In a stunningly original paper Gojko Barjamovic, Thomas Chaney, Kerem A. Coşar, and Ali Hortaçsu use the gravity model of trade to infer the location of lost cities from Bronze age Assyria! The simplest gravity model makes predictions about trade flows based on the sizes of cities and the distances between them.
Tag: science
SI Updates
The updated constants include
the Boltzmann constant (which relates temperature to energy), and
the Planck constant (which can relate mass to electromagnetic energy),
the charge of the electron and
the Avogadro constant (the quantity that defines one mole of a substance).“There are no dramatic changes. The Boltzmann constant is very consistent with earlier values. The temperature experts requested 8 digits for the constant and the last digit happened to be 0”.
The Planck constant has shifted downward by 15 parts per billion from its earlier value, due to new data collected since 2014. The Planck constant was determined by 2 experimental techniques, known as the Kibble balance and the Avogadro method. All of the measurements that were used for determining the new Planck value met previously agreed-upon international guidelines for levels of accuracy and consistency with one another.
The Planck constant can be used to define the kilogram, and using a fundamental constant for defining mass will solve many problems. Mass must be measured over a very large scale, from an atom to a pharmaceutical to a skyscraper. “At the low end, you currently use 1 type of physics to determine mass; at the high end, you use another type of physics”.
But the Planck constant will provide a consistent way for defining mass across all of these scales, with whatever laboratory method is used to measure mass.
The volt will change as well, since the Planck constant will also help to define it in the revised SI. A volt based purely on the fundamental constants will be very slightly smaller, ~100 parts per billion, than the current scientific realization of the volt, established in 1990. The top-level metrology labs will have to recalibrate their high-precision voltage measurements.
Learning by reproducing
Students taking Stanford’s Advanced Topics in Networking class have to select a networking research paper and reproduce a result from it as part of a 3-week pair project. At the end of the process, they publish their findings on the course’s public Reproducing Network Research blog. It’s well worth having a look around the blog: the students manage to achieve a lot in only 3 weeks! In the last 5 years, 200 students have reproduced results from 40 papers.
In ‘Learning networking by reproducing research results’ the authors explain how this reproduction project came to be part of the course, what happens when students try to reproduce research, and the many benefits the students get from the experience. It’s a wonderful and inspiring idea that I’m sure could be applied more broadly too.
Mass Extinction Overrated?
After decades of researching the impact that humans are having on animal and plant species around the world, Chris Thomas has a simple message: Cheer up. Yes, we’ve wiped out woolly mammoths and ground sloths, and are finishing off black rhinos and Siberian tigers, but the doom is not all gloom. Myriad species, thanks in large part to humans who inadvertently transport them around the world, have blossomed in new regions, mated with like species and formed new hybrids that have themselves gone forth and prospered. We’re talking mammals, birds, trees, insects, microbes—all your flora and fauna. “Virtually all countries and islands in the world have experienced substantial increases in the numbers of species that can be found in and on them,” writes Thomas in his new book, Inheritors of the Earth: How Nature Is Thriving in an Age of Extinction.
ML vulnerabilities
Identifying vulnerabilities in the ML model supply chain
we show that maliciously trained convolutional neural networks are easily backdoored; the resulting “BadNets” have state-of-the-art performance on regular inputs but misbehave on carefully crafted attacker-chosen inputs. Further, BadNets are stealthy, .i.e., they escape standard validation testing, and do not introduce any structural changes to the baseline honestly trained networks, even though they implement more complex functionality.
Floating aluminum
a form of aluminum that floats on water.
If you restructure aluminum at the molecular level, as Boldyrev and colleagues did using computational modeling, you could produce an ultra-light crystalline form of aluminum that’s lighter than water
Octopus City
A group of scientists discovered an underwater “octopus city” off the coast of Australia in Jervis Bay, and they’ve named it “Octlantis.” This discovery of octopuses interacting in a high-density den challenges scientists’ previously held belief that octopuses are solitary and antisocial creatures.
UV life
red dwarfs may not be as habitable as we thought, as they’re low on uv radiation, which is crucial for RNA formation
ultraviolet radiation may even have played a critical role in the emergence of life here on Earth. As such, determining how much UV radiation is produced by other types of stars could be one of the keys to finding evidence of life any planets that orbit them.
Nutrient collapse
rising co2 levels mess with plant nutrients, in a bad way.
Rising CO2 revs up photosynthesis, the process that helps plants transform sunlight to food. This makes plants grow, but it also leads to them pack in more carbohydrates like glucose at the expense of other nutrients that we depend on, like protein, iron and zinc.
Nanodrills
Researchers demonstrated single-molecule nanomachines that can target diseased cells and then kill them by drilling through the cell membrane. The single-molecule nanomotors are 1-billionth of a meter wide and spin at 3m rotations per second. They’re activated by ultraviolet light and could also be used to deliver drug treatment into the cells
Gregor J. Rothfuss 