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Roko comments on Max Tegmark on our place in history: "We're Not Insignificant After All" - Less Wrong

18 [deleted] 04 January 2010 12:02AM

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Comment author: Mitchell_Porter 04 January 2010 07:13:20AM 3 points [-]

Tegmark:

this brief century of ours is arguably the most significant one in the history of our universe: the one when its meaningful future gets decided

There are at least two dubious inputs going into a statement like this. (And I see you making such a statement yourself, on your homepage, Roko!)

The first one is definitely a mistake, but perhaps not a very consequential one. Even if we accept, for the sake of argument, the proposition that the state of the visible universe indicates an absence of spacefaring intelligent life elsewhere, that is not the whole universe! All we can see is what is within our past light-cone. We have no information on what has happened in those galaxies since then - and in some cases, we are referring to billions of years. And then there's the whole rest of the universe, possibly infinite in extent, with which we have not yet interacted.

So the idea that the future of the entire cosmos hinges on what happens on Earth in the next few years is hyperbole, even if one accepts the usual premises.

The second dubious ingredient to these judgments is the premise itself. I discern two arguments in favor of the proposition that the universe is empty of intelligent life (among people who make statements like this):

1) The visible universe appears to be explicable entirely in terms of natural astrophysical structures. If there were galactic intelligences, they wouldn't let the stars shine freely into space, they'd surround them with Dyson spheres so as to harvest that radiative output for computational or other purposes, or they would otherwise engage in works of astrophysical engineering.

2) If Earth was in a region of space controlled by an alien intelligence, life, history, and evolution as we know it would not have happened. There would have been some sort of intervention, whether benevolent, or just to appropriate the atoms of this solar system for technological projects and other alien purposes.

Argument 1 is interesting but not exactly conclusive. Lots of the universe is dark matter. It may be that the dark matter has been appropriated by spacefaring intelligences and used so as to make every photon count, and that the regions of the universe which are visibly emitting light are interzones - demilitarized wilderness areas, regions where an aeon-long process of scouting and negotiation is occurring, and so forth. In fact, I find this interpretation rather more sensible than the assumption of a wholly uninhabited universe. But it's still very hypothetical. It's hard to even comprehensively list all the uncertainties which one must guess about in order to produce scenarios like this. You need to guess at the frequency with which spacefaring intelligence appears in the universe, the frequency with which it becomes expansionist, the difficulties associated with expansion, the stability of value systems and civilizational tendencies over million-year periods (if a super-civilization decides to end itself, it should be good at doing so; suicidal tendencies only have to rise to the top once; and millions of years offers a very long time for them to do so).

As for argument 2, well, there are certainly alien value systems which would leave us alone, though I have no idea how likely such value systems are to arise. But in any case, the idea that we are in a wilderness area between the local dark-matter civilizations is sufficient to explain why we've been left alone, without having to posit a completely empty universe.

Comment deleted 04 January 2010 12:09:19PM [-]
Comment author: Mitchell_Porter 05 January 2010 04:27:24AM 6 points [-]

Why does every alien race act the same and try to look invisible? Game theory. They all know that evolution will have produced unacceptable value systems elsewhere in the universe. They all know that they risk losing everything if they come into conflict with a superior hostile power. But a strategy of persistent stealth means that at least a certain amount of value will be achieved. So, they live in the dark matter and they don't advertise their presence by visibly messing with the light matter.

I'm not actually saying this is how it is. But it is a hypothesis (one of many, see below) consistent with all the data we have.

even the high entropy photons that one would normally expect an information processing entity to excrete as waste heat?

Maybe they pipe their waste heat into supermassive black holes.

Regarding the cosmic distribution of dark matter: On my reading there are two levels of structure inferred. There is a dark matter halo around most galaxies, and then there are filamentary networks on the supergalactic scale. The most common view is that it consists of exotic particles, not in the Standard Model, which gravitate but do not radiate. The filaments formed after the big bang due to gravitational clumping, and in turn seeded the formation of the galaxies from light matter.

If you accept that view, then the dark matter is not light matter with all the light being harvested, as I originally suggested. It's just a separate type of matter which doesn't glow in the first place. So if I want to promote the universal stealth hypothesis, perhaps I should deemphasize the role of dark matter and just emphasize the imperative to be invisible, to blend in against the natural cosmic backdrop.

However, our theories about the dark matter are rather tentative, and if you did assume a significant population of galactic and intergalactic civilizations with a common invisibility imperative, I wonder if that would make it plausible that far more of the dark matter is just light matter being kept dark. I don't know the astrophysical reasoning well enough to judge. But there is an issue here which I don't think astrophysicists and cosmologists have ever systematically considered: if large portions of the universe are already artificial, how would that affect our cosmological theories? A lot of cosmology involves elaborate inferences from data like observable atomic abundances. If that data is systematically skewed by biogenic or technogenic influences, then so are the inferences.

And speaking of tentativeness, and of elaborate inferences, all these future scenarios and cosmological theories (and the idea that most of the universe is destined to be converted to computronium is a cosmological theory) are hypotheses built on hypotheses. I think we are in a realm here where it is not rational to pretend to be Bayesian and assign these hypotheses probabilities. I suspect that the most we should say is that we have a list of qualitative hypotheses, each of which are internally consistent and consistent with the data, and then perhaps a list of increasingly dubious lesser hypotheses, which we can affirm to be unlikely for some reason or other. But it's not as if we even know the extent of the hypothesis space. An important aspect of the situation is that our list of "possible and not obviously unlikely" scenarios may grow at any time.

However, not only do people not adhere to this standard of objectivity, I doubt that it would even be advisable to enforce this as a norm, except reactively, after new hypotheses are invented and advocated enthusiastically, or new turns of argument are constructed. Thus, I was criticizing Tegmark and you for saying these things about the future as if you really do know them to be likely, but then I went and said I preferred my own idea about how everyone is hiding in the dark matter. Well, that was psychologically accurate, but I "preferred" it because it gave me more to think about - the stratagems and counter-stratagems of these hypothetical civilizations, and so forth. On purely epistemic grounds, I see no reason to prefer that scenario over the one you were originally advancing, namely, there are no civilizations or intelligences of cosmic extent already existing in the observable universe. The Great Filter might really be that strong; I don't know; it's consistent with everything I do know, so I must regard it as possible.

However, if we had both adhered to the principle of being agnostic on matters we don't actually know about, this exchange might never have occurred, and certain possibilities might never have been explored and critiqued. Then again, maybe agnosticism is so psychologically difficult that one should not worry about asserting it too much; the challenge will always be to assert it enough to rein in some of the false claims of knowledge which abound everywhere.

Returning to the original scenario, one more thought. It has a rather more pessimistic interpretation: that perhaps our past light-cone contains many examples of civilizations which got this far and were then destroyed. On that view, the odds are actually against us.

P.S. by referring to galactic "wilderness" I didn't imply a nature-loving value system. Wilderness simply means, a region not transformed by technology or civilized management. Wilderness zones may exist for reasons other than being nice. Maybe they only care about certain phenomena or possibilities which simply don't exist here. The more dubious aspect of this idea is not that they let us suffer, but rather that they are letting us develop technologically, to the threshold of being a threat to their own purposes.