Alexander S. Popov (1859-1905), Inventor of Radio (Soviet Union, USSR 1925)

Stamp Alexander S. Popov (1859-1905), Inventor of Radio it reflects the thematic directions:

Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe.Modern science is typically divided into two or three major branches: the natural sciences (e.g., physics, chemistry, and biology), which study the physical world; and the behavioural sciences (e.g., economics, psychology, and sociology), which study individuals and societies.The formal sciences (e.g., logic, mathematics, and theoretical computer science), which study formal systems governed by axioms and rules, are sometimes described as being sciences as well; however, they are often regarded as a separate field because they rely on deductive reasoning instead of the scientific method or empirical evidence as their main methodology. Applied sciences are disciplines that use scientific knowledge for practical purposes, such as engineering and medicine

Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates oscillating electrical energy, often characterized as a wave. They can be received by other antennas connected to a radio receiver, this is the fundamental principle of radio communication. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.