Month: June 2020

Enlarge / Police using facial recognition software could possibly identify thousands of Americans nationwide as participants in protests against police brutality and overreach. Including this group in Minneapolis, Minnesota, on June 5. (credit: Scott Olson | Getty Images)

Secretive facial-recognition firm Clearview AI is facing new questions from lawmakers, in addition to lawsuits, as concerns about its software are amplified during the wave of nationwide protests against police brutality.

Sen. Edward Markey (D-Mass.) today demanded to know what law enforcement agencies are working with Clearview potentially to identify protesters who are out in support of black communities and against police violence. "As demonstrators across the country exercise their First Amendment rights by protesting racial injustice, it is important that law enforcement does not use technological tools to stifle free speech or endanger the public," Markey wrote in a letter to Clearview (PDF). "The risk of such omnipresent surveillance also runs the risk of deterring Americans from speaking out."

Law enforcement agencies in several cities where protests have taken place are using digital surveillance tools. According to a BuzzFeed report, many law enforcement agencies in and near Minneapolis—where current national protests began after police were recorded killing George Floyd—use Clearview and other similar platforms to identify individuals.

Enlarge / This was the Cassini spacecraft's view of Saturn's polar hexagon in 2014. (credit: NASA)

Ever since Voyager 2 revealed Saturn’s unique hexagon-shaped clouds at its north pole, the feature has been a puzzle, and the search for a combination of factors responsible has included computer modeling as well as physical modeling with things like rotating tanks of fluid.

Most ideas have centered around (pun intended) a phenomenon known as “Rossby waves.” The meanders of Earth’s jet streams are a familiar example of this phenomenon. And, in various experiments, researchers have gotten Rossby waves to stabilize in a hexagonal pattern in conditions meant to relate to Saturn’s pole.

But Harvard’s Rakesh Yadav and Jeremy Bloxham felt these studies were a little shallow—not in a pejorative sense, but literally. On Earth, it’s easy enough to decide how to size an atmospheric model, because it’s very clear that it stops at the surface. For Saturn, it’s a little more debatable how thick you need to make your model to represent the behavior of the giant planet’s outer atmosphere. The researchers wanted their simulation to extend deeper to see what kind of impact convection from below would have.

Enlarge / Lab technician setting fire to a ball with hydrogen blowtorch. (credit: JohnAlexandr | Getty Images)

Hydrogen is not your friend. This was the first lesson I learned when I sent a PhD student off to study hydrogen reactions on a surface. Hydrogen is explosive over a huge range of concentrations, making even the tiniest leak an invitation to study the joys of high-velocity stainless steel, with an added bonus of third-degree burns. I’ve now learned that the situation is actually worse than I thought, because hydrogen is also able to burn in very confined spaces as well.

Fire needs three things: fuel, oxygen, and heat. If you have a well-mixed fuel-oxygen combination, the first two aren’t going to be a problem, so you just need to add heat. When ignition is sparked off, the fuel and oxygen are quickly exhausted locally, so a front of combustion will expand outward from the ignition point, consuming the fuel and oxygen as it goes. For that expansion to take place, the heat generated from combustion must be transferred outward with the flame front, otherwise the gas will not be hot enough to ignite.

In a large space, this is not a problem, because gases don’t take much energy to heat up. In a confined space, though, the walls start to play a role. Energy will go into heating the walls, but the wall temperature may never get above the ignition temperature of the gas. So, if the walls are close enough, a spark will not result in a propagating flame front; instead, the flame dies locally. For hydrogen, though, the story turns out to be a bit more complicated.