Tag Archives: Space

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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A Galaxy On Earth

Our galaxy has about three hundred billion stars, and Earth today has about seven billion people. Assuming only half as many useable planets as stars, we could combine these two numbers into an initial crude guess for the size of a galactic civilization, and define a “galaxy of people” to be a thousand billion billion (or 1021) people. Now consider some famous galactic civilizations in science fiction.

One of the most popular science fiction stories ever was Issac Azimov’s Foundation series. It tells of the fall and rise of a galaxy-wide civilization, whose capital, Trantor, was a planet-wide city a kilometer deep into the ground. Trantor’s population was said to be forty billion, in a galaxy with millions of populated planets and a total population of a million billion (or one millionth of a “galaxy” as defined above).

Star War‘s Coruscant is also a planet-wide city and capital of a galaxy wide civilization, with planetary population of a thousand billion, in a galaxy also of millions of planets and a total population of a million billion. Some say Coruscant’s buildings averaged two kilometers tall. In Star Trek‘s Federation of 150 planets a few centuries hence, which controlled a few percent of the galaxy, each planet had no more than about our Earth’s seven billion, though some say the Federation held ten thousand billion people.

These all seem like dramatic underestimates to me. If Earth were paved over with a city the density of Manhattan today (1.6 million in 59 square kilometers), Earth would have a population of 14 thousand billion. Since Manhattan now has an average building height of 25 meters, a two kilometer deep version could hold a million billion people, and a two thousand kilometer deep version (Earth’s radius is 6400km) could hold a billion billion people.

There is roughly another thousand times as much useable material nearby, in other planets, comets, and the sun itself, allowing a solar-system population perhaps a thousand times larger. This brings us to a thousand billion billion, or a “galaxy” of people, the same as my initial crude population estimate for an entire galaxy above, and vastly larger than most science fiction galaxy estimates.

Furthermore, android ems (whole brain emulations in simulated bodies) could take up a lot less space than humans. I once somewhat conservatively estimated that an em might stand at 1% of human height (and run one hundred times faster). Since such an em would take up only one millionth of a human’s volume, a two kilometer deep Earth city could hold a “galaxy” (or thousand billion billion) of ems. And a solar system civilization might fit a billion billion billion ems, or a million “galaxies.”

Of course we have a long long way to go, not only to generate such huge populations, but also to develop the energy, manufacturing, heat-dumping, etc techs to allow us to support them. And yes, eventually we would run out of energy and material near our Sun, and need to go elsewhere to grow.

But we have strong economic reasons to stay close to one another as long as there is enough energy and material nearby, and especially as long as we continue to innovate. So most of our descendants’ economy should stay close to our sun until congestion here gets severe. We may well have a solar system population of a billion billion billion before the time comes when most of our descendants are closer to other stars.

Most science fiction seems to vastly underestimate the population that a single planet or star can hold, and the strength of the economic pressures to keep an economy close together, rather than spread across vast distances. Someday we will learn to tell stories that treat planets and stars as the vast spaces of possibilities that they really are.

Added 11a: Even an unmodified sun radiates enough energy to cover the calorie consumption of over a hundred “galaxies” of humans, and far more ems.

The timescale to grow from today’s population to a “galaxy” of descendants would be 600 years at an industry-style 15 year doubling time, 40 millennia at a farming-style thousand year doubling time, and four years at at next-singularity-style monthly doubling time.

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Space vs. Time Genocide

Consider two possible “genocide” scenarios:

  • Space Genocide – We expect the galaxy to have many diverse civilizations, with diverse behaviors and values, though we don’t know much about them. Their expansion tendencies would naturally lead to a stalemate, with different civilizations controlling different parts of the galaxy. Imagine, however, that it turns out we luckily have a chance to suddenly destroy all other civilizations in the galaxy, so that our civilization can expand to take it all over. (Other galaxies remain unchanged.) Let this destruction process be mild, such as sudden unanticipated death or a sterility allowing one last generation to live out its life. There is a modest (~5%) chance we will fail and if we fail all civilizations in the galaxy are destroyed. Should we try this option?
  • Time Genocide – As their tech and environments changed, our distant ancestors evolved differing basic behaviors and values to match. We expect that our distant descendants will also naturally evolve different basic behaviors and values to match their changing tech and environments. Imagine, however, that it turns out we luckily have a chance to suddenly prevent any change in basic behaviors and values of our descendants from this day forward. If we succeed, we prevent the existence of descendants with differing basic behaviors and values, replacing them with creatures much like us. There is a modest (~5%) chance we will fail and if we fail all our descendants will be destroyed or exist in a mostly worthless state. Should we try this option?

Probably, more people can accept or recommend time genocide than space genocide, even if success in both scenarios prevents the existence of a similar number of relatively alien creatures, to be replaced by a similar number of creatures more like us. This seems related to our tending to admire time-stretched civilizations (e.g., Rivendale) more than space-stretched civilizations (e.g., Trantor), even though space-stretched ones seem objectively more prosperous. But what exactly is the relation?

The common thread, I suspect, is that the far future seems more far, in near/far concrete/abstract terms, than situations far away in space, or in the far past. The near/far distinction was first noticed in how people treated the future differently, and our knowing especially little detail about the future makes it especially easy to slip into abstract thought about the future.

As we are less practical, more idealistic, and more uncompromising in far mode, we see civilizations time-stretched into the future as more ideal, and we are more willing to commit genocide to achieve our ideals regarding such a civilization, even at a substantial risk.

Of course the future isn’t actually any less detailed than the past or places far away in space. And there isn’t any good reason to hold the far future to higher ideals now than we’d be inclined to want when the future actually arrives. If so, time-genocide should be no more morally acceptable than space-genocide. Beware the siren song of shiny far future thought.

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Space vs. Time Allies

Consider two possible civilizations, stretched either across time or space:

  • Time: A mere hundred thousand people live sustainably for a billion generations before finally going extinct.
  • Space: A trillion people spread across a thousand planets live for only a hundred generations, then go extinct.

Even though both civilizations support the same total number of lives, most observers probably find the time-stretched civilization more admirable and morally worthy. (more)

Our distant ancestors struggled against nature and other species, but competed most directly for mates and resources with others in their species, especially others in the same generation. More distant generations, like grandparents or grandkids, tended more to be allies in their efforts to promote their genes and culture. Because of this, Katja and I suggested, humans evolved intuitions that see time-stretched civilizations as more full of comforting allies, and hence more worthy, than space-stretched civilizations.

Modern economies, however, differ in many important ways from the forager bands where these intuitions evolved. So let us compare the relative promise of time-stretched versus space-stretched modern economies with similar total numbers of people.

  • Scale Economies – Spatially large civilizations can specialize more in the production of goods and services, and take advantages of economies of scale, to get more of everything. Temporally large civilizations, in contrast, can only take advantage of scale economies for extremely durable goods like music. This issue favors spatial stretching.
  • Dependence Fragility – The more that the parts of a civilization depend on one another, the more that damage to one part can put the whole at risk. In a time stretched civilization a very bad outcome for any one generation risks the destruction of all future generations. It is a long chain of dependence that is only as strong as its weakest link. In contrast, a space stretched civilization allows for more redundant and parallel dependence paths. It can be more like a net that holds even when many of its strands are broken. This issue favors spatial stretching.
  • Innovation – A finite speed of light imposes delays on how fast innovations developed in one part of a spatially separated civilization can be used elsewhere.  [Added 8a: parallel innovation attempts also make info delays.] The more that a civilization is time-stretched, as opposed to space-stretched, the smaller are such delays. Our civilization is now compact enough that such delays are only a minor issue. This will also cease to be an issue when innovation has ended, i.e., when we have basically discovered all that is worth knowing. This issue favors time-stretching, but only during a (perhaps short) innovation era and only for very spatially stretched civilizations.

Overall, for similar numbers of total people, modestly spatially-stretched civilizations seem more promising. Thus in contrast to our evolved intuition that temporal associates are our allies while spatial associates are our rivals, spatial associates seem to actually be more useful, and hence are more naturally our allies. Beware relying on ancient evolved intuitions.

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Is Time Us, Space Them?

(This post co-authored by Robin Hanson and Katja Grace.)

In the Battlestar Galactica TV series, religious rituals often repeated the phrase, “All this has happened before, and all this will happen again.” It was apparently comforting to imagine being part of a grand cycle of time. It seems less comforting to say “Similar conflicts happen out there now in distant galaxies.” Why?

Consider two possible civilizations, stretched either across time or space:

  • Time: A mere hundred thousand people live sustainably for a billion generations before finally going extinct.
  • Space: A trillion people spread across a thousand planets live for only a hundred generations, then go extinct.

Even though both civilizations support the same total number of lives, most observers probably find the time-stretched civilization more admirable and morally worthy. It is “sustainable,” and in “harmony” with its environment. The space-stretched civilization, in contrast, seems “aggressively” expanding and risks being an obese “repugnant conclusion” scenario. Why?

Finally, consider that people who think they are smart are often jealous to hear a contemporary described as “very smart,” but are much happier to praise the genius of a Newton, Einstein, etc. We are far less jealous of richer descendants than of richer contemporaries. And there is far more sibling rivalry than rivalry with grandparents or grandkids. Why?

There seems an obvious evolutionary reason – sibling rivalry makes a lot more evolutionary sense. We compete genetically with siblings and contemporaries far more than with grandparents or grandkids. It seems that humans naturally evolved to see their distant descendants and ancestors as allies, while seeing their contemporaries more as competitors. So a time-stretched world seems choc-full of allies, while a space-stretched one seems instead full of potential rivals, making the first world seem far more comforting.

Having identified a common human instinct about what to admire, and a plausible evolutionary origin for it, we now face the hard question: do we embrace this instinct as revealing a deep moral truth, or do we reject it as a morally irrelevant accident of our origins? The two of us (Robin and Katja) are inclined more to reject it, but your mileage may vary.

(This is cross-posted at Meteuphoric.)

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The Mysterious Desert

How bright is our future? That depends greatly on how feasible is interstellar travel. And we don’t really know that, because we are still pretty ignorant about what lies between the stars. Oh it all looks pretty empty, but looks could be deceiving. If you look at a logarithmic map of the universe, the scales on which we seem the most ignorant (below 10Bly) are the three orders of magnitude between the furthest planets and the nearest stars. Now we see clues that unexpected and powerful things happen there:

Between May 2009 and May 2010, IceCube detected 32 billion cosmic-ray muons, with a median energy of about 20 TeV. These muons revealed, with extremely high statistical significance, a southern sky with some regions of excess cosmic rays (“hotspots”) and others with a deficit of cosmic rays (“cold” spots).

Over the past two years, a similar pattern has been seen over the northern skies by the Milagro observatory in Los Alamos, New Mexico, and the Tibet Air Shower array in Yangbajain. … It’s a mystery because the hotspots must be produced within about 0.03 light years of Earth. Further out, galactic magnetic fields should deflect the particles so much that the hotspots would be smeared out across the sky. But no such sources are known to exist.

One of the hotspots seen by IceCube points in the direction of the Vela supernova remnant … almost 1000 light years away. Cosmic rays coming from such large distances should be constantly buffeted and deflected by galactic magnetic fields on route, and should thus have lost all directionality by the time they reach Earth. …

There could be a “tube” of magnetic field lines extending between the source and our solar system, funnelling the cosmic rays towards us. … [This] theory is highly speculative. … Others have proposed that … solar magnetic field lines cross and rearrange, converting magnetic energy to kinetic energy – could be accelerating local cosmic rays … creating the observed hotspots. … “That’s also crazy, but it is at least less crazy than other explanations.” (more)

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