[Ultra-Tech] Conservative hard SF... but not implausibly conservative

[Michael Thayne]

Originally Posted by Anthony

Outside of what we think of as hard sciences: they have a culture that has managed to cope with what we would see as insanely low growth rates. A 2.3% growth rate, which we consider reasonably healthy though not spectacular, is a factor of 10 increase in economy in a hundred years, which will put you at a type II civilization in about 1,000 years and a type III in another 1,000 years, and would consume the entire energy output of the observable universe in another 1,000 years. If they're 'only' a type II civilization in a million years, their growth rate is 0.0023%.

Economic growth is not quite the same thing as growth in energy consumption. Quick googling suggests energy per capita grew fourfold between 1820 and 2000, with population growing sixfold. That's a 24-fold increase in our total civilizational energy consumption in 180 years, or about 1.8% per year. Still, by my math, if current growth trends continue, in theory we'd be looking at Type III status in about 3,000 years.

This can't be right, though, because the galaxy is more than 3,000 light-years across. That brings me to a tricky question I was thinking about in the OP, but didn't want to get into that early: what's the lower-bound rate for how fast you can colonize a galaxy? This depends on a lot of factors—most fusion rocket we're sure we can build, whether antimatter propulsion will ever become practical, what's the smallest self-replicating machine we're sure we can build, etc. Anyone want to weigh in on those questions?

[Michael Thayne]

Originally Posted by ericthered

Isaac Arthur is very good, and he has a great respect for physics that serves the channel well.

The problem is there are days of material up there, and I wouldn't describe his future as "conservative SF". Its got some strong transhuman leanings, though he tends to seriously consider whether a given option would be adopted or not. He also thinks that strong AI (or at least human level) and mind uploading are very doable, though he emphasizes the uploading, not the strong AI.

From the channel:

• Building Big is usually just a matter of resources.*
• Space habitats are more efficient than terraforming.
• If you can feed your populace from food grown in artificial structures, you can house them luxuriously.
• Automation is world-changing, and we're on the cusp of achieving a lot of it, rather than finally winding down.
• Post-scarcity is temporary, limited, comparative, and often gradual.

I think those parts will be the most useful to you in building your setting.

*he actually describes how to build a "solid" ringworld without breaking the laws of physics. Its utterly nuts, but physically possible. The key is active support structures.

I mostly agree with this, though lately I've moved towards questioning whether mind-uploading will ever be cheap. We're nearing the limits of the shrinking transistor paradigm; proposals for where to go next are out there, but somewhat speculative. (Specific proposals get discussed in "Ultra-Tech Too" in the Tech and Toys III issue of Pyramid.) I can see progress grinding to a halt at roughly what Ultra-Tech calls TL9, which is enough to support ghost brain emulations running on the largest supercomputers, but not a world where biosapient labor is obsolete.

[Michael Thayne]

One potential issue with mega-projects is finding heavier elements in sufficient quantity. Some proposals I've seen assume you'd need to fuse light elements from gas giants into heavier ones. It's not clear to me, though, whether efficient processes for doing this are known to exist or not, or whether you'd wind up with mostly helium and a relatively modest supply of heavier elements.

[Johnny1A.2]

Originally Posted by Michael Thayne

I considered titling this post "minimum technological capabilities for precursors", but people tend to read "precursors" as "sufficiently advanced aliens" (i.e. ones whose technology is indistinguishable from magic), which is very much not what I want. Rather, I'm interested in this: if you have a civilization that's been around for a million years, but the setting is making very conservative assumptions about what things are possible in principle, what technology will they have?

The answer is probably close to what Ultra-Tech calls "conservative hard SF", i.e. mostly limited to TL9, but that can't be the whole answer. For example, some form of Dyson sphere is almost certainly possible to build, it would just take a long time. Many examples of human genetic engineering that Bio-Tech lists as TL10-11 are almost certainly possible as well. In particular, if we know something exists in nature, and it isn't at odds with the energy requirements of a large brain, then it's probably possible to engineer a parahuman that has the trait, even if it takes centuries of trial and error.

Conversely, some TL9 technologies are of questionable feasibility. For example, the idea of a fast-acting and safe "sleep gas" (UT160) is highly questionable, no matter how much Hollywood seems to believe such a thing already exists.

Thoughts? What other TL10-11 tech belongs on the "definitely" list? What other TL9 tech belongs on the "questionable" list?

This really has no valid answer.

A civilization a million years older than us is further from us than we are from the Neandertals. Unless it just so happens that we've finally learned the real rules and there's no much left to find, it's not clear that we can even say anything about what kind of magic they might 'plausibly' possess.

Just for illustration, imagine a Roman in the time of Augustus Caesar trying to figure out what a civilization even 2000 years away might 'plausibly' have. He wouldn't even be able to express or define the context.

[Andreas]

Originally Posted by Michael Thayne

This can't be right, though, because the galaxy is more than 3,000 light-years across. That brings me to a tricky question I was thinking about in the OP, but didn't want to get into that early: what's the lower-bound rate for how fast you can colonize a galaxy? This depends on a lot of factors—most fusion rocket we're sure we can build, whether antimatter propulsion will ever become practical, what's the smallest self-replicating machine we're sure we can build, etc. Anyone want to weigh in on those questions?

The most important factor tends to be travel speed. Once resources are availible, exploting them takes very little time in comparison (as can be seen from Anthony's example), unless you have travel much faster than the speed of light.

This makes it rather simple. The time needed is only slightly longer than the time it takes for your fastest spacecraft (among those large enough to construct self sustaining infrastructure on arrival) to reach the part of the galaxy farthest away from the starting point.

[Anthony]

Originally Posted by Andreas

This makes it rather simple. The time needed is only slightly longer than the time it takes for your fastest spacecraft (among those large enough to construct self sustaining infrastructure on arrival) to reach the part of the galaxy farthest away from the starting point.

Well, that depends somewhat on the lifespan of your transports. There's a difference between remaining functional for a thousand years and remaining functional for a million years.

[sir_pudding]

Originally Posted by Michael Thayne

How does throwing lots of resources at the problem of death work in detail? If aging is all about DNA damage, injecting someone with cloned stem cells that you've gone to great effort to remove all damage from might work. Or maybe you could extensively re-engineer the human body to stop aging entirely. But I'm not sure we understand aging well enough to state with confidence that these things are possible.

If I could definitively answer this, I would have patents worth trillions and probably the Nobel. However, aging isn't an inevitable consequence of biological systems, but rather a beneficial trait that evolved in multicellular organisms and there are organisms that are biologically immortal. I certainly can't speak about a nonspecific alien biology in anything but the broadest terms. Any solution to longevity is probably a complex one, since the causes of senescence in vertebrates are myriad, no one technology is adequate.

To be clear, I'm not assuming the species' technological limits are self-imposed, a la the Vilani from Traveller. I'm trying to make pessimistic assumptions about what is physically possible, and see what we get.

In which case then they don't have a million year old civilization. That technology is extremely optimistic, much more than any of the things you are keen to dismiss.

Is this right? What are the materials engineering requirements to make the statite Shkadov thruster work? Is it within the realm of near-future solar sail designs, or does it require significant advances in materials engineering?

It doesn't, I think, require materials that violate any known properties of matter. It probably requires materials we don't have now, but if that is your restriction, they don't have a Dyson swarm either.

[Andreas]

Originally Posted by Anthony

Well, that depends somewhat on the lifespan of your transports. There's a difference between remaining functional for a thousand years and remaining functional for a million years.

That would make a difference, but not a large one. You could just stop at other star systems on the way and build more transports. The travel distance to the farthest point of the galaxy will only be sligtly longer even if they only remain functional for thousands of years.

With 10% of light speed and transports which remain functional for three thousand years, you would have to make roughly 250 stops along the way. Even if each stop takes one thousand years, that would just add roughly thirty percent of the time it would take to travel without building new ships.

[Anthony]

Originally Posted by Andreas

With 10% of light speed and transports which remain functional for three thousand years, you would have to make roughly 250 stops along the way. Even if each stop takes one thousand years, that would just add roughly thirty percent of the time it would take to travel without building new ships.

I was assuming a more reasonable 1% of c, but yeah, it's not likely to make a drastic difference. In any case, based on the fact that the aliens aren't here, we're forced to conclude one of two things:

1. Interstellar colonization is functionally impossible.
2. We're the first.

[Andreas]

Originally Posted by Anthony

I was assuming a more reasonable 1% of c, but yeah, it's not likely to make a drastic difference. In any case, based on the fact that the aliens aren't here, we're forced to conclude one of two things:

1. Interstellar colonization is functionally impossible.
2. We're the first.

Yes, the speed doesn't matter much since the number of stops don't grow much faster than the time it would take to travel straight there (at least not unless speed times how long the ships last becomes small enough that it is difficult to find reasonable good candidates to stop at along the way).

Well, we don't quite have to be the first one, but others have to be very rare (a small enough number to make it reasonably likely that all of them are either, very far away, very recent, unwilling to expand much or having failed in their expansion attempt)