Links for June 2015

  • Arrow bending.
  • Casting a fireant colony in molten aluminum:
  • The Crossrail tunnel boring machine in London.
  • The best introduction for laymen to the how and why particle physics experiments are built the way that they are: the Particle Adventure.
  • I have been saying for years that the mostly-positive metric is hands-down the better convention. Peter Woit gathers reasons.
  • Korea’s Team KAIST Wins the 2015 Darpa Robotics Challenge.
  • I share Noah Smith’s enthusiasm for experiments in economic policy. I subscribe to the philosophy that (perhaps charitably) models folks’ political biases as strong Bayesian priors. Whenever we have weak evidence, we are pulled to favor the hypothesis that leans strongest toward our biases while still being minimally compatible with the evidence. Although folks’ beliefs would track truth better if they could reduce bias, and I am pessimistic about this improving, we can still pull different sides together by compiling better evidence.

    There are uncountable fierce political battles that are usually considered intractably ideological, but which I have been convinced by others actually would yield considerably under the introduction of robust, unambiguous evidence. It’s darkly satisfying to think “my opponent ignores reason, so it doesn’t matter what evidence we collect; I’ll just have to beat him with rhetoric”, but this is a mistake largely grounded in a lack of appreciation for how weak the evidence we typically collect really is. Most of the vast resources we individuals put into pitched verbal battles would be better spent on ambitious controlled experiments, e.g., Robin Hanson’s call for larger scale version of the Oregon Medicaid and RAND health insurance experiments.

  • Airplanes use air taken directly from the engine to pressurize the cabin, known as bleed air.
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Links for May 2015

  • Are those cocky physicists-turned-biologists living up to their reputation and embarrassing themselves by ignoring epistasis, epigenetics, and gene-gene interactions? Steve Hsu says no, citing the strong success of additive models in twin studies, and the theoretical explanation from stability for the same.
  • An excellent video (from here) depicting a 1956 vision of the future of autonomous driving.

    (H/t Tyler Cowen.)
  • I’m pretty skeptical of the feasibility Elon Musk’s Hyperloop concept, based on earlier criticism, but an unaffiliated company just signed a contract for the land to build a 5-mile test track, and Musk himself claims a different test is coming to Texas. Note however that the first company is long on hype, short on details.
  • All these amateurs and celebrities have been talking about the long risk of recursively self-improving artificial intelligence, but don’t the actual AI researchers think this is a bunch of hooey? Only if you cherry pick, notes Scott A. In particular, if you’re willing to trust the survey skills of people with skin in the game, then

    …a survey of AI researchers (Muller & Bostrom, 2014) finds that on average they expect a 50% chance of human-level AI by 2040 and 90% chance of human-level AI by 2075.

  • If you are a freshman or sophomore undergrad, GiveWell is hosting a one-week summer fellowship that may be of interest.
  • Rockets engine tanks are often designed with excess hydrogen relative to their oxidizer because the unburnt hydrogen has a higher exit velocity for a given temperature, increasing specific impulse.
  • I have some comments on this critique of the PhD Thesis that’s been making the rounds.

    He would much prefer to see theses’ introductory sections “written along the lines of a good review article, where the student does a critical appraisal of the state of the field”


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Links for April 2015

  • The recently completed Effective Altruism Handbook is a collection of key articles which cover a lot of the movement’s basic arguments. It’s available here as a PDF. There are also two new EA books coming out by Peter Singer and Will MacAskill (with annoyingly similar titles…). And here is the Huffington Post’s take on all the noise at Harvard.
  • Authorea authors write on the problems with peer review associated with hyperspecialization:

    [T]he average number of authors per paper has been steadily increasing in the last few decades, while the number of referees per paper has not.


  • Relatedly, the new Leiden Manifesto argues against giving bibliometrics (h-index, etc.) a leading role in the hiring and funding processes. Although I agree with much of it, they take a wishy-washy stance that dilutes its effectiveness. I once compared the objectivity of citation metrics to a vote by spectators about who ran the fasted 100 yard dash, and my opinion has only gotten more pessimistic since then.
  • Some good modern discussion of the theory of a Land Value Tax by Bryan Caplan, Jeff Kaufman, and Noah Smith. Some of their disagreement is semantic (i.e., compared to which platonic ideal are we calling something a “friction”, versus an inherent problem?), but it’s still illuminating.
  • Now you can get your raw genetic data for SNPs for free, so long as you allow your data to be used anonymously for research.
  • Here is a toy models for Gompertz’s law of human mortality, that the human mortality rate grows roughly exponentially, across many times, places, and cultures. However, it’s more complicated than that:

    The Gompertz–Makeham law states that the human death rate is the sum of an age-independent component (the Makeham term, named after William Makeham and an age-dependent component (the Gompertz function, named after Benjamin Gompertz), which increases exponentially with age.

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Links for March 2015

  • The eclipse seen from an airplane, time lapse:
  • A 2003 proposal [PDF] to send a probe to the center of the earth riding a $60 million slab of molten iron:

    This proposal is modest compared with the space programme, and may seem unrealistic only because little effort has been devoted to it. The time has come for action.

  • Will the paternoster be reborn?:

    (HN Comments.) This could alleviate a serious limiting factor for extremely tall skyscrapers, which use a surprisingly large fraction of their square footage for elevators.
  • Toward a systematic assessment of the rent hypothesis.

    Rent…is…a payment for a resource in excess of its opportunity cost, one that instead reflects market power. There has been, for the last few years, a “big idea” floating around the economics conversation that these rents are growing — that unearned gains are eating up an larger share of income. Let’s call it “the rent hypothesis.” It’s an appealing idea from a certain perspective. It seems to explain a lot.

    Trying to spot rents is, in this sense, a bit like trying to spot a black hole… the idea is to spot rents by what is missing, by the presence of a contradiction where only rents can fill the gap. This is a fun game to play, but it ends up being pretty unconvincing.

    What, then, might a more convincing analysis show in support of the rent hypothesis? Here are four ideas….

  • The physical appearance of the ISS, from first principles: Why Does The International Space Station Have Such A Weird Shape?
  • National Science Foundation to require open access after one year:

    NSF will require that either the version of record or the final accepted manuscript in peer-reviewed scholarly journals and papers in juried conference proceedings or transactions must:

    • Be deposited in a public access compliant repository designated by NSF;
    • Be available for download, reading and analysis free of charge no later than 12 months after initial publication;
    • Possess a minimum set of machine-readable metadata elements in a metadata record to be made available free of charge upon initial publication;
    • Be managed to ensure long-term preservation; and
    • Be reported in annual and final reports during the period of the award with a persistent identifier that provides links to the full text of the publication as well as other metadata elements.
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Links for February 2015

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Links for January 2015

  • There’s been some coverage of using etching to produce superhydrophobic metals. Unfortunately, it probably suffers from the same durability issues (no resistance to being destroyed through normal wear) as previous techniques that used special chemical coatings.
  • A funnel plot is a quick graphical way to check for publication bias on a topic.
  • Apparently, the best way to avoid a fight with a confrontational Red Kangaroo (the largest kangaroo species) is to give a deep cough. This is a signal of submission by subdominant males, and can assure the dominant male that you aren’t challenging him. Otherwise…

  • Daniel Dennett, synthesizing Anatol Rapoport, on how to compose a successful critical commentary:

    • You should attempt to re-express your target’s position so clearly, vividly, and fairly that your target says, “Thanks, I wish I’d thought of putting it that way.
    • You should list any points of agreement (especially if they are not matters of general or widespread agreement).
    • You should mention anything you have learned from your target.
    • Only then are you permitted to say so much as a word of rebuttal or criticism.

    If only the same code of conduct could be applied to critical commentary online, particularly to the indelible inferno of comments.

    But rather than a naively utopian, Pollyannaish approach to debate, Dennett points out this is actually a sound psychological strategy that accomplishes one key thing: It transforms your opponent into a more receptive audience for your criticism or dissent, which in turn helps advance the discussion.

    (H/t Rob Wiblin.) Although most folks have heard and approve of many of these tips, it’s common for people to get lazy about implementing them because, frankly, it’s kind of a lot of work.

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Links for December 2014

  • Steve Hsu notes that BGI has applied preimplantation genetic diagnosis (PGD) using next-generation sequencing techniques. Previous uses of PGD have only used simple screening methods, like searching for single-nucleotide polymorphisms, to avoid implanting embryos with a handful of well-understood genetic defects (which are then destroyed). Next generation methods have the potential to sequence most/all of the genome, allowing for traits influences by many genes to be selected for, like height and intelligence.
  • Crab housing exchange.
  • That the National Reconnaissance Office publicly releases the mission patches for their highly classified satellites is well-known on the internet, but I hadn’t realized that there was reason to think that classified details had been accidentally leaked through them in the past.
  • If correct, this is a surprisingly comprehensive and intuitive answer to many aspects of human bilateral (a)symmetry:

    Most of our asymmetry is due to just two organ systems: the GI tract and the heart. The concept that best explains the shape of both of these systems is the idea that a long organ that has to fit in a small body does so by being wound up.

    The heart could be composed of a linear arrangement of a pump, the lungs, and then a second pump. In some organisms like the worm, the heart is a linear pump. However the human body cannot accommodate a linear arrangement and thus we have what is effectively a tube curled up on itself.

    The GI tract is the same story. It would be hugely long if a linear, thus it has to be wound up inside of us. There is no symmetrical way to wind it up. Many organs like the pancreas and the liver actually bud off of the GI tract during development so the asymmetry of the GI tract explains the asymmetry of many of the other abdominal organs.

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Links for November 2014

Almost all the links this month are space related. I promise I spend time thinking about other things but…there’s just a lot of cool space-related links on the internet.

  • Video of the night sky with the stars stabilized so you can watch the ground spin around.
  • For several years the ESA worked on a spacecraft that would test the idea of deflecting a comet with a high-speed impactor. It was brilliantly named Don Quijote, with the rash impactor craft “Hidalgo” rushing in to the target with the observation craft “Sancho” watching from a safe distance. Unfortunately, it looks like the project stalled years ago, but a proposed joint NASA-ESA mission Asteroid Impact & Deflection Assessment (AIDA) could carry the torch [PDF] by targeting the asteroid 65803 Didymos. Didymos is actually a binary system, with a large primary asteroid and a smaller secondary asteroid orbiting it. When the impactor strikes the primary (speed ~ 6.25 km/s), it would induce perturbations to the orbit of the secondary observable from Earth. A 2019 launch and 2022 impact date have been chosen so that Didymos will be passing close to the Earth and the impact event will be visible to ground-based radar.
  • Half of all stars are not in galaxies?

    Astronomers have spotted a faint cosmic glow, unseen until now, that may come from stars that float adrift between galaxies. The discovery suggests that as many as half of all stars in the Universe lurk outside galactic boundaries….The stars were probably tossed there when galaxies collided.

    I don’t understand how this is still uncertain given our knowledge of galaxy and structure formation. But in any case, it’s interesting to note that the large majority (85%) of all the stars we see in the night sky are within 1,000 light years of Earth.

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