Birth of the radio

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Issue Time: Nov 23,2019

Summary

Radio, short for radio technology, is a technical discipline that specializes in the use of radio waves to transmit a variety of information. As early as 2,000 years ago, people discovered electrical and magnetic phenomena. China invented Sinan as early as the Warring States Period (475-211 BC). The true understanding and widespread application of electricity and magnetism by humans has only been more than one hundred years old. Under the impetus of the first industrial revolution, many scientists have made in-depth and meticulous research on electrical and magnetic phenomena, and thus made significant progress. It has been found that charged objects repel each other and attract opposite sex, which is similar to magnetic phenomena. In 1785, the French physicist Coulomb put forward the "Coulomb's law" that later generations called on the basis of summing up the predecessors' understanding of electromagnetic phenomena, which unified the phenomenon of electricity and magnetism. In 1800, the Italian physicist Volt developed a chemical battery and obtained a continuous battery by manual method, which created important conditions for future generations to study the relationship between electricity and magnetism. In 1822, on the basis of a lot of work done by the predecessors, the British Faraday proposed the law of electromagnetic induction, which proved that "magnetic" can produce "electricity", which laid the foundation for the principle of generators and motors. The research on the basic laws of electromagnetism made by scientists during this time played an important role in the birth of radio. The development of electromagnetics first caused a revolution in communication methods. In 1837, the American painter Morse designed a more practical telegraph machine to transmit information on the basis of his predecessors. Later, he established the world's first telegraph line between Washington and Baltimore. In 1876, Bell of the United States invented the telephone and realized the earliest analog communication of human beings. After 1880, the use of cable telegraphs and wired telephones to transmit information has begun to be applied, and humans have entered the era of wired and electronic communications. On the basis of summing up the work of the predecessors, Maxwell of the United Kingdom proposed a complete "electromagnetic theory", which is represented by four differential equations. This is what the later generations call "Maxwell's equations." Maxwell concluded that the moving charge can generate electromagnetic radiation, forming an invisible electromagnetic wave that gradually spreads outward. Although he did not put forward the term "radio", his electromagnetic theory has already told people that "electricity" can be spread "wirelessly". In 1887, the German physicist Herz was the first to artificially generate electromagnetic waves, and experimentally confirmed the existence of electromagnetic waves. Italy's Marconi and Russia's Popov obtained radio communication success in different countries at almost the same time (1895 and 1896). Their creative labor opened a new chapter in the development of electromagnetics, radio. Technology has been born as a new science.

Today, radio and television, which use radio waves to transmit sound and image programs, have penetrated into every corner of social life and become a companion to hundreds of millions of people. Radio was not invented by one or two people. It was the result of the gradual development of human civilization. However, some people played a more important role in it. The reason why Maxwell was called the primula of radio communication was because at that time, people already knew that "electricity" could produce "magnetic", "magnetic" could produce "electricity"; knowing to use electromagnetic principle to make motors and transformers; The nature of the relationship between electricity and magnetism is still unclear. For electromagnetic waves that exist with certain electrical and magnetic phenomena, it is not known. Maxwell is a very outstanding electromagnetic theorist. On the basis of summing up the experience of the predecessors, he used a very incisive and subtle mathematical equation to clarify the basic relationship between the electric field and the magnetic field, and established a rigorous electromagnetic field theory. Based on his mathematical analysis, Maxwell pointed out that as long as there is an alternating electric field, an alternating magnetic field can be generated around it; conversely, as long as there is an alternating magnetic field, an alternating electric field can be generated around it. In this way, the changing electric field produces a changing magnetic field around it, and the changing magnetic field generates a changing electric field in the vicinity. If so, will the electric field and the magnetic field not pass further and further? According to this, Maxwell believes that the moving charge can generate electromagnetic radiation, forming an invisible electromagnetic wave (referred to as electric wave) that gradually spreads outward. This conclusion was published more than a hundred years ago. This conclusion tells people that "electricity" can be spread "wirelessly." Later facts proved that Maxwell's electromagnetic wave theory is completely correct. In addition, he also derived that electromagnetic waves have the same propagation speed as light waves, thus revealing the intrinsic uniformity of light and electromagnetic phenomena.