- Plutonium-238 is the isotope used in the radioisotope thermoelectric generators which crucially powered Voyager 1 & 2, Cassini–Huygens, and New Horizons. However, the US quit producing it in the ’80s, and the national stockpile for space exploration has dwindled to essentially zero, forcing some missions like the Juno spacecraft to use solar panels (which are significantly suboptimal at Jupiter’s distance from the sun). However, Oak Ridge National Lab just produced first new batch (50 g) of Plutonium-238 in almost 3 decades. The next probe to use the material will be the Mars 2020 rover.
Animation of how magnetic declination (the difference between the local north magnetic field and the direction to true geographic north) varies over time and location.
The two singularities are the north and south magnetic poles. The dipole moment of the Earth is usually lined up roughly with the rotational axis, although it may flip occasionally. During the flipping transition, the magnetic field will vary wildly.
- Elon Musk explains the experimental progression leading up to the much-discussed successful recovery of the Falcon 9 first state. Here’s the video in case you missed it, and here is helicopter footage of the landing. Musk on reusing this particular rocket: “We’ll probably keep this one on the ground – its unique because its the first one we landed.” Here is the deployment of the multi-satellite payload.
- Lots of good links from Scott Alexander as usual: How much of the accepted wisdom about good creative writing can be attributed to the CIA’s attempt to counter the spread of communist ideas? Facebook releasing details on machine learning hardware. The residents of Yiwu, China’s “Christmas Village,” manufactures 60 percent of the world’s Santa hats, tinsel, and mistletoe.
If you’ve been thinking about taking the Giving What We Can pledge, their New Year’s Pledge Drive would be a great time to make the jump. Last year’s event features 80 people taking the pledge, with even more expected this year. Here’s Jonathan Courtney making their pitch:
- Kathryn Schulz: “The best facts I learned from books in 2015“. (H/t Tyler Cowen.)
- Highly oblique, high-resolution satellite image of Colorado, with commentary.
- Steve Hsu on Terrance Tao on intelligence and genius. See also this 2012 discussion of a deep result about the iterated Prisoner’s dilemma that I hadn’t heard about. (Edit: Previous discussion on LessWrong. H/t Carl Shulman.)
- A simple explanation of Chinese characters. (Too simple?) Also: constructing Chinese fonts.
- Scott Aronson resumes his role as chief explainer of D-wave on his blog and the MIT news Q&A.
- Toward a complete, low-side effect method of eliminating pain? (New Scientist, original Nature paper.
“Does Science Advance One Funeral at a Time?” by Pierre Azoulay, Christian Fons-Rosen, Joshua S. Graff Zivin
We study the extent to which eminent scientists shape the vitality of their fields by examining entry rates into the fields of 452 academic life scientists who pass away while at the peak of their scientific abilities. Key to our analyses is a novel way to delineate boundaries around scientific fields by appealing solely to intellectual linkages between scientists and their publications, rather than collaboration or co-citation patterns. Consistent with previous research, the flow of articles by collaborators into affected fields decreases precipitously after the death of a star scientist (relative to control fields). In contrast, we find that the flow of articles by non-collaborators increases by 8% on average. These additional contributions are disproportionately likely to be highly cited. They are also more likely to be authored by scientists who were not previously active in the deceased superstar’s field. Overall, these results suggest that outsiders are reluctant to challenge leadership within a field when the star is alive and that a number of barriers may constrain entry even after she is gone. Intellectual, social, and resource barriers all impede entry, with outsiders only entering subfields that offer a less hostile landscape for the support and acceptance of “foreign” ideas.
(H/t Robin Hanson.)
- Good Reddit comment on floating nuclear power plants.
- Noah validating my pre-existing beliefs: academic obscurantism as a cartel mechanism. Physics has much less than most subjects, but is not off the hook. Best place to look is in specialties that lack objective metrics of success…
Beginner talk on adaptive meshes for turbulence simulations from the SpaceX guys.
Neat visualization of mesh refining in response to a re-entry shockwave at 24:15. The combustion simulations at 36:20 is also recommended. The gridlines saturate at the pixel in the video, which is far coarser than the smallest tracked length scale, so it doesn’t really do justice to the exponential computational speed up afforded by the adaptation compared to a uniform simulation.
- OpenAI is stupendously funded to the tune of $1 billion. It’s weird that they sit down for a Wired article, but then announce on a Friday evening, which is typically the time to announce things to minimize publicity. Maybe they thought this got them the minimum widespread exposure for the maximum nerd exposure? Wired article. (The HN comments are low quality.) Scott Alexander worries that open AI makes about as much sense as open nuclear.
- “Mysterious Detour While Driving? It Could Be Due to the Curvature of the Earth.”
- ‘t Hooft’s guide “How to become a GOOD Theoretical Physicist” gets a facelift. I love this guide because of the philosophy it represents. Although the chances of someone becoming a good theoretical physicist by self-study are negligible, there is a primal sense in which we should build a world where this is possible, at least in principle. A similar sensibility is behind viXra.
I’m quite glad to see Sean Carroll emphasizing (back in February) how nice it would be if we had an objective principle for identifying the branches of the wavefunction.
Which saddens me, as an MWI proponent, because I am very quick to admit that there are potentially quite good objections to MWI, and I would much rather spend my time discussing those, rather than the silly ones. Despite my efforts and those of others, it’s certainly possible that we don’t have the right understanding of probability in the theory, or why it’s a theory of probability at all. Similarly, despite the efforts of Zurek and others, we don’t have an absolutely airtight understanding of why we see apparent collapses into certain states and not others. Heck, you might be unconvinced that the above postulates really do lead to the existence of distinct worlds, despite the standard decoherence analysis; that would be great, I’d love to see the argument, it might lead to a productive scientific conversation. Should we be worried that decoherence is only an approximate process? How do we pick out quasi-classical realms and histories? Do we, in fact, need a bit more structure than the bare-bones axioms listed above, perhaps something that picks out a preferred set of observables?
Within the consistent histories formalism, this issue manifests as Kent’s set selection problem, as I have belabored many times before.
- The Flynn effect is strongest on the parts of IQ tests that have the /least/ cultural baggage and are the /most/ abstract. Maybe people these days are just as smart, but have more practice with abstract reasoning?
- GitXiv links arXiv CS articles to github repositories. (H/t Paul Ginsparg. I guess my names just aren’t that original.)
- What Y Combinator companies want in developer hires. (Not good for academics…)
Nice advertisement for the Stellerator fusion experiment about to turn on in Germany.
- On the historical fixation and dispersal of medical knowledge about scurvy.
“What Makes Geeks Tick? A Study of Stack Overflow Careers” by Lei Xu
Many online platforms such as Yahoo! Answers and GitHub rely on users to voluntarily provide content. What motivates users to contribute content for free however is not well understood. In this paper, we use a revealed preference approach to show that career concerns play an important role in user contributions to Stack Overflow, the largest online Q&A community. We investigate how activities that can enhance a user’s reputation vary before and after the user finds a new job. We contrast this with activities that do not help in enhancing a user’s reputation. After finding a new job, users contribute 25% less in reputation-generating activity on Stack Overflow. By contrast, they reduce their non-reputation-generating activity by only 8% after finding a new job. These findings suggest that users contribute to Stack Overflow in part because they perceive this as a way to improve future employment prospects. We provide direct evidence against alternative explanations such as integer constraints, skills mismatch, and dynamic selection effects. The results also suggest that, beyond altruism, career concerns play an important role in explaining voluntary contributions on Stack Overflow.
(H/t Tyler Cowen.)
- I am just now becoming aware of “mileage brokers“. This is apparently why many small 3rd party airline ticket booking services can offer such cheap flights, but are widely known for random cancelations and awful customer service. It’s unclear to me which 3rd party booking services are mileage brokers.
- There’s an arXiv for biology: Biorxiv. (H/t Steve Hsu.) Not sure what they bring to the table.
This link ticks several checkboxes on the social-media-content coolness scale: Training falcons with drones. Mostly it’s about teaching the birds to fly higher than they normally would by luring them. Here’s the lure being captured:
- GiveWell’s list of top charities has been updated. Same contenders, ranked this year and with new discussion about allocation and room for more funding. See also this good post, especially with regard to coordinating with other donors and dealing with incentive issues.
“The $75,000 problem for self-driving cars is going away“:
The cost of LIDAR, a key component of self-driving cars, is falling fast:
“Our customers are telling us they want it to be below $100, that’s kind of the roadmap we’re working from in the back of our mind,” Eggert said.
Velodyne is developing a sub-$500 LIDAR sensor, the VLP-32, that it says will be powerful enough for high-level assisted driving, and autonomous driving. (It declined to reveal exact technical specifications.) Velodyne has development contracts with two manufacturers, one in North America and one in Japan, to deliver the sensor in the first four months of 2016.
And the new sensor isn’t going to be a hulking piece of equipment either. It’s small enough that some players have expressed interest in putting the sensor in vehicle side mirrors. Others may put it on the roof, the easiest way to get a 360-degree view.
Quanergy chief executive Louay Edlada believes LIDAR will cost below $100 in five years. It’s releasing a solid state LIDAR — meaning none of the parts move — next month for $250.
- Nice concise article on the economics of hidden-city ticketing.
- Sour candy is made with sour sanding. Jeff Kaufman says just buy some, so I did.
- Will MacAskill rebuts lame criticism of Zuckerberg’s donation.
- Someone patented the general idea of including a “loading screen game”, i.e., a low-overhead game that the player plays while waiting for a main game to load from memory. The patent just expired. Can anyone possibly argue that this sort of patent incentivized research that otherwise wouldn’t have happened?
Visual comparison of bridge lengths, by main span:
Click for full-size, and then roll-over with your mouse. Golden Gate is orange (label in bottom left).
Cambridge secures large new grant from Leverhulme Trust to start center devoted to AI and future of humanity. Seán Ó hÉigeartaigh explains the connection to the Centre for Study of Existential Risk (CSER):
While this proposal was developed by us at CSER (with collaboration from the ‘spokes’ at FHI etc), it will operate as a standalone centre physically, administratively, and in terms of funding, although the centres will collaborate closely. None of the funding will go to CSER.
There will be some differences, namely:
– Leverhulme CFI is broader in its focus on AI, encompassing a broader look at long-term opportunities and challenges of AI (“puerto rico agenda”, if you will), rather than CSER’s somewhat tighter focus on AI safety/risk, although safe and beneficial development of AI will be at its core. It won’t focus on other technologies (unless related, like neuro).
– CSER is broader in its focus on risk, encompassing e.g. bio risk, extreme climate, and future threats.
The plan we’ll be working to will be to develop long-term secure funding for both.
- I didn’t know a rogue planet was identified with reasonable confidence back in 2012 and directly imaged in infrared.
- SciRate and PubPeer host commenting on academic papers. Will be very interesting to see if either can ever take off. (Old discussion from me.)
- “Google is ramping up hiring for its ambitious plan to make ‘energy kites’“.
Alternating tread stairs allow for extremely steep stairs without making the tops of each step too short. Fantastic lego model illustrating the idea:
- Even if this proposal for an alternate track drug approval process is net positive sum (probable but not obvious), people will die on a regular basis from drugs that are not effective. I am skeptical voters will allow that situation to persist.
“Why Our Theories of Innovation Fail Us” by Peter J. Denning, Nicholas Dew
Only 1 in 500 patents makes its inventor money, and businesses are awash in great ideas of dubious market value (only about 4% make money).1 So why do people think innovation begins with a creative idea, is sold through an imaginative story, and diffuses through society because of novelty and merit? Innovators mobilize people to adopt ideas. Although they might start with idea creation, innovators focus mostly on other aspects: market offers, market testing, beta prototyping, production, sales, and customer-support infrastructures that companies use to get products adopted. In fact, 90% of innovation is in fostering adoption.1,4 Ideas are often stories invented after the fact to explain innovations that already emerged, as with the iPhone example discussed later in this column. Yet the media telling of the story makes it sound as if ideation—the creation of ideas—is 90% of the work of innovation. Ideation has produced many inventions that never became innovations because no one adopted them. Many people are misled by stories that inaccurately equate innovation with invention. People who believe these stories put too little effort into adoption and are disappointed by their low success rates
(H/t Robin Hanson.)
- John Cochrane responds to Noah Smith on level effects vs. growth effects, with rebuttal by Smith. This is a good example where both arguers are pretty smart, but refuse to clean up their semantics and boil down arguments because they are too distracted by politics and posturing. Too bad.
Baboon matriarchies are serious business:
After the matriarch died last year, a vicious battle erupted among the female baboons at the Toronto Zoo for her throne that endured for months, prompting a brief closure of the exhibit and providing a fascinating glimpse into the animals’ behaviour.
Medical records show numerous injuries among five of the six female olive baboons, from deep lacerations near their eyes to hair ripped out and tail injuries. At least two required surgeries to close deep gashes.
The exhibit was closed for several days because “there were some injuries that we thought best to keep them at the back because our visiting public don’t know baboon behaviour,” said Maria Franke, the curator of mammals at the zoo.
The baboon house — the area not open to the public where the animals eat and sleep — also had to be modified to allow for more space and additional escape routes, Franke said.
Now, Dutton said, two females sit on the throne in an uncomfortable truce, with the rightful heir biding her time until the older one dies.
Baboons, both in the wild and at zoos, have societies that are run by females — and that dominance runs through family lines. So the oldest daughter of the matriarch is the rightful heir to become queen.
- Protecting dolphins and other “bycatch” from tuna fishing is a hairy affair.
- Nice post from 2012 by Michael Nielsen explaining key ideas in Judea Pearl’s Causality.
- Genetically modified salmon approved.
Back in March, astronomers found a system with multiple images due to gravitational lensing, where a supernova had gone off in one of the images but (due to a slightly longer light path) not the other. The full development of the supernova in the lagging images should be visible in 2016.
In 1964, Refsdal hypothesized that a supernova whose light traversed multiple paths around a strong gravitational lens could be used to measure the rate of cosmic expansion. We report the discovery of such a system. In Hubble Space Telescope imaging, we have found four images of a single supernova forming an Einstein cross configuration around a redshift z = 0.54 elliptical galaxy in the MACS J1149.6+2223 cluster. The cluster’s gravitational potential also creates multiple images of the z = 1.49 spiral supernova host galaxy, and a future appearance of the supernova elsewhere in the cluster field is expected. The magnifications and staggered arrivals of the supernova images probe the cosmic expansion rate, as well as the distribution of matter in the galaxy and cluster lenses.
Presumably this supernova is too far away to be useful for neutrinos or anything like that.
- Sea creature makes a thousand eyes from its shell. (H/t Tyler Cowen.)
Antibiotic resistance from animal husbandry.
The argument I hear against becoming overly worried about bacterial resistance induced by overuse of antibiotic is this: The cellular machinery bacteria must assemble to be resistant to antibiotics is metabolically costly. It’s true that the bacteria whose main environment is saturated with a certain antibiotic will eventually develop resistance, e.g. in bacteria moving from hospitalized human to hospitalized human, or bacterial living on farms which employ antibiotics. But as soon as you stop using the antibiotic routinely, the bacteria will naturally shed the resistant abilities because it’s energetically favorable to do so. (The article simply notes, without explanation: “In the end, though, VRSA turned out not to be much of a threat: In 15 years, there have been only 14 such infections in the United States.”)
One counterargument is this: assembling cellular machinery is indeed costly, but once the resistance mechanism has been cracked it’s relatively cheap to keep a copy of the instructions for doing so, either as some trace background level of plasmids, or as dormant DNA in bacteria that requires activations by external stressors from the antibiotic. Once the selection process, which is induced by rampant use of antibiotics, produces the instructions, these instructions can potentially lie dormant for very low cost. (A counter-counterargument is that even DNA has storage costs in the form of mutational load.)
I wish I knew how these argument are used by the experts, and whether there is consensus. I suspect that, like many similar policy concerns, this ultimately boils down to fights over how to wisely apply the precautionary principle.
Lots of articles recently about the centennial of general relativity showing an elderly Einstein when he had crazy grey hair and was just hanging around the IAS. Just remember that all the insights happened in his 20’s and early 30’s, when he looked like this:
- Megan McArdle: “How to Win Friends and Influence Refugee Policy“.
- I figure these ideas are well-worn to (and maybe mostly dismissed by) folks who think about the future of computational architecture, but this talk on robust, massively parallel, but inexact digital computation was interesting and accessible to an outsider like me. (Watch on 2x speed!) It seemed to me that, however robust his toy sorting machine was to the sorts of noise he had in mind, it relies crucially on finding rules for the microscopic elements that don’t create weird edge cases, get catastrophically stuck, etc. But maybe the idea is that you can use some strong method to prove theorems about safety properties of these microscopic elements, and then use those elements confidently to messily slap together complicated algorithms. (HN comments.)
- Cracked covers the ISIS magazine. All issues can be found here. (Warning: Some gruesome images.) The production value is very high. It’s generally chilling to read.
- Nasa orders SpaceX crew mission to ISS.
- Pigeon-guided bombs (an alternative to Kamikazes). This prompts a gruesome image-recognizer-as-a-resource sort of thinking: what are the smallest/cheapest/least-sentient brains out there that are capable of 3D guidance?
- Now possible to get a credit card that draws from a Bitcoin account. Note however the caveats in the HN comments.
I had not realized how dense Saturn’s rings are. I figured they only looked solid from far away, but up close there are miles and miles between rocks. (The asteroid belt, of course, has stupendously large distances between objects.) But the volume of many of Saturn’s rings are ~3% rock!
Compared with most other astronomical objects, the ice and rock particles in Saturn’s rings are extremely close together. On average, about 3 percent of the total volume of the disk is occupied by solid particles, while the rest is empty space. This may sound small, but it means the typical separation between particles is only a little over three times their average diameter. Assuming a value of 30 centimeters for the latter, the rocks would be as close as one meter away from each other. There is no hard and fast rule, however, due to density variations across the rings and the wide spectrum of particle sizes.
That mean’s that artistic depictions like this
are totally realistic! Rocks would range in size between dust grains and houses. The rings are between tens of meters to several kilometers thicks. If you were inside the ring, you would be weightless in a field of floating boulders. However, if you pushed off one and launched yourself on a slow trajectory out of the ring, you might rise above it, but then would slowly fall back down. The arc would take a few house (since ring orbit times are ~10 hours), and you would have a chance to stop your self by pushing off one of the boulders as you re-entered the ring.
- I only just recently found out that Stack Overflow is doing documentation.
- The techniques behind in-flight wifi.
The legendary Charlie Bennett describes the first working prototype of a quantum encryption device:
Charlie and John Smolin
Open Philanthropy Project looks to fund scientific policy think tank:
It appears to us that the strongest scientific funders have little interest in policy analysis and advocacy, while the strongest funders of policy analysis and advocacy tend not to take interest in the scientific research issues discussed in this post. We’re interested in the idea of combining – in a dedicated organization – great scientists and great policy analysts, in order to put in the substantial amount of work needed to develop and promote the best possible proposals for improving science policy and infrastructure. It would be a high-risk, potentially very high-return project to attempt. We aren’t aware of any attempts to do something along these lines at the moment, and we think it could be a risk worth taking.
So far, we haven’t been able to find a person or organization who seems both qualified and willing to lead the creation of the sort of organization described in this post. We plan to continue looking for such a person or organization, while continuing to discuss, refine and reflect on these ideas.
- Oldest known pants are 3,000 years old. Pants were invented for horse riding.
- Air Force Pilot Brian Udell’s First hand account of his F-15 ejection at 780 mph.
- The Space Doctor’s Big idea. (Einstein’s general relativity explained using the thousand most common words in the English language.)
Obviously the “default” subreddit are all well known, but its worth meditating on the fact that /r/photoshopbattles is a collaborative art form (and competition) which basically had no analog a couple of decades ago. Of course, there are many places on the internet that have been hosting this sort of process (Deviant Art comes to mind especially), but reddit is fully mainstream.
Another reddit phenomenon is the AMAs, especially for non-celebrities. I utterly take these for granted now, but less than a decade ago it was an absolute revelation to get detailed, first person perspective on what its like to be in uncountable different roles. Reading the guy describe being a subway sandwich maker was fascinating. Who knew that, with all the hassles, low pay, and low status, he said the one thing he still liked about the job after years was…making sandwiches!
Review of the DJI Phantom 3 drone, a consumer quadracopter for taking video.
These things are getting really impressive.
- “Worry about the culture people, not about the election.” This sort of result is behind my general skepticism of the overall importance of election campaigning. Although there are exceptions, I think of close election outcomes in winner-take-all settings are like the choice of when to tack in a sailboat. Tacking feels like a big change of direction, but actually the thing that matters is the overall heading. If you tack in one direction for a little longer, you’ll just end up compensating later. The thing you need to influence is the heading.
- The world’s worst password requirements list.
The Laser Geodynamics Satellites:
The spacecraft are aluminum-covered brass spheres with a diameter of 60 cm and masses of 400 and 411 kg, covered with 426 cube-corner retroreflectors, giving them the appearance of giant golf balls. 422 of the retroreflectors are made from fused silica glass, while the remaining 4 are made from germanium to obtain measurements in the infrared for experimental studies of reflectivity and satellite orientation. They have no on-board sensors or electronics, and are not attitude-controlled…They orbit at an altitude of 5,900 kilometres (3,700 mi), well above low earth orbit and well below geostationary orbit at orbital inclinations of 109.8 and 52.6 degrees…Measurements are made by transmitting pulsed laser beams from Earth ground stations to the satellites. The laser beams then return to Earth after hitting the reflecting surfaces; the travel times are precisely measured, permitting ground stations in different parts of the Earth to measure their separations to better than one inch in thousands of miles…The LAGEOS satellites make it possible to determine positions of points on the Earth with extremely high accuracy due to the stability of their orbits…The high mass-to-area ratio and the precise, stable (attitude-independent) geometry of the LAGEOS spacecraft, together with their extremely regular orbits, make these satellites the most precise position references available.
- Just enough about the various offices controlled by the Queen of England to make you sure you don’t want to learn more.
- How snowmaking works. (H/t Will Riedel.)
- The design of triage tags is a grim science.
- Introduction to protein folding for physicists [PDF].
Merry Christmas everyone! Here’s some holiday cheer from Boston Dynamics.
…something something, robot reindeer overlords…
LaTeX in commentsInclude [latexpage] to render LaTeX in comments. (More.)
- PhysWell (13)
- Comments on Weingarten's preferred branch (19)
- Jess Riedel (5) Unfortunately, I still don't think this is a great framing of the problem that... – Dec 22, 11:57 AM
- Jess Riedel (4) > The derivation of branching we agree remains an incomplete project... But for sure... – Dec 22, 11:56 AM
- Jess Riedel (3) I would very much like to read your 1973 preprint! Please re-consider uploading it.... – Dec 22, 11:55 AM
- Jess Riedel (2) > There is an ensemble of possible final states. I just reach my hand... – Dec 22, 11:55 AM
- Jess Riedel (1) > Construction of branches from environmentally induced decoherence... is intrinsically approximate and requires the... – Dec 22, 11:50 AM
- Don Weingarten Finally, I think you are right that my proposed account of the preferred basis problem... – Dec 17, 5:18 PM
- Don Weingarten 4) As far as eventual thermalization of everything, I pretty much agree with your list... – Dec 17, 5:06 PM
- Don Weingarten 3) Consistent histories: Ugh. A sore point. I think I am actually by some measure... – Dec 17, 5:02 PM
- Don Weingarten 2) Not sure I understand your point about adding entropy. There is an ensemble of... – Dec 17, 4:59 PM
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