Tag Archives: Space

Beware General Visible Prey

Charles Stross recently on possible future great filters:

So IO9 ran a piece by George Dvorsky on ways we could wreck the solar system. And then Anders Sandberg responded in depth on the subject of existential risks, asking what conceivable threats have big enough spatial reach to threaten an interplanetary or star-faring civilization. … The implication of an [future great filter] is that it doesn’t specifically work against life, it works against interplanetary colonization. … much as Kessler syndrome could effectively block all access to low Earth orbit as a side-effect of carelessly launching too much space junk. Here are some example scenarios: …

Simplistic warfare: … Today’s boringly old-hat chemical rockets, even in the absence of nuclear warheads, are formidably destructive weapons. … War, or other resource conflicts, within a polity capable of rapid interplanetary or even slow interstellar flight, is a horrible prospect.

Irreducible complexity: I take issue with one of Anders’ assumptions, which is that a multi-planet civilization is … not just … distributed, but it will almost by necessity have fairly self-sufficient habitats that could act as seeds for a new civilization if they survive. … I doubt that we could make a self-sufficient habitat that was capable of maintaining its infrastructure and perpetuating and refreshing its human culture with a population any smaller than high-single-digit millions. … Building robust self-sufficient off-world habitats … is vastly more expensive than building an off-world outpost and shipping rations there, as we do with Antarctica. …

Griefers: … All it takes is one civilization of alien ass-hat griefers who send out just one Von Neumann Probe programmed to replicate, build N-D lasers, and zap any planet showing signs of technological civilization, and the result is a galaxy sterile of interplanetary civilizations until the end of the stelliferous era. (more)

These are indeed scenarios of concern. But I find it hard to see how, by themselves, they could add up to a big future filter. Continue reading "Beware General Visible Prey" »

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Good Job Templeton

Whatever else the Templeton Foundation may have done wrong, they have done very right by funding the research behind two new papers, to appear in the Astrophysical Journal. The first paper reviews what evidence of aliens we should expect to see:

We motivate the \^G infrared search for extraterrestrial civilizations with large energy supplies. We discuss some philosophical difficulties of SETI, and how communication SETI circumvents them. We review “Dysonian SETI”, the search for artifacts of alien civilizations, and find that it is highly complementary to traditional communication SETI; the two together might succeed where either one, alone, has not. We discuss the argument of Hart (1975) that spacefaring life in the Milky Way should be either galaxy-spanning or non-existent, and examine a portion of his argument that we dub the “monocultural fallacy”. We discuss some rebuttals to Hart that invoke sustainability and predict long Galaxy colonization timescales. We find that the maximum Galaxy colonization timescale is actually much shorter than previous work has found (<109 yr), and that many “sustainability” counter-arguments to Hart’s thesis suffer from the monocultural fallacy. We extend Hart’s argument to alien energy supplies, and argue that detectably large energy supplies can plausibly be expected to exist because life has potential for exponential growth until checked by resource or other limitations, and intelligence implies the ability to overcome such limitations. As such, if Hart’s thesis is correct then searches for large alien civilizations in other galaxies may be fruitful; if it is incorrect, then searches for civilizations within the Milky Way are more likely to succeed than Hart argued. We review some past Dysonian SETI efforts, and discuss the promise of new mid-infrared surveys, such as that of WISE. (more)

The second paper describes a plan to look for some key evidence:

We describe the framework and strategy of the \^G infrared search for extraterrestrial civilizations with large energy supplies, which will use the wide-field infrared surveys of WISE and Spitzer to search for these civilizations’ waste heat. We develop a formalism for translating mid-infrared photometry into quantitative upper limits on extraterrestrial energy supplies. We discuss the likely sources of false positives, how dust can and will contaminate our search, and prospects for distinguishing dust from alien waste heat. We argue that galaxy-spanning civilizations may be easier to distinguish from natural sources than circumstellar civilizations (i.e., Dyson spheres), although Gaia will significantly improve our capability to identify the latter. We present a “zeroth order” null result of our search based on the WISE all-sky catalog: we show, for the first time, that Kardashev Type III civilizations (as Kardashev originally defined them) are very rare in the local universe. More sophisticated searches can extend our methodology to smaller waste heat luminosities, and potentially entirely rule out (or detect) both Kardashev Type III civilizations and new physics that allows for unlimited “free” energy generation. (more)

I’ll be quite surprised if they see anything, as I find hard to believe that, if they have existed nearby for a billion years, aliens wouldn’t already be plenty visible in their first result. But the issue is plenty important enough to look carefully anyway.

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Adam Ford & I on Great Filter

Adam Ford interviewed me again, this time on the Great Filter:

We have three main sources of info on existential risks (xrisks):

  1. Inside View Analysis – where we try to use our best theories to reason about particular causal processes.
  2. Earth Track Records – the empirical distribution of related events observed so far on Earth.
  3. The Great Filter – inferences from the fact that the universe looks dead everywhere but here.

These sources are roughly equally informative. #2 suggests xrisks are low, even if high enough to deserve much effort to prevent them. I’d say that most variations on #1 suggest the same. However, #3 suggests xrisks could be very high, which should encourage more xrisk-mitigation efforts.

Ironically most xrisk efforts (of which I’m aware) focus on AI-risk, which can’t explain the great filter. Most analysis efforts also focus on #1, less on #2, and almost none on #3.

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Factory+Files Future

The difficulty of practical interstellar travel is horrendously underestimated. … Known physics will never deposit living people on Earth-like planets around other stars. (more)

That was Donald Brownlee, who said something similar in our film. It occurs to me that skepticism about cryonics and interstellar travel have similar roots, and that understanding this is useful. So let me explain.

Imagine that one tried to take a rock, say this fossil:


and put it somewhere on Earth so that it could be found in a million years. Or that one tried to throw this fossil rock so that it would pass close to a particular distant star in a million years. Few would claim that doing so is impossible. Most would accept that these are possible, even if we require that the rock (plus casing) remain largely unchanged, i.e., retain its shape and maybe even most of its embedded DNA snips.

So skepticism about making people last a long time via cryonics, or about getting people to distant stars, is mainly about how people differ from rocks. People are fragile biological systems than slowly degrade with time, and that can be easily disrupted by environmental disturbances. Which justifies some doubt on if the human body can survive long difficult paths in space-time.

So why am I more hopeful? Because there are (at least) two ways to ensure that a certain kind of object exists at certain destination in space-time. One way is to have an object of that kind exist at a prior point in space-time, and then move it from that prior point to the destination. The other way is to build the desired object at the destination. That is, have a spec file that describes the object, and have a factory at the destination follow that spec file to create the object. One factory can make many objects, factories and files can be lighter and hardier than other objects, and you might even be able to make all the particular factories you need from one smaller hardier general factory. Thus it can be much easier to get one factory+files to a distant destination than to get many desired objects there.

Yes, today we don’t have factories that can make humans from a spec file. But if our society continues to grow in size and abilities, it should be able to do the next best thing: make an android emulation of a human from a spec file. And we should be able to make a spec file from a frozen brain plus a generic spec file.

If so, a frozen brain will serve as a temporary spec file, and we will be able to send many people to distant stars by sending just one hardy factory there, and then transmitting lots of spec files. The ability to encode a person in a spec file will make it far easier to send a person to a wide range of places and times in the universe.

See David Brin’s novel Existence for an elaboration on the throwing rocks with files theme.

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Cross Of The Moment Film

In 2002, Jacob Freydont-Attie made the ok movie String Theory (decent camera work & acting, good characters, some compelling interactions, & non-sensical physics mumbo-jumbo). He’s now working on a non-fiction film Cross of the Moment, “on the greater philosophical issues of life on Earth.” He just posted a 24 minute draft of the first of five parts, on the Fermi Question. He interviews myself and Donald Brownlee and Peter D.Ward, authors of the book Rare Earth. The other two were interviewed indoors, I was outdoors. It seems to me that indoors looks better.

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NASA Goddard Talk Monday

This Monday at 3:30p I talk on interstellar colonization at the Engineering Colloquim of NASA Goddard:

Attempts to model interstellar colonization may seem hopelessly compromised by uncertainties regarding the technologies and preferences of advanced civilizations. However, if light speed limits travel speeds and reliability limits travel distances, then a selection effect may eventually determine behavior at the colonization frontier. Making weak assumptions about colonization technology, I use this selection effect to predict colonists’ behavior, including which oases they colonize, how long they stay there, how many seeds they then launch, how fast and far those seeds fly, and how behavior changes with increasing congestion. This colonization model might explain some astrophysical puzzles, predicting lone oases like ours, amid large quiet regions with vast unused resources. (more here; here)

Added: Slides, Audio

I’m also talking on helping now vs. later at the DC Less Wrong Meetup Sunday (tomorrow), 3p in the courtyard of the National Portrait Gallery.

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Financing Starships

A science advisor to the not-entirely-realistic recent movie Gravity said:

Often a story worth telling can fall apart if there is a complete dedication to perfect science. The goal is to make everything seem grounded enough in the physical world that it seems real. So story trumps science every time. (more)

Even the science fiction that tries hardest for realism usually sacrifices it for a better story. It isn’t just that authors make accidental mistakes due to a lack of attention. Quite often, realism gets in the way of the story, because realism conflicts with our tastes in stories. That is, many features we want in stories (like good beating evil) are intrinsically unrealistic.

This is why I think it important to highlight story unrealism, especially the unrealism intrinsic to the stories said to be most realistic. Its not just gotchas to show off how much you know, or teach in the process. Its also to counter the popular illusion that stories are how-to manuals, there to teach us about reality in a fast and fun way.

Many have praised Charlie Stross’s novel Neptune’s Brood, released in July. I also enjoyed it. But economists such as Krugman and Tabarrok have praised its econ realism, and I haven’t found anyone criticizing that. So I guess such criticism is up to me (again). (I have thought about related issues before; see here, here.)

The following quotes give the setting of Neptune’s Brood. (Worry not; I give no spoilers.)
Continue reading "Financing Starships" »

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Today Is Filter Day

By tracking daily news fluctuations, we can have fun, join in common conversations, and signal our abilities to track events and to quickly compose clever commentary. But for the purpose of forming accurate expectations about the world, we attend too much to such news, and neglect key constant features of our world and knowledge.

So today, let us remember one key somber and neglected fact: the universe looks very dead. Yes, there might be pockets of life hiding in small corners, but for billions of years billions of galaxies full of vast resources have been left almost entirely untouched and unused. While we seem only centuries away making a great visible use of our solar system, and a million years from doing the same to our galaxy, any life out there seems unable, uninterested, or afraid to do the same. What dark fact do they know that we do not?

Yes, it is possible that the extremely difficultly was life’s origin, or some early step, so that, other than here on Earth, all life in the universe is stuck before this early extremely hard step. But even if you find this the most likely outcome, surely given our ignorance you must also place a non-trivial probability on other possibilities. You must see a great filter as lying between initial planets and visibly expanding civilizations, and wonder how far along that filter we are. In particular, you must estimate a substantial chance of “disaster”, i.e., something destroying our ability or inclination to make a visible use of the vast resources we see. (And this disaster can’t be an unfriendly super-AI, because that should be visible.)

Assume that since none of the ~1020 planets we see has yet given rise to a visible expanding civilization, each planet has a less than one in 1020 chance of doing so. If so, what fraction of this 1020+ filter do you estimate still lies ahead of us? If that fraction were only 1/365, then we face at least a 12% chance of disaster. Which should be enough to scare you.

To make sure we take the time to periodically remember this key somber fact, I propose that today, the day before winter solstice, the darkest day of the year, be Filter Day. I pick the day before to mock the wishful optimistic estimate that only 1/365 of the total filter remains ahead of us. Perhaps if you estimate that 1/12 of the filter still lies ahead, a filter we have less than a 2% chance of surviving, you should commemorate Filter Day one month before winter solstice. But then we’d all commemorate on different days, and so may not remember to commemorate at all.

So, to keep it simple, today is Filter Day. Take a minute to look up at the dark night sky, see the vast ancient and unbroken deadlands, and be very afraid.

What other activities makes sense on Filter Day? Visit an ancient ruin? A volcano? A nuclear test site? The CDC? A telescope?

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Two Kinds of Panspermia

Caleb A. Scharf offers an interesting argument against interstellar panspermia:

You and I, or fluffy bunnies and daffodils are all unlikely candidates for interplanetary or interstellar transferral. The sequence of events involved in panspermia will weed out all but the toughest or most serendipitously suited organisms. So, let’s suppose that galactic panspermia has really been going on for the past ten billion years or so – what do we end up with? …

Life driven by cosmic dispersal will probably end up being completely dominated by the super-hardy, spore-forming, radiation resistant, chemical-eating, and long-lived but prolific type of critters. …

The problem, and the potential paradox, is that if evolved galactic panspermia is real it’ll be capable of living just about everywhere. There should be stuff on the Moon, Mars, Europa, Ganymede, Titan, Enceladus, even minor planets and cometary nuclei. Every icy nook and cranny in our solar system should be a veritable paradise for these ultra-tough lifeforms, honed by natural selection to make the most of appalling conditions. So if galactic panspermia exists why haven’t we noticed it yet? (more)

I see two rather different interstellar panspermia scenarios:

  1. Space-centered – As Scharf says, life might mainly drift from one harsh space environment to another. Yes sometimes life would fall onto and then prosper on someplace like Earth, but being poorly adapted to space such planet life would contribute less to future space life. Under this scenario life must on average grow in common space environments, and so we should see a lot of life out there in such environments.
  2. Planet-centered – Alternatively, space life might usually die away, and only grow greatly in special rare places like planets (or perhaps comets). In this scenario the progress of life would alternate between growth on planets (or comets) and then decay in space. A similar scenario plays out when seeds like coconuts drift between islands in the ocean – seeds die away during ocean journeys, and then multiply on islands. In this scenario life would be adapted both to grow well on planets, and to decay as slow as possible in space.

Scharf’s argument weighs against a space-centered scenario, but not a planet-centered scenario. Of course there is actually a range of intermediate scenarios, depending on how wide a range of environments let life grow.

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Tube Earth Econ

Imagine someone plans to build a gas station far out in an isolated desert. They plan to sell gas and snacks to the truck drivers who come out to deliver gas and snacks. Want to invest?

No? How about if they also sell gas and snacks to passing explorers, out there to signal toughness? Yes, explorers won’t look as tough if they buy gas and snacks from your station. But if the station can lure enough not-so-tough explorers, maybe you’d want to invest.

How about if they also plan to dig oil wells and an oil refinery to make the gas they sell, and a hothouse farm and food processing factory, to grow food for the snacks they sell? How about if they plan to run all this entirely by robots? This plan would make me even less likely to invest. After all, you’d need even more customers to justify a larger scale operation, and I had doubts about enough explorer customers to justify a simple gas station.

This is my reaction to the recent news that some famous investors will spend millions trying to mine asteroids (see here, here, here). Their first product would be rocket fuel to sell to passing NASA rockets. I’m skeptical that NASA wants to buy enough fuel to cover their costs, and I don’t see a flood of other customers eager for robot space gas stations. This new firm also talks about shipping metals like platinum back to Earth, but that seems even crazier anytime soon.

To explore this general issue, let us imagine Tube Earth. While our Earth is a sphere of rock with a 40,000 km circumference, Tube Earth is a very long cylinder of rock with a circumference 1/6 as large, to give it the same surface gravity as Earth. Tube Earth also rotates 24 hours in a day, and has a sun nearby.  The closest spot on the tube to the sun is its “center,” which has Earth-like average surface temperature and seasonal variation. There would be less local temperature variation, as all nearby parts of a tube get the same sunlight.

A length of this tube about twice Earth’s circumference would have about the same surface area as Earth. Imagine that an area of this size held a mix of land and water similar to Earth’s continents. Imagine also that more such clusters of continents are spread all along this tube, spaced roughly twenty Earth circumferences apart. In between is mostly open ocean, with a few small islands.

The tube slowly gets colder millions of km from its center, as those places are further from it sun. Life is spread all along the tube, but so far humans and civilization have only evolved on one near-center cluster of continents. It would take an old style (~12 knot) sailing ship about 4 years to travel in a straight line from one cluster to another, and it would take a jet airliner about 40 days to fly there. Both would need refueling along the way.

My big question here is: how would history, and economic growth, have played out differently on Tube Earth? With all that land out there to colonize, how much more activity would be dedicated to spreading out across the tube? How far would be the furthest flag, subsistence farming town, and modern industrial city at any one time?

My guess is that Tube Earth would look a lot more like our Earth than most space colonization fans expect. Explorers would not have even reached the nearest other continent cluster until the 1800s, and even now there’d be only a few small colonizes there, mostly practicing subsistence agriculture. A several year shipping time would make it very expensive to import modern equipment, and greatly discourage the shipping of mining minerals or farmed food back to the central cluster. Mostly they’d work harder to get more minerals and food from nearby mines and farms.

By 2010 Tube Earth would be lucky to have one monthly airline flight to the next cluster, and a very expensive but welcomed internet connection. Lots of stories would take place there, and it would offer an escape for well-off religious or political refuges. But overall it wouldn’t matter much, because of its huge transport costs.

The key point to note here is that other continent clusters on a Tube Earth are vastly more hospitable and easier to reach than the nearest asteroids or the Moon are from Earth. And the rest of the solar system is even worse. So if other continent clusters would by now matter little for a Tube Earth, asteroids aren’t going to matter much on Earth for a long time to come.

Added: Karl Smith calls it “Invest for Prestige/Get Conned”

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