand years, by the time you receive message from their arrival, both their as our language will have evolved by 1100 years. So yeah you are right, cultural decay (or rather "change") is a big problem.

Currently our governments are run by humans with all the human failings. Instability, corruption, etc are components of the governments due to our human nature. You are right that it would be hard for human run governments to colonize the galaxy as due to the light speed limit, we can't achieve transport scales needed for a human-run civilization.

However, we won't need humans to run the governments. In the future we'll be able to engineer and build extremely intelligent AI systems with multiple layers of error checking to withstand decay for trillions of years. You think that sounds undoable? Check how many cells humans are made out of and how well they work together for decades.

The unsolvable political problem will just be turned into a solvable engineering problem.

Those AI systems would run key parts of the governments and economies themselves (entirely without needing human help) and enforce a set of basic rules like preventing nuclear weapons, bioweapons, torture, etc alongside ensuring they are the most powerful factor in those places, i.e. are able to fend off any kind of attack. Otherwise they won't interfere with human matters and let humans govern themselves with the human imperfections.

Basically, they'd provide the "galactic federation layer" and ensure peace through their programming. Some factors of their programming could be changed by the human population, but others, like preventing nuclear weapons, couldn't. So even if the humans wanted, they wouldn't be able to wage catastrophic war with the neighbour planet, or at least specific types of war (allowing trade war but not allowing nuclear war). Even if the risk for interplanetary war is just 0.1% per year, over millennia that's a large number and interplanetary war can have major consequences.

To the present reader, those AI systems probably seem weird and dystopic, but I think we are already evolving towards them. Already, many parts of the governments and economies of various countries are being automated. One day in the future the automation will have minimized human involvement enough so that you can think about von Neumann probes.

The first people to develop AI ran governments will probably be the dictatorships who want absolute control and micromanagement (single-operator government). But in general, the systems are more efficient than chaotic systems, and with increasing perfection of the technology, once a system is a dictatorship, it probably won't change back to a non-dictatorship without outside interference. It's important to eventually remove human control from them as otherwise over the millions of years, eventually someone will figure out how to flip the switch and create dictatorships. So it's kinda important to get the "right" set of rules into these computers.

Already building these computers is a huge project that would take a long time to get it right. But it's an easier task for humans to do than running an intergalactic civilization.

Also note that those systems don't have to necessarily deal with humans in their current form. They could also deal with human simulations uploaded to the cloud and the systems would just provide the resources to run that cloud. The "real world" might become utterly uninteresting to humans.

It is not necessarily true that more time is spent aboard a ship than light would spend taking the same path, as measured by an external observer.

If you had a ship capable of accelerating at 1g indefinitely, then as measured by the crew, they could cross the galaxy in only 24 years.

https://en.wikipedia.org/wiki/Space_travel_using_constant_ac...

I like everything else you wrote.

This is why when you're calculating the actual value of time dilation, it considers what fraction of speed of light you're traveling. Because if you were the traveler, time dilates and length contracts EXACTLY enough to make light appear to travel at 1c (regardless of your own speed).

Time dilation is only 1/2 the story. The other half is distance measurements get distorted.

People in the spaceship see the same maximum velocity of objects they pass aka c. However, if a huge measuring tape with say light year tick marks passing them they are going to measure it’s speed at say .99 c and the time between tick marks is X. Alternatively, at .999c they would get a new time period Y. However the difference between X and Y is not simply .999/.99 but rather a more complex relativistic adjustment.

However, this is only important for people on the spaceship. For people staying home the it takes 3.5x the energy to hit .999c vs .99c yet it’s only shaving 1% off the observed travel time. Which is unlikely to be considered worth it by just about any civilization baring significant changes to the laws of physics.

Particle physics get matter to 99.9999% of c which causes crazy time dilation to the particles and nothing to the scientists. Further, constant 1g acceleration of a starship to high fractions of c is basically science fiction. Not even matter anti matter reactions can keep up those energy demands for very long.