- Gates on refrigeration using intermittent power for rural vaccine delivery.
- Multiple camera views of Tomahawk Missile test, including from F-18 chase plane.
- Suggested thesis topics to maximize impact on the world for grad students. (After you select a academic subject, just click all the “areas of interest” to see the complete list of suggested thesis topics in that subject.)
My non-profit, the Berkeley Existential Risk Initiative, is aiming to distribute around $750k in grants to individuals or small groups for projects to reduce x-risk, in annualized amounts up to $300k: http://existence.org/project-grants-1/
…Thanks to Jaan Tallinn for his incredible moral support, and funding for the program!
- Ground is about to be broken on the factory for constructing spaceships that will deliver human beings to Mars.
- Self-driving cars are probably worth $0.5T to $5T per year. Each day the tech is delayed costs more than a $1B.
- It’s a sorta-misconception that US corporations must strictly maximize profits (or, more generally, shareholder value). As long as the corporate leaders aren’t stealing for their own benefit, the courts generally give wide latitude to their strategies and goals, including very tenuous argument about improving communities and generating goodwill. However, the details are complicated; there have been at least a couple cases where leaders explicitly endorsed leaving huge rewards on the table in order to pursue goals that had no benefit to shareholders whatsoever, and they were successfully sued. The most recent and relevant one in 2010 pitted Craigslist founder Craig Newmark against his investor eBay. In response, some state (including the all-important Delaware) have recently created the category of benefit corporations which are for-profit (normal taxes, etc.), but are legally guaranteed the right to pursue social goals that do not benefit shareholders at all.
- Polemical but engrossing double book review by Tim Maudlin on external reality and misunderstood history of science.
- Heinz-Dieter Zeh, grandfather of decoherence, has died. (H/t Peter Woit.) A true intellectual pioneer, he launched my field of study during an era when working on quantum foundations was punished even more strongly than today.
- Dive bombers:
A dive bomber is a bomber aircraft that dives directly at its targets in order to provide greater accuracy for the bomb it drops. Diving towards the target simplifies the bomb’s trajectory and allows the pilot to keep visual contact throughout the bomb run. This allows attacks on point targets and ships, which were difficult to attack with conventional level bombers, even en masse.
The Junkers Ju 87 or Stuka (from Sturzkampfflugzeug, “dive bomber”) is a German dive bomber…Upon the leading edges of its faired main gear legs were mounted the Jericho-Trompete (Jericho trumpet) wailing sirens, becoming the propaganda symbol of German air power and the blitzkrieg victories of 1939–1942.
The Stuka’s design included several innovative features, including automatic pull-up dive brakes under both wings to ensure that the aircraft recovered from its attack dive even if the pilot blacked out from the high g-forces… Extensive tests were carried out by the Junkers works at their Dessau plant. It was discovered that the highest load a pilot could endure was 8.5g for three seconds, when the aircraft was pushed to its limit by the centrifugal forces… The pilot would regain consciousness two or three seconds after the centrifugal forces had dropped below 3g and had lasted no longer than three seconds.
- On the Cyrillic alphabet in math, complete with awesome Venn diagram of character appearances in Cyrillic, Greek, and Latin alphabets.
- Alex Tabarrok on what crypto is good for:
Hayek called decentralized institutions spontaneous orders because he implicitly assumed that all such decentralized institutions were spontaneous, i.e. unplanned. Only in very recent years have economists and computer scientists developed the understanding and tools that are necessary to design decentralized orders–orders that are planned but not controlled. Today smart contracts on blockchains like Ethereum have the potential to create a sophisticated set of global common resources that will form the foundation for much of the economic and social structure of this century–this is the opportunity of the blockchain commons.
- AI Impacts’ list of promising research projects, potentially suitable for independent work. (H/t Alyssa Vance.)
- The Frisch-Peierls Memorandum (full text) from 1940 first realized that the critical mass of uranium-235 (~1 kg) was vastly smaller than for the common isotope uranium-238 (many tons). This means a weapon could be delivered by airplane, and hence had enormous military implications.
- Rob Wiblin has been putting out a lot of great 80,000 Hours podcasts recently. Some of it re-visits topics you’ve probably heard of if you’re an EA nerd, but even then it’s more in depth than usual. And some are pretty original.
Incidentally, the 80,000 Hours podcast webpages are basically the best designed I’ve ever seen: key summary points, full transcript, links to further reading. Top notch.
- Are the principles of quantum mechanics or of general relativity more likely to persist in the hypothetical fundamental theory that limits to both of them in their respective regimes? Sean Carroll and Matt Liefer, two of the most philosophically sophisticated physicists on the planet, debate:
- The end is nigh: Witten has started writing about quantum information.
- SpaceX is getting closer to recovering the fairing. They are $5M each, a surprising 10% of the $50M Falcon-9 launch price. And Elon Musk thinks full second stage reuse is possible.
- Bitcoin prices on a log scale.
The Brightline high-speed train, the only privately owned and operated passenger rail system in the U.S., took its inaugural run to Miami on Friday filled with politicians and reporters. The public can ride starting May 19….The Brightline will connect Miami with service that already links Fort Lauderdale and West Palm Beach….The company has spent about $1.5 billion and plans to invest a total of around $3.2 billion on the Florida train, which will eventually run to Orlando.
- ArXiv Sanity for HEP. (H/t Luis Batalha.)
- Interesting commentary on flaws and insights of Feynman. I think there are a lot of ways to interpret what’s going on here, and I don’t think “Feynman didn’t like mathematics” is a good summary. What exactly Feynman did and didn’t like, and what aspects of physics and math have been emphasized/neglected as physics has ground to a halt over the past decades, is something that requires more ideas in philosophy of science to analyze.
- Researcher boycott of new journal Nature Machine Intelligence.
- Unibio uses bacteria to turn natural gas into animal feed.
- One way to force metals into amorphous (glassly) atomic structures is with melt spinning:
Melt spinning is a technique used for rapid cooling of liquids. A wheel is cooled internally, usually by water or liquid nitrogen, and rotated. A thin stream of liquid is then dripped onto the wheel and cooled, causing rapid solidification. This technique is used to develop materials that require extremely high cooling rates in order to form, such as metallic glasses. The cooling rates achievable by melt-spinning are on the order of 104–107 kelvins per second (K/s).
- Voxels vs. polygons.
- SkyLab was big inside.
- NTSB preliminary report on pedestrian fatal accident with Uber self-driving car:
According to data obtained from the self-driving system, the system first registered radar and LIDAR observations of the pedestrian about 6 seconds before impact, when the vehicle was traveling at 43 mph. As the vehicle and pedestrian paths converged, the self-driving system software classified the pedestrian as an unknown object, as a vehicle, and then as a bicycle with varying expectations of future travel path. At 1.3 seconds before impact, the self-driving system determined that an emergency braking maneuver was needed to mitigate a collision (see figure 2). 2 According to Uber, emergency braking maneuvers are not enabled while the vehicle is under computer control, to reduce the potential for erratic vehicle behavior. The vehicle operator is relied on to intervene and take action. The system is not designed to alert the operator.
- I recently realized that all wallets designs are stupid: basically every wallet you see, whether bifold or trifold, horizontal or vertical credit card placement, ultimately end up stacking every card on top of each other when the wallet is closed. So you can never be thinner than the total thickness of all the cards. But if you were to place the cards in two stacks (long edges near so it doesn’t get too big), your wallet can be half the thickness. Would be slightly wider, but that seems easily worth it. I looked around online and no one even talks about it until I found a single company that makes this design. They even have a video talking about the theory. But the problem is that the quality of this particular company is bad. All the Amazon reviews complain about the cards falling out, etc.
- Scott Aaronson on the separation of BQP from the polynomial hierarchy.
- On jump cuts:
A jump cut is a cut in film editing in which two sequential shots of the same subject are taken from camera positions that vary only slightly if at all. This type of edit gives the effect of jumping forwards in time….This kind of cut abruptly communicates the passing of time as opposed to the more seamless dissolve heavily used in films predating Jean-Luc Godard’s Breathless, when jump cuts were first used extensively. For this reason, jump cuts, while not seen as inherently bad, are considered a violation of classical continuity editing, which aims to give the appearance of continuous time and space in the story-world by de-emphasizing editing. Jump cuts, in contrast, draw attention to the constructed nature of the film.
Continuity editing uses a guideline called the “30 degree rule” to avoid jump cuts. The 30 degree rule advises that for consecutive shots to appear “seamless,” the camera position must vary at least 30 degrees from its previous position. Some schools would call for a change in framing as well (e.g., from a medium shot to a close up). Generally, if the camera position changes less than 30 degrees, the difference between the two shots will not be substantial enough, and the viewer will experience the edit as a jump in the position of the subject that is jarring, and draws attention to itself. Although jump cuts can be created through the editing together of two shots filmed non-continuously (spatial jump cuts), they can also be created by removing a middle section of one continuously filmed shot (temporal jump cuts).
- Follow-cam for paragliding:
- Rock-hewn churches in Lalibela, Ethiopia:
In a mountainous region in the heart of Ethiopia, some 645 km from Addis Ababa, eleven medieval monolithic churches were carved out of rock. Their building is attributed to King Lalibela who set out to construct in the 12th century a ‘New Jerusalem’, after Muslim conquests halted Christian pilgrimages to the holy Land. Lalibela flourished after the decline of the Aksum Empire.
The churches were not constructed in a traditional way but rather were hewn from the living rock of monolithic blocks. These blocks were further chiselled out, forming doors, windows, columns, various floors, roofs etc. This gigantic work was further completed with an extensive system of drainage ditches, trenches and ceremonial passages, some with openings to hermit caves and catacombs.
(H/t Tyler Cowen.)
- First class of AI fellows from OpenPhil.
- 49bc goes back to the sacred texts in the aftermath of the 51% attack against Bitcoin Gold:
Satoshi really downplayed 51% attacks in his/her original whitepaper:
> The incentive may help encourage nodes to stay honest. If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments, or using it to generate new coins. He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth.
Apparently he didn’t realize that coins could quickly be transferred to other crypto and not held, so who cares about the value of the stolen goods.
- On mobs and the law. (H/t Robin Hanson.)
- jhayward on the November 2015 test launch of a Trident D5 ballistic missile off the California coast:
The video from the last test of Trident D5, launched from offshore, was unreal. Someone happened to catch it with a good lens from a fairly dark hilltop, and then spacecraft experts annotated the video to point out what was going on. You could see the bus rotating and ejecting warheads (or decoys) all the way through its inventory.
- Atmospheric science for tidally locked exoplanets.
The planet’s water is boiled on the day side and frozen on the night side. But winds transport the water vapor from the day side toward the night side to freeze. This can create a cold trap: all of the planet’s water can be locked up in a giant layer of ice on the permanent-night side. Dry day side, ice-covered night side…. When a layer of ice gets thick enough, its bottom layer melts from the pressure. This causes the ice to flow downhill, like glaciers do on Earth. So a hot [tidally locked] planet’s thick night side ice cap spreads out and slowly flows toward the day side. There may be a trickle of water that flows into the light to be evaporated all over again. Our models project that there are characteristic wind patterns that pile clouds up in a specific region on the night side (gory details here). The planet’s non-uniform appearance can really look like an eyeball. Rivers that flow from the night side to eventually evaporate on the day side might even look like veins.
- Apparently the Catalina Sky Survey, in coordination with the spectacularly named Planetary Defence Office, is able to identify and track objects just 10 feet across at the distance of the Moon. (H/t Viva Horowitz.)
- On being woken up by a person, rather than an alarm clock, as part of a military shift change:
I always slept more soundly when I was getting a “shake” versus relying on my alarm clock. It’s very comforting to know that you’re absolutely going to be woken up when you asked to be and not have to worry about your phone being on charge or accidentally sleeping through an alarm. It also meant you didn’t have to do time zone maths when you went to bed and that your alarm wouldn’t wake your cabin mates.
- On the theory of the sound barrier: “Schematic of the subsonic and supersonic variations of drag coefficient for an airfoil, illustrating the position of the transonic regime for which virtually no information was available in the 1930s and 1940s.”:
The plot is now known to look like this
- The amount of time it takes food to pass through a person is overwhelming dominated by the large intestines:
Digestion time varies between individuals and between men and women. After you eat, it takes about six to eight hours for food to pass through your stomach and small intestine. Food then enters your large intestine (colon) for further digestion, absorption of water and, finally, elimination of undigested food.
In the 1980s, Mayo Clinic researchers measured digestion time in 21 healthy people. Total transit time, from eating to elimination in stool, averaged 53 hours (although that figure is a little overstated, because the markers used by the researchers passed more slowly through the stomach than actual food). The average transit time through just the large intestine (colon) was 40 hours, with significant difference between men and women: 33 hours for men, 47 hours for women.
- Ira Glass covers the writer’s room at The Onion (2011).
- “Traumatic License: An Oral History of Action Park“. Wikipedia:
The original Action Park was open until 1996 and featured three separate attraction areas: the Alpine Center (featuring an alpine slide), Motorworld, and Waterworld. The latter was one of the first modern American water parks. Many of its attractions were unique, attracting thrill-seekers from across the New York City metro area. The park’s popularity went hand-in-hand with a reputation for poorly designed, unsafe rides; under-aged, under-trained, and often under-the-influence staff; intoxicated, unprepared visitors; and a consequently poor safety record. At least six people are known to have died as a result of mishaps on rides at the original park. It was given nicknames such as “Traction Park”, “Accident Park”, and “Class ActionPark” by doctors at nearby hospitals due to the number of severely injured customers they treated. Little action was taken by state regulators despite a history of repeat violations. In its later years, personal injury lawsuits led to the closure of more and more rides, and eventually the entire park.
(H/t Gwern.) A movie is being made about the park starring Johnny Knoxville.
- Also from Gwern, the split-brain consciousness study fails to replicate: “Split brain: divided perception but undivided consciousness” (Pinto et al 2017):
In extensive studies with two split-brain patients we replicate the standard finding that stimuli cannot be compared across visual half-fields, indicating that each hemisphere processes information independently of the other. Yet, crucially, we show that the canonical textbook findings that a split-brain patient can only respond to stimuli in the left visual half-field with the left hand, and to stimuli in the right visual half-field with the right hand and verbally, are not universally true. Across a wide variety of tasks, split-brain patients with a complete and radiologically confirmed transection of the corpus callosum showed full awareness of presence, and well above chance-level recognition of location, orientation and identity of stimuli throughout the entire visual field, irrespective of response type (left hand, right hand, or verbally). Crucially, we used confidence ratings to assess conscious awareness. This revealed that also on high confidence trials, indicative of conscious perception, response type did not affect performance. These findings suggest that severing the cortical connections between hemispheres splits visual perception, but does not create two independent conscious perceivers within one brain.
- And Gwern covers Joel Spolsky’s discussion of the commodification of product complements. (HN comments.) One thing I hadn’t seen emphasized: Although this seems vaguely bad in the sense that one company is hurting another company, it is, as far as I can tell, a net-positive for society, at least insofar as we consider the commodification of products to be an efficient final end point for a mature industry. (It can always be the case that non-commodity rents cross-subsidize other sorts of innovation.)
- “Daala is a video coding format under development by the Xiph.Org Foundation under the lead of Timothy B. Terriberry mainly sponsored by the Mozilla Corporation.” Surprisingly to me, current video codec sound very nonoptimal (at least according to the people building the replacement). More here.
- Nix’s spin is chaotic:
This animation illustrates how Pluto’s moon Nix changes its spin unpredictably as it orbits the Pluto-Charon system. The view is from the centre of the system as the moon circles around it. The time-lapse animation is based on a computer simulation which calculated the chaotic movement
- “Starting June 30, Swedish researchers will no longer be publishing in Elsevier and will not have access to Elsevier magazines.” And there is wider progress on Open Access science in Europe. If the circa-2022 target date for universal open access established by several countries and organization is met, it will have been a full three decadesSee Fig. 1b here. a since the arXiv become standard in physics (which unambiguously demonstrated the technical feasibility). This is not a very impressive coordination performance by humanity.
For research papers protected by a paywall, the study found Sci-Hub’s reach is greater still, with instant access to 85% of all papers published in subscription journals. For some major publishers, such as Elsevier, more than 97% of their catalog of journal articles is being stored on Sci-Hub’s servers—meaning they can be accessed there for free.
The complete 60-terrabyte Sci-Hub database is available as a collection torrents.
- Bloomberg profile of Saildrone.
- Equiconsistency as a partial end-around for Gödel incompleteness:
In mathematical logic, two theories are equiconsistent if the consistency of one theory implies the consistency of the other theory, and vice versa. In this case, they are, roughly speaking, “as consistent as each other”.
In general, it is not possible to prove the absolute consistency of a theory T. Instead we usually take a theory S, believed to be consistent, and try to prove the weaker statement that if S is consistent then T must also be consistent—if we can do this we say that T is consistent relative to S. If S is also consistent relative to T then we say that S and T are equiconsistent.
- The 80k job board is stacked with sexy high-impact jobs. Remember, probably no one will care about they stuff your’re currently researching.
- The inside of giant cryogenic tank used to transport liquid natural gas by ship:
- Kissinger on AI risk:
Heretofore, the technological advance that most altered the course of modern history was the invention of the printing press in the 15th century, which allowed the search for empirical knowledge to supplant liturgical doctrine, and the Age of Reason to gradually supersede the Age of Religion. Individual insight and scientific knowledge replaced faith as the principal criterion of human consciousness.
Information was stored and systematized in expanding libraries. The Age of Reason originated the thoughts and actions that shaped the contemporary world order.
But that order is now in upheaval amid a new, even more sweeping technological revolution whose consequences we have failed to fully reckon with, and whose culmination may be a world relying on machines powered by data and algorithms and ungoverned by ethical or philosophical norms.
(H/t Samo Burja.) I did not find anything new in this article but, you know, Kissinger.
- Automated BMW Car Factory:
- If you didn’t already know, the reboot of LessWrong is out of beta mode. The early writing of Eliezer Yudkowsy made a large impact on how I see the world, and it’s available in curated “sequences” of blog posts.
- Chaitin’s constant has a bit less personality than the demons of Maxwell and Laplace, but it has been described demonically by Philip Davis, professor emeritus at Brown:
Omega: Chaitin’s Demon
Definition: Ω is the probability that a random program on a universal Turing machine will halt under the probability distribution that a program of length k has probability 2^–k. In its ambiguity, Ω is something like the god Jupiter—now a swan, now a bull, depending on the opportunities available…
…Ω is not really a number; it’s a definition or a process or a demon. Yes, I would locate Ω among the great demons of physics and mathematics: Laplace’s Demon can predict the future location of every particle in the universe using Newtonian mechanics; Maxwell’s Thermodynamic Demon can separate out the high-velocity molecules in a container of gas. For all I know, there might be a Quantum Demon who, knowing things forbidden by the Uncertainty Principle, could produce a few small surprises in the laboratory. I always thought that a Diagonalizing Demon (now resident in every text on set theory) helped Georg Cantor write down every existing number on a list and still find another number not on the list. As Sol Feferman pointed out, all non-computability results are ultimately based on the method of diagonalization applied to idealized computers. Now in Ω we have something even more amazing: Ω is Chaitin’s Demon, and it can reveal the answers to all mathematical questions, past, present, and future…
- Kayak finally adds an option to incorporate baggage fees and their ilk into the prices returned by their flight search: “Fee assistant“. Should have existed 3 or 4 years ago, but better late than never!
- South Korea’s president and foreign minister both credit Trump for the North-South peace talks. Of course, North Korea says it wasn’t Trump so….who are you going to believe?
- Evidence that the stagnation/maturation process seen in Wikipedia is a universal feature of wikis:
This graph shows the number of people contributing to Wikipedia over time:
The number of active Wikipedia contributors exploded, suddenly stalled, and then began gradually declining. (Figure taken from Halfaker et al. 2013)
The figure comes from “The Rise and Decline of an Open Collaboration System,” [PDF] a well-known 2013 paper that argued that Wikipedia’s transition from rapid growth to slow decline in 2007 was driven by an increase in quality control systems. Although many people have treated the paper’s finding as representative of broader patterns in online communities, Wikipedia is a very unusual community in many respects. Do other online communities follow Wikipedia’s pattern of rise and decline? Does increased use of quality control systems coincide with community decline elsewhere?
…a group of us have replicated and extended the 2013 paper’s analysis in 769 other large wikis. We find that the dynamics observed in Wikipedia are a strikingly good description of the average Wikia wiki. They appear to reoccur again and again in many communities.
- “But one of the great arbitrages in finance—in life—is being immune to embarrassment.”
- In light of the James Webb Space Telescope: Where Do We Go from Here? Astrobiology Editorial Board Opinions.
- NASA to include the Mars Helicopter Scout with the Mars 2020 rover:
The primary objective of this helicopter is to explore the terrain ahead of the rover to provide overhead images with approximately 10x greater resolution than orbital images, and would display features that may be occluded from the rover cameras. Such scouting by the small helicopter would enable the rover to drive up to three times as far per sol. The helicopter would fly no more than 3 minutes per day and cover a distance of about 600 m (2,000 ft) daily. It would use autonomous control and communicate with the rover directly after landing.
The rover (not the helicopter) will also “will test technology to produce oxygen from Martian atmospheric carbon dioxide”.
- The Great Pyramid of Giza “was the tallest man-made structure in the world for more than 3,800 years”.
- Witness, arguably, the end of Moore’s law.
- Baidu vs. Waymo:
Beijing-based Baidu, which operates China’s largest internet search service, reported to California’s Department of Motor Vehicles (DMV) that its self-driving cars had “disengaged” from autonomous control every 41 miles (65.9 kilometres), compared with every 5,596 miles for Waymo.
- Google research on limited-domain natural-language interaction.
- GiveWell now has a video tour of its cost-effectiveness model:
- Eli Dourado of Boom makes the case for actually thinking you could make a commercially viable supersonic airliner:
The Concorde entered service in 1976, and program launch was in the Kennedy administration. It would be surprising if technology didn’t advance enough to bring huge improvements over that time period.
There are broadly three enabling technologies, plus a couple of economic factors. Technologies:
1. Carbon fiber. With the 787, we finally have a transport-category aircraft with significant amounts of carbon fiber that has gone through full FAA certification, which significantly lowers the barrier to us using it. Carbon fiber does a lot for us. It is lighter and stronger than aluminum, but it is also more thermally stable. Concorde grew about 15 inches in flight as its temperature rose in flight. Our leading edges will reach over 300ºF at Mach 2.2, and our plane will grow less than an inch in flight. That is a significant maintenance cost reducer. Carbon fiber also enables more complex geometries without expensive tooling costs. Our plane won’t have a straight line on it. We can take better advantage of area ruling to improve aerodynamics. In contrast, Concorde’s fuselage was a cylindrical tube.
2. Engines. There is a (much slower) Moore’s law for engine cores; they get better at a rate of around 1 percent a year. Move 50+ years forward from when Concorde’s engines were designed and you have a real improvement. Concorde used 4 turbojets (i.e, zero bypass ratio) and we have 3 medium-bypass turbofans. Plus no afterburners are needed. When Concorde used afterburners to punch through the transonic regime, they had a 78% increase in fuel flow for a 17% increase in thrust.
3. Computational fluid dynamics. Concorde is all the more impressive for the fact that it was designed with slide rules and wind tunnels. Wind tunnel tests are expensive, taking six months and costing millions of dollars. We can do virtual wind tunnel tests in software in about 30 minutes. We still use tunnels to closely test harder aspects of the design (e.g., low-speed handling qualities), but we have much more rapid design iteration than Concorde could have hoped for.
On the economics, we are right-sizing the aircraft. Concorde had 100 seats, but it usually flew with a very low load factor (half-empty). Our design has 55 seats, which is similar to the premium cabin on today’s widebody subsonic airliner. What this means is that any route that can sustain widebody subsonic service today will basically work supersonically. We expect much higher load factors, which are helped by business class fares and a lower number of seats to fill relative to Concorde.
This leads to economies of scale. Whereas Concorde really only was profitable between New York and London, Boom flights make economic sense on hundreds of global routes. Which means we’ll sell more planes and drive maintenance costs down further. Only 14 Concorde units ever saw commercial service. Ultimately, when Concorde shut down, it was because Airbus stopped making spare parts. In contrast, one public report by the Boyd Group estimated supersonic demand at 1300 planes. With almost two orders of magnitude of planes in service, we’ll achieve much better scale on maintenance.
- Tour of a beef processing plant with Temple Grandin
(who was praised by Hanson). This 2013 study suggested that more than a tenth of cattle aren’t adequately stunned prior to slaughter, and this 2018 study gives a similar or larger fraction for the number of cattle that must be struck multiple times by a captive bolt stunner.
- “Why Men Love War“.
- Subtle statistical errors may account for discrepancy in measurements of Hubble constant, but physicists are not (and are not incentivized to be) good at this stuff.
- When pilots Chesley Sullenberger and Jeffrey Skiles made a successful water landing on US Airways Flight 1549, they used the gaze heuristic. Skiles:
It’s not so much a mathematical calculation as visual, in that when you are flying in an airplane, things that— a point that you can’t reach will actually rise in your windshield. A point that you are going to overfly will descend in your windshield.
(H/t Konstantinos Katsikopoulos.) Here’s the full air traffic conversation.
- Balgair on spacecraft failure rate estimates:
I used to do reliability analyses for a large aerospace contractor, I may have some insights. The stuff I worked on was not HSF (Human Space Flight) just automated sats and the like. Each and every single part is spoken for and tallied. Each resistor on a PCB, each explosive bolt, each screw and panel. All of it has a lifetime curve, typically a Bathtub plot, to an extreme degree. Resistors were tested in vast batches, over vast I-V ranges, in hard radiation and vacuum, in vibe, for long periods. You calculate it all out. Something approaching the far upper reaches of the expected ‘black swans’ is tested and the part is proofed against it. Our stuff was just comms and the like, granted, but even then, the expected lifetime of each satellite was fairly well known out to about 20 years in orbit. A typical figure for a 15 year mission was a 75% chance of it making it the whole way, including launch. It’s checked to an extreme degree. I’ve had people come back and correct an un-dotted ‘i’ symbol in a handwritten notebook. Really.
- American physicist difficulty in replicating Russian measurements of the quality factor of sapphire — a case study of tacit knowledge. (H/t Michael Nielsen.)