Tag Archives: Space

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:

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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Our Quiet Galaxy

Part of our surviving the great filter was our galaxy having especially few collisions with other galaxies:

The Milky Way and Andromeda are siblings, … we used to think they were near-twins. .. [But] the black hole at [Andromeda's] heart is more than a hundred times as massive as ours. And while our galaxy is strewn with about 150 of the bright galactic baubles known as globular clusters, Andromeda boasts more than 400. … Whereas Andromeda is a pretty well-adjusted spiral, the Milky Way is an oddball – dimmer and quieter than all but a few per cent of its peers. That is probably because typical spirals such as Andromeda are transformed by collisions with other galaxies over their lifetimes. …

The Milky Way must have lived relatively undisturbed. Except for encounters with a few little galaxies such as the Sagittarius dwarf, which the Milky Way is slowly devouring, we wouldn’t have seen much action for 10 billion years. Perhaps that is why we are here to note the difference. More disturbed spirals would have suffered more supernova explosions and other upheavals, possibly making the Milky Way’s rare serenity especially hospitable for complex life. (more)

So alien life is more likely to be found in our galaxy than in random galaxies. More generally, the more steps in the filter that are spatially correlated like this, the more likely that if life is anywhere out there, it is especially near to us.

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Galaxy Calc Shows Aliens

What makes a planet a good host for life? That is, what does a planet need for life to originate there and then evolve to something at the human level? Astronomers today say a planet at least needs a star that 1) lasts long enough, 2) has enough heavy elements, and 3) is not too often hit by nearby supernovae or gamma ray bursts. Using such criteria, several astronomers (mentioned below) have tried to calculate “galactic habitable zones,” i.e., galactic distributions of good-for-life planets, in both space and time. Such calculations are far more important than I had realized – they can help say how common are aliens! Let me explain.

Imagine that over the entire past and future history of our galaxy, human-level life would be expected to arise spontaneously on about one hundred planets. At least it would if those planets were not disturbed by outsiders. Imagine also that, once life on a planet reaches a human level, it is likely to quickly (e.g., within a million years) expand to permanently colonize the galaxy. And imagine life rarely crosses between galaxies.

In this case we should expect Earth to be one of the first few habitable planets created, since otherwise Earth would likely have already been colonized by outsiders. In fact, we should expect Earth to sit near the one percentile rank in the galactic time distribution of habitable planets – only ~1% of such planets would form earlier. If instead advanced life would arise on about a thousand planets, Earth should sit at the 0.1 percentile rank. And if life would arise on a thousand planets, but only one in ten such life-full planets would rapidly expand to colonize the galaxy, Earth should again sit near the one percentile rank.

Turning this argument around, if we can calculate the actual time distribution of habitable planets in our galaxy, we can then use Earth’s percentile rank in that time distribution to estimate the number of would-produce-human-level-life planets in our galaxy! Or at least the number of such planets times the chance that such a planet quickly expands to colonize the galaxy. If Earth has a low percentile rank, that suggests a good chance that our galaxy will eventually become colonized, even if Earth destroys itself or chooses not to expand. (An extremely low rank might even suggest we’ll encounter other aliens as we expand across the galaxy.) In contrast, if Earth has a middling rank, that suggests a low chance that anyone else would ever colonize the galaxy – it may be all up to us.

At the moment published estimates for Earth’s time percentile rank vary widely. An ’04 Science paper (built on an ’01 Icarus paper) says: Continue reading "Galaxy Calc Shows Aliens" »

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