Braking trains can vaporize sand to create emergency grip

When a train driver slams on the brakes, the physics of the journey changes instantly from smooth gliding to a desperate fight for friction. Because steel rails are incredibly slick, engineers use a system called sanding to prevent the wheels from sliding like a puck on ice. In an emergency at 100 miles per hour, high-pressure nozzles blast a stream of specialized sand directly into the gap between the wheel and the track. The intense heat and pressure of the friction can actually vaporize some of these grains, creating a gritty, glass-like coating that helps the train grip the rail.