UFO Stylized Social Facts

Even though many or even most UFO sightings are best explained as delusions, hoaxes, and ordinary stuff misunderstood, there appears to be a large remnant (>1000) that are much harder to explain, and which show consistent patterns. Such as ~30-1000 second episodes peaking near ~9pm (tied to local sideral time), at random spatial locations, of quiet lights or objects in the sky with intelligent purposes and amazing speeds and accelerations. Sometimes confirmed by many people and recorded by many instruments.

If they aren’t delusions, hoaxes, or misunderstandings, the main remaining explanations are a) some sort of secret society or agency that arose on and is tied to Earth, or b) some sort of aliens. I’m not saying its aliens, but in this post, it’s aliens. That is, here I want to “go there”, and think about how best to explain UFOs, if they are in fact aliens.

Many have worked on trying to explain UFOs in terms of their immediate physical effects. I kinda like “laser pointers for cats” style theories wherein aliens in orbit send beams to paint a local disturbance, while using telescopes to watch local reactions. But these details aren’t that important for whether we believe that UFOs are aliens, as aliens would almost surely be a lot more advanced than us, and so plausibly capable of a wide range of such approaches.

No, it seems obvious to me that the main reason that most resist believing that UFOs are aliens (or secret societies for that matter) is the apparent implausibility of the social thesis. We find it hard to integrate this hypothesis with the rest of our social world views. That is, with our views on what agents can exist, how they are socially organized, and the sorts of behaviors that we expect of social agents within particular kinds of organizations. If aliens are around, why haven’t they made more direct contact, or built more obvious stuff, or traded with us, or conquered or killed us?

If the main block to believing in UFOs as aliens is a lack of a plausible enough social theory of aliens, then it seems a shame that almost no one who studies UFOs is a social science theorist. As I’m such a person, why don’t I step in and try to help? If we can find a more plausible social theory, we could become more willing to believe that UFOs are aliens. And if we can’t, we can at least confirm more expertly that the usual reluctance is justified; the social theories you’d have to invoke are so crazy unlikely that yeah, we gotta attribute UFOs to delusions, hoaxes, and misunderstandings, no matter what our eyes and instruments seem to say.

In social science, we often prepare for theorizing about a topic by first summarizing its “stylized facts”. These are key data patterns in need of explanation, phrased in language that is closer to theory. In this post, I will attempt this “stylized fact” exercise for UFOs-as-aliens. In my next post I’ll take my shot at explaining them. Here are three key stylized facts:


1. LIMITATION – The very idea that UFOs are aliens, rather than a secret society on Earth, implies either a completely independent origin from us, or that any common ancestor was long ago. (~100Myr+.) So unless aliens civilizations are very short-lived, then any modest randomness in the timing along either evolutionary path implies that one of us reached our current level of civilization millions of years before the other. And since we just got here, it must be they who reached our level millions of years ago.

(Note that having a civilization last for many millions of years is itself quite an achievement. Which raises obvious questions: what sort of genetic, cultural, organizational, etc. changes were required to achieve that, and at what cost came such longevity?)

If UFOs on Earth are aliens from elsewhere, then there are in fact aliens out there, who can and do travel between the stars. Because here they are, aliens who have actually traveled between the stars. So right off the bat we must reject theories that say that such travel is impossible or crazy impractical. Or that some motivational convergence ensures that advanced life almost never does actually travel.

Now put these two facts together: they’ve been around for millions of years, and they can and do travel between the stars. With millions of years and this same tech they used to get here, they could have gone everywhere. The big dramatic implication: they could have remade the universe, or at least a big chunk including our galaxy, but have not done so. Somehow they have self-limited their expansion.

(Note that in addition to limiting their expansion, aliens behind UFOS also seem to have limited their tech; UFO tech seems advanced, but not 100Myr+ level advanced.)

Now one possibility that I want to note, and set aside, is that the universe is in fact chock full of aliens who have in fact remade it, but that we are fooled to see otherwise by crazy advanced tech wielded by a vast tightly-coordinated alien conspiracy based on arbitrary inscrutable motives. Like theories of powerful intrusive gods and simulation managers with arbitrary inscrutable motives, it is not that such theories are impossible, but that they offer little room for structured analysis. I see little to gain from discussing them.

Stylized fact #1: UFO aliens are very old, and could have remade universe, but some self-limit stops them.


2. CORRELATION – This failure to remake the universe gets more puzzling the more common are aliens in space and time. If UFOs-as-aliens are as thick on all planets at all times as they are here and now, then there must be a crazy huge number of well-hidden alien facilities out there where UFO equipment is made, repaired, refueled, staffed, etc. All strongly limited to ensure that it never remakes its local universe.

Worse, there have been literally an astronomical number of opportunities for any one deviant alien to start to remake its local universe. If a deviation could last long enough, to acquire enough local resources and power, other aliens would have a hard time shutting it down without also acquiring similar levels of local resources, and thus also remaking their local universe. Even if some sort of local conformity pressure tends to stop most deviations, that pressure has to be crazy extreme reliable to work everywhere always in a vast densely populated universe.

The simplest way to resolve this puzzle is to posit that aliens are in fact pretty rare, and that they coordinate to preserve that rarity. After all, the fewer are the possible alien travel events, the higher of a deviant event chance that we can tolerate in our theory of their behavior.

(If aliens are very short-lived, then there have to be even huger numbers of them for one to be here now, requiring an even more crazily-low chance of any of them allowing any deviations.)

Besides perhaps interstellar travel being impractical, advanced life arising very extremely rarely is the simple story most of us most start out with to explain our empty universe. And even if one must postulate that aliens are only extremely rare, not very extremely rare, to explain humanity’s early arrival in the universe, that still means aliens are so rare that we won’t meet them for roughly a billion years.

But for aliens that rare we have a different problem: why are they right here right now, but almost nowhere else? Something has caused a huge correlation between them and us, so that even though aliens are rare enough for their facilities to stay hidden, and even though they have created local pressures to ensure that they only rarely travel or have opportunities to try to remake the universe, they’ve made an exception for traveling to be with us here now.

The rarer are such aliens, the more time they’d need to get here from where they started. So either they’ve been around for a very long time, and decided to come here based on what Earth looked like a very long time ago, or they happened to start very close to us, a remarkable spatial coincidence in need of explanation.

Stylized fact #2: UFO aliens are rare and self-limited, and yet are here now.


3. INDIRECTION –  We can think of a number of plausible practical motives for rare self-limited aliens to make an exception to visit us. First, they may fear us as rivals, and so want to track us and stand ready to defend against us. Second, if their limitation policies are explicit and intentional, then they’d anticipate our possibly violating them, and so want to stand ready nearby to enforce their limitation policies on us.

In either of these two cases, aliens might want to show us their power, and even make explicit threats, to deter us from causing problems. And note the big the question of why they don’t just destroy us, instead of waiting around. A third possible motive that can explain this is that the origins of independent aliens like us are a rare valuable datapoint to them on far-more-capable aliens who they may fear eventually meeting. In this case they’d probably want to stay hidden longer, and then maybe destroy us later.

Note that all of these motive theories suggest a substantial ability of these aliens to organize and plan actions on the basis of such abstract, collective, and long-term considerations. A very decentralized alien society might not be capable of it, nor perhaps of maintaining whatever pressures prevent their own travel and remaking the universe.

The most striking fact about UFO encounter events is how little they seem to accomplish, not for any of these goals, nor for any other easily identifiable practical goals. Advanced aliens could surely monitor us sufficiently from a distance unseen, and to control us via commands or threats would require much more direct contact. These UFO events don’t help them collect useful info or resources, nor do they much limit or expand our info, powers, or resources. Yes they show some of us that the universe can look weird, but surely they know that we know that fact regardless.

Now we humans are widely known to often act on indirect motives, not tied very closely to simple direct practical outcomes. Many animals “play.” Human ancestors who did things for “symbolic” reasons are often seen as especially “advanced”. People today often have “obsessions” that make them spend far more on some things than practical ends can explain. Lazy secure organizations are at times quite “wasteful”, doing things that pretend to achieve practical ends, but in fact achieve them at best quite ineffectively. And I’ve recently coauthored a book on how common are hidden motives in humans today; many things we do just don’t much accomplish the goals to which we give lip service, like learning at schools, and healing at hospitals.

So it isn’t crazy to think that aliens might have indirect obsessive lazy motives for UFO encounters, motives hidden perhaps even from themselves. But this case, of overcoming the usual coordinated limits to fly to a distant star just to glow-buzz their treetops, seems spectacularly extravagant even by the standards of dreamtime humans today.

To do this, aliens need a sufficient level of “slack” resources available to spend on such symbolic activities. And even with hidden motives and lazy organizations, we humans usually at least make up vague stories about practical ends served by our actions, even when such stories don’t stand up to close scrutiny. So a decent theory of aliens should explain their level of slack, and suggest some ideas for what stories aliens are telling themselves about the ends they accomplish via UFO encounters. And why they haven’t just destroyed us.

Stylized fact #3: Alien-driven UFO encounters accomplish little, yet must somehow be justified to them. 


And those are the key stylized facts that a social theory of aliens must explain. Again, it is the lack of seeing a sufficiently plausible explanation of such facts that is why most are reluctant to believe in UFOs-as-aliens. (Yes, many are not so reluctant, but mostly because they don’t understand enough to be puzzled.)

Added 31Mar: My explanation attempt is here.

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Given Our Date, Is Sun Birth Late?

In our grabby aliens paper, we use a simple model that predicts the appearance of advanced life in terms of when habitable stars are formed, how long they last, and the hard steps power law of when advanced life appears within a planetary habitable lifetime window. We showed that this is well approximated by a power law during grabby alien birthdates, and that humanity looks quite early relative to its predictions.

Using this same model, we can also ask: how early or late is the sun’s birthdate, given our current appearance date?  This graph shows the percentage of dates that are after our sun’s birthdate of 9.23Gyr, for stars that give rise to advanced life at 13.77Gyr:

Unless the max planet lifetime is very short, our Sun’s birthdate starts to look substantially late for powers above about five. So either the power is below five, or panspermia happened, in which case Earth’s star had to come later to come after the earlier star of Eden. And in which. case, the power is probably high, as it would be the sum of hard steps on both Earth and Eden.

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Are Expansive Aliens Obvious?

In our 3 parameter model of where are the grabby aliens in space and time, each parameter can be estimated using existing data: our current date, the dates of major events in Earth history, and the fact that we don’t see aliens clearly visible in our sky.

That last “fact” might seem most open to question, so what if we reject it? Well if we still assume that we would have noticed being directly inside a grabby-controlled volume, then our model still applies. That is, we would still know where grabby aliens are distributed in time, and they’d be distributed the same shape in space, except that their density in space rises by a factor of one thousand for every factor of ten by which their speed falls.

Instead of our usual assumption, that we would have by now noticed differences between volumes controlled or not by grabby aliens, we’d be in a world where they make their spherical-until-meeting volumes look only subtly different, a difference that we have not yet noticed.

In this case, there could be hope for astronomers to search the sky for subtle circular borders in the sky between GC volumes and surrounding volumes. The next two graphs show, as a function of power n and speed ratio s/c, distributions over how many such volumes there would be in the sky, and their total length in radians of their borders on the sky. (The maximum length of a circle on the sky is 2π radians.)

These distributions are mainly due to varying birthdate; earlier civilizations see fewer others in their sky.

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Power Laws Approximate Appearance

Feb. 1, we posted our first grabby aliens working paper, and yesterday we just posted our first revision, which is 85% longer:

If Loud Aliens Explain Human Earliness, Quiet Aliens Are Also Rare

Robin Hanson, Daniel Martin, Calvin McCarter, Jonathan Paulson

The hard-steps model of advanced life timing suggests humans have arrived early. Our explanation: “grabby” civilizations (GC), who expand fast and long, and change their volumes’ appearances, set an early deadline. If we might soon become grabby, today is near a sample GC birthdate. Fast GC expansion explains why we do not see them. Each of our three model parameters is estimable from data, allowing detailed GC predictions. If GCs arise from non-grabby civilizations (NGCs), a depressingly low transition chance (~10^-4) seems required to expect even one other NGC ever active in our galaxy.

After we learned that Jay Olson had previously said many of the things that we said, we went looking for new things to say. One of them is results on the tension between optimism for our future and optimism for SETI. I’ll describe some more additions in posts soon.

We also fixed some minor errors. And while before we just claimed that a simple power law well approximates the appearance function for advanced life, this time we got around to showing it:

These graphs show the % error between a more realistic model for the timing of advanced life, and a best approximating power law. That % error is averaged over the actual times when grabby aliens would appear according to that power law, assuming that humans today have a certain rank within that distribution. The error seems quite acceptable, <~10%, for powers of 2 or more.

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Super Hostile Takeovers

For a brief period in the late ’50s, until the mid-’60s, when modern hostile takeover techniques were perfected, we had a pretty much unregulated market for corporate control. Shareholders received on average 40% over the pre-bid price for their shares. But… 1968 … Williams Act … made it vastly more expensive for outsiders to mount successful tender offers. The highly profitable element of surprise was removed entirely.

The even stronger inhibition on takeovers resulted from actions taken by state legislatures and state courts in the ’80s. The number of hostile tender offers dropped precipitously and with it the most effective device for policing top managers of large, publicly held companies. … now, with the legal power to shift control in the hands of the incumbent [managers], they, rather than shareholders, will receive any premium paid for control. … It should come as no surprise then that, as hostile takeovers declined to 4% from 14% of all mergers, executive compensation started a steep climb. (more)

As this quote shows, current laws make it crazy hard to buy public firms, which has the effect of greatly entrenching CEO power and raising their compensation. Like blackmail laws, this is another way in which law goes out of its way to favor powerful elites. Law pretends to dislike and oppose elite dominance, but key details show otherwise.

Even during U.S. historical period when takeovers were easiest, still “shareholders received on average 40% over the pre-bid price for their shares.” That means those trying to takeover in essence faced a 40% tax; no point in taking over a firm if you can’t make it worth at least this much more. So this most effective device for policing top management would be even more effective if we could cut this tax, so takeovers could help in more cases.

The key problem is that when a takeover attempt starts to buy up lots of stock in a firm, people start to notice and then bid up their prices, expecting that a takeover will improve the value of the firm. Can we fix this problem?

Yes, consider that when the government wants to buy a bunch of land properties to build a project like a road, it faces a similar problem, that after the first few purchases the other property owners will greatly raise their price, knowing that the government can’t do its project without all the needed properties. 

The standard solution to this problem is eminent domain, where the government forces them all to sell at some official “market price”. But, as I’ve discussed, a better solution is to use a Harberger tax, where each property owner must always declare a value for their property, a value which is used both to set their property tax, but also to be an always-available sales price for the property. These values will generally be reasonable, due to owners trying to avoid paying high taxes, allowing the government or any other party to quickly assemble large property bundles for any big project without needing any special powers.

We could use the same trick for stocks. Tax stock ownership, and require every stock owner to declare a value for their stock, a value used both to set their tax, and also available to takeover attempts as a sales price. Then a takeover could happen overnight, as 51% of the stock is suddenly purchased at its declared Harberger tax value.

Most speculators might want to declare a value just above the current stock price, and we’d make it easy for them to just declare a percent increment, like say “My value is always 10% over the current market price.” If most did that, a takeover might only face a 10% tax, instead of the 40% tax described above.

I gotta admit that cases like current policy discouraging hostile takeovers makes me despair of trying to introduce any more complex or less effective innovations. The case for allowing more hostile takeovers seems to me especially simple and strong. If even a change this valuable and simple can’t be done, what hope is there for other policy changes?

Added 3p: The tax seems to be about the same size today, but so the main extra problem now is allowing far fewer takeovers:

In large-sample studies, the winning offer premium typically averages approximately 40%–50% relative to the target price two calendar months before the initial bid announcement. (more)

Of course we should also make it easier for someone who owns 51% of stock to actually control the firm. So not using poison pills, staggered boards, supermajority voting rules, voting vs non voting stock, required prior notice of or plan to purchase, etc.

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Live And Learn

In my last four posts you’ll see a pattern repeated twice: first I participate in “ground” talk on a particular issue, then I stand back and reflect on some patterns in that ground talk. I see this as a healthy way to think about social behavior.

If I only participated in each topic, I’d miss the chance to notice key social patterns up close. A great pleasure and power of being a social scientist is that most all social behavior you see around you is grist for your mills.

If I only thought about behaviors from a distance, without participating in them, I’d miss many crucial details useful in testing broader theories. Yes, by participating I risk collecting biases due to my particular stances, biases that my block me from seeing larger pictures. That probably does happen, maybe even a lot. But this still seems like a good mix.

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Who Wants Good Advice?

Bryan Caplan:

1. Finish high school. 2. Get a full-time job once you finish school. 3. Get married before you have children. ….
While hardly anyone explicitly uses [this] success sequence to argue that we underrate the blameworthiness of the poor for their own troubles, critics still hear this argument loud and clear – and vociferously object. … Everyone – even the original researchers – insists that the success sequence sheds little or no light on who to blame for poverty. … talking about the success sequence so agitates the critics.

A scene from the excellent documentary Minding the Gap:

Bing: Do you, do you feel, like, concerned that [your young son] Elliot’s going to grow up, like, messed up?
Zack: Sigh. I’m 50/50 about it.
Lately I have been concerned over my influence on him, and as he gets older, how he’s gonna look at the difference between the [middle class] way his family lives and the [lower class] way I live. And.
A lot of people grow up and they are [starts a denigrating head wiggle and affected speaking style] nununu, fucking, I’m gonna play football, and I’m gonna go to college and I’m gonna get this nice office job and start a family and have 2.5 kids and a car and a garage and everything’s just gonna be nice. And I’ll buy a boat and a snow mobile. [end nodding and affected style]
I’m like ‘Fuck you, you piece of shit.’ Like, just cause you’re too fucking weak to make your own decisions and decide what you want to do with your own life, doesn’t mean everyone else has got to be like you.
Ha, ha, I don’t know, fuck, ha ha. I, ah, ask me another question. (1:10:52-1:12:00)

Zack seems to have long been well aware that he flouted the usual life advice. He lashes out at those who do, and he seems quite sensitive about the issue. Much like all those sociologists sensitive about discussing or recommending the success sequence.

Many people, including myself and Bryan, think it is a shame that so many seem worse off from making poor lifestyle choices, and so are inclined to recommend that good advice be spread more widely. However, what if most everyone who makes poor choices is actually well aware of the usual good advice when they make their poor choices? And what if they like having the option to later pretend that they were unaware, to gain sympathy and support for their resulting predicaments? Such people might then resent the wider spreading of the good advice, seeing it as an effort to take away their excuse, to blame them for their problems, and to reduce their sympathy and support.

That’s my best guess interpretation of the crazy paranoid excuses I’ve heard to oppose my free agents for all proposal. (If you doubt me, follow those links.) It would cost nothing to give everyone an agent who gets ~15% of their income, and so has a strong incentive to advise and promote them. Yet I mainly hear complaints like that such agents would: force clients to work in oppressive company towns, censor media to cut any anti-work messages, lobby for higher taxes, or send out minions to undermine promising artistic careers. Even though becoming an agent gives you no added powers; you can only persuade.

In a poll, most oppose even a test of the idea:

My conclusion: most people are well aware of a lot of advice, widely interpreted as good advice, that they don’t intend to follow. So they don’t actually want agents to give them good advise, as others would hear about that and then later give them less sympathy for not following the good advice that they have no intention of following. Yes, their children and other people in the world might benefit from such advice, but for this issue they are too focused on themselves to care.

Note this theory is similar to my standard theory of why firm managers don’t want prediction markets on their deadlines. Early market estimates take away their favorite excuse if they miss a deadline, that all was going well until something came out of left field and knocked them flat. Its so rare a problem that it couldn’t be foreseen, and will never happen again, so no need to hold anyone responsible.

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Sell Tax Rights To Make Agents

Assume the federal government is owed X% of a certain person’s future wages w(t). Or some fixed function F(w(t)). You might not think the government entitled to such income taxes, but you gotta admit the odds of changing this situation anytime soon look slim.

I propose that the government auction off this right to collect these income taxes. Ideally at birth, if not sooner. Government could use the auction revenue to pay off part of its government debt, and thus in effect convert one kind of debt into another. So the government’s expected tax revenue need not suffer.

This selling-tax-rights action would create a job agent out of the auction winner. Someone with an incentive to try to help and promote this taxpayer, to get them to earn more money, and thus to pay more taxes to their agent. The auction would find the person or organization who thinks they can do this job best, and if they actually succeed then they would benefit. And if this system works on average then the government also gains in expectation at auction time.

This system would probably also benefit the taxpayer themselves, as we aren’t giving the agent any powers but persuasion. The agent can suggest options and strategies to the taxpayer, and can recommend the taxpayer to others. But the taxpayer and others can ignore any of this advice, and can refuse to divulge any info to this agent.

The agent could at any time sell their agency role to anyone else who thought they could do a better job. This might be to the parents or schools of children. For adults, it might be to an employer. Or adults might buy the rights to become their own agent, maybe taking out loans to pay for that. As long as these various agents do a better job advising and promoting the taxpayer than would the government, this system becomes a net win for all parties, at least in expectation.

You might worry that an agent would threaten their taxpayer, saying that unless the taxpayer does certain unpleasant things the agent will refuse to advise or promote them, and thus somehow trash their career. This seems an unlikely problem to me, but if this issue becomes a dealbreaker, I know how to use conditional speculative markets to solve it, at the cost of a bit more mechanism complexity.

You might worry that an agent would be mistaken about their ability to help, and thus harm their taxpayer in the process of hurting themselves. Thinking you were protecting both parties, you might regulate who is allowed to become an agent, and what agents are allowed to do. I don’t recommend this path, but I admit that only severe regulation might kill off most benefits of this system.

If the taxpayer dies, then of course their agent stops getting paid. So agents will want to advise on health, in addition to careers. And on anything that promotes health. For example, if getting happily married helps careers, the agent will want to advise on that. If a taxpayer emigrates, their target nation might not accept this taxation transfer system, in which case the agent would also lose. But this is a standard reason nations have given for not allowing citizens to emigrate; as the world hasn’t accepted that argument for nations, I don’t see why they’d accept it for agents.

Once the rights to tax revenue is sold to agents, governments would lose a direct incentive to provide services to citizens in order to increase citizen income. But governments would retain the incentive to create the appearance of high future income, to induce higher auction prices. And modern governments mainly choose service levels to citizens based on the threats and actions of voters, not based on government calculations on tax revenue.

What about non-federal governments? Well they could just collect their taxes as usual. Or their taxes could also be auctioned off at birth, and then the federal government could over time reimburse the jurisdiction where the taxpayer resides for their lost taxes. This second approach seems preferable, as it creates stronger agent incentives.

And that’s my proposal. Looks like a clear win-win for everyone. What don’t you like?

Added 10p: Please note that I did not propose to give agents control over how taxes are collected. This is not about “tax-farming.” No need or reason to change the tax collection process for this system. The IRS collects taxes because it is assigned to do so, not because the rest of the government gets to spend the money right then. I collects taxes nearly the same no matter who gets the tax revenue or when.

Yes, agents would want to lobby for higher taxes, while taxpayers want to lobby for lower taxes. Taxpayers have more votes, however, to influence policy, and their long term incentives are for good tax levels. Note that a similar problem is that governments can print money to avoid having to pay their debts, yet this only rarely actually happens. Just as governments are afraid to scare bondholders, since that raises the interest rates they pay, governments should be afraid to scare tax auction bidders, as that would lower their auction revenue.

There is a reasonable concern that taxpayers might try to commit to trash their lives, or to emigrate, until they are sold their agent rights. Or until a secret ally can buy their rights. As with insurance fraud, it probably works sufficiently well to call this behavior fraud, criminalize it with large penalties, and offer rewards to those who report violations. And we don’t have to let emigrants who stop paying taxes ever return.

Many offer the generic works-against-anything argument “We can’t allow a conflict of interest to exist between two groups, as the bad side might lobby harder”. Here the groups are agents and taxpayers re tax levels.

If there any doubts re if individual taxpayers would benefit, let’s only auction the rights for a random half (or tenth) of the population. That would also reduce problems with changing enforcement and revenue patterns. And maybe also only for newborns whose parents approve.

Added 20Mar: Another solution to the fiscal discipline problem is to put the auction revenue into a separate trust fund like we do with social security payments. Also, see my next post for a poll on this topic.

Added 21Mar: Here is a related proposal. Also, maybe once a year the government can include info on how to contact your agent in the mail they send you about your taxes. See more comments on the idea here.

Added 22Mar: Most who dislike seem mainly offended by their not being able to pick their agent. But if the relation is much more productive in that case, then target-picked agents should be able to win auctions, and get other agents to sell the role to them.

Added 24Mar: We should also note that this would allow ordinary people to invest more easily in, and diversify more over, a whole new class of assets. That should be worth something in terms of reducing risk for any given average return.

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Our Default Info System: Status And Gossip

Around 1988-1990, I was working on the idea of “hypertext publishing”, which today we call the web. I was invited to give a talk to a few (<10) academics working on computer based info systems, I think at Xerox PARC. I argued that we then were hampered by our poor systems for finding out what other people had done and said.

One of the audience members said that, via gossip, he had no problem finding out what others were doing in his field. If anything was important, he’d hear about it via gossip, and if someone didn’t have enough status to get people to gossip about his work, it couldn’t be important enough for him to attend to.

Today, a physics academic told me (and a few others) that it isn’t a problem that physicists can’t be persuaded by contrarian arguments published in respectable peer reviewed physics journals, as they won’t read or consider it if it goes against their prior expectations. He said what really matters is your status, not whether you’ve published or where. Gossip about high status people gets their arguments considered even without publication, and no one else’s arguments matter anyway. Low status people can contribute by working out the details of high status people’s arguments.

And from a sociological point of view, of course, they are both correct. In a world that has decided that only arguments from high status people are worthy of considering, each one of them can safely ignore all the others. Even if some low status person somehow forces the world to hear and be persuaded by their argument, the high status people can and will close ranks to ensure that this low status person gains minimal concrete advantages from it, to make sure everyone learns the lesson about going through proper channels.

I presume you can see the social problem here, of insufficient information aggregation and intellectual progress. They can probably see it too, if forced to think on it. But why should they, and even if they saw the problem why should they risk personal prestige to change things, as success just makes it easier for others to compete with them.

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What Holds Up A North Pole of Dust?

I recently came across this news item:

Factoring in gravitomagnetism could do away with dark matter

By disregarding general relativistic corrections to Newtonian gravity arising from mass currents, … Ludwig asserts [standard] models also miss significant modifications to [galaxy] rotational curves … because of an effect in general relativity not present in Newton’s theory of gravity — frame-dragging … Ludwig presents a new model for the rotational curves of galaxies which is in agreement with previous efforts involving general relativity. … even though the effects of gravitomagnetic fields are weak, factoring them into models alleviates the difference between theories of gravity and observed rotational curves — eliminating the need for dark matter.

My initial reaction was skeptical snark. Yes, gravity has a magnetism, just as does electricity, and yes magnetism can push on stuff in a way that mimics the effects of dark matter. But I knew that this is an old hope, usually dropped after people do a standard quick calculation and see that its effect looks really weak, given the usual speeds of stars rotating in a galaxy.

But then a few days later I actually read the paper, and found myself impressed and persuaded. When I tweeted this fact, I got a lot of indignant pushback. Many said there’s no point to a paper that explains galaxy rotation curves, if it doesn’t also explain all the other data said to support dark matter. Many publicly said that the paper is almost surely wrong, because of the usual quick calculation. For example Garrett Lisi posted this:

Yet I could prod few of these denouncers to actually read the paper. (And most who did seemed to fail some basic comprehension tests.) Some even said I have too few physics journal publications (only 3) to speak publicly on the topic; I should leave that to those who refused to read the paper.

But the whole point of news and research is be surprised to learn things you’d didn’t expect. Why even have news or research if you will only allow them to confirm what you expect? The author, Gerson Ludwig, is well aware of the usual expectations, and published his finding saying they are wrong in a good peer reviewed journal. Furthermore, Ludwig is part of a research tradition of a least 5 papers I’ve found (1 2 3 4 5), all of which say there’s much less need to invoke dark matter to explain galaxy rotation curves if one does calculations closer to full general relativity. If even after that everyone is going to reject the idea based on priors and a quick heuristic calculation, why do research?

So I decided to dig into this paper, to see if I couldn’t either find its mistake or explain its reasoning better. Bottom line: I found a big very questionable assumption made not only by Ludwig, by also by the other 4 papers. See if you can spot it before I tell you.

For planets orbiting stars, or moons orbiting planet, it is widely accepted that simple Newtonian gravity is an excellent approximation. But when this approach was used to study orbits of stars around galaxies, it was found to badly predict their orbital speeds (i.e., “rotation curves”). To explain this puzzle, many posit a lot more “dark matter” than what is easily seen, distributed quite differently than the stuff we easily see.

Even though the usual quick calculation suggests it won’t make a difference, a number of authors have tried to calculate these rotation curves using something closer to (but still far from) full general relativity (GR). And all of those (that I’ve found) claim that it makes a big difference, enough to solve the puzzle. For which they are also widely criticized, because priors and usual quick calculation.

Ludwig tried a standard approximation to GR that is closer than Newton, but still linear, one which we understand well as it is very like Maxwell’s equations for electromagnetism:

Here E is gravity’s “electric” field that pushes still stuff toward each other, and B is gravity’s “magnetic” field, that in addition pushes away from each stuff that is moving in parallel.

As star-star collisions are very rare, Ludwig assumes a time-invariant (i.e., “equilibrium”) rotationally-symmetric system of zero-pressure (p=0) dust that only moves in the azimuthal direction. (That is “around” the galaxy, in a direction perpendicular to the radial and vertical dimensions). This implies that E and B have only radial components ERBR and vertical components EZ, BZ, and also that:

The first (radial balance) equation says that magnetism is only a big effect on star motions in galaxies if vB becomes comparable in magnitude to E, while the second (axial balance) equation says that E and vB are in fact comparable in magnitude! Yes these are talking about different (R vs. Z) components of these vectors, but over the whole galaxy these components are connected in ways that ensure that large values of one component in one place imply large values of the other component in other related places. For example, here is a calculated B field around a spinning uniform mass sphere:

 

Thus Ludwig finds gravitomagnetism to be always important for equilibrium rotating gravitating dust! Using his model, he does a decent job of predicting rotation curves for three galaxies, using only mass distributions estimated from the light we see, though he allows some corrections and fits the ratio of mass to light to each galaxy.

So how could the usual quick calculation go so wrong here? Well, consider a point as indicated by the big red arrow here near the “North Pole” of this galaxy.

Gravity’s E should be pulling it downward, toward the center, but according to the only-azimuthal motion-assumption it is not falling down. Yet according to Equation 2.2 above, if the pressure is zero then the only other force left to hold it up is v x B. So of course these assumptions must imply a large magnetic field B, with a comparable influence to E.

But is this right, and if not which of Ludwig’s assumptions is wrong, or at least high questionable? I say it is his assumption of zero pressure, an assumption also made by all of the other related papers I found. Ludwig justifies his zero-pressure assumption by saying that stars almost never collide. But the concept of pressure just doesn’t depend much on collision rates!

Consider that astronomers usually say that what “holds up” stars near the red arrow is momentum. Previously, their velocities started high closer to the center, and declined as they climbed the gravitational potential to reach near that red arrow. They have recently or will soon stop rising and begin to fall back toward the center.

One can tell exactly this same story about atoms in an atmosphere. Even if they never collided, their average density and velocity would still change just the same with altitude as they flew up from the ground. Atmospheric “pressure” declines with altitude because the number of atoms that pass through any given area (and how fast and massive) declines, not because they actually collide. Pressure tells of momentum transfer that would happen if the objects moving through a plane were instead to bounce off that plane; but they don’t actually have to bounce for there to be pressure.

So similarly the usual picture of galaxies “held up” by momentum is actually a picture of a non-zero pressure, a pressure highest near the center and declining away from it, and a pressure strong enough to counter gravity and “hold up” the average density of stars near the North pole. So the pressure is not near zero, even though collisions are very rare.

What about Ludwig’s empirical fits? Well he never compares them to models using non-zero pressure, so his fits don’t tell us which better explains rotation curves, pressure or gravitomagnetism. Same for all the other papers in his area.

So yes, the skeptics were right; Ludwig’s analysis contains a big questionable assumption, and so their quick calculation doesn’t obviously mislead here. And yes if you are busy and this is not your area it makes sense to just ignore his paper if you think it unlikely to be right. But if you are going to publicly denounce it as mistaken, especially on the basis of your high level of physics authority, it is more helpful if you do what I’ve tried to do, namely try to find and publicize its error, or publicly admit if you can’t. That’s how research moves forward.

Added 16Mar: These authors got at least five publications out of their mistakes, and no serious academic journal would consider publishing my rebuttal. As those publications are full of complex math and technical work, and my blog post looks doesn’t show much technical prowess. Which shows a well-known big bias in academia (econ too, not just physics): why bother to learn the concepts deeply if you can get many more publications and prestige via more manipulation of symbols you insufficiently understand? Why bother to look for such errors in others’ work if you can’t get publication credit from it? Even if you do make a conceptual mistake, your referees aren’t likely to notice, and even if someone publicly shows the mistake, that will likely be someone/someplace with too little academic prestige to count, or even be noticed.

 

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