Promotional image of smartphone app.

In late December, Google and Apple removed the ToTok social messaging app from their marketplaces after US intelligence officials told The New York Times it was a tool for surreptitious spying by the United Arab Emirates government. About a week later, Google reinstated the Android version of the app with no explanation, a move that confounded app users and security experts. Now Google has once again baffled industry watchers by once again banishing the app without saying why. (Apple, meanwhile, has continued to keep the iOS version of ToTok out of the App Store.)

Over the past few days, Play

Wok tossing has long been suspected of causing the high shoulder injury rate among Chinese chefs.
Enlarge / Wok tossing has long been suspected of causing the high shoulder injury rate among Chinese chefs.

Hunting Ko and David Hu/Georgia Tech

Fried rice is a classic dish in pretty much every Chinese restaurant, and the strenuous process of tossing the rice in a wok over high heat is key to producing the perfect final product. There’s always chemistry involved in cooking, but there’s also a fair amount of physics. Scientists at the Georgia Institute of Technology have devised a model for the kinematics of wok-tossing to explain how it produces fried rice that is nicely browned but

top floor of test house
Enlarge / The top floor of our test house is relatively straightforward—although like many houses, it suffers from terrible router placement nowhere near its center.

Jim Salter

Here at Ars, we’ve spent a lot of time covering how Wi-Fi works, which kits perform the best, and how upcoming standards will affect you. Today, we’re going to go a little more basic: we’re going to teach you how to figure out how many Wi-Fi access points (APs) you need, and where to put them.

These rules apply whether we’re talking about a single Wi-Fi router, a mesh kit like Eero, Plume,