Now I get to do something with that force scale I built. I had a request some time ago to talk about friction. Friction is surprisingly complicated. When two surfaces rub against each other, why is ...

Without the force called friction, cars would skid off the roadway, humans couldn't stride down the sidewalk, and objects would tumble off your kitchen counter and onto the floor. Even so, how ...

This article has been updated to include comments from Raymond Goldstein and Patrick Warren. It is a mathematical puzzle that stumped Galileo, but researchers in France think they have discovered how ...