The death of Heike Kamerlingh Onnes (Dutch physicist) occurred on February 21, 1926. Onnes was one of the most prominent Dutch physicists, internationally recognized for his discovery of superconductivity and for successfully liquefying helium. He was awarded the Nobel Prize in Physics in 1913 for his pioneering research in the field of low-temperature physics. Born in Groningen, Netherlands, Onnes spent most of his professional life at Leiden University. In 1908, he became the first scientist to liquefy helium, reaching a temperature of 4.2 Kelvin, which paved the way for further research in low-temperature physics. In 1911, he discovered the phenomenon of superconductivity, a state in which certain materials exhibit zero electrical resistance at extremely low temperatures. This discovery had a profound impact on the development of modern technology and scientific research. Onnes's death on February 21, 1926, marked the end of the career of one of the pioneers of experimental physics. His memory remains alive in the global scientific community, and his achievements continue to inspire future generations of researchers. This date was officially designated in the Gregorian calendar to honor Onnes's significant role in the advancement of physics.
