Human Learning and Memory, by Dadid A. Lieberman (2012)
A well-written overview of current knowledge about human learning and memory. Of special interest:
Just finished reading Happiness: A Very Short Introduction by Daniel M. Haybron. It was an excellent read, and well worth my time.
Everything is heritable:
Politics/religion:
Statistics/AI/meta-science:
Psychology/biology:
Astronomy:
Economics:
Philosophy:
Fiction:
Misc:
"On The History and Future of Cosmic Planet Formation"
This is extremely relevant to my interests.
I'd be interested in an extrapolation of their model of planet formation into the future. It imputes Earth as having formed after 80% of currently existing terrestrial planets and 50% of giant planets. What will the figure be in 5 gigayears when star formation ceases in our galaxy?
What will the figure be in 5 gigayears when star formation ceases in our galaxy?
I'm not sure about our galaxy, but don't they calculate the net across all planets and estimate the earth is in the 8th percentile of all planets (ie early)? That was the headline result which made Robin Hanson tweet about it, which is how it caught my interest.
A more detailed reading of the paper now that I'm home from work produces the following:
They project their models forward for the combined Milky Way / Andromeda system, and find that if you assume most available gas in both galaxies will eventually form stars, our solar system comes in at the 39th percentile - about 61% of terrestrial planets are modeled as coming after ours. If in a complication to this model the merger itself pushes some of this gas into a form that can not form stars, we will be further along in the distribution. See http://www.dailygalaxy.com/my_weblog/2014/02/giant-elliptical-galaxies-why-are-they-red-and-dead.html for reasons such an outcome is possible. I might need to pass this onto some of my astronomer friends.
The 8% figure for the whole universe assumes the eventual conversion of all baryonic mass within dark matter haloes into stellar system mass.
This does not fit with my previous reading on the way that star formation apparently shuts down in galaxies over time (quickly for giant ellipticals, slowly for spirals) and data I have seen both elsewhere and in a brief glance at one of their references indicating rapid decay in average star formation rate across the universe over time. Data I have seen elsewhere, covered in my recent astrobiology post, actually supports a rather small amount of additional stars formed over the history of the universe, tapering down slowly and focused in spiral galaxies.
I don't know if there is a known mechanism that would allow that amount of gas to accrete, and my cursory beginnings of looking at their references digs up a few places indicating that while some of it will probably fall in to the star-forming discs of galaxies in a sufficiently cool state, most of it will probably not be able to contribute to star formation. From one of their references, Adams & Laughlin 1997: "Additional gas can be added to the galaxy through infall onto the galactic disk, but this effect should be relatively small (see the review of Rana, 1991); the total mass added to the disk should not increase the time scale [of star formation] by more than a factor of 2."
I'm quite confused by all this. Part of this certainly comes from a major difference in approach between this work, which appears to focus on imputing star formation trajectories as galaxies gain mass by comparing galaxies of different sizes, and much previous work I have looked at involving galaxy classification into star-forming and non-star-forming subpopulations across the history of the universe. More digging is required on my part to reconcile all this, and it may be an area of contention. May be worthwhile to dig up some old astronomy friends of mine. Overall though I am rather skeptical of the significance of the 8% figure at this time. Will get back to you after more looking.
UPDATE!
I have sent a few emails out to friends and have been directed back at an old professor of mine who studies star formation at cosmological timescales, but they are very busy and I don't know if I will hear back from them in a reasonable period that will allow a response in this thread to be seen.
Been really busy recently between dealing with peer review of a paper and TAing a course and trying to keep various projects in my PhD going, but in between I've been looking around. My summarized conclusions follow:
It would appear that the papers linked to use a set of somewhat uniformitarian assumptions about galaxy formation and history that are not necessarily accurate. Most importantly, it assumes that ALL star forming gas within a galaxy's dark matter halo will eventually collapse, accrete, and form stars. This assumption appears to not be a good one.
When you look out into the universe, the vast vast majority of elliptical type galaxies are very red and are not forming stars, whether they have an internal reservoir of gas within their dark matter halo or not – see the link I posted in my other comment to this comment. Grand spirals are mostly forming stars at a steady clip, with only a few tapering down and turning 'green' or eventually 'red' from their initial 'blue' status. Recently, a project called GalaxyZoo which has automated and crowdsourced the analysis of huge numbers of new galaxies observed in the Sloan Digital Sky Survey has taken a very quantitative look at star formation across galaxy types in the universe, and come up with some striking conclusions:
http://blog.galaxyzoo.org/2014/02/21/the-green-valley-is-a-red-herring/
http://arxiv.org/abs/1402.4814
http://arxiv.org/abs/1501.05955
These studies were able to get more information than the instantaneous rate of star formation, and look back along the history of the galaxies by looking at light of different frequencies – huge stars that dont live long make lots of ultraviolet, stars like our sun peak in the green light, while long lived stars peak in the red. They were able to see that among elliptical galaxies, the tiny fraction that are star-forming mostly show evidence of recently being involved in mergers, and that all those that are red and green colored show spectral patterns indicative of very rapid shutdown of star formation, faster than can be accounted for by star formation eating up available gas. They call this fast star-formation shutdown 'quenching'. Something about their formation, either primordially or via mergers of spirals, puts their gas into forms that cannot form stars. The prime suspect is the initiation of regular energetic outbursts from their large central black holes, heating the gas and rendering it too turbulent.
This actually dovetails interestingly with another problem in astrophysics: the 'cooling paradox'. In short, about 90% of the baryonic mass of the universe is in the form of X-ray hot gas clouds blanketing entire galaxy clusters (largely outside the dark matter halos of individual galaxies). This gas is ridiculously thin and immensely hot, and radiating energy rapidly in the X-rays. It turns out that when you figure out how much mass is in these gas clouds and how much energy they are radiating in the X-rays, they should cool and sink down to the centers of the clusters on a timescale of gigayears, probably turning into cool gas flows onto the large galaxies at the centers of these clusters. But they don't. Looking back in time across the universe they are at more or less the same temperature now as they always have been and never seem to cool despite the fact that they are radiating energy. In recent years, for various reasons (images of turbulence in the gas, calculations of the available energy) the prime suspect for the energy source keeping these gas clouds energized has become supermassive black hole jets.
Anyways, as for spiral galaxies, they were able to model the distribution they saw (most of which are forming stars at a steady rate, some of which are tapering off, and some of which are red and dead) as a mixture of populations. One population is forming stars at a steady slowly decreasing rate, much like ours. Another is quenching on a much slower timescale than ellipticals, indicative of a cut-off of gas inflow into their star-forming discs and star formation then slowly depleting their reservoir of gas over a 1-2 gigayear timescale, likely caused by events in their immediate galactic neighborhood disrupting the inflows of cool gas within their dark matter halos onto their star forming discs.
So, when the originally posted paper notes that in the Andromeda/Milky Way system our star shows up as in the 39th percentile, that is assuming that ALL gas in both galaxies will form stars either before or after they merge, when that is not necessarily a given. There is a very good chance that the merger will produce an ellipical with a very rapid quenching period indicative of processes going on that put the star forming gas into a form that cannot form stars. As such, we are almost certainly after the 39th percentile, by a quantity I am unprepared to address (though doing some naive by-hand projections of their curves, I think it winds up being over the 50th percentile).
Similarly, when they claim that we are in the 8th percentile of planets formed universally, it is a bit off base. It assumes all gas in galactic dark matter halos will eventually form stars. A very large fraction of galaxies are large ellipticals which seem to not form stars, no matter their gas status. Of the spiral galaxies available, a subset are having their star formation quenched on gigayear timescales by processes relating to the prevention of gas inflow. And those that undergo mergers (a constantly increasing number) will almost all cease star formation in a rapid quenching very shortly after merging.
The literature I have talked about in the past, looking empirically at star formation rates across time in the universe, have seen the results of these quenching events in the rapid shutdown of star formation starting 11 gigayears ago and continuing to this day. Non-quenched galaxies continue forming stars (less vigorously than early in their lives but still) but a larger and larger fraction of galaxies are quenched, their gas prevented from cooling and condensing to form stars. I am unprepared to extend the analysis of our place in the planet-formation order to the universe as a whole other than to note that we are probably somewhere between the 33rd and 66th percentile of our galaxy, a fairly typical large star-forming spiral. I also note that figure 2 (top right panel) of the original "on the history and future of cosmic planet formation" paper shows a universal rate of terrestrial planet formation that looks rather like a skewed sigmoid, with Earth coming after the period of most rapid formation but the rate leveling off slower than it ramped up, rather than a curve that will continue to >10x as high a number of planets formed as existed when Earth was formed. It seems to me that our position in time and in star-order is unremarkable.
The original paper that sparked this discussion uses a number of simplifying assumptions that don't seem to carry over to the empirical studies; I think the empirical studies are more useful even if the exact mechanisms of galaxy star formation quenching and gas inflow prevention are still kind of up in the air with a few popular frontrunners.
EDIT: There is also the question of what model to use for the production of Earthly terrestrial planets, and if these are likely to be found in giant ellipticals versus spirals. The former contributed much more star formation to the early universe than to the current era, and these stars being unsuitable would explain us showing up a bit late as revealed by some of the purely empirical data I've seen. The paper that started this discussion did take this into account in their galactic and universal curves, with an absolute minimum metallicity cutoff for terrestrial planet formation and assumed that formation was equally likely for stars of all metallicities above that. I don't think anyone really understands this aspect terribly well...
I wonder if this quenching is just a temporary delay, and once whatever energy source that prevents hot gas from cooling and collapsing runs out, another wave of star formation happens, 10, 20 or more gigayears into the future.
Heck of a good question. On the one hand, you'd expect that anything that can intersect with the black hole would eventually do so until it all ran out and the black hole quieted down, unless low-angular-momentum ellipticals are so chaotic that more just keeps raining down. On the other hand, these black holes only grow and aren't getting any smaller (on the timescales that matter (seriously it would take so long for a supermassive black hole to evaporate that the relevant question is 'is matter infinitely stable or only nearly infinitely stable')).
I do know that a feedback mechanism has been proposed to keep cluster gas clouds a consistent temperature, in which comparitively tiny amounts of cluster gas inflow increase the activity of the black holes proportional to the amount of cool inner-cluster gas and thus a negative feedback loop is closed and the clouds remain fairly stable.
Gwern, why do you categorise genetics under everything is heritable while other topics are given traditional names? By the way, thanks for your consistent and interesting contributions to media threads. Can you tell us a bit about your information diet? Any particular news sites or hubs your frequent?
Gwern, why do you categorise genetics under everything is heritable while other topics are given traditional names?
That's not quite right. I categorise genetics research under biology/psychology. What goes under 'everything is heritable' is specifically, behavioral genetics and all research undermining the default blank-slate, standard-social-model, cultural-marxist views which are still so overwhelmingly dominant in sociology, anthropology, psychology, and politics. By pulling them out like that, I help highlight that there is a large, old, well-developed, repeatedly empirically confirmed, consistent body of theory & results which is continually growing and confirming the genetic underpinnings and which gives us strong predictions & priors about many phenomenon - rather than some ad hoc, unprincipled, idiosyncratic one-offs & anomalies which apply to only a handful of things, if even that.
Any particular news sites or hubs your frequent?
Reddit, Hacker News, my RSS feeds, following citations in papers, that sort of thing.
Kickstarter Economics-- details about how to estimate what you need for your project, how to manage perks, etc.
I'm fascinated by short online text by GiveWell explaining their theory of 'Sequence v.s. cluster thinking' [described here). Sequence in this context doens't refer to sequences, but rather working from a common unit of measurement like money, or a DALY to value something. To illustrate, $5 USD can get me 20 minutes of sex in Bolivia. A subject theory of value is based off that value thought in 'sequence' would be: If I can get more pleasure for less money then some thing is worth it, if I can get less pleasure with more money only then it's overpriced. Cluster thinking, in contrast, appears to be an informal version of multicretion decision making where knightian uncertainty is handled as uncertain without connotations of risk (thereby falling privy to critiques like pascal's mugging, if I'm correct).
https://www.youtube.com/watch?v=EKWGGDXe5MA
Richard Feynman gives a lecture on how computers work. The target audience is the average person. He uses the analogy of a filing system to describe what computers do.
Ancillary Justice, by Ann Leckie. I thought the space opera genre was dead. I spoke too soon (though some would call it literary scifi instead). Most enjoyable science fiction I've read in years, blasted through it in two days.
The main character is the last remaining fragment of a troop transport ship from the expansionist imperial Radch, which has absorbed a large fraction of the human diaspora at a time in which most people think about the home world of humanity the way most people think about the finer points of australopith ecology today. Troop transports transport 'ancillaries' - Human bodies under their control. There is wireless hardware in their heads that moves information but that's not really the mode of control. Ancillaries have also undergone what can be called an 'ego transplant' such that their sense of self is the same as that of the (intelligent) ship. The ship and all its ancillaries share an 'I' and act accordingly even when communication is cut off and coordination is difficult, much like split brain patients. A ship is nearly completely destroyed in an act of treachery, leaving only one living ancillary bearing its identity.
Things I loved (which may or may not do it for others):
Mythology and religion and culture galore, from many long separated worlds and from societies that have lived in space for just as long (to quote a friend, "i love how the book manages to get across how simultaneously pretty and ugly Radch culture is").
Playing with language, with different things differently able to be expressed with different connotations in different languages and the main language spoken not having gendered pronouns (all being shown in English as 'she' when that language is spoken, and the main character having trouble with gendered languages and gender in general).
One of the strongest evocations of place and setting I have seen in scifi.
A narrator that doesn't understand their own mind that well and is frequently in denial, forcing a show don't tell style and reading between the lines.
All characters with rather extended sensoriums and communication options compared to humans today via various enhancements and implants as a matter of course.
The Lord of the Radch, a being using ancillary-style ego manipulation and wireless connectivity to maintain thousands of bodies across the empire in an asynchronous, yet still remarkably unified self for thousands of years despite any one body lasting only 200 or so. Identity is played with extensively throughout.
The ending is a bit rushed. Here's hoping the sequel is good, it just arrived in the mail.
The ending is a bit rushed. Here's hoping the sequel is good, it just arrived in the mail.
I thought the sequel was more boring. The structure of the books doesn't really work very well as a series, I feel. The things that I found most appealing about Justice were the new kind of narrator (in the flashbacks, when the same events are described from multiple viewpoints of the same character), and the gradual puzzle of figuring out how the universe works. But at the end of Justice that's all over, there is just a single ancillary left, and the whodunnit-mystery has been explained. So then Sword is a lot less novel, just another space opera...
Just finished it. I agree it was definitely not as good as the first one. It started out strong but then got kind of bogged down in the Fleet Captain pulling an Awn, the big conflict at the start of the novel is all but unaddressed, and it completely wasted Tisarwat's potential. Still enjoyable in many places to me (I was bursting out laughing for several minutes at 'this granite folds a peach!') but definitely less so. Hopefully its middle book syndrome and the third can come back...
I didn't like Ancillary Justice so much FWIW - I didn't find the culture so compelling, and the lead's morality was jarring to me (she seemed less like someone who was seeing the flaws in the culture she was raised in and more like someone who had always instinctively had a western liberal morality that they'd been suppressing to fit in).
Do you have a view on The January Dancer? I loved that - modern space opera, with some interesting cultures, but also a compelling plot on the sci-fi side.
(I wish my relatives had better taste in movies.)
RED
Another viewpoint :-)
RED is a kinda-action movie that doesn't take itself seriously at all. There is absolutely nothing serious or grim about it -- it's a "turn it up to eleven and have fun" thing. Bruce Willis is just being Bruce Willis, but John Malkovich and Helen Mirren are both very good. I found the movie funny much more often than once every half an hour. It's not (and doesn't pretend to be) deep or intellectual and it's not especially satisfying in any particular way -- however it's a mindlessly fun way to spend an hour and a half, provided you dont' mind mindless fun. The sequel is worse, as usual.
Mr. Robot: USA show about a team of computer hackers trying to overthrow an evil corporation's dominance of the economy. The show tries to depict hacking realistically, without resorting to much Hollywood Hacking. It's as much about the main character's delusions, paranoia, and depression as it is about the central plot. Strongly recommended, don't let the network it airs on discourage you from giving it a shot.
Another tranche of shows watched with my group, though they don't really end up as recommendations:
Blood Blockade Battlefront: Started with some fun action, and a very cool-looking setting, but decayed rapidly - the plot arc it tried to set up towards the end was just dull. Avoid
Knights of Sidonia (season 2): Shifts much more towards the harem antics than the serious sci-fi; also some massive power inflation which could easily have been thematic but... isn't. I greatly enjoyed it, but only recommended to people who enjoy light comedy/romance.
Fate/Stay Night: Unlimited Blade Works: Had its moments, and definitely has the production values; when it's good, it's very good. But massively wordy (arguably too faithful an adaptation), slow and self-indulgent. Again only for fans of the genre.
Kyousougiga: This I do recommend. A show that respects the viewer's intelligence; the depths are there if you want to peer into them, but it keeps things interesting - or at least active - on the surface level too. And it's got some wonderfully creative visuals.
Your Lie in April: Romance/melodrama, done reasonably well, and with beautiful visuals and sound - I particularly like the fact that this show is willing to make you sit and listen to a musical performance for minutes at a time. But has no ambition beyond its genre; you know whether you're the target audience for this or not.
Madoka Rebellion: Fun for fans, but far too self-indulgent for anyone else. The plot is awkward and undermines some of the series. I enjoyed seeing beloved characters at play, and there's one very fun fight, but it's all fanservice.
Emilie Simon's Roses never fall in love
A lovely song I discovered posted by a popular poster on a curious forum called sociopath world.
I tried to organise a community meetup. Despite much interest and claims to the contrary, no one turned up. I suppose they weren't so brave without a screen in front of them.
Postrock: El Ten Eleven's Fast Forward:
Touhou:
Sanjay Bakshi: "The Prejudices of Mr. Market" Google Talk, one hour.
Finding good investments by identifying systematic undervaluation by the market-- for example, the market tends to overreact to CEOs who make big mistakes, but some CEOs learn from their mistakes. There may be one extremely competent company who's selling what generally looks like a commodity.
Prejudices are shortcuts in order to avoid handling large amounts of information, but if you can pay attention to actual information, you can do better than most people.
I wrote a tool to help you resort your media ratings, in case you find yourself rating everything either '4' or '5' on Goodreads: http://www.gwern.net/Resorter
This is the monthly thread for posting media of various types that you've found that you enjoy. Post what you're reading, listening to, watching, and your opinion of it. Post recommendations to blogs. Post whatever media you feel like discussing! To see previous recommendations, check out the older threads.
Rules: