The Hidden Physics Behind Umbrellas, Springs, and Superconductivity

Umbrellas rely on a metal spring hidden inside the main rod, which consists of multiple cylinders that open up in succession when you press a button. This spring acts as a mechanical battery to store mechanical energy when compressed. British physicist Robert Hooke discovered 350 years ago that the force exerted by a compressed spring depends on how much it is compressed, a relationship known today as Hooke's law. Spring strength is measured in newtons per millimetre, or N/mm, where a newton equals the force of a medium-sized apple. While a battery socket spring handles about 1 N/mm, larger springs in train and metro rail coaches reach strengths of hundreds of N/mm to stabilise rides over uneven terrain. At an atomic level, the elastic force created by springs is secretly an electromagnetic force driven by positively charged nuclei and negatively charged electrons. When materials are pushed, positively charged atomic nuclei come closer than normal and push back against each other. When metals are cooled to very low temperatures, atoms can help create an attraction between two negatively charged electrons, forming a Cooper pair named after U.S. physicist Leon Cooper who won a 1972 Nobel Prize for the discovery. This electron pairing leads to superconductivity, where a metal conducts electric currents without any resistance. Aluminium becomes a superconductor at minus 271.9 degrees Celsius, though scientists still study the phenomenon within quantum condensed matter physics.