What is pelican crossing in the UK? Answer by Yīng Míng | 赵英明, London "Black Cab" driver: "Pelican Crossings were introduced to solve the "flashing amber" problem, and replaced the Belisha Beacons with a pair of traffic lights controlled by a button box on the support pole."

When are polynomials ever used in the real world? Answer by Senia Sheydvasser, PhD in Mathematics: "Let's talk about knots, polynomials, quantum mechanics, and money."

Can someone help me intuitively understand how a wave function works and the role of probability in quantum mechanics? Answer by Mark John Fernee: "I think that one of the primary questions to answer is, why is the wavefunction necessary? The short answer is: Interference."

Can you describe what Rwanda was like before it was occupied by Germany during the colonial era? Answer by Stephen Tempest, MA in Modern History: "Control of cattle was central to socioeconomic status in the Kingdom of Rwanda."

Why are logic errors more difficult to fix than syntax errors? Answer by Joe Zbiciak: "To most folks, it looks relatively normal, although you might vaguely sense something is off..."