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Comment by ncmncm | Hacker News Reader

The whole concept of Dyson Spheres, or anything even vaguely like that, is totally absurd. (Even Dyson said so.)

Any space-faring culture will have mastered controlled fusion long ago, and have entirely left behind any material dependence on stars. The best places to live, then, are out in the Kuiper belts and beyond, where unlimited room and cold are available for free, and valuable gases are lying about, frozen. Inner planets are for extreme primitives. If aliens got here, they would find Triton much more interesting than Earth, except maybe as a curiosity.

Expanding menace civilizations will run up against overwhelmingly more advanced stable cultures before long and be contained or destroyed, so odds are none could get here before that happens.

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What seems downright absurd to me is to dismiss the obvious fact that while a star might be incredibly inefficient relative to a working fusion reactor, the actual energy output of a star will far outstrip that which can be collectively produced by artificial fusion for many centuries and millennia to come.

Stars provide in abundance and for free, energy, mass (even for heavier elements they far outstrip that available on planets, asteroids, and comets), a star system spanning magnetosphere for protection from the interstellar medium, and a massive gravity well which can be used to anchor planets and mega structures alike

While it's true that we won't strictly "need" them once we have working fusion, they are likely to be the hotspots of civilisation for a long time to come, probably as long as the stellar epoch of the universe is in play (so 100+ billion years).

"Hotspots" is the key term here.

For most high-civilization activities, heat is pollution, something that must be extracted and shed, in volume. Out in the Kuiper belt, cold is abundant and free.

For most high-civilization activities, a gravity well is an anchor chain. Out in the Kuiper belt, material resources, including frozen fusible gases, are abundantly accessible with very little annoying gravitation.

For many high-civiliation activities, proximity of other entities that could be put at risk, or that might put you at risk, creates hazards. Out in the Kuiper belt, room enough for anything is abundant and free.

Extreme primitives like us and bacteria, who don't have abundant private energy sources, welcome the low-intensity energy influx from a nearby star. For anybody even mildly sophisticated, the energy is uselessly diffuse. At the same time, it keeps everything at a noisily high temperature that interferes with signal integrity and fine-grained processing.

This is too much of an extrapolation even by the standards of envisioning things like Dyson Swarms. You are assuming that:

* It is possible to export or even host consciousness onto a digital medium - we still have no evidence for this

* All or most civilisations ultimately will want to transition entirely into a digital existence - the "entirely" part is important. If even 1% of a K-2 civilisation decided to stay organic, that would still lead to a Dyson swarm with a population approaching trillions.

* Civilisations of this tech level would do a cost benefit analysis and decide that the several orders of magnitude more resources on a star is outweighed by the inconvenience of a gravity well - I don't think orbital rings are that mass or energy intensive to build and run for this to make any sense

* There will be no future use of waste heat or method of disposal that goes beyond simple dispersal - the jury is still out on that, it may be possible to dispose of waste heat directly onto a black hole. If this turns out to be correct, the energy of a star is more than enough to power a sufficiently powerful laser array to create many in the gigatonne range.

>Expanding menace civilizations will run up against overwhelmingly more advanced stable cultures before long and be contained or destroyed, so odds are none could get here before that happens.

This seems like an interesting thought experiment care to expand on that?

An expanding menace culture will also be young, just because anything growing fast can't have been doing it for long. By comparison, a stable culture can stay that way indefinitely, spending its resources accumulating knowledge and skills instead of on expanding, and so can accumulate a very great deal of both over a vast stretch of time. It has perhaps less access to materials, but a solar system has a great deal of material to start with, and it is not stretched thin.

When an expanding menace tries to absorb the ancient stable culture, it has key disadvantages. Its attention is spread over activities on a large periphery, and its stores of knowledge and weaponry are limited. The ancient culture has been found by many menaces before, and survived them all. It knows of other old, stable societies, and they may even have evolved a common plan for dealing with menaces.

It is conceivable that the expanding menace would try to flow around the old stable societies, like a river around rocks, without threatening them enough to provoke a backlash, but that runs against the logic of expansion.

So, odds are any expanding menace will encounter one of them, or more than one, if needed, before it gets to us. Each such encounter will be an existential challenge at bad odds, which multiply out increasingly close to zero.

Thus, the stable condition of a galaxy is a sparsely occupied archipelago of deeply ancient, unassailable cultures not interested in expansion, so not visiting, e.g., us, with the occasional rash of menace, dealt with firmly.

Are you arguing that the expanding menace culture must be young because such cultures wouldn't last long because of conflict? I think a lot depends on how densely populated the universe is. At a limit imagine one long lived intelligence per galaxy. You could have a poisonous disease the size of a galaxy 10 million years old sending out spores to poison adjacent galaxies. Maybe we are even the present genesis of this.

As you adjust down you could trivially and likely have tens of light years between cultures or even hundreds on average if intelligent cultures are short lived or particularly rare. Expanding menaces could be automated and self replicating and designed to create an expanding zone of safety for an old stable society in a way that isn't easily traceable to the old stable society.

> "Are you arguing that the expanding menace culture must be young because such cultures wouldn't last long because of conflict?"

It's young because it's expanding. To first order, divide the radius by the rate of expansion and you get when it started. The society that bides its time for millions of years and then turns menace does not pass the smell test. Every year they go without menacing, the less likely they ever will.

Anyway, whoever's (1) inside the perimeter, (2) is a bad trading partner, and (3) not burnt is a pretty good bet for who's responsible. If there are two plausible candidates, they are better both dealt with.

It's also true that they don't last long because of conflict, but that's secondary.

A sorcerer's apprentice scenario is conceivable only in the short term. To maintain expansion demands adaptation to an increasing variety of new challenges, whose variety and strength increase as the fourth power of expansion radius. (Three dimensions for space, one for age of opponent.)

One can invent myriad obscure scenarios, of decreasing likelihood. It's a big universe, rashes happen, but it's a big universe, so they mostly happen somewhere else.

this is an interesting observation, and it plays out exactly like this many times over in the 'Stellaris' RTS game.

Stable societies that stick to their own region while prioritizing research ('growing tall' is the name for the strategy) tend to win out in battles against those that 'grow wide', grabbing all resources and expanding into them with little regard to research and personal affairs.

Those that 'grow wide' tend to win the games through simple attrition on a long time-span at the end-game phase. Simple resource volume tends to be able to win against vastly superior forces, much like a StarCraft 'zerg-rush', and the superior force usually loses in a 'death by a thousand cuts' fashion -- but individual battles before this phase of the end-game are almost exclusively won by small civilizations that 'grow tall', much like the 'stable culture' of your example.

The 'Growing Tall' strategy tends to be the one chosen by players who like to end games early and play aggressively against the other players -- contrary to the sedentary and passive method of play that the strategy facilitates.

In Stellaris, everybody starts at the same time, right? And, close enough together that they are sure to encounter one another pretty early? And, material resources actually matter?

It seems like being equipped to, say, cause a solar flare to sterilize an offending planet would tend to discourage an aggressor before their ships got used up. Probably a flare wiping out a neighboring planet (e.g. one like Venus) first would convey the message adequately.

Unless you can harvest interstellar medium at scale stars are where most mass is locked up, conveniently in a single place even. Outer belt objects are quite small in volume in comparison and inconveniently far from each other.

The outer belt objects are small compared to planets, but are enormous considered as extracted volume, and uncountably numerous; whereas on inner planets you are effectively limited to the solidified skin at the bottom of an annoying gravity well, bathed in heat that must be shed.

Kuiper belt distances are inconvenient only when you are in a hurry and have limited speeds. Given fusion propulsion, nothing inside a solar system is especially far from anything else. But a large volume to operate in, which grows as r^3, is valuable, and an unlimited sink of cold, moreso.

If you need more mass, Neptune is right there.

Good point - the exposed surface are for easy mining is pretty massive for outer system objects & accessible without the need for advanced stuff like planet cracking and solar lifting.

At 1G acceleration, nothing in the Kuiper belt is more than a few days away. You can send out robots if you need more mass than you have on hand.

Or, maybe you are robots, and can take 100G. Then the Oort cloud is your playground.

With sustained > 1G we are effectively talking torch drives, not just "normal" fusion drives. Not many technologies we know of that might pull that off, possibly with the exception of nuclear salt water rocket.

Anything we could ever cobble together is necessarily unspeakably primitive when compared to what the Oort Cloud "elder gods" perfected lo untold eons before primates first chipped rocks.

To add, we are only just beginning to experience a hint of the plague of excess exhaust heat. It only gets worse, and the Third Law of Thermodynamics is a harsh mistress.

Well, for how bad it can get one can check Puppeteers home world in Nivens Known Space universe - that damn planet shines white in visible spectrum in many places due to waste heat and they indeed had to move it farther from their sun.

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