Tag Archives: Space

Earth Is Not Random

By Robin Hanson · April 1, 2011 9:00 am · Comments (11)

The great filter is whatever obstacles stand in the way of simple dead matter eventually giving rise to a visibly expanding interstellar civilization. It is now confirmed that a non-trivial chuck of that filter is in planets having special orbits that let climates be stable over time:

Planetary anthropic selection, the idea that Earth has unusual properties since, otherwise, we would not be here to observe it, is a controversial idea. This paper … [compares] Earth to synthetic populations of Earth-like planets … [for] high (or low) rates of Milankovitch-driven climate change. Three separate tests are investigated: (1) Earth-Moon properties and their effect on obliquity; (2) Individual planet locations and their effect on eccentricity variation; (3) The overall structure of the Solar System and its effect on eccentricity variation. In all three cases, the actual Earth/Solar System has unusually low Milankovitch frequencies compared to similar alternative systems. All three results are statistically significant at the 5% or better level, and the probability of all three occurring by chance is less than 10^-5. It therefore appears that there has been anthropic selection for slow Milankovitch cycles. This implies possible selection for a stable climate, which, if true, undermines the Gaia hypothesis and also suggests that planets with Earth-like levels of biodiversity are likely to be very rare. Continue reading "Earth Is Not Random" »

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Are Gardens Fertile?

By Robin Hanson · March 8, 2011 10:40 pm · Comments (6)

Cosmologists tend to think that the physics we see around us is not universal. There is instead a vast “landscape” of possible ways a local physics could be, and different (large far away) places in the universe embody or express these different physics.

When adjacent space-time places have different local physics, there must be a common “meta” physics that describes their border. This meta-physics will say how often places of one type lead to places of other types nearby, including “ends” where nothing is nearby.

Let us distinguish two special kinds of places:

  • Gardens support life and possibly civilization.
  • Fertile places tend to lead to more fertile places nearby.

The existence of any fertile place implies an expected infinity of connected fertile places. Thus when meta-physics maintains a one-to-one state map across a time dimension, there should be no finite upper bound to the entropy of a fertile place. Thus the entropy at a fertile place is always vastly lower than is possible, and entropy would increase in some local time direction. Since this low entropy should infect adjacent places, non-fertile places “close enough” to fertile ones should also have entropy increasing away from the fertile side. Thus we can explain our local “arrow of time” by assuming that our place is connected to a fertile place in our distant past.

Is our garden fertile? If both gardens and fertile places are rare, and these properties are not very correlated, then fertile gardens would be especially rare – it would be quite unlikely that our garden is fertile. In this case, while our universe is infinite, our future is finite, and will see and influence only a finite amount before our space and entropy run out.

Cosmologists today, however, tend to think that fertile places are not very rare. They expect places with a “positive vacuum energy” and a “low vacuum decay rate” to generate many “baby universes”, and that many of these baby universes also satisfy this description. In fact, they guess that our place here satisfies this description, and so is fertile. (This is, basically, Sean Carroll’s account of our arrow of time.)

But a whole lot of guess work goes into all this. For example, it could be that vacuum decay rates are much higher, and that baby-universe-generating rates are much lower, than they’ve guessed. My guess is that this property of being fertile is rarer than cosmologists now guess, which lowers the chance of our garden being fertile.

A correlation between being a garden and being fertile might result if civilizations tended to work to increase the rate at which their places lead to more places nearby. But it might be that for most gardens there isn’s much civilizations can do.  In which case if fertile places are rare, then most gardens are not fertile, our future is finite.

Finally, even if our place is fertile, it might be that the border between our place and other different places has no “hair” letting us send specific influences from here to there. In this case, our future influence would still be finite.

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Aliens Not So Strange

By Robin Hanson · February 6, 2011 7:45 pm · Comments (17)

If the Martian life form transpires to be eerily similar, this might only show that Life … in reality has very few options. … No sentient forms weaving their existence in vast interstellar dust clouds, farewell to bizarre filamentous species greedily soaking up the intense magnetic fields of a crushingly oppressive neutron star and on even Earth-like planets no forms that we might as well call conceptualized pancakes. … Contrary to received neo-Darwinian wisdom, life on Earth at any level of organization—from molecular to societal— will provide a remarkably good guide as to what ought to be ‘out there’.

So argues Simon Conway Morris, from inside view considerations. I think he’s mostly right, but based on an outside view.

Here it is: when relevant parameters can vary by large magnitudes, the most common type of thing is often overwhemingly more common. For example, processes that create and transmute elements vary greatly in their rates. So even though there are over a hundred elements in the periodic table, over 90% of all atoms are hydrogen, so the odds that two randomly selected atoms are the same element is >80%.

Similarly, since the influences on how many eyes a human has vary greatly across eye numbers, most humans have the same number of eyes: two. Most humans do not have the same last name, however, since rates of gaining or changing names do not vary by huge factors.

The same principle applies to life. Life might have evolved in a great many kinds of environments, based on a great many sorts of elements, and using many types of organization. To the extent that some environments are far more common, or are far more supportive of high rates of biological activity, most biological activity in the universe should occur in the few most common and supportive environments. Similarly if some elements or organizations are far more supportive of biological activity and innovation, most life should use those elements and organization.

I expect cosmic environments to vary enormously in both volume and in support for biological activity. I also expect some types of elements and organizations to be far more supportive of biological activity and innovation. I thus expect most life to be based on similar elements and organizations, to originate and be active and innovative in places similar to where our life orginated and is most active and innovative.

This view is supported by the fact that the assumption that life originates via the entropy of sunlight hitting “dust” predicts many cosmological parameters. In ’08 I reported:

This causal entropic principle so far successfully predicts dark energy strength, matter fluctuation ratio, baryonic to dark matter ratio, and baryonic to photon matter ratio! … A simple reading of the principle is that since observers need entropy gains to function physically, we can estimate the probability that any small spacetime volume contains an observer to be proportional to the entropy gain in that volume. … Exclud[ing] entropy of cosmic and black holes horizons, … ignor[ing] future observers getting far more efficient and aggressive in using entropy, … they estimate that, aside from decaying dark matter, near us most entropy is made by starlight hitting dust, and most of that is in the past.

Our life probably started from sunlight hitting “dust” (including planets). More quotes from Simon Conway Morris: Continue reading "Aliens Not So Strange" »

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Cosmic Coordination

By Robin Hanson · December 7, 2010 10:00 am · Comments (31)

The universe looks dead. If it is actually teeming with ancient advanced life, why don’t any of them use all those resources we see? Yes, there might be other even more attractive resources we don’t see, but it still seems odd none specialize in using what we do see. Yes everything might be under the control of a unified collective, who agree on a preference to keep the universe looking dead. But pretty much any observation could be explained as due to a vast unified ancient power with an arbitrary preference to make the universe appear a certain way. (more)

I’ve posted before that coordination is harder than most folks realize. Today I’d like to emphasize that coordination on the largest scales of space and time, across the entire visible universe, should be the very hardest. Our far minds tend to assume that stuff at this furthest scale is the simplest, with the fewest relevant details, suggesting easy coordination. After all, if there’s just a few kinds of creatures, each with a few kinds of preferences and ways to act, then a simple mechanism might well be up to the task of coordinating them. But in fact creatures the size of stars or galaxies could have vast complex detail, diverging immensely across the universe, and changing greatly over billions of years. Their ability to monitor each other and enforce any agreements must surely be challenged by the vast distances and times involved. And for agreements to not use ample resources, there would remain great temptations to use such resources secretly, perhaps to support a breakout from the coordination regime.

Yes, billions of years also offer a long time to find and implement the best possible coordination mechanisms. But if those mechanisms must be in place before substantial expansion begins from some central origin, that seems to require maximal development of coordination technology at a cosmically very early development stage. If coordination is hard, that seems an extremely high hurdle.

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Berserker Breakout

By Robin Hanson · December 4, 2010 2:45 pm · Comments (32)

The universe looks dead. If it is actually teeming with ancient advanced life, why don’t any of them use all those resources we see? Yes, there might be other even more attractive resources we don’t see, but it still seems odd none specialize in using what we do see. Yes everything might be under the control of a unified collective, who agree on a preference to keep the universe looking dead. But pretty much any observation could be explained as due to a vast unified ancient power with an arbitrary preference to make the universe appear a certain way.

Moving to scenarios where many powers compete, one proposed explanation is that we are in a berserker equilibrium, where everyone hides for fear of being destroyed by others in hiding. For example:

The Inhibitors from Alastair Reynolds’ Revelation Space series are self-replicating machines … dormant for extreme periods of time until they detect the presence of a space-faring culture and proceed to exterminate it even to the point of sterilizing entire planets.

Or consider the zoo of competing self-replicators from David Brin’s story Lungfish:

The Anti-Maker … does not waste its time destroying biospheres, or eating up solar systems in spasms of self-replication. It wants only to seek out technological civilizations and ruin them. … Berserkers, … wreckers of worlds, were rare. … And there were what appeared to be Policeman probes, as well, who hunted the berserkers down wherever they could be found. … Harm … did not seek out life-bearing worlds in order to destroy them. Rather it spread innumerable copies of itself and looked for other types of probes to kill. Anything intelligent. Whenever it detected modulated radio waves, it would hunt down the source and destroy it.

I have an open enough mind here that I think Earth should keep quiet until we’ve studied this issue more. But I really have trouble seeing how this could be a stable equilibrium for a billion years among competing space species.

First, when something becomes visible, your killing it would seem a “public good” act which benefits all species, but mainly costs yours. Your killing action takes up your resources, and risks making you visible to be destroyed by others. Unless you think this new visible thing is especially likely to compete with your siblings, relative to other competitors, you’d rather wait and let something else destroy it.

Second, it must be possible to reproduce in order to compensate for wear and tear. After all, if the mere act of reproducing yourself made you so visible that you’d probably be destroyed, on average population sizes would fall to extinction. But if reproducing to compensate for decay works on average, why not reproduce more to grow in number? If observers can’t tell the purpose of a reproduction, then only density dependent death could keep populations in check. The ability to find and kill others without getting killed yourself in the process would somehow have to rise naturally with the density of creatures.

Once the local density of creatures had risen to some local limit, the most common species there could consider attempting a “breakout,” via a burst of rapid aggressive reproduction to overwhelm the ability of other species to contain it. Once enough copies were created in a large enough volume, the low density of other nearby species might be insufficient to stop the breakout species from expanding indefinitely.

There are many more complex strategies that seem attractive, compared to a simple direct breakout.  For example, fake breakout attempts could be created to induce retaliation by other species, depleting their resources and revealing their locations. One might then target them for attack before making one’s main breakout attempt in the now weakened region.

I’m not saying it is obvious that a long term berserker equilibrium is impossible, but I do have great doubts. And I’d love to see (and even help with) attempts to find stable equilibria within computer simulations of such scenarios.

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At Least Two Filters

By Robin Hanson · November 28, 2010 11:00 am · Comments (72)

Where lies the great filter, i.e., the obstacles that make it extremely unlikely that any one chunk of pre-organic matter originates a visibly expanding interstellar civilization? While it seems unlikely our ancestors passed through much of a filter in the last half billion years, our descendants may face a big filter in the next few thousand years, and there may have been big filters associated with the origin of life, the spread of life, the invention of complex cells, sexual reproduction, or multicellular life.

In many folks eyes, an elegantly simple resolution, which is likely because of its simplicity, is to assume there is just one huge filter: the origin of life. Assuming that first step is enormously hard allows one to think all the other steps are pretty easy. They wouldn’t be sure things of course, but conditional on a big enough origin-of-life filter, one wouldn’t have a strong reason to fear that common analyses underestimate future filters.

Unfortunately, the elegantly simple hypothesis that the great filter is mainly a big origin-of-life filter seems at odds with our best evidence. Why? Because if the spread-of-life step had the weakest possible associated filter, then life spreading must be easy. Over billions of years life could have spread to many star systems from its place of origin:

Life could spread across a galaxy via giant molecular clouds reliably collecting life from the stars they drift near, and then passing that life on to a few of the thousands of new stars they create.

If over billions of years life spread to many hundreds, or even billions, of star systems, and no substantial filters stood between arrival of life near a star, and its eventual development of advanced technical civilizations like ours, then why would we now see no any evidence of other civilizations? Yes it is possible that we are the very first, but that hypothesis is of course unlikely by default.

It seems to me that if the great filter is to consist of just one big step, the only plausible possibility is the development of multi-cellular life. All the steps before that one seem able to spread to other star systems via single-celled life hidden in dust, and it seems we haven’t had a big filter step since the multi-cellular innovation.

So if the idea of just one big filter appeals to your sense of elegance, you’ll have to presume that life, including complex life with sexual reproduction etc., is very common in our vast universe, but that Earth is one of the handful of places in all that vastness with multi-cellular life.

If you don’t find that plausible, well then you’ll have to grant there are at least two filters. And if two, why not three? So you must find the possibility of a third filter in our future plausible; beware future filters.

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Starflight Review

By Robin Hanson · November 23, 2010 8:45 pm · Comments (32)

In a recent article, Ian Crawford briefly reviews the technical feasibility of starflight.  The main limit is economic: an ability to collect 50,000 tons of (deuterium/helium-3) nuclear fuel (the same weight as today’s total annual uranium mined, but vastly harder to collect) and launch that into space seems nearly sufficient. But of course with advanced robotics, nanotech, etc., that much may not be necessary:

The most technically mature concepts for achieving rapid interstellar travel are those based on nuclear fusion propulsion, of which the Daedalus study (Bond et al., 1978) is still the most detailed engineering assessment available in the literature. Daedalus was designed to accelerate a 450-tonne scientific payload to 12% of the speed of light. … This would permit a travel time of 36 years to the nearest star, although the resulting vehicle would be very massive (requiring approximately 50,000 tonnes of nuclear fuel) and far beyond present capabilities to construct. …

In the decades following the original Daedalus study, technical advances in a number of fields have occurred which may make fusion-powered vehicles of the Daedalus type more practical. … Developments in miniaturization … would ensure that a much less massive payload would be required … The National Ignition Facility … is, albeit unintentionally, building up technical competencies directly relevant to the development of fusion-based space propulsion systems. …

Impacts with interstellar grains will be potentially damaging for space vehicles. … However, the problem is not as severe as [many fear]. … The size of typical interstellar grains … in the solar neighborhood are expected mostly to be submicron in size. … The mass of a 1 um [= 10^-6 m] radius grain of silicate composition is 10^-14 kg, and its kinetic energy at 0.1c is 4.5 J. … Continue reading "Starflight Review" »

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Light Rights Tangles

By Robin Hanson · November 9, 2010 5:00 pm · Comments (23)

We are a long way from running out of room, rocks, and sunlight on Earth, but eventually, probably well within a thousand years, our descendants will colonize our Solar System in earnest. When they do, they will have to answer some key property rights questions:

  • How do things go from unowned to owned? An auction? First to touch/use in some way?
  • What orbital rights-of-way can be owned? Only Sun-centered spheres? Any initially used orbit and any changes that don’t intersect other used orbits?
  • Who can block what sunlight? Let anyone block anything? Can’t block used light without permission?

On this last question, I can see light rights easily evolving as did water rights on Earth, where those using some water for a while gained a right to keep on using it. However, on reflection this seems like a mistake for sunlight. Imagine one gained a right to sunlight in a certain orbit after one had used it that way for a while. Once there came to be lots of complex orbits of things using sunlight, it would become very hard to contract with all those light owners to put together the rights to build something large orbiting closer to the sun. Such a new close thing would naturally block many far away things.

Yet the long term efficient use of sunlight would probably involve fewer big collectors orbiting close to the Sun. Thus a natural initial way to allocate light rights would lead naturally to an inefficient long-term allocation of those rights. So it might be better to start the light rights system off differently. I suggest having the property rights be that anyone can block anyone’s light as long as doing so is accidental and doesn’t seem especially targeted at blocking their light. This system would eventually allow a smoother transition to the more efficient arrangement of having fewer big close light collectors.

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Beware Future Filters

By Robin Hanson · November 4, 2010 4:30 pm · Comments (64)

Though we can now see over 1020 stars that are billions of years old, none has ever birthed a visible interstellar civilization. So there is a great filter at least that big preventing a simple dead star from giving rise to visible colonization within billions of years. (This filter is even bigger given panspermia.) We aren’t sure where this filter lies, but if even 10% (logarithmically) of it still lies in our star’s future, we have less than a 1% chance of birthing a wave. If so, either we are >99% likely to always forever more try to and succeed in stopping any capable colonists from leaving here to start a visible colonization wave, if given such a choice, or we face poor odds of surviving to have such a choice.

Back in March I noted that Katja Grace had an important if depressing insight:

Back in ‘98 I considered the “doomsday argument” … [but] instead embraced “self-indication analysis”, which blocks the usual doomsday argument.  In ‘08 I even suggested self-indication helps explain time-asymmetry. … Alas, Katja Grace had just shown that, given a great filter, self-indication implies doom!  This is the great filter … Alas I now drastically increase my estimate of our existential risk; I am, for example, now far more eager to improve our refuges.

Katja has just finished her undergrad honors thesis at ANU, which reports that all three of the main ways to pick a prior re indexical uncertainty (on who am I in this universe) imply that future filters are bigger than we’d otherwise think.  And not just by small amounts – the bigger the filters, the bigger the boost to future filters.

Now existential risk is important even if its odds are low – so much is at stake in whether our descendants die out or colonize a big chuck of the visible universe. But the bigger the odds, the more important it gets. Let’s review the main ways to estimate existential risk:

  1. Inside Model – using an internal model of how a particular risk process works, use your best guesses on likely model parameters to estimate the chance this process happens.
  2. Outside Scaling – Use prior rates of smaller events similar to a particular risk, and how such rates scale with size, to estimate the chance of events so big as to be a filter.
  3. Doomsday Argument – Assuming self-sampling and a reference class, estimate the chance of doom soon based on our time order in the reference class.
  4. Great Filter – Using estimates of total filter size and the chances of prior filters of various sizes, to estimate distributions over the total future filter size.
  5. Indexical Filter Boost – Redo the great filter analysis given all the main ways to get indexical priors, and weigh answers accordingly.

Now while many folks use approach #1 to estimate big chances of particular dooms, most such “models” have little formal structure; they are mostly vague intuitions.  So this approach usually influences my opinions rather weakly. Approach #2 is pretty solid, but usually leads to pretty low estimates. Using this approach, war and pandemics seem most likely to destroy half of humanity, but not very likely, and the odds of destroying us all see much lower. Approach #3 gets some weight, but less for me as I find self-sampling pretty implausible relative to self-indication.

This leaves #4, #5 as the main reasons I worry about existential risk. So having to take #5 seriously in addition to #4 is quite a blow. There is some tension between this and the results of #2, so I must wonder: what big things future could go wrong where analogous smaller past things can’t go wrong? Many of you will say “unfriendly AI” but as Katja points out a powerful unfriendly AI that would make a visible mark on the universe can’t be part a future filter; we’d see the paperclips out there.  Neither would the risk that our descendants’ values diverge from ours, nor  the risk of a rapidly expanding wave of (nanotech) grey goo – only slowly spreading grey goo could count in the future filter.

Browsing Nick Bostrom’s survey, that leaves us with: weak grey goo, engineered pandemics, sudden extreme climate change, nuclear war, totalitarianism ends growth, and unfriendly aliens. While these all risks seem apriori unlikely, either the entire great filter is in our past, or one of these (or something not listed) is far worse than it seems. But which?

Also, how likely is it really that such events would destroy all advanced life on Earth, to prevent other primates or mammals from recreating intelligence? After all the fact that human level intelligence arose so soon after human size brains appeared suggests that it was not a past filter of ours. The most likely resolution of all this still seems to me that almost all the filter is in our past, perhaps at the origin of life. But I’m not willing to bet our future on that.

The good news is that refuges seem effective against most these risks.  While unfriendly aliens mights dig us out of any holes, and prevent other Earth life from re-evolving intelligence, the other risks aren’t intelligent enough for that.  So: let’s make more and better refuges, and for #$@&* sake please stop broadcasting to aliens!

Added 10a: Refuges would also not protect much against totalitarian world culture and/or government that stops growth. So let’s also try extra hard to avoid that too.

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Boo Dark Powers

By Robin Hanson · October 30, 2010 9:15 pm · Comments (39)

To mark Halloween, I hereby endorse mild regulation to discourage the summoning of dark supernatural powers which might destroy us all. Seriously. Anders Sandberg:

The San Marino scale for assessing the significance of messages that could be received by aliens … is a scale from 1 to 10 based on how easily detected the transmission is, and how much information about humanity it contains. Past deliberate transmissions have managed to reach 8, ‘far reaching’. Even planetary radar manages to reach a level of 6, ‘noteworthy’.

So, how far does these [recent] advertisements go? The Deep Space Communications dish is apparently 5 meter in diameter … The Dwingeloo telescope used for the Klingon invitation is a bit larger, 25 meters, but again the transmission power is unclear. … The level 8 signal from the Arecibo used about half a million Watts of power, making it far more powerful than anything these telescopes can achieve. … It hence seems that compared to past messages these adverts are unlikely to matter: we are already transmitting other messages, these just add to the choir. …

How much should small groups of people be allowed to risk the future of humanity with low probability? Not everyone agrees that the risk from alien contact is negligible: even a very low probability times a great harm can be relevant. … Should we be equally concerned with occultists trying to summon world-changing supernatural powers? There are probably many more people today who believe in supernatural entities than mere aliens, and that some interactions with them could be harmful. Yet there are no attempts at formulating risk scales for ritual magic. … Even if we were to analyse them rationally, we need to have an ‘ultraviolet cut-off’ for the infinite number of possible-yet-exceedingly-unlikely possibilities we could worry about. How to rationally decide on this cut-off seems problematic.

Even if the risk from recent ads is only 1/1000 of the risk of other prior transmissions, since I’m not sure how big was their risk I’m reluctant to conclude that the smaller ones are “unlikely to matter.” Perhaps 1/1000 of a bigger risk is still big enough to matter. So I’d support mild regulation to discourage such transmissions, big and small.

On which risks should matter, I’d prefer to use odds from a prediction market to decide. And my guess is that they’d give non-trivial (well over one in a million) odds both that our transmissions might alert hostile aliens, and that one could “summon world-changing supernatural powers.” So I’d also support mild regulation to discourage actions that might risk our descruction by terrible supernatural dark lords. Perhaps that sounds silly, but to disagree you either have to support our destruction by dark powers, or disagree that policy should be based on market odds.

Added 1Nov: Many of you talk as if one would have to go through a phone-book length list of potential disasters before one came to this one.  But surely this is one of the top ten disasters of concern in fiction, and would be similarly high in surveys.  Yes, you might not take it seriously, but others clearly do. The question is: what probability to use in policy when people disagree on probabilities. Surely the right answer is some sort of weighed average of opinion, and while willingness to bet is a great way to weight opinions, surely most any neutral approach will give a high enough probability of disaster here to justify substantial concern.  And this justifies “mild” regulation, which looks for the easy wins of large harm reduction at low cost.  Now it might turn out that there just don’t exist any feasible mild regulations, but we should at least consider some options before drawing that conclusion.

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