Monthly Archives: December 2020

Long Views Are Competitive

(I thought I’d said this somewhere before, but this is closest I’ve found.)

In all human decisions, we face two main issues:
A) What do we want?
B) What must we accommodate?
When we are rich and our universe is mild, we can focus on that first consideration. But when we are poor, or in a harsh universe, we must attend more to the constraints that our universe imposes on our choices. (E.g., ems being poor let me say much about them in Age of Em, without knowing what they want.)

Compared to most animals, humans live a lot in artificial worlds, pursuing artificial ends. That is, rather than focusing on making sure that we have enough food and protection from elements and predators, we pursue art, stories, love, connection, honor, glory, etc. And we build artificial environments to help us better purse such artificial ends. In our minds, we do these things because they are more what we want, while we pursue food, protection, etc. more because we must accommodate starvation, predation, etc.

But of course at larger social and evolutionary levels, we humans want what we want because such wants helped our ancestors to survive and reproduce. Because cultures and genes must accommodate a competitive environment of other cultures and genes. In fact, evolving cultures and genes focus overwhelming on such accommodation; they have nothing else they want.

Our evolved habits don’t now have individual humans attending much to the long term future. We sit in equilibria where collective action problems discourage such attention. For example, as each kid shares only half our genes, they get only half as much of our attention. But someday, I predict, our descendants will take much longer views, and more directly take long run constraints into account in their decisions. Such as from competition.

Today, some people claim to take long views. But such people seem to focus overwhelmingly on debating what they collectively want, and attend little to the constraints that the universe imposes on such long term plans. Especially competition; most self-described “long-viewers” today assume that competition can be controlled and overruled, so that they need not consider it as a constraint on their plans.

This seems completely wrong to me. It seems obvious that it is easier to focus on what you want when your focus is short term.

For example, if your personal focus is only on the next 24 hours, you need to make sure you don’t put a plastic bag on your head, or fall off a cliff. But you don’t need to work, eat, or even drink. You can mostly make art, fall in love, etc. with abandon. You can even freely betray your associates to achieve such ends. If your focus is on the next decade, in contrast, you need to attend more to working, eating, drinking, and preserving your relationships. You will be competing with other workers for jobs, and with other people for relations.

For another example, if we look at the level of a nation focusing on a two year pandemic, one needn’t worry much about excessive borrowing, failing to teach students, or eroding public confidence in its institutions. In contrast, those seeking to help their nation prosper over a century should worry about its fertility, debt, savings rates, and institution quality, and especially about how these compare to foreign rivals.

A firm with a mildly higher cost of production can be pretty sure to stay in business for the next year, but is less likely to stay in the black for decades. Similarly, the longer a species has a persistent disadvantage relative to a rival, the less likely it is to survive that rival.

People who really cared a lot more than most do about the long term future should therefore focus more than do most on competition. On how competitive constraints will limit what they can achieve. On what competitive units will exist and to which they should ally themselves in order to achieve their ends. And what their strategy will be to win these competitions. (Yes, such strategies will likely include some kinds of cooperation.)

So why don’t self-described “long-viewers” attend much to competition? Probably because they mainly use long-term talk as a way to signal values to associates. Just as in most politics, science fiction, and futurism.

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The Long Term Future of History

Assuming that dark energy continues to make the universe expand at an accelerating rate, in about 150 billion years all galaxies outside the Local Supercluster will pass behind the cosmological horizon. It will then be impossible for events in the Local Group to affect other galaxies. Similarly it will be impossible for events after 150 billion years, as seen by observers in distant galaxies, to affect events in the Local Group. (More)

My last two posts suggested that the average spacing between independently-originating aggressive alien civilizations is roughly 1-4 billion light years. If we can eventually get light signals from galaxies that are roughly 100 billion light years away today, this suggests that we’ll be able to dimly see the first billion or so years of the history of a few tens to hundreds of such alien civilizations. But just seeing them dimly won’t really tell us that much about them, and we may be terribly curious to know much more.

Aliens who aspire to win in the great universal meme evolution contest should seek to take advantage of this curiosity, by sending out messages about themselves and their memes. There are two obvious ways to do this. They can either sent data in light (or other fast particle) signal messages, or they can send physical emissaries that carry lots of data with them.

Over these distances, data sent by physical emissaries goes slower, and is sent directly to fewer locations, but its quantity can be far more. However, it will be harder to believe that the emissary data you receive is actually the data that was originally sent. Especially if it is passed on via several intermediary civilizations. In contrast, while less data can be sent in light signals, not only does it go faster, but one can have stronger confidence that the signal received was actually the signal sent.

The possibility that history may be rewritten is a problem not only for emissaries, but also for ourselves. In fact, the most trustworthy data on our own history might be the signals that we sent out long ago to others, which they then simply reflect back to us. By mixing up the signals that you send out with the signals you reflect back to others, you give them a modestly stronger incentive to read what you send.

To believe our reflected signals, we’d need to encrypt what we send our outgoing signals in some way to make it very hard for them to change them without corrupting them. However, if there are cryptographic hash scheme that can’t be cracked over billions of years by civilizations eager to change history, we could use this not only to trust our reflected signals, but also to let distant aliens verify that the large data they get via emissaries was actually the data that we sent out long long ago.

As with all cosmic beacons, there’s be an advantage to coordinating on where to look when to see them. Such as sending a signal right after seeing a gamma ray burst, and in the exact opposite direction so your signal follows the burst. Then listeners look for your message right after seeing a burst, and in that same direction.

Added 24Dec: As I’ve discussed before, humans cultures had separated diversity for ~1Myr, and now have much stronger  integration, but will again diversify in 1Kyr+ as we spread out among the stars. It seems a similar pattern will play out among alien civs later. They go from separated diversity for 1st ~1Byr, to much stronger integration at ~1-100Byr, but then they diversify again as they lose contact w/ each other after that.

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How Far To Grabby Aliens? Part 2.

In my last post, I recommended these assumptions:

  1. It is worth knowing how far to grabby alien civs (GCs), even if that doesn’t tell about other alien types.
  2. Try-try parts of the great filter alone make it unlikely for any one small volume to birth an GC in 14 billion years.
  3. We can roughly estimate GC expansion speed, and the number of hard try-try steps in the great filter.
  4. Earth is not now within the sphere of control of an GC.
  5. Earth is at risk of birthing an GC soon, making today’s date a sample from GC time origin distribution.

I tried to explain how these assumptions can allow us to estimate how far away are GC. And I promised to give more math details in my next post post. This is that next post.

First, I promised to elaborate on how well tn works as the chance that a small volume will birth a GC at time t. The simplest model is that eternal oases like Earth are all born at some t=0, and last forever. Each oasis must pass through a great filter, i.e., a sequence of hard steps, from simple dead matter to simple life to complex life, etc., ending at a GC birth. For each hard step, there’s a (different) constant chance per unit time to make it to the next step, a chance so low that the expected time for each step is much less than t.

In this case, the chance of GC birth per unit time in a small volume is tn, with n = h-1, where h is the number of hard steps. If there are many oases in a small volume with varying difficulty, their chances still add up to the same tn dependence as long as they all have the same number of hard steps between dead matter an a GC.

If there are try-once steps in the great filter, steps where an oasis can fail but which don’t take much time, that just reduces the constant in front of tn, without changing the tdependence. If there are also easy steps in this filter, steps that take expected time much less than t, these just add a constant delay, moving the t=0 point in time. We can accommodate other fixed delays in the same way.

We have so far assumed that, one the prior steps have happened, the chance of each step happening is constant per unit time. But we can also generalize to the case where this step chance per time is a power law tm , with t the time since the last step was achieved, and with a different mi for each step i. In this case, h = Σi (1+mi). These step powers m can be negative, or fractional.

Instead of having the oases all turn on at some t=0, oases like Earth with a chance tn can instead be born at a constant rate per unit time after some t=0. It turns out that the integrated chance across all such oases of birthing a GC at time t is again proportional to tn, with again n = h-1.

A more elaborate model would consider the actually distribution of star masses, which have a CDF that goes as m-1.5, and the actual distribution of stellar lifetime L per mass m, which has a CDF that goes as m-3. Assuming that stars of all masses are created at the same constant rate, but that each star drops out of the distribution when it reaches its lifetime, we still get that the chance of GC birth per unit time goes as tn, except that now n = h-1.5.

Thus the tn time dependence seems a decent approximation in more complex cases, even if the exact value of n varies with details. Okay, now lets get back to this diagram I showed in my last post:

If the GC expansion speed is constant in conformal time (a reasonable approximation for small civ spatial separations), and if the civ origin time x that shapes the diagram has rank r in this civ origin time distribution, then x,r should satisfy:

((1-r)/r) ∫0x tn dt = ∫x1 tn (1 – ((t-x)D/(1-x))) dt.
Here D is the space dimension. D = 3 is appropriate on the largest and the small many-star scales, but D = 2 across galaxy disks, and D = 1 in filaments of galaxies. This equation can be solved numerically. The ratio of the time from an GC origin til that GC directly meets aliens, relative to universe age at civ origin, is (1-x)/x, and is shown in this table:

The x-axis here is the power n in tn, and the y-axis is shown logarithmically. As you can see, aliens can be close in the sense that the time to reach aliens is much smaller than is the time it takes to birth the GC. This time til meet is also smaller for higher powers and for more spatial dimensions.

Note that these meet-to-origin time ratios don’t depend on the GC expansion speed. As I discussed in my last post, this model suggests that spatial distances between GC origins double if either the median GC origin time doubles, or if the expansion speed doubles. The lower is the expansion speed relative to the speed of light, the better a chance a civ has of seeing an approaching GC before meeting them directly. (Note that we only need a GC expansion speed estimate to get distributions over how many GCs each can see at its origin, and how easy they are to see. We don’t need speeds to estimate how long til meet aliens.)

To get more realistic estimates, I also made a quick Excel-based sim for a one dimensional universe. (And I am happy to get help making better sims, such as in higher dimensions.) I randomly picked 1000 candidate GC origins (x,t), with x drawn uniformly in [0,1], and t drawn proportional to tn in [0,1]. I then deleted any origin from this list if, before its slated origin time, it could be colonized from some other origin in the list at speed 1/4. What remained were the actual GC origin points.

Here is a table with key stats for 4 different powers n:

I also did a version with 4000 candidate GCs, speed 1/8, and power n = 10, in which there were 75 C origins. This diagram shows the resulting space-time history (time vertical, space horizontal):

In the lower part, we see Vs where an GC starts and grows outward to the left and right. In the upper part, we see Λs where two adjacent GC meet. As you can see, for high powers GC origins have a relatively narrow range of times, but a pretty wide range of spatial separations from adjacent GC.

Scaling these results to our 13.8 billion year origin date, we get a median time to meet aliens of  roughly 1.0 billion years, though the tenth percentile is about 250 million years. If the results of our prior math model are a guide, average times to meet aliens in D=3 would be about a factor two smaller. But the variance of these meet times should also be smaller, so I’m not sure which way the tenth percentile might change.

A more general way to sim this model is to:

  • A) set a power n in tn and estimate 1) a density in space-time of origins of oases which might birth GCs, 2) a distribution over oasis durations, and 3) a distribution over GC expansion speeds,
  • B) randomly sample 1) oasis spacetime origins, 2) durations to produce a candidate GC origin after its oasis origin times, using tn , and 3) expansion speed for each candidate GC,
  • C) delete candidate GCs if their birth happens after its oasis ends or after a colony from another GC colony could reach there before then at its expansion speed.
  • D) The GC origins that remain give a distribution over space-time of such GC origins. Projecting the expansion speed forward in time gives the later spheres of control of each GC until they meet.

I’ll put an added to this post if I ever make or find more elaborate sims of this model.

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How Far To Grabby Aliens? Part 1.

Many have tried to estimate how far away are aliens. For example, some apply the Drake equation, which is the product of 7 parameters, some of which can vary over quite wide ranges. Resulting estimates tend to be quite uncertain and disputable.

In this post, I introduce a more precise and definitive answer, at least for one especially important kind of alien. My median estimate is that, if we survive, we will meet this kind of alien in roughly a half billion years. In this post, I’ll try to give key intuitions. In my next post, I’ll give more math details.

We are now quite early in the history of the universe. Some of the stars around us will last a thousand times longer than our Sun. This key fact makes it hard to believe that, if Earth did not exist, no other civ (civilization) would ever colonize this area. If civs were that hard to make, then our civ shouldn’t be so early.

We should instead guess that eventually the universe will be mostly filled with civs, and thus one of the key constraints on the origin of any one civ is a need to pass a local great filter, going from no life to simple life to complex life to intelligence, etc., before some other civ arrives to colonize that area, and prevent new pics there.

That is, one key kind of alien is a “grabby civilization” (GC), which rapidly expands its sphere of control, and within that sphere a GC prevents the origin of any other GC. (Though it may allow the origin or continued existence of other kinds of aliens. And this “grabby” label says little about what happens when it directly meets another civ.)

It looks like there is a non-trivial chance that we here on Earth will give birth to such an GC near here. And soon. (Say within a million years.) I’m not here claiming (nor disputing) that this would be a good idea, or even that this chance is especially large. But this chance does seem real enough to justify treating our date now, 13.8 billion years after the Big Bang, as a data point drawn from the distribution of GC origin dates. Allowing us to draw inferences about that distribution.

My strategy will be to describe a mathematical model of this distribution that is both well-grounded theoretically, and also simple enough to allow concrete analysis and inference. One result of which is concrete estimates on how far away are the nearest aliens.

My mathematical model has just three parameters, two of which are already known to within roughly an order of magnitude, and the third of which we can infer about that well from our one timing data point. The first parameter is the speed at which an GC expands to colonize the space around it. At least until it directly meets another GC. This speed must be less than the speed of light, and grabbiness would tend to push an GC to higher speeds, but it isn’t clear just how much less than light speed an GC will have to accept.

The second parameter is the number of hard try-try steps in each local great filter. The fact that we now see no alien civilizations anywhere strongly suggests that any one oasis (e.g., planet) has a very low chance to start from simple dead matter and then give rise to a clearly visible civilization. Assume that this dead-matter-to-visibility filter has a similar size to the filter for dead matter giving rise to an GC. Assume also that even if there are also other try-once steps in this GC filter, the try-try steps are by themselves sufficiently hard that any one oasis (like Earth) is quite unlikely to, by itself, get through its great filter by today’s 13.8 billion year date. (Easy steps just create time delays, and any steps near the border between easy and hard give nearly mixed effects.)

These assumptions imply that the chance that any one small volume actually gives birth to an GC by a particular time t since the Big Bang is (after a time delay) proportional to tn, where n is near the number of hard try-try steps. (I’ll elaborate on this relation in my next post.)

The third parameter sets a constant in front of tn, an overall filter strength. This gives an absolute chance that the great filter is passed in one of the oases in a small standard volume by a particular date t. Our key datum of our being near ready to start an GC at 13.8 billion years after the Big Bang lets us estimate this filter constant. Given it, and also estimates on the other two parameters of speed and number of hard steps, we can infer our distance to the nearest aliens.

If that claim surprises you, consider the following diagram:

Assume that potential GC origins are uniformly distributed in space. If we integrate the probability density tn-1 over the yellow region, and then renormalize, that renormalization in effect sets the value of the overall filter strength, relative to the origin time of that one civ in the diagram.

If we then assume that this civ origin time is at the median of the renormalized distribution that we’ve calculated, we get a self-consistent model that gives an exact answer for the spacing between such civs! Yes, this model is only in one dimension, and doesn’t fully allow for variation in GC origin locations and timings. But it shows how it is possible to get a spacing between civs from only an expansion speed, a number of hard steps, and a sample origin time.

Note two key symmetries of this simple model. First, we get exactly the same model if we both double the duration from time start to this GC origin, and also the spatial distance between GC origins. Second, we get exactly the same model if we double both the expansion speed and the spatial distance between GC origins. Thus given a power n, an expansion speed, and a median GC origin time, the model is fully determined, setting a complete space-time distribution over GC origins and spheres of control.

In sum, it is possible to estimate how far away in space and time are the nearest aliens, if one is willing to make these assumptions:

  1. It is worth knowing how far to grabby aliens (GCs), even if that doesn’t tell about other alien types.
  2. Try-try parts of the great filter alone make it hard for any one oasis to birth an GC in 14 billion years.
  3. We can roughly estimate the speed at which GCs expand, and the number of hard try-try steps.
  4. Earth is not now within the sphere of control of a GC.
  5. Earth is at risk of birthing a GC soon, making today’s date a sample from GC time origin distribution.

In my next post I’ll give more math details, and discuss what concrete estimates they suggest about aliens.

Added: Here is a 2 hour interview I did with Adam Ford on this topic.

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Re Privacy Wars, Sue For Peace

Imagine: your relative is a celebrity, currently the focus of a media scandal. You and other relatives are talking together, strategizing. Reporters are asking for interviews, and digging into your world, probably via both legal and illegal means. What should you do?

Some of you say to fight, fight, fight. Threaten legal action, hire a security team, and threaten any relative who doesn’t hold a hard line with expulsion from the family. This is about moral absolutes, after all, and “extremism in defense of liberty is no vice.” Give ’em an inch and they’ll take a mile. So never ever compromise.

Others of you suggest compromise. Hold a press conference and directly tell reporters many of the things they want to know. Enough to make them likely sufficiently satisfied to let up on their digging. It wouldn’t be an explicit deal, but they have limited resources and plenty of other things to do. And if they dig more, they may find new issues to focus on.

This second group is usually right. Peace is usually better than war. Maybe in some cases reporters couldn’t be placated, and would still push into all your private niches. But usually not. This is the idea behind the proposal of my last post. Biometrics is getting cheaper and more reliable, our imperfectly-secure smart-phones know a great deal about us, and the people and organizations around us have strong reasons to want to know a few key things about us.

So let’s compromise, I say. Find a way to set up a system to give those people and orgs around us the few key bits that are they most want to know, and that we don’t so much mind them knowing. And then maybe they won’t work so hard to extract this key info out of all the cues that we naturally leak. Key info that they likely could get anyway if they worked hard enough and coordinated, and as a side effect they may obtain and use other info that we might rather keep private.

When conflicts gain a moral color, it can look bad to advocate compromise. But in general, war is bad, peace is good, and compromise can bring peace.

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Reliable Private-Enough Physical Identity

“Your papers, please” (or “Papers, please”) is an expression or trope associated with police state functionaries, allegedly popularized in Hollywood movies featuring Nazi Party officials demanding identification from citizens during random stops or at checkpoints. It is a cultural metaphor for life in a police state. (More)

When we share public spaces with mobile active things like cars, planes, boats, pets, drones, guns, and soon robots, we are vulnerable to being hurt by such things. So most everywhere on Earth, we require most such things to show visible registered identifiers. (Land also requires such registration, and most smart-phones contain them.) This system has some obvious advantages:

  1. If such a thing is actually used to harm us, and if we can remember or record its identifier, then we can look it up to find a human we might hold responsible.
  2. If such a thing does not show a visible identifier, we can immediately suspect it is up to no good, and pull away to limit harms.
  3. If you ever lose a registered thing, its finder can find you via the registration system, and return it.
  4. Registration discourages theft, as fully effective theft then requires also changing a registration entry.
  5. The identifier offers a clear shared unique index or “name” to facilitate records and discussion about the item.

Oddly, humans are the mobile active things to which we are usually the most vulnerable, and yet we don’t require humans to show visible registered identities in shared public spaces. As a result, it is harder to tell if a human is allowed to be where we see them, and if they hurt us and run away, then we face larger risks of not finding someone we can usefully hold responsible. Humans can also as a result be more easily lost or stolen.

Because of this problem, a great many organizations require humans who try to enter their spaces to, at their entrances, show a registered identity. And many of these orgs require that visible ID tags be continually shown within their spaces. Even more orgs (such as stores) require such identifiers on their responsible representatives, even if not on visitors. In fact, most orgs would probably require everyone in their spaces to have IDs this if were cheap; they relent mostly out of fear of extra costs and discouraging visitors. Continue reading "Reliable Private-Enough Physical Identity" »

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Social Proof, But of What?

People tend to (say they) believe what they expect that others around them will soon (say they) believe. Why? Two obvious theories:
A) What others say they believe embodies info about reality,
B) Key audiences respect us more when we agree with them

Can data distinguish these theories? Consider a few examples.

First, consider the example that in most organizations, lower level folks eagerly seek “advice” from upper management. Except that when such managers announce their plan to retire soon, lower folks immediately become less interested in their advice. Manager wisdom stays the same, but the consensus on how much others will defer to what they say collapses immediately.

Second, consider that academics are reluctant to cite papers that seem correct, and which influenced their own research, if those papers were not published in prestigious journals, and seem unlikely to be so published in the future. They’d rather cite a less relevant or influential paper in a more prestigious journal. This is true not only for strangers to the author, but also for close associates who have long known the author, and cited that author’s other papers published in prestigious journals. And this is true not just for citations, but also for awarding grants and jobs. As others will mainly rely on journal prestige to evaluate paper quality, that’s what academics want to use in public as well, regardless of what they privately know about quality.

Third, consider the fact that most people will not accept a claim on topic area X that conflicts with what MSM (mainstream media) says about X. But that could be because they consider the media more informed than other random sources, right? However, they will also not accept this claim on X when made by an expert in X. But couldn’t that be because they are not sure how to judge who is an expert on X? Well let’s consider experts in Y, a related but different topic area from X. Experts in Y should know pretty well how to tell who is an expert in X, and know roughly how much experts can be trusted in general in areas X and Y.

Yet even experts in Y are also reluctant to endorse a claim made by an expert in X that differs from what MSM says about X. As the other experts in Y whose respect they seek also tend to rely on MSM for their views on X, our experts in Y want to stick with those MSM views, even if they have private info to the contrary.

These examples suggest that, for most people, the beliefs that they are willing to endorse depend more on what they expect their key audiences to endorse, relative to their private info on belief accuracy. I see two noteworthy implications.

First, it is not enough to learn something, and tell the world about it, to get the world to believe it. Not even if you can offer clear and solid evidence, and explain it so well that a child could understand. You need to instead convince each person in your audience that the other people who they see as their key audiences will soon be willing to endorse what you have learned. So you have to find a way to gain the endorsement of some existing body of experts that your key audiences expect each other to accept as relevant experts. Or you have to create a new body of experts with this feature (such as say a prediction market). Not at all easy.

Second, you can use these patterns to see which of your associates think for themselves, versus aping what they think their audiences will endorse. Just tell them about one of the many areas where experts in X disagree with MSM stories on X (assuming their main audience is not experts in X). Or see if they will cite a quality never-to-be-prestigiously-published paper. Or see if they will seek out the advice of a soon-to-be-retired manager. See not only if they will admit to which is more accurate in private, but if they will say when their key audience is listening.

And I’m sure there must be more examples that can be turned into tests (what are they?).

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If Aliens Are Near

Most of us have core beliefs about which we feel pretty confident, but to which we get emotionally attached. One useful exercise to help overcome such attachment is to think explicitly about how you would change other beliefs if you became convinced that a central belief were wrong.

I suggest this mostly as a private exercise, as I worry it won’t go well if critics can selectively demand: “You think you’re so rational; tell us what you’d believe if X were wrong” for any X they like. Similarly to how it wouldn’t go well if critics could selectively demand that rivals reveal nude or other severely unflattering pictures of themselves. Such tests might go better if applied uniformly applied to all, but that’s harder to arrange.

Even so, I’m inspired today to try one version of this exercise: what else would I think if I thought aliens were actually near?

My best guess is that the universe is vastly larger in space than the distance we can see. And so in all that vast volume, there are probably aliens. Even intelligent civilized aliens. But my estimate is that the nearest such are very far away, outside the visible universe. (Low intelligence alien life may be closer.) So if you offered evidence purporting to convince me otherwise, I’d be initially skeptical. If I were willing to give you the benefit of the doubt, I’d guess that you’d made an analysis mistake somewhere.

If you somehow managed to convince me of your evidence, my guess is that it would be regarding aliens who are very far away, but just not quite as far as I’d thought. And if you convinced me that no, aliens have frequently been visiting us here on Earth lately, I’d be a lot more surprised. But what if you did in fact convince me?

My guess (revising my prior best guess) is that the most likely scenario consistent with this assumption is that these aliens are from one of the Sun’s sibling stars, born in the same stellar nursery that likely birthed 100 to 10,000 stars in the same ten million year period. There was only one Eden in the visible universe which managed to seed one star nursery with life. That Eden was in our galaxy, and that nursery was our Sun’s. Eden wasn’t well suited to support fragile multi-cellar life, but against great odds it created robust extremophiles that could travel far.

These sibling stars drifted far from their nursery over the last four billion years. (They can be identified from far away via their spectra.) Some were not seeded with life, and most of the rest remain far from creating intelligent civilizations. But some, like our Sun, have already done so. Many of those killed themselves, or locked themselves down to stay on their planet or in their star system. But one managed, many millions of years ago, to create a very stable civilization that could travel to other stars.

For some unknown reason, this one successful civilization has strongly limited its internal variation, to prevent any of its parts, or later sibling civilizations, from mass colonization of the universe. Many stable civilizations will develop a ruling body with strong central control, and it seems hard to predict in general what such bodies will want or choose, other than that their choices must allow them to maintain control. So its not crazy to think that this first civilization might decide to prevent mass colonization, even if it allows limited development of a few key resources that we can’t now see.

Part of such prevention would be keeping tabs on, and limiting the growth of, life around sibling stars. Sterilization might be hard, and it is plausible that they’d be curious about and entertained by how life evolves around sibling stars.  So its not crazy to think they might make frequent if limited visits to Earth. And its further not crazy to think they might be sloppy about hiding their visits; maybe they feel very secure that we can’t threaten them, and maybe they get a kick out of being noticed.

Yes, I don’t like having to resort to multiple “not crazy” assumptions in my most likely scenario, but I am being forced to explain what I see as an unlikely scenario.

If these aliens have a policy of preventing mass colonization, they will have to step in at some point to limit Earth’s expansion. But they will have been preparing to do that for many millions of years, and may have already done this several times at other sibling stars. So our chances to defy their plans and expand anyway can’t be great.

Perhaps we have a greater chance to persuade them to change their policies. They may limit what those internal to their civilization are allowed to say on the subject, but it seems they’ve been more hands off with us, and they may allow many within their civilization to see and hear us. In which case we have a chance to persuade. Though we should expect that the more likely scenario is that they persuade us, fairly or unfairly, to endorse their policy.

If you ask me to tell the most realistic story I can wherein we see or meet aliens today, this is it. Not terribly likely, but at least not crazy. Which is actually an unusually high standard in science fiction.

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Searching For Eden

In my last post, I reviewed the standard theory that life on Earth got very lucky to complete a series of hard try-try steps to get to our human level before its window for life closes. I said that this theory has had only mixed success in predicting Earth history timings, and does noticeably badly in predicting that Earth should score well on the key figure of merit of (V*M*W)N, for number of hard try-try steps N, volume V, metabolism M, and time window W not used for easy steps. This seems a pretty big deal, as this is a pretty basic theory on a pretty important process. If we are very wrong about it, that’s important to know. (Just as its important to get to the bottom of credible UFO sightings.)

This evidence conflict might be tolerably weak if one only estimated N=1, one very hard step. But, I said, life designs look so complex and well-integrated that I estimate at least ten hard steps, much more than the few perhaps seen in Earth’s fossil record. This graph conveys a similar intuition, suggesting that those added hard steps happened either as many try-once steps very early in Earth history, or as many try-try steps before Earth.

In my last post, I suggested that this conflict could at least be cut by positing many hard try-once steps, instead of the usual hard try-try steps, early in Earth’s history. But now I’ll admit I don’t think that is enough. I find it hard to believe that more than half of (the integrated magnitude of) hard steps are of the try-once sort, and yet even N=5 gives a quite strong evidence conflict. So I’m forced to take seriously panspermia, the hypothesis that life had another oasis before Earth, and was transferred from that oasis to Earth very early in Earth’s history. Call that prior oasis “Eden”.

Yes, interstellar panspermia seems hard and risky, in effect adding another try-once great filter step which life must compete. Here’s a recent estimate:

But if this scenario allows an Eden with a volume times metabolism as large as Earth’s, and if there are R times as may oases that could support the more robust early sort of life, relative to the more fragile multicellular sort that comes later, then the relative chance of this Eden scenario, compared to just-Earth, is a factor of R*2N times the chance that Eden could successfully transfer life to another (any other) suitable oasis. If Eden’s volume times metabolism were larger that Earth’s, this factor gets larger. So even a low chance to transfer to another oasis might be more than compensated by such a factor.

If there really was an Eden, then finding it is likely to become one of the great historical quests of our descendants. So what can we say about Eden now, to advise this quest? Here are some clues:

  1. Until we replace our usual theory, we still probably want to use the usual figure of merit to predict Eden. Except N becomes the number of hard try-try steps that happen at Eden, and the time deadline for delivering life to Earth says that the time window W can only be extended by having an oasis that starts earlier. So Eden likely meets the usual constraints (like temperature), has a large volume V and metabolism M, and started early.
  2. A set of planets or moons that are close to each other in the same solar system may have a high enough rate of life traveling between them to count as one larger planet, thereby gaining a big advantage. The same may apply to stars that are close and have much moving stuff nearby to induce high rates of transfers. For example, if seeding one star in a stellar nursery effectively seeds S starts in that nursery, then the panspermia theory gets a factor of S boost relative to alternate theories.
  3. The more try-try hard steps that happened on Eden, as opposed to on Earth, the weaker is the evidence conflict re Earth. So maybe most such steps happened on Eden.
  4. Eden mainly needs to give rise to single-cell extremophiles that could travel well enough. So it needn’t support fragile multicellular life, and may work better if it has high (but not overly high) variability to encourage the evolution of robustness. So there seems to be a substantial R factor, and Eden may have been far from a gentle protective “garden”.
  5. Eventually, Eden would have been home to the sort of life that gave rise to Earth’s sort of life. With carbon, water, and DNA. So that rejects exotic hypothesized life such as made of silicon, or in plasmas or neutron stars.
  6. This robust single-celled life seems much less vulnerable to the gamma ray bursts, supernova, and asteroids that tend to kill off fragile life like us close to the galactic center. Or close to the large solar flares common near red dwarf stars. So while Earth was not allowed to be in such places, Eden is allowed there.
  7. Panspermia gets easier in places where stars are spaced closer together, as toward the galactic center. So all else equal, expect Eden in such places.
  8. However, if dormant cells only survive between stars for a million years, then if its dust or rock travel host moved at a typical relative velocity of 30km/s, it could only travel 100 light years in that time, which doesn’t get you far in the galaxy. Thus either Eden was quite near to Earth when Earth acquired life, or dormant life can last much longer, or hosts could fly much faster.
  9. The usual analysis of interstellar panspermia gets pretty low rates. But the chance of panspermia should be increased by the density of stuff flying around near the travel origin and destination locations. Such stuff can kick up life from Eden, and help grab stuff traveling past Earth. Earth had lots of stuff flying about when its solar system formed, and that was embedded in larger complex turbulent dynamic molecular clouds which had more stuff flying about. So if Eden was close to Earth then, Eden was plausibly in a similar cloud area then, which helped induce the travel origin. Seems worth analyzing how molecular clouds change panspermia rates.
  10. Life could have continued on Eden long after it sent life to Earth, but the selection effect of seeing our existence doesn’t enhance the chance of that. The higher is our estimate of the number of oases to which Eden life would have spread, the easier it will be to find such life out there. But unless that chance is enormous, or R is enormous, we expect Eden and any of its other descendants to be quite hard to find. Stars that are siblings of our Sun, born in the same nursery, seem good candidates.
  11. The hypothesis of two prior oases in sequence, instead of one, would also be penalized by a low chance of transfer between them, but might allow a larger total time window W, and a boost in R via more possible oases. Furthermore, this scenario might allow a split wherein try-try steps happen in the oasis with a large figure of merit, but try-once steps happen in multiple parallel small oases, giving them a larger chance of success.
  12. Life in the atmosphere of a brown drawf seems an interesting possibility, but it seems harder for passing stuff to kick out or grab life from such a reservoir. Those things seem easier for life on a planet near a red dwarf, but those may suffer too much variability.
  13. Life may have been possible in a few places 10-17 million years after the Big Bang, from heavy elements formed by supernovae in rare star-forming fluctuation regions that constitute ~10-17 of all matter.
  14. (I’ll add more here as I or others suggest them.)

Added 17Dec: Note that a prediction of the Eden scenario is that the earliest and simplest form of life on Earth is likely a form that enabled panspermia, staying alive but dormant deep in rock for long periods. So life now deep in rock on Earth is predicted to be early and simple, instead of being variations on surface life that migrated down and colonized deep rock.

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Try-Try or Try-Once Great Filter?

Here’s a simple and pretty standard theory of the origin and history of life and intelligence. Life can exist in a supporting oasis (e.g., Earth’s surface) that has a volume V and metabolism M per unit volume, and which lasts for a time window W between forming and then later ending. This oasis makes discrete “advances” between levels over time, and at any one time the entire oasis is at the same level. For example, an oasis may start at the level of simple dead chemical activity, may later rise to a level that counts as “life”, then rise to a level that includes “intelligence”, and finally to a level where civilization makes a big loud noises that are visible as clearly artificial from far away in the universe.

There can be different kinds of levels, each with a different process for stepping to the next level. For example, at a “delay” level, the oasis takes a fixed time delay D to move to the next level. At a “try once” level, the oasis has a particular probability of immediately stepping to the next level, and if it fails at that it stays forever “stuck”, which is equivalent to a level with an infinite delay. And at a “try try” level, the oasis stays at a level while it searches for an “innovation” to allow it to step to the next level. This search produces a constant rate per unit time of jumping. As an oasis exists for only a limited window W, it may never reach high levels, and in fact may never get beyond its first try-try level.

If we consider a high level above many hard try-try levels, and with small enough values of V,M,W, then any one oasis may have a very small chance of “succeeding” at reaching that high level before its window ends. In this case, there is a “great filter” that stands between the initial state of the oasis and a final success state. Such a success would then only tend to happen somewhere if there are enough similar oases going through this process, to overcome these small odds at each oasis. And if we know that very few of many similar such oases actually succeed, then we know that each must face a great filter. For example, knowing that we humans now can see no big loud artificial activity for a very long distance from us tells us that planets out there face a great filter between their starting level and that big loud level.

Each try-try type level has an expected time E to step to the next level, a time that goes inversely as V*M. After all, the more volume there is of stuff that tries, and faster its local activity, the more chances it has to find an innovation. A key division between such random levels is between ones in which this expected time E is much less than, or much greater than, the oasis window W. When E << W, these jumps are fast and “easy”, and so levels change relatively steadily over time, at a rate proportional to V*M. And when E >> W, then these jumps are so “hard” that most oases never succeed at them.

Let us focus for now on oases that face a great filter, have no try-once steps, and yet succeed against the odds. There are some useful patterns to note here. First, let’s set aside S, the sum of the delays D for delay steps, and of the expected times E for easy try-try steps, for all such steps between the initial level and the success level. Such an oasis then really only has a time duration of about W-S to do all its required hard try-try steps.

The first pattern to note is that the chance that an oasis does all these hard steps within its window W is proportional to (V*M*(W-S))N, where N is the number of these hard steps needed to reach its success level. So if we are trying to predict which of many differing oases is mostly likely to succeed, this is the formula to use.

The second pattern to note is that if an oasis succeeds in doing all its required hard steps within its W-S duration, then the time durations required to do each of the hard steps are all drawn from the same (roughly exponential) distribution, regardless of the value of E for those steps! Also, the time remaining in the oasis after the success level has been reached is also drawn from this same distribution. This makes concrete predictions about the pattern of times in the historical record of a successful oasis.

Now let’s try to compare this theory to the history of life on Earth. The first known fossils of cells seems to be from 0.1-0.5 Ga (billion years) after life would be possible on Earth, which happened about 4.2 Gya (billion years ago), which was about 9.6 Ga after the universe formed. The window remaining for (eukaryotic) life to remain on Earth seems 0.8-1.5 Ga. The relatively steady growth in max brain sizes since multi-cellular life arose 0.5 Gya suggests that during this period there were many easy, but no hard, try-try steps. Multi-celluar life seems to require sufficient oxygen in the atmosphere, but the process of collecting enough oxygen seems to have started about 2.4 Gya, implying a long 1.9 Ga delay step. Prokaryotes started exchanging genes about 2.0 Gya, eukaryotes appeared about 1.7 Gya, and modern sex appeared about 1.2 Gya. These events may or may not have been the result of successful try-try steps.

Can we test this history against the predictions that try-try hard step durations, and the window time remaining, should all be drawn from the same roughly exponential distribution? Prokaryote sex, eukaryotes, and modern sex all appeared within 0.8 Ga, which seems rather close together, and leaving a long uneventful period of almost ~2 Ga before them. The clearest hard step duration candidates are before the first life, which took 0.0-0.5 Ga, and the window remaining of 0.8-1.5 Ga, which could be pretty different durations. Overall I’d say that while this data isn’t a clear refutation of the same hard step distribution hypothesis, it also isn’t that much of a confirmation.

What about the prediction that the chance of oasis success is proportional to (V*M*(W-S))N? The prediction about Earth is that it will tend to score high on this metric, as Earth is the only example of success that we know.

Let’s consider some predictions in turn, starting with metabolism M. Life of the sort that we know seems to allow only a limited range of temperatures, and near a star that requires a limited range of distances from the star, which then implies a limited range of metabolisms M. As a result of this limited range of possible M, our prediction that oases with larger M will have higher chances of success doesn’t have much room to show itself. But for what its worth, Earth seems to be nearer to the inner than outer edge of the Sun’s allowable zone, giving it a higher value of M. So that’s a weak confirmation of the theory, though it would be stronger if the allowed zone range were larger than most authors now estimate.

What about volume V? The radii of non-gas-giant planets seems to be lognormally distributed, with Earth at the low end of the distribution (at a value of 1 on this axis):

So there are many planets out there (at r=4) with 16 times Earth’s surface area, and with 64 times the volume, ratios that must be raised to the power of N to give their advantage over Earth. And these larger planets are made much more of water than is Earth. This seems to be a substantial, if perhaps not overwhelming, disconfirmation of the prediction that Earth would score high on VN. The higher is the number of hard steps N, the stronger is this disconfirmation.

Regarding the time window W, I see three relevant parameters: when a planet’s star formed, how long that star lasts, and how often there are supernova nearby that destroy all life on the planet. Regarding star lifetimes, main sequence star luminosity goes as mass to the ~3.5-4.0 power, which implies that star lifetimes go inversely as mass to the ~2.5-3.0 power. And as the smallest viable stars have 0.08 of our sun’s mass, that implies that there are stars with ~500-2000 times the Sun’s lifetime, an advantage that must again be raised to the power N. And there are actually a lot more such stars, 10-100 times more than of the Sun’s size:

However, the higher metabolism of larger mass stars gives them a spatially wider habitable zone for planets nearby, and planets near small stars are said to face other problems; how much does that compensate? And double stars should also offer wider habitable zones; so why is our Sun single?

Now what if life that appears near small long-lived stars would appear too late, as life that appeared earlier would spread and take over? In this case, we are talking about a race to see which oases can achieve intelligence or big loud civilizations before others. In which case, the prediction is that winning oases are the ones that appeared first in time, as well has having good metrics of V,M,W.

Regarding that, here are estimates of where the habitable stars appear in time and galactic radii, taking into account both star formation rates and local supernovae rates (with the Sun’s position shown via a yellow star):

As you can see, our Sun is far from the earliest, and its quite a bit closer to galactic center than is ideal for its time. And if the game isn’t a race to be first, our Sun seems much earlier than is ideal (these estimates are arbitrarily stopped at 10Ga).

Taken together, all this seems to me to give a substantial disconfirmation of the theory that chance of oasis success is proportional to (V*M*(W-S))N, a disconfirmation that gets stronger the larger is N. So depending on N, maybe not an overwhelming disconfirmation, but at least substantial and worrisome. Yes, we might yet discover more constraints on habitability to explain all these, but until we find them, we must worry about the implications of our analysis of the situation as we best understand it.

So what alternative theories do we have to consider? In this post, I’d like to suggest replacing try-try steps with try-once steps in the great filter. These might, for example, be due to evolution’s choices of key standards, such as the genetic code, choices that tend to lock in and get entrenched, preventing competing standards from being tried. The overall chance of success with try-once steps goes as the number of oases, and is independent of oasis lifetime, volume, or metabolism, favoring many small oases relative to a few big ones. With more try-once steps, we need fewer try-try steps in the great filter, and thus N gets slower, weakening our prediction conflicts. In addition, many try-once steps could unproblematically happen close to each other in time.

This seems attractive to me because I estimate there to be in fact a great many rather hard steps. Say at least ten. This is because the design of even “simple” single cell organisms seems to me amazingly complex and well-integrated. (Just look at it.) “Recent” life innovations like eukaryotes, different kinds of sex, and multicellular organisms do involved substantial complexity, but the total complexity of life seems to me far larger than these. And while incremental evolution is capable of generating a lot of complexity and integration, I expect that what we see in even the simplest cells must have involved a lot of hard steps, of either the try-once or the try-try type. And if they are all try-try steps, that makes for a huge N, which makes the prediction conflicts above very difficult to overcome.

Well that’s enough for this post, but I expect to have more to say on the subject soon.

Added 19Jan: Turns out we also seem to be in the wrong kind of galaxy; each giant elliptical with a low star formation rate hosts 100-10K times more habitable Earth-like planets, and a million times as many habitable gas giants, than does our Milky Way.

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