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The Fermi Paradox revisited; random despatches from the front line

The Fermi Paradox probably doesn't need much introduction; first proposed by Enrico Fermi, it's one of the big puzzlers in astrobiology. We exist, therefore intelligent life in this universe is possible. The universe is big; even if life is rare, it's very unlikely that we're alone out here. So where is everybody? Why can't we hear their radio transmissions or see gross physical evidence of all the galactic empires out there?

If you aren't familiar with the Fermi Paradox, click that Wikipedia link above. Truly, it's a fascinating philosophical conundrum — and an important one: because it raises questions such as "how common are technological civilizations" and "how long do they survive", and that latter one strikes too close to home for comfort. (Hint: we live in a technological civilization, so its life expectancy is a matter that should be of pressing personal interest to us.)

Anyway, here are a couple of interesting papers on the subject, to whet your appetite for the 21st century rationalist version of those old-time mediaeval arguments about angels, pin-heads, and the fire limit for the dance hall built thereon:

First off the block is Nick Bostrom, with a paper in MIT Technology Review titled Where are they? in which he expounds Robin Hanson's idea of the Great Filter:

The evolutionary path to life-forms capable of space colonization leads through a "Great Filter," which can be thought of as a probability barrier. (I borrow this term from Robin Hanson, an economist at George Mason University.) The filter consists of one or more evolutionary transitions or steps that must be traversed at great odds in order for an Earth-like planet to produce a civilization capable of exploring distant solar systems. You start with billions and billions of potential germination points for life, and you end up with a sum total of zero extraterrestrial civilizations that we can observe. The Great Filter must therefore be sufficiently powerful--which is to say, passing the critical points must be sufficiently improbable--that even with many billions of rolls of the dice, one ends up with nothing: no aliens, no spacecraft, no signals. At least, none that we can detect in our neck of the woods.
The nature of the Great Filter is somewhat important. If it exists at all, there are two possibilities; it could lie in our past, or in our future. If it's in our past, if it's something like (for example) the evolution of multicellular life — that is, if unicellular organisms are ubiquitous but the leap to multicellularity is vanishingly rare — then we're past it, and it doesn't directly threaten us. But if the Great Filter lies between the development of language and tool using creatures and the development of interstellar communication technology, then conceivably we're charging head-first forwards a cliff: we're going to run into it, and then ... we won't be around to worry any more.

But the Great Filter argument isn't the only answer to the Fermi Paradox. More recently, Milan M. Ćirković has written a paper, Against the Empire, in which he criticizes the empire-state model of posthuman civilization that is implicit in many Fermi Paradox treatments. As he points out, for a civilization to be visible at interstellar distances it needs to be expanding and utilizing resources in certain ways. There is a widespread implicit belief among people who look at the topic (exemplified by the space cadets infesting the comments on this essay of mine) in manifest destiny, expansion to fill all possible evolutionary niches, and the inevitability of any species that develops the technology to explore deep space using that technology to colonize it. As Ćirković points out, this model is based on a naive extrapolation of historical human models which may be utterly inapplicable to posthuman or postbiological societies. Moreover, an alternative "successful" model for a posthuman civilization exists in the form of the stable but non-expansive "city-state". Ćirković explores the implications of non-empire advanced civilizations for the Fermi paradox and proposes that such localized civilizations would actually be very difficult to detect with the tools at our disposal, and may be much more likely than aggressively expansionist civilizations.

Finally, for some extra fun, here's John Smart pinning a singularitarian twist on the donkey's tail with his paper Answering the Fermi Paradox: Exploring the Mechanisms of Universal Transcension:

I propose that humanity's descendants will not be colonizing outer space. As a careful look at cosmic history demonstrates, complex systems rapidly transition to inner space, and apparently soon thereafter to universal transcension. For sixty years answers have been attempted for the Fermi paradox, yet the vast majority neglect what may be the most parsimonious explanation—a process of constrained universal transcension. I propose that any species or von Neumann probe complex enough to improve its intelligence while traveling through interstellar space would transcend shortly after beginning its journey, and less complex probes would not be sent for information theoretic reasons. The discrete universe that creates multi-local computational complexity rapidly becomes an "informational desert" (a well simulated past) to the leading edge of each local emergent intelligence.
The jury is still out on the whole singularitarian hypothesis, and especially on the more speculative stuff about our posthuman descendants bootstrapping themselves all the way into "'intelligent' cosmological developmental singularities, highly compressed structures, censored from universal observation, which are very likely distantly related to the quasars and black holes" (ibid.), but it's certainly one possible answer; as Seth Lloyd demonstrates in his Nature paper on The Ultimate Limits to Computation, when you approach maximum utilization of matter and energy for computation what you end up with begins to look startlingly like a black hole. If we follow the posthumans by assuming that truly advanced civilizations will use computational systems rather than unorganized matter, then it's down the rabbit hole that we're heading, which fits neatly with the city-state model that Ćirković explores. (Although no discussion on the subject would be complete without mentioning the dissidents; so let's just say, Rudy Rucker disagrees.)

Finally, for a fun long-range perspective, here's John Baez on the end of the universe, and to take it one step beyond, a brief run-down on the perplexing topic of Boltzmann brains, a topic which may itself have further implications for the Fermi Paradox.

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141 Comments

1:

Milan M. Ćirković's answer seems pretty close to the answer in Accelerando.

Personally I like to imagine they're here and watching us, perhaps in the form of un-detected utility dust. Either that or we're some school-kid's homework project...

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2:
Either that or we're some school-kid's homework project...
Which would explain why the hypothetical Intellegent Designer didn't do such a good job. 8-)
3:

Just one thought about the radio transmissions: part of the reason is that a lot of searcher were confined in their frequency range. Most notably the 21.3 cm wave of hydrogen. For some reason people thought that this would be a likely wavelength that aliens might be using. Now imagine we'd be on alpha centauri: when would have been the last hydrogen wave radio transmission that we'd have heart? Well, there was none or only a few. The frequency is of no technical importance, has no characteristic that makes it especially useful for interstellar communication. It is just an arbitrary frequency. If we don't use it - why should they?

It would be better to have no assumptions and keep our ears (and antennas) open.

It is just 15 years ago that people thought that exoplanets were a rare thing, and nobody of scientific note had even thought of the possibility of finding a giant planet in an orbit lasting as little as 4 days or less. We're an ignorant bunch - which is something that we should account for before we say that there's nothing out there that we could identify (even with current techological limitations) as a sign of extraterrestial life.

4:

Also, even the "city-state" or "down the rabbit hole" options are quite heavily value laden. For example, city-states don't necessarily imply turning away from the stars - they trade and explore and communicate. In fact, a lot of historical city states existed because they substituted the sea - world trade, intellectual cosmopolitanism - for the territory they lacked.

Our Hanseatic future...

Further, talking about "down the rabbit hole" implies there's some kind of moral inferiority about this option to the 50s US Teddy Roosevelt with Rockets worldview. After all, does anyone think science would stop in such a scenario - wouldn't those beings be sending out hyper-miniaturised probes, smart dust, to explore the universe, if just for fun?

But no, you've got to have teh space farmers an lasers an stuff. Which, come to think of it, is a special case of the longstanding and genuinely evil motif of the city-as-whore, Handler statt Helden etc etc...a fave of our friend Leo Strauss, and James Kunstler for that matter.

5:

Radio Lab has some good episodes around this question. And it has some good episodes around totally unrelated questions. So there.

6:

I've always thought we have a "great filter" coming up , one which is almost impossible to escape. If you extrapolate the curves of "destructive power available to a given individual" expressed in area affected and "area of distribution of population" they will cross at a point about 40 years ago. That's mutually assured destruction for you.

But if you extrapolate the "destructive power available to _any_ individual" with the rise of nanotech, bioengineered pathogens etc, we will soon be entering the time where that deluded person will not be selected by rising to the top of their party/ running a country/ being good at nuclear physics and having a spare bit of plutonium. Anyone out of a few billion who attempts geocide will have the resources to do such a thing.

One final factor which makes this all but inevitable, to my mind, is the type of intelligence which achieves this power is probably also the type of intelligence which can be wrong, which can hold false beliefs about, say, the existence of an afterlife which justifies killing the entire race to bring them all into heaven.

Simply stated: in a gravity well, the energy available to distribute and sustain a breeding population off-planet exceeds the energy needed to destroy the population of that planet.

There are some massive assumptions in this which makes it's generalisation to the Fermi paradox problematic (the pattern of distribution of energy amongst individuals, location in a gravity well etc). This doesn't mean that it's not a Great Filter we face right now.

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7:

Speed of light is a serious issue. One might conjecture that all the interesting stuff will be happening very close to other interesting stuff due to the speed of light. It's obvious even now with bleeding-edge machine-driven electronic capitalism.
Players in electronic markets are now working on sub-10-millisecond time scales (for market makers at least), and the response time to required to be competitive is dropping rapidly. A log-linear plot shows (assuming continuing reductions in time to respond to new information) that players will need to be within a kilometer of the exchange they compete in within the mid-teens, within a single building a few years later, a small sphere (with serious cooling issues) several years later.

I haven't the foggiest conjecture how this all plays out with multiple centers of interest (e.g. exchanges in major cities separated by thousands of kilometers by historical accident).

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8:

Re 3: 'The frequency is of no technical importance, has no characteristic that makes it especially useful for interstellar communication.'

Not so. It's the absorption frequency of hydrogen, the most abundant element in the visible (that is, excluding dark matter) universe. Our own astronomers run sky surveys at that frequency for reasons unrelated to SETI and it seems reasonable to expect that alien astronomers might do so as well. See for example planetary.org/programs/projects/setiathome/setiathome_20040804.html

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9:

Here is a stupid theory for you.

They don`t communicate with radio, but with messenger ships, because they are afraid of other civilizations. Also, difference bitween 100% and 90% of speed of light is not that big.

Paranoia filter.

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10:

Hi Charles, do you think that the Fermi paradox is the main concern for hard science fiction? I believe it does. It can be limiting of course, so of course sometimes you just don't want to discuss the issue. But if you write hard SF you just cannot pop in a few alien cultures in the 21st without some hard questions why we didn't notice them before.

I mean, even Star Trek had to answer that question (we don't have warp drives, so they don't bother with us).

I have a hard time believing SF that just populates the universe with aliens without trying to explain why we don't notice them now. And in my experience the SF that tries to explain this paradox leads to the best stories.

11:

@8:

I know that it is an absorption frequency of hydrogen, which makes it all the worse for communication. I get the point that it is a frequency that everyone is quite likely to look at with relatively sensitive equipment, but if you really want to try to maximize the signal strength on the receiving end, you will use anything BUT an absorption frequency of the ubiquitous hydrogen.

It's like trying to find out whether a TV program is American or not by listening for the acoustic signature of the words SHIT and FUCK. Everyone knows they come up regularly in conversations in America, so this should be reliable way to distinguish American language programs from others, shouldn't it?

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12:

As far as the development of technological civilizations, even if we had the same scientific knowledge that we have now, would we have developed anything like the level of technological advancement that we have now without the discovery of oil and its uses? Compared even to other fossil fuels, could a "steam" powered economy have emerged anything like ours today? Sure, we could have discovered and utilized electricity, but not on the global scale we have now. Could we have even gone to the moon (or just into space) without the use of petroleum in manufacturing and fabrication?

It may simply be that even though conscious and intelligent life is possible throughout the universe, the energy requirements of technological life are too great for them to last very long.

13:

Meller, if they're afraid of other people they'll communicate by tightbeam/laser. In fact they'll do that *anyway*, because it's vastly more efficient than broadcasting.

This is one problem with looking for broadcasts on the hydrogen line: off planetary surfaces broadcasting is inefficient, so in the end for sheer efficiency's sake everyone will migrate to tightbeaming who can do so. (On the surface of planets with magnetospheres it's useful, but only because most of the energy will bounce around the planet, i.e. *not* be radiated to somewhere where we could pick it up).

The other problem is that, well, its the hydrogen absorption line! If you want to transmit signals a long way you do *not* use that frequency, because it gets absorbed by the most common element out there!

The only circumstances in which aliens would want to broadcast such signals is if they're actively *trying* to send out 'hey, look at us!' signals to the local stellar area, probably by tightbeaming to lots of candidate stars. In *that* case, and *only* in that case, does using the hydrogen absorption line make sense, because it *is* a frequency that everyone who knows about spectra will realise is significant on a universal scale, and thus it's an arbitrary frequency which maybe disconnected species can independently decide to use.


--- If, that is, they think like us. This seems to me to be impossibly unlikely: our psychology, like the rest of our biology, is the product of too much chance to be replicated by another instance of the evolutionary process. What's the chances of aliens even being tetrapods? Low, I'd say. Really really low. They'd probably still have a cellular structure of sorts because, well, that's useful to keep yourself from mixing up with your neighbours or dissipating into the surroundings. But everything else is a toss-up with unknowns on all sides... the question will probably be not `do they think like us?' but `do they have anything we'd recognise as a psychology at all?'. Most terrestrial species don't: even most of those with nervous systems don't --- quick, what's the psychology of a bee? --- and of those terrestrial organisms we might plausibly consider intelligent, the only ones we've been able to communicate with at all are close relatives, those optimized for great ability at mimicry (e.g. parrots) or those that we modified (e.g. dogs). Octopuses and squid are certainly intelligent in a sense, as are some cetaceans, but communication? Hardly. They're too different. And they're close relatives, under a gigayear removed from us and so close on maps of global genetic diversity that if you print them on A4 paper we overlap at the same point. (Most of the tree of life is bacteria, of course.)

(SF works that try to construct radically different alien psychologies seem to be rare, as befits most SF's job of mirroring our concerns: the only works that occur to me right now are Terry Carr's _The Dance of the Changer and the Three_ and Peter Watts's _Blindsight_. Warning: both are quite depressing, and the creatures in the first story *are* very similar to us in some ways: e.g. they have a recognisable psychology. Hey, it's old stuff, the boundaries were closer in those days.)

14:

One more thing: before you think `of course aliens will have nervous systems', those too are the product of chance and necessity[1], specifically, peripheral nerves at least appear to be heavily derived hacks on blood vessels, and even now similar signals are used to guide neurons to their destination and to guide blood vessels. And they appear to have evolved only once (unlike, say, eyes). Will aliens have had the same fluke event? I doubt it.

There are so *many* crucial fluke events behind things that we consider ordinary and boring.

Hell, forget 'will they be tetrapods?'. Will they even have *mitochondria*? The Oxygen Catastrophe took about a billion years to raise oxygen levels in the ocean to the point where you had to be oxygen-tolerant or die, and most things died: but survivors are found on all branches of life, and there are multiple tolerance methods known, so aliens being tolerant of oxygen is plausible. But learning to *use* it, well, that seems to have been a one-off, the citric acid cycle being a result of contingent cooptation of lots of stuff evolved for other reasons: ATP synthase also seems to have evolved exactly once, from some older secretion system, and *everything* that uses oxygen uses ATP synthase. After that distant prokaryote learned to handle oxygen, it swapped the trick with lots of other prokaryotes, but some prokaryote becoming a mitochondrion was again a one-off event: and if you can't burn oxygen, is your metabolism even going to be fast enough for nervous systems to be worthwhile? Of course there's no requirement for multicellular organisms to need mitochondria: maybe they're doing all the necessary stuff on their cell walls like mitochondria and aerobic prokaryotes do. But now your cells have to be small, or really oddly shaped...

The thing about aliens is, they'll be *alien*.

(Warning: my molecular biology knowledge has numerous gaping holes in it, but I *think* the stuff above is right. If it's wrong, please say! The broad outline, `le hasard et la nécessité', is definitely right.)

15:

I'm reading The Day of the Triffids for bookgroup Saturday. There's a great filter!

16:

John Henning: Oil is more convenient than, say, running vehicles on charcoal gas -- but that was done in Europe (and I think in Brazil) during WW II.

If our world collapses back to early stone age, lasting just long enough to use up the last of the easily-reachable oil, the next civilization might run on alcohol.

17:

For some reason, scientists haven't extended the Fermi Paradox to crosstime travel. If crosstiming is relatively easy, there are umpteen Earthlike Earths where crosstiming civilizations could sprout. Why haven't we been visited by technologically-superior Neanderthalers, descendants of Siberian apes, or descendants of Edicarian fauna?

18:

Dan: er, because crosstiming is very nearly impossible? The most you can do is get some interference fringes from very nearby universes. Unless we're wrong, of course, but it seems to me that if we *are* wrong, the most that's possible is like with time machines: perhaps you can build a 'crosstime machine' that allows travel to all many-worlds universes that forked off from that in which it was built: but if that's it, you'll never see visitors from some branch which has crosstime travel when you do not.

(also, because plants aren't very good at building stuff. ;} )

19:

Ah, the Fermi Paradox, my very favourite example of the Retrospective Fallacy.

Nix: some prokaryote becoming a mitochondrion was again a one-off event

Well, not exactly. I'm not 100% sure about mitochondria, but there's good evidence for multiple endosymbiotic origins of chloroplasts, which is basically the same process. There's even a group (the Rhodophytes, if memory serves), that have a quadruple chloroplast membrane, having co-opted their chloroplasts by enveloping an entire other alga that was already using them... It's probably an accident of history that this process happened multiple times, giving rise to multiple phyla of eukaryotic "plants". I think most of the prokaryotes that became their chloroplasts would have had their own oxidative electron-transport chain, but the hosts already had mitochondria so they got rid of that.

Hell, we're not even very good at noticing intelligence when it's right under our noses (and I mean elephants, not the underwater sex maniacs). And less than 100 years ago there were tribes in Amazonia and New Guinea who were totally unaware of the supposedly world-spanning empires they shared a planet with. I don't think that's too bad a metaphor for what could easily happen between two technological species of radically different ages.

The think that bothers me the most about the Fermi paradox is the hubris. How long have we really been in a position to notice anything untoward in the cosmos around us? Even really close to us? Less than 100 years. Less than 50, realistically. How big is the galaxy, and how old? Even if it's swarming with other intelligent species, what are the chances of us noticing one in the incredibly short length of time we've so far been capable of same? Especially given all the constraints other people have mentioned? I wouldn't give you tuppence for that sampling design in my day job :)

20:

Actually, it's not the Rhodophytes, they're a pretty large group and the one I'm trying to think of is a bit obscure. Cryptophytes, possibly.

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21:

Or the idea that someone/something is KILLING them off and our neck of the woods was "weeded" "recently".. ?!
:)

22:

There are, of course, other "hard" Fermi dodges. I like to summarize them in one or two words that any sci-fi reader should be able to decode.

1. Technological Quarantine (cf. Star Trek)
2. Sociological Quarantine (ie. no demonstrated ability to play nicely with the other children)
3. Medium Rare (eg. 1 per galaxy average)
4. Ancestor Simulation (cf. C Stross)
5. Alien aliens (ie. the difference is more than ears or foreheads)

There are many others, of course! :)

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23:

The Fermi Paradox probably doesn't need much introduction

I wish that were true. I've never seen a discussion of the Fermi Paradox in which its fundamental point (universality) was not misunderstood by at least half the commenters, if not also by the author of the essay.

Sadly, it turns out to be the author again in this case, as in your nasty remark about "space cadets".

24:

Chris L: Chlorarachniophytes? (See e.g. ).

25:

Del, be careful, or Charlie may set his ninjas on you. (That part of the space cadet thread had me laughing so hard it hurt for a while.)

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26:

To me it becomes relatively easy to understand.

Intelligence develops up to the level when it can download the total brainstate of an individual and simulate it. From that point forward reality, the universe that the entity perceives, is mutable. In essence every individual can create their own personal heaven, and evolve and develop however they wish. Weirdos can make it hard for themselves in any way desired. There are no limits.

Next to that the 'real' world is a poor and limited alternative. A prison next to the freedom to go anywhere, do anything.

Is it any wonder the only groups still locked up are those who haven't quite realised where the key is? We are maybe a few decades from walking out the door ourselves. Next to that, no other course is as easy or positive.

27:

The solution to Fermi Paradox is obvious. Even our own electro-magnetic footprint is getting smaller and smaller: well-comressed and well-encrypted communication signals are indistinguishable from thermal noise. The period of time during which a civilization is emitting low-entropy, high-power radio signals might not exceed 200 years and it is rather unlikely that this extremely short period of two civilizations overlap.

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28:

I just couldn't help it;

http://xkcd.com/384/

If I had a personal choice - completely without study, research or any qualification to say so - I'd go for the sheer alieness of any other 'civilizations'.

What in the hell makes anyone think, for a start, another specied would even care if the rest of us are out here? You asume a psychology even remotely similar to ours - created over generations of tradition, belief, war...

If we ever encounter anything it'll likely be a pure accident. Not on our side perhaps, but defiantely on theirs.

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29:

I just love Boltzmann brains, of course a few problems arise as, by current thinking, they should be far more common than universes like ours. This leads to problems that really spook the fundamentalist materialists who call themselves agnostics, or even real agnostics like me, in fact even true believers, spook us enough so we carefully don’t think about them too much.

In short, while the vast majority of Boltzmann brains will do the “dissolving back into the equilibrated ooze? thing and be quite short lived as suggested in “Boltzmann’s Anthropic Brain? not all will be. Eventually, in the infinity of space-time, one will emerge with the right design to survive and even prosper where it finds itself (my guess is in whatever underlies space-time) and grow in both complexity/intelligence and power.

Given a few billion years (it is very unlikely to encounter another Boltzmann brain in that short a period) it is likely to become both bored and lonely, once it works out what lonely is.

Given that few billion years of growing intelligence and power, it is also likely to be in a position to do something about both problems. Oh! And it is very unlikely to be stupid enough to just do the easy thing and make another like itself (that growing intelligence thing).

“In the beginning God created the heaven and the earth (the universe). 2 And the earth was without form, and void; and darkness was upon the face of the deep (space-time). And the Spirit of God moved upon the face of the waters (space-time). 3 And God said, Let there be light: (the Big Bang) and there was light. 4 And God saw the light, that it was good? (Genesis 1, King James Bible)

Hey! It’s as good a creation myth as anyone else’s. :)

30:

Stephen @28, it's also extremely heretical, insofar as my knowledge of Christian (never mind Jewish, or Muslim) theology suggests that you've invoked a god which is basically just a random thermodynamic fluctuation and who invented us not because it's all-powerful and benign but because it got bored ...

(Heh.)

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31:

Seriously, I’ll argue that Fermi Paradox is answered by a combination of:

1. Daniel Nagy’s suggestion that efficiency and data compression considerations mean that more advanced civilizations are hard to detect by radio waves.
2. All of Shan’s, especially Sociological Quarantine.
3. The Olduvai (http://en.wikipedia.org/wiki/Olduvai_theory) theory as alluded to by John Henning.
4. The Rare Earth hypothesis (http://en.wikipedia.org/wiki/Rare_Earth_theory).
5. A bit of just about everything else that has been suggested.
6. Common sense and well founded caution: Most sensible, advanced technological civilizations go to a great deal of trouble NOT to advertise their presence.

In short, there ain’t really no Fermi Paradox, the really surprising thing would be for the ambassador to Earth from the Alpha Centauri system to land her ship on the White House lawn tomorrow.

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32:

#27 There is a Clark's law variation for this: Any sufficiently advanced communication is indistinguishable from noise.
We are surrounded by (apparent) noise. We cannot rule out advanced communication as its source.


33:

This conversation is caught up too much with communication (because of SETI) and recognizing alien beings, rather than their effects on the universe.

It really doesn't matter what aliens are like physically, mentally or whatever. If they are in any way expansive, just within their solar system, then some would modify that solar system and the results might be visible and long lasting, even if the civilization disappears. Dyson spheres being one example. If there are many civilizations, one might expect that a lot of different cultures might form, some going to posthuman singularity, others traditionally expansive.

But we don't see that, or rather, we don't see anything that we must interpret as a non-natural phenomenon in the universe. That is as true today as when Fermi asked the question.

SETI assumes that even planetary based civilizations might try signaling over interstellar distances, but it seems fairly clear that if they are doing so, they are not sending signals that state "This is a message". In this case, my sense is that we may be as foolish as new Guinean tribesmen wondering why they don't hear massive drums from over the oceans. We may be currently oblivious to some communication technology that is in widespread use, perhaps that signals at FTL speeds.

Finally we may have to accept that we are alone in the universe. There is no Great Filter, we are the first species to gain intelligence and technologies. The future is open to us if we don't screw up.

34:

Bill@32 "We are surrounded by (apparent) noise. We cannot rule out advanced communication as its source."

This is not a useful hypothesis if we cannot distinguish between natural and artificial phenomena. It is a bit like arguing we can't rule out that we live in "the Matrix" because the Matrix so perfectly mimics reality. (But cf Rucker's argument why this is not true).

However, whatever the encoding, we might expect the power spectrum of of natural phenomena to have anomalous spikes due to transmission strengths. SETI looks for carrier waves by looking for high strength parts of the radio spectrum in the background noise. Again, SETI does not find unequivocal cases, arguing that there are no encoded transmissions that we have detected.

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35:

Has anybody but Lem done the Boltzmann Brain idea? (The Cyberiad) It's (imho) a particular formulation of a rather fundamental question.

Dan G. - the crosstime travel thing. There are a lot of dodges as an sf technique. Someone mentioned that the only sites available are within the history of the traveller _after_ it is turned on. Another is to posit that it's like radio; you can send all you want, but unless there's a receiver out there, it's a pretty pointless enterprise. So, no vast undeveloped and primitive worlds to escape to, no way to play the Gunpowder God, unless you posit something like Egans' technique for interuniversal travel. More fundamentally, the question goes to what sort of habital environments are accessible to us. Thousands of years ago, it was a generic far-distant land, perhaps across the sea. More recently, space. And now there are the relatively new ideas of other universes, and 'virtual environments' whose substrates are computer hardware. So maybe there are other places that are far more interesting and easy to get to that we're just not aware of yet. Maybe there's billions of hyper-advanced civilizations in every cubic meter of space living down at the Planck scale. Maybe there are structures Like Farmers' deliberately created universes, or Egan's New Territories. Or like Monty Python's Completely Different.

The point is, the more we look, the duller space looks, quite frankly. Develop star travel, and for a sum of trillions(or quadrillions) of dollars one can travel to Alpha Centauri, Sirius, Vega, Betelguese only to find rocks, rocks, and more rocks. Perhaps in a cube a hundred light-years on a side there's single-celled life, a thousand and there's multi-celled animals, ten thousand, intelligent life. That's a lot of work for very little pay-off. When the public found out that, at best, Mars may have primitive life on the order of those like our own stromatolites, interest, and the resources attendant upon that interest, rapidly dwindled. It may well be that it simply makes good economic sense to go exploring in other directions, von Neumann probes notwithstanding.

Who knows? Maybe twenty years from now, quantum computing technology will connect us with those worlds where Neanderthals reign supreme, or intelligent dinosaurs - at a billionth the cost of space flight. Or something not forseen at all now, but completely plausible in hindsight.

36:

I'm not convinced by the Boltzmann's Brain stuff, specifically the idea that a Boltzmann Brain is more likely to "appear" than a universe like our own.

Most theories of the Big Bang start with a great deal of matter (quarks or something even more primitive) at -very- high energy. I'm not sure how much entropy is packed into such a thing, but what little organization there is seems to be much less than contained in a Boltzmann Brain. It's the difference between a high-resolution photo of something black (i.e., many repeating instances of something, all identical) and a high-resolution photo of something very complex (such as a brain).

You can compress the description of a primitive universe (using Zip, of course, to compactify the small number of particles and laws needed) into something very small, but you can't do that with the contents of a brain, and there is no path I can see that leads from the simple primitive universe to a single disembodied brain without going through something like our own universe on the way. A simple primitive universe ancestral to our own seems much, much more likely than one ancestral to, or worse consisting of, a Boltzmann Brain.

Perhaps this is just a failure of imagination on my part, but based on the above I think the BB idea is fatally flawed.

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37:

I've always thought that trying to hear ET via radio (SETI), is somewhat like trying to detect intelligence in the Americas by building a giant ear-trumpet on the west coast of Ireland. I guess that is a version of the filter.

Assuming they exist, as to why they haven't popped round for a cup of tea: it may be that Einstein and co are right (I hope not, though I don't expect to ever find out). And, let's face it, as earlier articles indicated, the jet lag is a killer.

If they are anything like us, I really don't think I want them to visit -- history teaches me what we do when we pop round. And if they are not like us, I know what we are like, so it's probably better for them they don't call: maybe The Day The Earth Stood Still was a documentary.

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38:

# 16
Our civilisation ALREADY runs on alchohol!

# 22 - other Fermi dodges ....
some already mentioned by others:
a] "Orbitsville" aka Dyson Spheres all over the place
b] Comms via tightbeams for greater efficiency, and paranoia
c] We are using the wrong equipment ("Drums across the Ocean" @ #33)
d] We are on the wrong side of the SINGULARITY - about which, an interesting (?) sideline - I'm currently dipping into Stephen Oppenheimer's "Out of Eden", and on P17 of the hbk edition is a graph (fig 0.2) showing human physical and cultural development.
It's going singularly vertical already, since the time-axis is 2.5 million years long, with the cultural (including scientific) zooming upwards at an ever-increasing rate.
{ Bldaes, points, shellfishing, fishing, microliths, beads, images, use of metals, writing, musical notation, chemistry, faster-than-animal transport, electronics .... }
We ARE IN THE SINGULARITY NOW, it is just that is happening slowly, and people have only just noticed.
It is also proabably a time of maximum danger, since the forces of reaction and religion will try to stop it by any means, including killing us all, but that's another story.

What IS obvious is that our detection-rate for planets elesehwere is going up rapidly, as the equipment improves.
I'm reminded of the spouting of some religious nutter (Maistre?) about how the astronomers could look at the stars all they wanted, but they would never find anything useful about them, or from them - in the same year as Fraunhofer was perfecting the spectroscope!

What is also obvious is that we are missing something, or several somethings.
The previous posters who have talked about really alien civilisations definitely have a point.

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39:

Assuming a round-trip timelag of a few years, which terrestrial political entities would have the apparent stability to be worth talking to?

Would Buckingham Palace, or the Cold War Kremlin, make more sense than the White House?

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40:

G. Tingey @38: "We ARE IN THE SINGULARITY NOW, it is just that is happening slowly..."

This is not just a tautology about playing with coordinate scales. I tried to sell it to Charlie during a panel at Philcon '06: that our characteristic state *as a species* is that moment when, running downstairs too fast, it occurs to you that you might in fact be falling...

And our characteristic solution is an unpredictable but impressively gibbon-like swing to a lower point on some other log curve.

Herb Stein (1960s economic adviser): "Things that can't go on forever... don't."

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41:

35: "When the public found out that, at best, Mars may have primitive life on the order of those like our own stromatolites, interest, and the resources attendant upon that interest, rapidly dwindled."

Mars probes launched in the 1960s: 13 (3/1)
Mars probes launched in the 1970s: 11 (7/2)
Mars probes launched in the 1980s: 2 (0/1)
Mars probes launched in the 1990s: 7 (2/0)
Mars probes launched in the 2000s: 9 (6/0, with 2 in transit)

The first number in the brackets is the number of successful missions. The second is the number of partially successful missions. It looks to me like the late Cold War wasn't a good time for interplanetary research but things have been recovering since the fall of the Soviet Union (Causality not necessarily implied).

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42:

In terms of successful and partially successful mission, the 1970s (which post-date the point at which it became painfully clear Mars was a hostile world) are the high point so far.

43:

Nix @ 13 (and tp1024 @ 11):
The other problem is that, well, its the hydrogen absorption line! If you want to transmit signals a long way you do *not* use that frequency, because it gets absorbed by the most common element out there!

Minor correction: It's the main spectral line of (neutral) atomic hydrogen, which means it applies to both absorption and emission.

More to the point, the available hydrogen in our galaxy is very rarely dense enough to cause significant absorption; the galaxy is mostly transparent to 21-cm radiation.

44:

I'm surprised nobody's mentioned Greg Bear's answer to the Fermi Paradox in The Forge of God:

The universe is silent for the same reason forests are largely silent - baby creatures making too much noise attract the predators.

45:

G. Tingey @ 38:
I'm reminded of the spouting of some religious nutter (Maistre?) about how the astronomers could look at the stars all they wanted, but they would never find anything useful about them, or from them - in the same year as Fraunhofer was perfecting the spectroscope!

You're probably thinking of the French philosopher Auguste Comte, who claimed that humans would never be able to learn the chemical composition of stars. (I don't think he qualifies as a "religous nutter", though.)

46:

Maybe we are the result of a perverse band of a race that came here and were into beastiality...

that would explain centaurs, fauns, minotaurs and humans (which are half ape, half alien)...

this band fiddled with humans and other species... problem is the leaders of their species (or another species) caught them in the act of their perversion and stopped them...

much like humans try route out perverts that molest animals and children.

LOL

47:

David Brin posted about this subject a little while ago, I think he was a little peeved that no one was referencing one of his papers. Can't say if it's good or not, but I thought I'd throw it in.


http://davidbrin.blogspot.com/2008/05/signs-of-life-still-in-enlightenment.html

http://www.brin-l.com/downloads/silence.pdf

48:

In the beginning the Universe was created.

This had made a lot of people very angry and been widely regarded as a bad move.

Many races believe that it was created by some sort of god, though the Jatravartid people of Viltvodle Six believe that the entire Universe was in fact sneezed out of the nose of a being call the Great Green Arkleseizure.


The point is - we just don't know!

Fascinating entry and i'm liking the direction the comments are taking it, hope it doesn't turn into space cadet v2.0. Never did manage to slog my way through all those comments.

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49:

Alex: This is not a useful hypothesis if we cannot distinguish between natural and artificial phenomena. It is a bit like arguing we can't rule out that we live in "the Matrix" because the Matrix so perfectly mimics reality. (But cf Rucker's argument why this is not true).
Yeah, a tongue-in-cheek QED was tempting. But I don't see any strong argument against the efficient-communication-looks-like-noise argument.

Lack of obvious large-scale structural engineering is the most troubling to me.
The speed of light issue may help here. At human speed it doesn't matter much at planetary scales but Dyson Spheres are a bit sluggish. At machine intelligence speeds, both planets and Dyson Spheres are too big.

Another depressing alternative, not directly mentioned here, is that god made the universe, and being lazy filled it out with matter and photons just far enough out to last the planned duration of the universe from our POV. Though as a friend points out, we don't know what a lazy god would actually do. It could be that Martin Luther and espresso and smallpox are desired side effects of the creation of galaxy clusters.

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50:

41: James, the probe count is nice, but I'm talking about public interest. I remember when Pathfinder/Sojourner made it's big splash (was that really ten years ago!?!?!?); in my circle, there was a lot of buzz, and the Hot Wheels Sojourner went next to Doc Oc on one of my co-workers monitors. But outside of that . . . big yawn. None of my partner's friends knew anything about it, or greatly cared, for example.

Now, if Sojourner had found, say, banths . . . As for myself, I thought back in the 70's that it was only a matter of time before my wallet would be made of Martian Moleskin.

51:

Bill Arnold @49: How large would the infrastructure have to be for us to detect it, here and now? We can detect, from a distance:

a) Stars. As long as they're still shining, or have a companion that is.

b) Really big planets with relatively short orbital periods.

c) Nebulas large enough to occlude stars, or internally lit.

There are some awfully large classes of infrastructure that fall below those detection limits... In fact, only a Dyson Sphere or a Ringworld would fall above them, and I've yet to be convinvced those are physically possible, saving the possibility of a $Weakly-Godlike-Entity.

52:

I haven't read all the comments so this may have been mentioned, but Stanislaw Lem imagined the "down the rabbit hole" idea, where intelligence concentrates itself into a black hole to maximize the amount of compuation it can do, in his 1981 story "Golem XIV" (written in the form of a lecture by a superintelligent A.I. on the topic of 'toposophy', i.e. the levels of possible intelligence, rather than a conventional narrative), which can be found in the book "Imaginary Magnitudes" (pages 96-99 of the story in my edition, which are on pages 222-225 of the book). Here's the most relevant chunk:

Meanwhile we come to the next transition of the mind. I would have to drop a library on you to describe this stage of cerebral activities, so I shall restrict myself to the principles. Thought strikes root in deeper and deeper layers of matter: its relay races first consist of moderately excited hadrons and leptons, and then of such reactions as require enormous quantities of energy to be channeled and controlled. There is no great novelty in this, for protein, which is undoubtedly unthinking in scrambled eggs, thinks in a skull: one has only to arrange the molecules and atoms properly. When that succeeds, nuclear psychophysics arises, and the tempo of operations becomes critical. This is because processes spread out in real time over billions of years sometimes have to be re-created in seconds. It is as though someone wanted to think through the whole history of life on Earth in detail, and in a few seconds, since to him it is a small but unavoidable step in his reasoning. The mind-carrying capability of a quantum speck, however, is interfered with by the electron shells of wandering atoms, so they must be squeezed and compressed--the electrons must be forced into the nuclei. Yes, my dear physicists, you are not mistaken in seeing something familiar in this, for the sinking of electrons into protons begins to occur, as in a neutron star. From the nuclear point of view this Intelligence, indefatigably working toward autocephalia, has become a star--a small one, to be sure, smaller than the moon, and almost imperceptible, radiating only in the infra-red, giving off the thermal waste of psychonuclear transformations. That is its feces. Beyond this, my knowledge unfortunately grows vague. The supremely intelligent heavenly body, whose embryo was the rapidly growing, multiskinned onion of Intelligence, begins to contract, gyrating faster and faster like a top, but not even its near-light-speed revolutions will save it from being sucked into a black hole, since neither centrifugal nor any other force can resist gravitation at the Schwarzschild horizon.

It is suicidal heroism when a seat of Intelligence becomes a veritable scaffold, for no one in the Universe is as close to nothingness as a mind which, in growing in power, engenders its own doom, although it knows that once it touches the gravitational horizon, it will never stop. So why does this psychical mass continue toward the abyss? Is it because it is precisely there, on the horizon of total collapse, that the density of energy and the intimacy of nuclear connections reach a maximum? Does this mind voluntarily float above the balck pit that opens inside it, in order at the rim of catastrophe to think with all the energy which the Universe pours into the astral gap of its fugues? In that borderland of stayed execution, where the conditions of the toposophical pinnacle of the world are fulfilled, should one suspect insanity rather than Intelligence? Indeed pity, if not contempt, is deserved by this distillate of million-year-long metamorphoses, this supremely wise leviathan condensed into a star, who worked so very hard and so increased its powers, in order finally to get atop a black hole and fall into it! That is how you see it, isn't it? But postpone your judgment for a while. I need only a few more moments of your attention.

...

I see a frightening-amusing feature in this edifice, whose total knowableness without reservation Einstein so confidently professed--he, the creator of a theory that contradicted his confidence, because it led to a place where it itself broke down, and where every theory must break down: in the world torn asunder. For it foretells sunderings and exits which it cannot itself penetrate; yet one can exit from the world anywhere, provided one strikes a blow at it, of the force of a star in collapse. Is it physics alone which appears incomplete under such constraints? Are we not reminded here of mathematics, whose every system is incomplete as long as one remains inside it, and which can be grasped only by going outside it, into richer domains? Where is one to look for them, if one stands in the real world? Why does the table made of stars always wobble on some singularity? Can it be that a growing Intelligence encountered the frontiers of the world, before it encountered its own? And what if not every exit from the Universe is equal to annihilation? But what does it mean, that one who leaves cannot return, even if surviving the transition, and that the proof of this impossibility of return is accessible here? Can it be that the Universe was designed as a bridge, designed to collapse under whoever tries to follow the Builder, so that they cannot get back if they find him? And if he does not exist, could one become him?

53:

DaveL wrote:
I'm not convinced by the Boltzmann's Brain stuff, specifically the idea that a Boltzmann Brain is more likely to "appear" than a universe like our own.

That's the whole point! The "Boltzmann Brain stuff" was never intended as anything other than a reductio ad absurdum for certain classes of cosmological theories...the point is that it spurs us to try to find what kind of cosmology would be necessary in order to have normal brains in young universes outnumber Boltzmann Brains in a very old universes, with the assumption being that the cosmology of the real universe/multiverse must be of this type. See this post and this one on the "Cosmic Variance" blog, for example.

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54:

Come to that, if Banks' "Culture" really existed, we would not be able to detect it, would we?

55:

FYI, my name is not "Henson", it is "Hanson." I'll blog on this topic soon at Overcoming Bias.

56:

Sorry, Robin: correction coming right up. (I assume you'll be blogging about the Fermi paradox, not common mis-spellings of your name :)

Care to provide a URL ...?

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57:

I'm still a big fan of one possible end of Moore's Law, maybe from Bell:

We run out of engineerable scale, and exponentiation by getting small ends. Thereafter, computation merely grows polynomially, as a sphere of computronium expanding at light speed.

Don't worry, it was offered as a joke (I think---it's full of conceptual puns.) But I hadn't really thought about the SpaceEmpire! connection of these thought experiments. Perhaps the space cadets get the hell off the planet plagued by maniacs with cheap energy, and then cease radiating so that the fatwas against them cannot be carried out.

I wonder what the difference in observable RF is between a broadcast TV planet and an IPTV over picocell planet.

58:

Years ago I started writing a novel, "Galactic Gangsta", which gave a tongue-in-cheek "answer" to Fermi's Paradox: Blame organized crime!

The universe of the plot is packed with life, but largely dominated by star-spanning machine AIs. These metal intelligences fear that organic life might threaten them, and work hard to keep the "organics" grounded in their home systems.

But instead of simply exterminating carbon-based life (like the "Berserkers" in Saberhagen's stories), the AIs recruit the "scum and villainy of the galaxy" into a band of armed thugs which is shipped around from star to star, in hibernation.

These "galactic gangstas" raid inhabited planets and accomplish several tasks for their machine "godfathers":

1. Destroy enough resources that the indigenous peoples can't escape their own planets/star systems;

2. Put the blame for the raids on organic life, allowing the AIs to extort precious metals from the planets in a protection racket ("Only we can protect you from the menace of carbon-based bipeds");

3. Assure the eternal safety of metal life from carbon life.

(The novel is still unfinished, but you can read the available chapters here:
http//yngve.bravehost.com/aboutgalacticgangsta.html )

As I said, it's tongue-in-cheek. I have NO idea how to resolve the Fermi Paradox (there's only one answer??), so keep speculating...

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59:

9: "They don`t communicate with radio, but with messenger ships, because they are afraid of other civilizations."

Interstellar rockets would be visible at light-year ranges.

http://www.projectrho.com/rocket/rocket3w.html

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60:

I'm surprised nobody's mentioned Greg Bear's answer to the Fermi Paradox in The Forge of God:

Alastair Reynolds' Inhibitors, too. But I prefer Terry Bisson's "They're made out of meat".

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61:

I've never seen a discussion of the Fermi Paradox in which its fundamental point (universality) was not misunderstood by at least half the commenters, if not also by the author of the essay.

This would be a good point to explain and enlighten then, no?

Sadly, it turns out to be the author again in this case, as in your nasty remark about "space cadets".

So Charlie's characterisation of certain blog posters reflects his misunderstanding of the universality of the Fermi Paradox?

You're not making the space cadets sound any better, or less petulant.

62:

I think #27 is spot on as to why we don't detect random alien signals emissions.

But there's another side to the Fermi Paradox. It's not just "Why can't we hear them?", but "Why aren't they *here*?"

My answer has some resonances with the Rudy Rucker essay linked to above. Assume a civilization exists that has sufficient resources to physically traverse interstellar distances. The power requirements to do that imply that this is, by our standards, an incredibly rich culture. Why would such a culture bother to undertake interstellar travel? Certainly not to steal water, as so much bad SF implies, nor for any other simple physical commodity. They would venture into space for much the same reason that we (still) do: knowledge that cannot be gotten without doing so. The one thing that earth has that no other planet has is our particular arrangements of biology, history, and culture. The scientific (and entertainment) value of observing these things seems likely to be far greater than that of interfering with them.

If there *are* aliens here, I suspect that they have something similar to Star Trek's Prime Directive -- only based purely on economic grounds, not moral ones.

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63:

Robin Hanson, have you read Clarke's short story "A walk in the dark"? Your analysis (and the resulting conclusion, if simple extraterrestrial life _is_ found), reminded me of the tale...

Best wishes,
-Jeff

64:

Alexx #62: That's a really neat answer. We're their Star Trek.

65:

Peter @#43, whoops, true, interstellar hydrogen is largely ionized, isn't it, so there goes that objection. I forgot which universal aeon I was living in for a moment there. ;)

DaveL @#36, you could use the same argument to 'prove' that biological brains and other ordered structures are impossible. i.e., your argument is flawed :)

Jay @#57, Hans Moravec already covered this in his strange work _Robot: Mere Machine to Transcendent Mind_, a sort of paean to the perils of prediction (although I don't think it was intended that way). It starts out rigorously logical and practical and then goes off the rails in remarkable style, with chapter 4 talking about easily foreseeable household robots, chapter 5 dragging in such things as the economics of complete mechanization, space elevators, and bush robots, and chapter 6 opening with 'a bubble of Mind expanding at near lightspeed' and dragging in fundamental limits to computation and the Bekenstein bound, the use of time machines for computation and much else... by chapter 7, he's pointing out that if you look at it right a randomly selected rock is an intelligent being (in fact an unlimited number of different intelligent beings), and one has to wonder if the whole book is one marvellous piss-take.

66:

I don't really believe this, but I thought someone ought to say it. Maybe the simplest explanation is true: maybe there really isn't anyone else out there.

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67:

Dave@66: For what it's worth, I'm increasingly of the view that there isn't anyone we'll ever reach or even contact.

Charlie, thanks for the links. I notice that none of Rucker's respondents seem interested in the world as a thing, or collection of things, in its own right, with a history and activities that aren't dependent on us at all. They're entirely concerned with vistas, basically - things to see and poke at, but not to regard anything more serious than a spectacle. Vearth doesn't even rise to the level of a moral patient, let alone a moral agent. Me, I take the existence of things outside my head seriously, and very much wish there to continue to be a reality larger than my desires.

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68:

DaveL #36: “I'm not convinced by the Boltzmann's Brain stuff, specifically the idea that a Boltzmann Brain is more likely to "appear" than a universe like our own.

“Most theories of the Big Bang start with a great deal of matter (quarks or something even more primitive) at -very- high energy. I'm not sure how much entropy is packed into such a thing, but what little organization there is seems to be much less than contained in a Boltzmann Brain. It's the difference between a high-resolution photo of something black (i.e., many repeating instances of something, all identical) and a high-resolution photo of something very complex (such as a brain).

“You can compress the description of a primitive universe (using Zip, of course, to compactify the small number of particles and laws needed) into something very small, but you can't do that with the contents of a brain, and there is no path I can see that leads from the simple primitive universe to a single disembodied brain without going through something like our own universe on the way. A simple primitive universe ancestral to our own seems much, much more likely than one ancestral to, or worse consisting of, a Boltzmann Brain.?

That was pretty much my thoughts too, until I was thinking about Dave’s posting above, then I realized that there were two serious problems with that argument, both related. The first is the unstated assumption that Boltzmann Brains have to start out as something at least as complex as a human brain, the second highly related problem is Physics.

You see, all the latest attempts by physicists at a Theory Of Everyone (TOE), that is, uniting Einstein’s physics and quantum physics, seem, as far as I can follow it, to demand that at the most fundamental level, way, way below atoms or even quarks, there is a structure. In one version of String Theory space-time consists of a kind of fabric made up of interlinked circles of “string?, kind of like chain mail.

To make things worse, it seems that the amount of information a volume can contain is dependent on its surface area, not its volume: This kind of indicates that at least one of the three dimensions is an illusion of some kind. What the hell that means I don’t know – maybe we are already in a black hole?

Anyway, as far as I can follow it, all these little sub-quantum rings or whatever process information, they kind of calculate quarks and atoms and thus people, whales and stars. In some senses they form a computer with unimaginably many components functioning unimaginable fast.

Ok! Ok! I know! Give a man a hammer and the whole world looks like a nail to him, and physicists and cosmologists do spend a lot of time with computers these days… still…

Anyway, it seems to me that long before this structure starts calculating atoms and stars random fluctuations will lead to quite simple patterns, some of which have the ability to reproduce, compete with each other, change, and thus be selected for greater complexity. I seem to remember a computer program called Life that did much the same thing on a much simpler scale.

Trouble is, if this were true, we wouldn’t have to worry about whether “normal brains in young universes outnumber Boltzmann Brains in a very old universes?: Boltzmann Brains all the way forward from a very young universe would outnumber any physically possible number of hard matter brains by an unimaginable multiple.

By the way, for the past seven thousand years or so most of those who made a living out of thinking and talking about this kind of thing referred to Boltzmann Brains as demons, angels, demigods, gods, that sort of thing.

Anyway, you see why, as I said in my first post, pondering of Boltzmann Brains kind of leads you into places you really don’t want to go.

Best thing possible, rules of physics we don’t yet know preclude them. Otherwise, everything changes, all our dreams of eternal, galaxy spanning civilizations are irrelevant because we are but the faintest shadow of the real game for intelligence.

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69:

Nix @#65: Yay, thank you---I knew that had to come from somewhere specific. If we could ever build Internet tools for searching for complex concepts I won't be as dependent on the kindness of strangers to get my attributions straight. (I'm sure there's a lot of money in higher and higher semantic levels of targeted advertising. The emergent AIs' first words will be "Help, I'm trapped in a pop-under factory!")

70:

Nix @65 and Jay @69, Actually, "Robot" is just a recapitulation of Moravec's earlier and even more interesting book "Mind Children" (1990).

If he'd gone the same way as Vernor Vinge, they'd have co-founded a major movement in SF.

(Jay, there's a reason my next major SF novel -- planned for publication in 2010 -- is titled 419.)

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71:

Charlie @ 70: Coooool. Hoping some stand-in for the Semantic Web meets Grubor's fate. AI Silent Spring.

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72:

If the Many Worlds interpretation is true, maybe we're just an extremely unlikely universe where there's only one intelligent species -- us. :)

I mean, if there are a near infinite number of universes, some of them have to be single-species ones...

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73:

Andrew #72,
Or, more likely, an extremely unlikely universe where technological intelligence evolves quite late and we are the first in our region of space.

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74:

Stephen Heyer #73

There is only one universe. How can it be likely or unlikely?

75:

Anatoly @74: how do you know there's only one universe? (See also: Graham-Everett-Wheeler many-worlds hypothesis.)

76:

How many universes are there?

Well... consider the history of cosmology from antiquity to today. The trend has always moved in one direction: Improved observations prove that the cosmos is much bigger and more complex than previously assumed.

My intuition is that this trend will only continue -- perhaps forever. Someone will always claim that "The universe is only this big" and always be proven wrong. And so it goes with the "There is only one universe" statement: it is unproven, hence it'll probably turn out wrong.

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77:

Charlie Stross #75

By definition of universe. As in "everything that exists". So all those many-worlds, if they exist, are part of the universe.

Maybe multiverse will be a better term, but I don`t like it.

A.R.Yngve #76

Everything you discover is part of one universe. Hence, it can`t be likely of unlikely, there is nothing to compare it with.

78:

Anatoly, your terminology needs updating. I suggest starting here.

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79:

Here, wikipedia has a nice definition:

"The Universe is most commonly defined as everything that physically exists"

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80:

Charlie Stross #78

Sorry, the word "multiverse" just sounds lame to me. Reminds me of "multimedia".

Maybe even better term is "Reality".

81:

Re: #70 -- I'm not quite sure I get the connection between Moravec-Vinge-robot-brainchilds (Minsky, where is Minsky? And Kurzweil?) on the one hand and Nigerian spammers on the other hand. I mean, I could imagine a number of not really far-fetched connections, but not a single one goes InstaClick at the moment. Maybe I have to wait until 2010.

82:

Till: I believe Kurzweil is very good at publicizing the ideas that were common currency on the Extropians mailing list in the mid to late nineties. Ken MacLeod and I hung out there in the very early 90s. I give him very little credit for inventing those ideas, because I'd seem 'em all a long time before he started writing about them.

(Hint: the stuff that came out in "Lobsters", in 1999, was partially catalysed by me dipping back into my old stomping grounds six or seven years later.)

Minsky is ... well, he devoted his career to pushing the idea of procedural AI, and aside from one howling mistake he did very well -- but I think he was trying to till barren soil.

Vernor has had the one huge idea in his career, which is as much as most first-rank SF writers can ever hope for. (This says nothing about his career as a computer scientist ;-)

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83:

Vernor has had the one huge idea in his career, which is as much as most first-rank SF writers can ever hope for.

Can't think of another in the same league as that one. Maybe Clarke and satellites.

(This says nothing about his career as a computer scientist ;-)

Might be where it came from, though.

84:

Clarke didn't really do fiction about satellites, which is what I was getting at -- to invent a fictional trope (and one that you can quantify in scientific terms) is rare. Larry Niven got there with Ringworld (the quintessential Big Dumb Object), for example. Greg Bear got there with genetics-as-a-computational-process in "Blood Music". William Gibson gave us cyberspace, while Ursula le Guin took the pre-existing assumptions of class and gender in SF and stuck several sticks of dynamite under them (in, for example, "The Dispossessed" and "The Left Hand of Darkness").

But a surprising number of SF writers never have a major idea in their entire career.

85:

Maybe the "major idea" would demand an own blog posting, but at the moment, there seem to be two different things mixed into it. One are genre-changing tropes: BDO, cyberspace/cyberpunk, taoistic anarcho-feminism as setting for SF. The other thing is more like a idea that is so big that it does not only change the genre, but also the consensual view of the world (or bring social or technical inventions forward). Singularities are own of these superbig ideas, virtuality could be another one, and the space race including satellites a third.

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86:

OK, Gibson I'll grant you. Ringworld's a poor man's Dyson Sphere IMO.

But a surprising number of SF writers never have a major idea in their entire career.

And a surprising number of SF readers keep buying their books nevertheless.

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87:

For the very good reason that major ideas aren't the only things that make sf (or anything else) worth reading, methinks.

Back at the tally: Olaf Stapledon, for the quintessence of the vast, vast, vast cosmic perspective, and Cordwainer Smith, for the ditto fused with compassion and humanism. (Stapledon isn't cruel, but whoever described his work as occupying chilly heights had it about right.)

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88:

Larry Niven got there with Ringworld (the quintessential Big Dumb Object), for example.

Dyson mentions (and dismisses) rings in his exchange with Poul Anderson:

" 1) A solid shell or ring surrounding a star is mechanically impossible. "

http://snipurl.com/29g6r

Now, I have no idea if Niven ever saw that.

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89:

For the very good reason that major ideas aren't the only things that make sf (or anything else) worth reading, methinks.

In the case of (anything else), that could certainly be true - in generic romance, major ideas might well get in the way, in vampire erotica they might positively distract the readership from more central pursuits, but I can't help feeling that complacency about their absence from SF might be a tad misplaced.

I mean, sure, if you've got well-developed characters or glistening prose or something. Don't come across many such myself but I could be reading the wrong stuff, wouldn't be the first time.

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90:

"A solid shell or ring surrounding a star is mechanically impossible."

ISTR Niven did at least calculate the strength requirement and postulate some new artificial form of matter which was able to take the strain.

91:

Adrian @90: alas, Niven missed out on some of the more interesting applications of Scrith. (A material that reflects 40% of neutrinos? And that can be fabricated in honking great rings? It's the ideal material to make a collimator for a supernova, and the Puppeteer inertialess drive gives us the tool with which to move either the collimator, or the star we're going to detonate to power the neutrino laser, into position. Given that about 90% of the output energy from a supernova comes in the form of neutrinos, something that can direct about 40% of that output is, ahem, militarily useful ...)

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92:

Adrian: Well, for starter, there's adventure. David Drake, for instance, mines history to great effect to tell ripping yarns. Not many big ideas in there, but I've enjoyed a lot of his books. H. Beam Piper also comes to mind - arguably his handling of paratime is a big idea, but what I re-read the Paratime Patrol stories for last week, while recuperating from the flu, was interesting people doing cool stuff. Just to grab handy examples.

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93:

Now I'm idly contemplating a story in which Charlie's "space cadets" are part of a general project to keep civilizations away from the Singularity. They tie it up in "doesn't quite work" ideas, misdirecting interest and invention so that the society comes right up to the brink and then collapses.

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94:

Well, I've often said that those who comfort themselves with the notion that sf is the 'literature of ideas' are just conning themselves :-) It's entertainment for the most part, on a par with genre romance, or genre detective stories, or genre fantasy - all of which I read. For sheer enjoymnet, you can't beat laying in bed feeding cheetos to your dogs from the bag by your side while reading a scene where Marlowe takes another shot to the head as he runs down another lead for his client. (Or wondering how Miriam is going to get herself out of this one - many thanks, Charlie. You've given me hours and hours of enjoyment. Higher praise I cannot give.)

That being said, sensawunda is a valid component to entertainment, and 'big ideas' do feed that itch. But notice, as Charlie says that Big Ideas are few and far between. Clarke may have had a few, Asimov had robots and psychohistory, but what did Heinlein have in that department? Not a whole lot. What about Kuttner, or Knight, or Kornbluth (well, he does seem to be famous amongst the noncognoscenti for 'The Marching Morons'.) Smith - nobody's idea of a great rider - had a great many of them, he single-handedly invented space opera.

Which suggests that most of the big ideas came early, and that it is getting harder and harder to think up new ones. Every so often you get an Egan. But not often enough, and it seems to me that our Egan's are coming further and further apart.

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95:

Given that about 90% of the output energy from a supernova comes in the form of neutrinos, something that can direct about 40% of that output is, ahem, militarily useful ...)

I dunno, sounds like a bit of a white elephant. What would you point it at, if your targets could shunt planets about willy-nilly? Another star? Big deal. This is not to say that the Pentagon wouldn't buy one.

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96:

Well, see, your story starts with this nerdy loaner type, gifted in the sciences or mathematics, perhaps, who notices something Isn't Right in his small hometown. Much Ado abut Something Ensues, involving some serious baddies. Only it turns out at the end of the first book that they were only a front group (in fact, they're seriously chastised for activating The One who had been isolated in the small hometown.) In book four of the series, we're up to channeling neutrino beams powered by energetic supernovae, inertialess dirigible planets, and we've still got at least three books to go. More if the franchise is farmed out.

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97:

Till @ 85:

genre-changing tropes: BDO, cyberspace/cyberpunk

Neuromancer significantly influenced research funding and development of information technology, in a way that the machine-mediated realities of Cordwainer Smith and Delaney's Nova did not. Everybody "visionary" could be assumed to have read it from about '87 to '95. In retrospect this sounds like "dude, 1984 was not a how-to guide" but hey, Reagan and Thatcher....

-----Neuromancer/Sprawl trilogy spoiler below-----

My favorite extropian quote is from 1973's Gravity's Rainbow, p 698 where Tyrone Slothrop is replying to his dad's worries about Tyrone not returning from an electro-trip:

"Ho, ho! Don't I wish! What do you think every electrofreak dreams about? You're such an old fuddyduddy! A-and who sez it's a dream, huh? M-maybe it exists. Maybe there is a Machine to take us away, take us completely, suck us out through the electrodes out of the skull 'n' into the Machine and live there forever with all the other souls it's got stored there. It could decide who it would suck out, a-and when. Dope never gave you immortality. You hadda come back, every time, into a dying hunk of smelly meat! But We can live forever, in a clean, honest, purified Electroworld---"
"---Sh*t that's what I get, havin' a double Virgo fer a son...."

There, I just saved you the trouble of reading Mona Lisa Overdrive. You can thank me later.

98:

Good thread, except for those jerks Nick Bostrom and Robin Hanson, who maintain that I don't exist, which I suppose has some bearing on the Fermi Paradox is you assume that I'm extraterrestrial.

At Caltech's Seminar Day yesterday, a.k.a. the lecture and barbecue day for alumni reunions, I ask Paul Rothemund why, if DNA and other macromolecules can be (via a biomolecular compiler) self-assembled into almost any sufficiently small shape, why we are not swamped with directed panspermia molecular Von Neumann molecules. He had no satisfactory answer.

Then I sang along to the Einstein song while Nobel Laureate David Politzer played the banjo. Politizer says that Physics is in deep doo-doo, which is shocking after centuries of success. Not being able to explain Dark Matter and Dark Energy, plus the cycle time between designing,m building, and analyzing the data from physics experiments having escalated from 6 months when he was a grad student to about 30 years today, makes it unclear that we'll ever figure out how things work.

Which, I point out, may explain "Where Are They?"

Waiting for their superconducting supercollider of LHC or whatever to get funded, which stops them from designing the Warp Drive.

Saw Dave Brin at the alumni event, albeit missed him at dinner the night before because he was hanging out with Fred Pohl at the Eaton Conference. Has Brin's periodic table of Fermi Paradox solutions been extended?

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99:

Bruce @ 93:

So instead of causality weapons, the Big E sends Jerry Pournelle. I love it.

100:

I tend to adhere to the view that the Fermi Paradox isn't a Paradox, and intelligent life is vanishingly rare. After all, how common can catastrophic collisons between primeval earthlike worlds and Mars-size bodies be? As in, collisions forceful enough to strip off ~70% of the Earthlike's primordial crust to a point where plate tectonics can exist as seems likely happened to the Earth?

"Without plate tectonics, new mountain belts could not form. Earth would be a Waterworld with occasional shield volcanoes emerging briefly above the waves. If regular catastrophic convective overturn occurred, as on Venus, life would have a precarious foothold indeed."

(Link: http://www.spacedaily.com/news/life-01x1.html)

101:

Wasn't the original version of a ringworld or Dyson sphere just a lot of discs that in sum occlude all light emitted by their star? They didn't have to be connected.

102:

DaveL @101 is correct: Dyson was speculating about collecting all the solar radiation output to power a Kardashev type II civilization, presumably living in spinning space habitats a la Gerard K. O'Neill.

The grotesque misinterpretation that is the solid inhabited shell simply doesn't work without magic wand/unobtanium technology to provide gravity. (Because? If you're standing on the inner surface of a massive sphere, the gravitational effect of all the points on the inner surface cancel out.)

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103:

Jay Carlson: Isn't it rich in narrative potential?

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104:

Bruce Baugh @ 103: Yeah, but my doctor tells me I should stop deliberately putting myself into paranoid situations....

There's also the matter of getting the narrative down on paper at all. Take a smart innocent hero going up against The Man. Local observers could see escalation ending with literally *supernatural* levels of stupid in their frame of reference, and I just don't know how you could write about that. Maybe a hard SF Illuminatus.

105:

I still hope that SETI succeeds in gravity waves, as I predicted in print back in 1980. However, he's a cool newly-tweaked alternative:

Galactic Neutrino Communication

Authors: John G. Learned, Sandip Pakvasa, A. Zee
Comments: 6 pages, 2 figures
Subjects: Popular Physics (physics.pop-ph); Astrophysics (astro-ph); High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph)

We examine the possibility to employ neutrinos to communicate within the galaxy. We discuss various issues associated with transmission and reception, and suggest that the resonant neutrino energy near 6.3 PeV may be most appropriate. In one scheme we propose to make Z^o particles in an overtaking e^+ - e^- collider such that the resulting decay neutrinos are near the W^- resonance on electrons in the laboratory. Information is encoded via time structure of the beam. In another scheme we propose to use a 30 PeV pion accelerator to create neutrino or anti-neutrino beams. The latter encodes information via the particle/anti-particle content of the beam, as well as timing. Moreover, the latter beam requires far less power, and can be accomplished with presently foreseeable technology. Such signals from an advanced civilization, should they exist, will be eminently detectable in neutrino detectors now under construction.

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106:

Waiting for their superconducting supercollider of LHC or whatever to get funded, which stops them from designing the Warp Drive.

The LHC is the work of Satan, I hope you realize.

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107:

The grotesque misinterpretation that is the solid inhabited shell simply doesn't work without magic wand/unobtanium technology to provide gravity. (Because? If you're standing on the inner surface of a massive sphere, the gravitational effect of all the points on the inner surface cancel out.)

So you live on the outside of the shell, which is the solution Pohl and Williamson hit on.

If we shelled the sun at 1 AU, the surface gravity would be very roughly 1 cm/s/s, if I haven't made a simple math error.

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108:

>solid inhabited shell

Would a rotating shell work (centrifugal forces) ?


109:

Charlie @#70: I had a copy of _Mind Children_ long ago but loaned it out and never got it back: I didn't mention it because I wasn't sure which came first or even if one was a retitling of the other...

110:

Charlie @#91, Larry Niven was never very good at thinking through the implications of his inventions. The thruster, gravity planer, and a *lot* of other stuff has fascinating (world-changing) possibilities that he never thought of.

I mean, compare Niven's treatment of the stasis field problem with Vinge's. Vinge *thinks things through*. Niven has the deep time consequences of stasis consist of one alien from the deep past... with no sign of social changes in the present caused by such things. Unlikely.

Niven uses ideas as one-shot narrative devices, so they keep piling up, half-baked.

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111:

By the way, Charlie, I find the city-state and computation density angles fascinating. Thanks very much for the links.

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112:

Would a rotating shell work (centrifugal forces) ?

Not if you wanted it to stay a sphere, unless you had a nigh-infinite modulus of rigidity.

114:

ISTM that most of explanations of the Fermi Paradox involve some application of the anthropic principle: frinstance, if we lived in a universe where there were alien civilizations within detection or traveling range of us, they'd be here, therefore we don't. I think we've been a little too eager (as a culture, if not as a species) to generalize our own experience and viewpoint to a universal principle. In particular, the assumption that a Kardashev Type 3 civilization would use techniques that leaked sufficient energy in the right patterns to be seen as obviously artificial at galactic or cosmological distances. I doubt we know enough about macro-engineering to make such statements. Basically anything we say about technologically-advanced alien species is pure speculation; pretending we have any reason to be confident in these analyses seems silly to me.

Shorter version: we don't have a clue, and don't have any idea about how to get one in the short-term.

115:

"Come to that, if Banks' "Culture" really existed, we would not be able to detect it, would we?"

No (the Culture has a few Dyson spheres, solid, but probably not within detection range) but then the Culture isn't using physics as we know it; a ship could hover above NYC at noon and go undetected. Or scan our planet from Alpha Centauri.

"If we shelled the sun at 1 AU, the surface gravity would be very roughly 1 cm/s/s, if I haven't made a simple math error."

But the fundamental problem is that the shell itself is under that gravity, and has only its own tensile strength to keep it up, and apparently would crumple and collapse with any known material.

116:

universality: the Fermi Paradox doesn't hinge on an idea that every technological civilization is expansionist. It hinges on the idea that if *at least one* civ is expansionist, then it can easily expand and visibly dominate a galaxy in short geological or astronomical time. (Deep historical time by our standards, though.) And thus expansion is selected for. A refutation has to argue that *every* civilization will be non-expansionist. Who's making the stronger claim?

Pro-paradox arguments extrapolate from the pattern of most life on Earth, and of most of human history (like the bit where Stone Age humans colonized almost every land niche from jungles to ice caps.) Anti-paradox arguments extrapolate from the past century or two of human history, specifically urbanization, electronic miniaturizations, and the Internet, then they call the pro-paradox people anthropocentric.

Note that even if mainline activity being increasingly localized were a universal long-term unbroken trend (strong claim!) that wouldn't mean impact need be increasingly local. The human race is majority urban now, but we scour the planet. We'd probably happily scour asteroids for platinum if we could -- the problem is technology and economics, not lack of raw desire for more stuff. Running all those computers takes a fair bit of our energy use.

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117:

A material that reflects 40% of neutrinos?

Reflects? I thought scrith *blocked* 40% of the flux. Which, of course, said to me that the Ringworld is going to melt, given the amount of energy a given star dumps out in neutrinos -- we're talking on the order of 10e10 per square centimeter per second, of various energies in the MeV range, for our own star.

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118:

"But the fundamental problem is that the shell itself is under that gravity, and has only its own tensile strength to keep it up, and apparently would crumple and collapse with any known material."

You can shell the sun by floating thin material on sunlight but this limits you to a very low value of kg/square kilometer. Swarming is far more sensible for many reasons.

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119:

"universality: the Fermi Paradox doesn't hinge on an idea that every technological civilization is expansionist. It hinges on the idea that if *at least one* civ is expansionist, then it can easily expand and visibly dominate a galaxy in short geological or astronomical time. (Deep historical time by our standards, though.) And thus expansion is selected for. A refutation has to argue that *every* civilization will be non-expansionist. Who's making the stronger claim?"

That is an interesting point of view. It makes a little bit of sense that most would not be. It probably is always going to be easier for a planetary civilization to fix problems on its own world rather than trying to colonize what are likely to be dead, dangerous and hostile environments on any nearby planet.

However, there is also the possibility that it is simply impossible for any sort of conceivable civilization to actually spread out from a planetary origin even if it wanted to. The material and energy resources may simply never be available to actually allow intelligent life of any kind to spread to other planets or other stars. Like others have posted, these theoretical interstellar civilizations often would have to be using something different than "physics as we know it," but maybe it is impossible to actually defy physics even a tiny bit.

If it were possible, then it seems likely we should have noticed something (maybe not - how could we tell with the equipment we have?), and maybe the reason we haven't seen even a hint of anything is that it isn't possible. Any intelligent and/or self-aware life is going to be limited to a planetary existence and that's it simply by the requirements of the physical universe.

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120:

Suppose there was runaway replication by a visiting probe that ended up consuming all the asteroids and they formed an opague shell, say, 2 AU in radius, and they also reflected back about 20% of the Suns output. What would be the implications for life on Earth?

121:

ScentOfViolets: first, you need to calculate the surface area of a shell 2AU in radius. (Hint: it's a very large number.) Then you need to look up estimates for the mass of the asteroid belt. (Hint: their combined mass is much less than that of our moon.) Then you need to figure out how thin you'd have to spread them to plate that surface. (Third hint: most studies of how a Dyson shell might be constructed that I've seen have talked in terms of dismantling Jupiter, and that's just for a shell of 1AU radius.)

Upshot: not terribly likely to happen. (Especially when you're talking about shifting most of the mass of the asteroid belt out of the plane of the ecliptic.) However, I've got a novella to write and I can't be bothered pulling out the pocket calculator, so I'll leave it to someone else to supply the detailed answer ...

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122:

Well, certainly it would be quite thin; most of the area would be a solar sail/solar cell for maneuvering, power, and perhaps imaging(if you want to go with a hard-sf slant on what a probe could plausibly look like.) But some of the light is reflected off this structure. And some of that light will impinge on Earth.

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123:

Don't see how a spherical shell around a star has much in the way of useful maneuvering to do.

124:

"It makes a little bit of sense that most would not be. It probably is always going to be easier for a planetary civilization to fix problems on its own world rather than trying to colonize what are likely to be dead, dangerous and hostile environments on any nearby planet."

There's recursion, though: an expansionist galaxy doesn't even need *one* expansionist civilization, in the sense of some sort of world-government deciding to be expansionist. It just needs one successful expansionist fringe of some civilization. It just takes one pregnant rat to colonize an island. So the question is more "what is the curve of minimal tech levels, resource command, and decision-maker population size for getting off a planet, or getting out of a solar system?"

Which is a rich question of its own, but basically the no-expansion case requires that all combinations of technology and social form (multi-government? Prestige race? Cathedral building? Libertarian?) result in very low probability of expansionism.

Or, as you say, that physics prevents it, but that seems terribly unlikely, given that we can imagine interplanetary or interstellar colonization right now, through multiple paths, the barriers to which are economics and current biology, not physics.

"If it were possible, then it seems likely we should have noticed something"

Not if we're first. And if intensive expansionism is likely -- if the galaxy is winner take all, first come first serve -- then it's likely we are first, precisely by virtue of being around. How many intelligent species should we expect to see per planet? No solid data, but extrapolating from the only example we have, we should expect *one*, because that's sufficient to take the whole planet in short order.

Some people like to refer to a Copernican principle of mediocrity, that we should be average. But we don't know what the distribution is to talk about averages. If expansionism is possible, the average number of intelligent species in a galaxy, or even a cluster, may be 1.

Conversely, if it's not possible, then the existence of aliens is pretty irrelevant, since we're not going to meet them.

125:

@Damien/#124:

Conversely, if it's not possible, then the existence of aliens is pretty irrelevant, since we're not going to meet them.

That's only half-true: maybe expansionism isn't (in the sense of "affordable") possible (say, economical, physical, ... limits), but that doesn't rule out the possibility of low rates of interstellar contact. Not the expansionist fringe, but the mad multi-billionaire.

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126:

A couple of points...

- I think mining a star would be the best source of material for a physical shell. Any civilization than can rip apart gas giants and build a 2AU structure should have no problems.

- For all we know, a Dyson Sphere might not need to be physical. Who knows what sort of space warping is possible. That might solve the problem of gravity as well, just change where "down" is...

- Regarding galactic colonization, it's not implausible that it would only take one ship departing from an inhabited world to spark the colonization of the galaxy. If the ship had the seeds of space industry in it, in theory it could convert an asteroid & comet belt into copies of itself and send them off to repeat at every star in the galaxy. Seeding worlds with life, terraforming, and colonization could be an afterthought. A million years to colonize a galaxy is pessimistic.

127:

Damien @ 115:

Of course, NASA has some plans for "scanning" any planets in Alpha Centauri from here. It's amazing what one could do with a massive space-based interferometer. For example, construct some Google Maps plugins for centaurian continents, and perform fairly detailed spectroscopic analysis.

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128:

Let me be clear: I was not proposing a Dyson Sphere intentionally constructed out of asteroidal material. My thought is what would be visible over interstellar distances that could be construed as signs of intelligent life? I think it was Larry Niven who proposed that a completely enclosed star might look like something natural, but really wasn't, say a brown dwarf if things are set up right, or maybe a red giant for beings whose chemistry runs a little hotter. Iow, we do see signs of large scale engineering, we just don't recognize it as such.

I tend to be skeptical of mega-engineering projects as signs of 'advanced' civilization, but what about unintentional artifacts? Say one of those pineapple-sized probes spawns a mutant intra-stellar explorer that doesn't shut off after a set number of replications, and it consumes an entire asteroid belt of resources? That would occult the star too, just like Niven's hypotheticals. But this time, it would be the result of unintentional consequences; something like 'grey goo in space'. I'm thinking of some version of Forward's starwhisp for this exercise, something extremely light, something that in the normal course of events would have been designed to have as small an impact on the environment as possible.

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129:

Even better, use the Sun itself as a gravitational lens. You don't have to go more than a hundred or so AU out, you can survey hundreds of systems in less than one tenth of one percent of the time it would take to get a realistic probe to even the nearest star . . . and it would be far, far, cheaper.

130:

Erik V. Olson @ 117:
Reflects? I thought scrith *blocked* 40% of the flux. Which, of course, said to me that the Ringworld is going to melt, given the amount of energy a given star dumps out in neutrinos -- we're talking on the order of 10e10 per square centimeter per second, of various energies in the MeV range, for our own star.

Given that the total energy in solar neutrinos is only ~ 10% of the energy in photons, it's unlikely that scrith will melt just from the extra energy input of the neutrinos....

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131:

129:

It's at least 550 AU and there are operational challenges involved:

http://www.sciencemag.org/cgi/content/abstract/205/4411/1133

Still an interesting idea, though.

132:

Scrith solar sails, driven by neutrino reflection, accelerate away from supernovae before the photons and gas and dust ever emerge.

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133:

Well, sure, there are challenges. But the question is what gives a better ROI, an interstellar probe, or a telescope? It is my thought that even a telescope placed so relatively far away is still a much better bargain. Finally, while all stars are interesting, some are more interesting than others. A good telescope would let us more effectively allocate limited resources.

134:

ScentOfViolets @ 133

A gravitational lens telescope using Sol as the lens gives a different kind of ROI, though. It would give us more information about more places in the universe, but it doesn't advance our ability to go to places; anyplace close can be scanned pretty thoroughly before we go with far less expensive instruments than that. I, personally, don't think that going somewhere close is necessarily better than looking at a lot of different places far away, but it's clear that a lot of people do from the constant debates about the allocation of NASA'a resources, and the drumbeat of "Humanity's Manifest Destiny in the Stars" that we hear in any discussion of long-term space prospects. My guess is that, when and if the question arises of whether to spend 1% of the Gross Solar Product on a manned expedition to Centauri or Tau Ceti, or sending a robot into the Oort Cloud to create a telescope, that the decision will be for the manned expedition.

135:

Nix @ 110:

I'd argue that there's actually a fair amount of thought about implications of new technology in Niven's stories, although he doesn't necessarily do it for everything. Some obvious examples: cheap and easy organ transplants; transfer booths; and the exploitation of "corpsicles".

As he pointed out in "Safe at Any Speed", one of the problematic implications of stasis fields is to make it harder to convincingly threaten characters with harm. That's probably partly why he stopped writing about them.

(And comparing Niven's initial explorations of stasis fields with something Vinge wrote almost twenty years later -- almost certainly having read Niven first -- is not really fair. "Hah, H.G. Wells never thought through the implications of time machines for cross-time conflicts the way Fritz Leiber and Poul Anderson did. What a piker!")

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136:

It would give us more information about more places in the universe

Pretty slowly, if it's orbiting 550 AU out.

137:

Wow, Rudy Rucker does hate you. It seems he specifically mentions how much he detests accelerando at least once per post for the two I've read. I attacked RR in a debate, I'll see how him and his henchmen like it :P (mind you it wasn't at all aggressive.)

I actually came up with my own concept for the Great Filter paradox (it's pretty homebrew though.) Essentially, the story this was in features a galactic network of FTL communication (facing some of the problems fast expanding broadband raises today.) Because it's FTL, and computing is powerful and ubiquidous, any handshake signals sent by radio could be intercepted on their way to the recipient and tampered with (made illegible, or, better yet, altered to seem like a declaration of planetary invasion?) Humanity got lucky when a lab accident reached into the dimension in which FTL communication was routed. Instant foot in the FTL door.

But then again Occam's razor eats this flight of fancy for breakfast, lunch AND dinner, I suppose.

138:

Peter Erwin@135, yeah, the time gap is notable, but there *is* a difference there. It's a difference in style, I think: Niven seems to start with a story and dream up appropriate McGuffins while Vinge starts with a single McGuffin (designed to produce the sort of story he wants to write) and works through all its implications. I guess it's a matter of taste which approach you prefer...

139:

"- Regarding galactic colonization, it's not implausible that it would only take one ship departing from an inhabited world to spark the colonization of the galaxy. If the ship had the seeds of space industry in it, in theory it could convert an asteroid & comet belt into copies of itself and send them off to repeat at every star in the galaxy. Seeding worlds with life, terraforming, and colonization could be an afterthought. A million years to colonize a galaxy is pessimistic."

Disagree on the last bit: at 0.1c it takes a million years just to cross a 100,000 light year galaxy. And 0.1c is about what would be easy to do if we could harness nuclear fusion portably *and* harness that energy in an effective space drive, which is two things we don't know how to do, on top of packing an industrialization seed into a ship. Plus this scenario assumes developing a new system to the point of being able to send out more probes, on the order of years or decades as opposed to thousands of years. So it's fairly optimistic, compared to 100 km/s probes taking a few hundred million years to spread...

...which is still fast enough to raise Fermi Paradox questions!

140:

It seems tome that technology level windowing is the Occam's Razor explanation to Fermi's Paradox :) Even on Earth, there are still some spots of isolation - humans living there are completely unaware of pervasive radio wave communication that are enveloping the planet.

141:

Gratuitous misanthropic quote: “I think the best sign that intelligent life exists elsewhere in the Universe is that none of it has tried to contact us yet? — Calvin of Calvin & Hobbes