On this day, 138 years ago, March 21, 1887 (February 27, 1887 in the lunar calendar), the existence of electromagnetic waves was confirmed by Hertz, marking a new era of radio communications. On March 21, 1887, the German physicist Hertz confirmed the existence of electromagnetic waves in experiments, leading to the birth of radio and opening up a new era of electronic technology. This marked the transition from "wired electrical communication" to "radio communication". On November 5, 1887, Hertz summarized this important discovery in a paper sent to Helmholtz entitled "On Induction Phenomena Caused by Electrical Processes in Insulators." Then, Hertz also confirmed through experiments that electromagnetic waves are transverse waves and have similar characteristics to light, such as reflection, refraction, diffraction, etc., and experimented with the interference of two rows of electromagnetic waves. At the same time, he confirmed that when traveling in a straight line, the propagation speed of electromagnetic waves is the same as the speed of light, thus comprehensively verifying the correctness of Maxwell's electromagnetic theory. It further improved the Maxwell equations to make it more beautiful and symmetrical, and obtained the modern form of the Maxwell equations. In addition, Hertz conducted a series of experiments. He studied the effect of ultraviolet light on spark discharges and discovered the photoelectric effect, which means that electrons are released from objects under the illumination of light. This discovery later became the basis for Einstein to establish the quantum theory of light. Heinrich Rudolf Hertz (February 22, 1857-January 1, 1894) German physicist who first confirmed the existence of radio waves in 1888. He also made great contributions to electromagnetism, so Hertz, the international unit of frequency, was named after him. He was attracted by optical and mechanical experiments as early as a teenager. At the age of 19, he entered the Dresden Institute of Technology to study engineering. Due to his hobby of natural sciences, he transferred to the University of Berlin the following year and studied under the guidance of Helmholtz, professor of physics. In 1885, he was appointed professor of physics at the University of Karlruhe. In 1889, he succeeded Clausius as professor of physics at the University of Bonn until his death. Hertz's greatest contribution to mankind was to experimentally confirm the existence of electromagnetic waves.