= 27d567bc2d48d9f40e9ccc20ea370b15)
Jack comments on Open thread, November 2011 - Less Wrong
You are viewing a comment permalink. View the original post to see all comments and the full post content.
= 783df68a0f980790206b9ea87794c5b6)
Loading…= b715d02e85f7b3b4ae65ca3d3e450868)
Subscribe to RSS Feed
Powered by Reddit
= f037147d6e6c911a85753b9abdedda8d)
You are viewing a comment permalink. View the original post to see all comments and the full post content.
Comments (209)
In one of the subthreads concerned with existential risk and the Great Filter, I proposed that one possible filtration issue is that intelligent species that evolved comparatively earlier in their planets' lifetimes or evolved on planets that formed much sooner compared to when their heavy elements were formed would have a lot more fissionable material (especially uranium-235), and that this might make it much easier for them to wipe themselves out with nuclear wars. So we may have escaped the Great Filter in part by evolving late. Thinking about this more, I'm uncertain how important this sort of filtration is. I'm curious if a) people think this could be a substantial filter and b) if anyone is aware of discussion of this filter in the literature.
If we had had more fissionable material over the last 100 years how would that have made nuclear war more likely?
If life had evolved say 2 billion years earlier than there would be about 6 times as much U-235 on the planet, and most uranium ores would be around 3% U-235 rather than 0.7% U-235. This means that making nuclear weapons would be easier, since obtaining enough uranium would be a lot easier and the amount of enriching needed would go down as well. For similar reasons it would also then be easier to make plutonium in large quantities. However, the fact that one would still need some amount of enrichment means that this would still be technically difficult, just easier. However, fusion bombs are much more effective for civilizations destroying themselves, and even with cheap fissiles, fusion bombs are still comparatively tough.
There's another reason that this filter may not be that big a filtration event: Having more U-235 around means that one can more easily construct nuclear reactors. Fermi's original pile used non-enriched uranium, so one can have a (not very efficient) uranium reactor simply from that without much work, and modern reactors can use non-enriched uranium (although that requires careful designs). But on a large scale, in such a setting, somewhat enriched uranium (compared to what we consider normal) would be much more common, and functional, useful reactors can be easily made with percentages as low as 2% of U-235, and in this setting most of the uranium would be closer to 3% U-235. So making nuclear reactors much easier means one has a much easier source of energy (in fact, on Earth, there's at least one documented case of such a reactor occurring naturally about 1.7 billion years ago ). Similar remarks apply to nuclear rockets which are one of the few plausible ways one can reasonably go about colonizing other planets.
So the two concerns are: a) how much more likely would it be for a civilization to actually wipe itself out in this sort of situation and b) how much is this balanced out by the presence of a cheap energy source and an easier way to leave the planet and go around one's star system with high delta-V?
Perhaps it makes it a little more likely for a civilization to end themselves but it doesn't seem to have the potential to be a great filter. It doesn't seem that likely that even a large scale war with fusion weapons would extinguish a species; and as you point out there is still quite a barrier to development of fusion weapons even with more prolific 235. So far in our history the proliferation of nuclear weapons seems to have discouraged wars of large scope between great powers. In fact two great powers have not fought each other since Japan's surrender. Granted this is a pretty small sample of time but a race without the ability to rationally choose peace probably has little chance regardless of 235 levels. So if there is a great filter here with species extinguishing themselves in war, more 235 makes it a little bit greater only.
What, exactly, would the increased uranium level do?
It doesn't seem to me that it would speed up the development of an atomic bomb much because you have to have the idea in the first place; and in our timeline, the atomic bomb followed the idea very quickly (what was it, 6 years?); the lower concentration no doubt slowed things by a few months or perhaps less than 5 years, but the histories I read didn't point to concentrating as a bottleneck but more conceptual issues (how much do you need? how do the explosive lenses work? etc.)
Nor do I see how it might speed up the general development of physics and study of radioactivity; if Marie Curie was willing to go through tons of pitchblende to get a minute bit of radium, then uranium clearly was nowhere on her radar. Going from 0.6 to 3% won't suddenly make a Curie study uranium ore instead.
The one such path would be discovering a natural uranium reactor, but how big a window is there where scientists could discover a reactor and speed up development of nuclear physics? I mean, if a scientist in the 1700s had discovered a uranium reactor, would he be able to do anything about it? Or would it just remain a curiosity, something like the Greeks and magnets?
Well, one issue is that it becomes easier for countries to actually get nukes once the whole technology is known. One needs to start with less uranium and needs to refine it less.
Regarding the Curies, while that it is true, it might be that people would have noticed radioactivity earlier. And more U-235 around means more radium around also. But I agree that this probably wouldn't have a substantial impact on when things would be discovered. Given how long a gap there was between that initial discovery and the idea of an atomic bomb, even if it did speed things up it is unlikely to have impacted the development of nuclear weapons that mcuh.
Your points about profileration and effectiveness seems to both be strong. Overall, this conversation makes me move my view in the other direction. That is, this seems to be not just not a strong filtration candidate, the increased ease of energy access argument seems to if anything push things in the other direction. Overall, this suggests that as far as presence of U-235 is concerned, civilizations that arise on comparatively young planets should have less not more filtration. This is worrisome.
Yes, but how much does this help? There are multiple methods available of varying sophistication/engineering complexity (thermal easy, laser hard); a factor of 6 surely helps, but any of the methods works if you're just willing to run the ore or gas through enough times.
That's a good point. So the only advantage comes from not needing as much uranium ore to start with and since uranium ore is easy to get already that's not a major issue.
I think it fails as a filter because even a huge nuclear war wouldn't wipe out eg cockroaches. Assuming "intelligent life evolves from multicellular life" is IID, with an early appearance it could happen a few times before the planet gets as old as ours. To wit: The only reason to think the dinosaur's extinction event wasn't nuclear war is a lack of fossilized technological artifacts; and it doesn't seem to have filtered us yet.
The only reason? The lack of creatures with appendages suitable for tool wielding or the evident brain capacity for the task doesn't come into it just a tiny bit?
Do we know that? Iguanodons for example have hands that look not all that terribly far off from hands suitable for tool use, some related species that we didn't find in the fossile record yet evolving proper hands doesn't seem impossible to me.
I have very little idea. Last I heard the brontosaurus doesn't even exist and the triceratops is really just an immature torosaurus. That gives a ballpark for how much confidence I can have in my knowledge of the species in that era.
This is incorrect. The name "brontosaurus" is incorrect. But the nomenclature correction to apatosaurus did not come with any change in our understanding of the species.
While that which was labelled brontosaurus was later subsumed into the previously identified genus apatosaurus the early reconstructed fossil which popularized our image of the brontosourus was also discovered to include a head based of models of camarasaurus skulls. That and it was supposedly forced to live in the water because it was too large to support itself on land. Basically the 'brontosourus' that I read about as a child is mostly bullshit.
Even this much I didn't have anything but the vaguest knowledge of until I read through the wikipedia page. As for possible tool capable appendages or even traces of radioactive isotopes I really have very little confidence in knowing about. It just isn't my area of interest.
Camarasaurus is a close relative, the use of it as a model for reconstructing the skull was deliberate. (Moreover, modern data shows that it was in fact quite a good reconstruction.) The water thing did turn out to be just wrong, but that's not any different than about the scale of change that has happened with a lot of dinosaurs (for example the changing understanding of how T-Rex hunted.) There's certainly been a lot of changes (although most of the brontosaurus stuff was known a very long time ago and just took a lot of time to filter through to popular culture), but none of it amounts to "brontosaurus" not existing.
Wikipedia is a pretty up-to-date source on dinosaurs, with lots of avid and interested editors on the topic. (The artistic reconstructions come close to being original research, but a reconstruction tends not to be used until it's passed a gamut of severely critical and knowledgeable editors.)
Remember that it's quite an active field, with new discoveries and extrapolations therefrom all the time. It surprises me slightly how much we know from what little evidence we have, and that we nevertheless do actually know quite a bit. (I have a dinosaur-mad small child who critiques the dinosaur books for kids from the library. Anything over a couple of years old is useless.)
I'm not exactly sure how much more or less common fossils are from various time periods but I think its fair to point out we have very few skeletons of certain hominids running around that fit that description in East Africa a few million years back.
Which dosen't change that you are right that it is very very unlikely to be the case that a tool using or very clever undiscovered species (at least to the extent needed to make the argument work) existed then. But we should keep in mind just what a puny fraction of extinct species are known to us.
Is this really important? The crucial point is some means for accumulation of cultural knowledge, which could well be implemented via tradition of scholarship without any support from external tools, and even failing that, ability (or just innate rationality) a couple of levels higher than human could do the trick.
Given runaway evolution of intelligence, it seem like ability to bear tools is irrelevant, and AFAIK evolution of human intelligence wasn't caused by the faculty of tool-making (so the effect isn't strong in either direction).
I find this comment extremely puzzling. How do you suppose an intelligent species could go about building nuclear bombs without the ability to use tools?
The relevant kind of "ability to use tools" is whatever can be used, however inefficiently at the beginning, to start building stuff, if you apply the ingenuity of an international scientific community for 100000 years to the task; not appendages that a chimp-level chimp can use to sharpen sticks in an evening. You seem to underestimate the power of intelligence.
This is directly analogous to AI boxing, with limitations of intelligent creatures' bodies playing the role of the box. I'd expect intelligent tortoises or horses should still be capable of bootstrapping technological civilization (if they get better than humans at rationality to sustain scientific progress in the initial absence of technological benefits, or just individually sufficiently more intelligent to get to the equivalent of the necessary culture's benefit in a lifetime).
There are a lot of species that are almost as smart as humans, and some even engage in tool use. (e.g. many species of corvids). But their tool use is limited, and part of the limit appears to be their lack of useful appendages and comparatively small size. In at least some of these species such as the New Caladonian Crow, tool techniques can be passed on from one generation to the next. This sort of thing suggests that appendages matter a fair bit.
(Obviously they aren't sufficient even when one is fairly smart. Elephants have an extreme flexible appendage, have culture, are pretty brainy, and don't seem to have developed any substantial tool use.)
Elephants or crows don't have scientific communities, so the analogy doesn't work, doesn't suggest anything about the hypothetical I discussed.
Yes (as pedanterrific noted). Unless the dinosours were sufficiently badass that they could chew on uranium ore, enrich it internally and launch the resultant cocktail via high powered, targeted excretion. That is one impressive reptile. Kind of like what you would get if you upgraded a pistol shrimp to an analogous T-Rex variant.
(Other alternatives include an intelligent species capable of synthesizing and excreting nano-factories from their pores.)
Replied to pedanterrific.
In response to that reply I note that I gave two examples of mechanisms by which a species might launch nuclear weapons without any ability to use tools. I could come up with more if necessary and a more intelligent (or merely different) mind could create further workarounds still. But that doesn't preclude acknowledging that the capability to use tools does give significant evidence about whether the species creates technology - particularly in what amount to our genetic kin.
Lack of fossilized evidence of technological artifacts is not the only reason to believe that the extinction of dinosours wasn't due to nuclear war. It is merely one of the stronger reasons.
Most of your assessment seems reasonable to me. However,
seems wrong. I haven't crunched the numbers, but I suspect that a species killing nuclear war would leave enough traces in the isotopic ratios around the planet that we'd be able to distinguish it from an asteroid impact. (The Oklo reactor mentioned earlier was discovered to a large extent due to tiny differences in expected verse observed isotope ratios.)
This was actually covered in a book I read (I think it was The World Without Us). Summary: even our reactors leave clear traces that will be detectable about as long as the mass extinction event we're causing. So a civilization and species-killing thermonuclear war would definitely be detectable by us.
Fair enough. I should have said "if the dinosaurs had been intelligent, and their extinction was due to nuclear winter following a large thermonuclear exchange, the history of our own species could still look substantially similar." Although evolution might have proceeded a bit differently with higher background radiation.
Phrased that way your point seems very strong. Indeed, dinosaurs died out only 65 million years ago, which isn't that long ago, especially in the context of this sort of filtration event.
Fallout is a technological artifact.
Yes, I'm not sure what your point is. Can you expand?
What you then provided as a counterexample of other reasons to reject this theory fits within the scope of things that are missing.
Ah ok. Yes, you're right, fallout should be covered for purposes of the original comment then.