Premium Physics Channel 2022-01-18 07:11
The birth of electromagnetic waves is the electric spark that ignites human civilization, and communication technology serves human society.
In the first issue of the mainland's first popular science program in the field of communications, "Communication Letter", presented by Science and Technology Daily, the World 5G Conference, and the Future Mobile Communication Forum, Cao Zexian, a researcher at the Institute of Physics of the Chinese Academy of Sciences, burned an interesting historical story.
Whether it is the close communication of body language such as eyes, or the long-distance communication of voices and official stations, or the transmission of more specific information such as fireworks and flags, since ancient times, communication has been the main means of production and life of human beings, and some ways are still used until now, such as flag language.
Cao Zexian said: "Don't think how smart today's communication methods are, before the use of electromagnetic waves, human beings have developed a set of quite effective and ingenious communication methods, from communication modes, coding, the use of carriers, to how to keep secrets and other elements, there should be some." ”
Nevertheless, the birth of electromagnetic waves is the electric spark that ignites human civilization, and communication technology serves mankind and society.
In the course of this history, how were the phenomena of electricity and magnetism discovered?
The discovery of static electricity originated from ancient Greek noblewomen wearing satin clothes to smoke cats at home.
Around 1600, a man named William Gilbert coined the word electricus.
Just as volts are the unit of measurement of electromotive force, the unit of measurement of magnetodynamic potential is Gilbert, from which it can be seen that Gilbert is extraordinary, and his great magnetic study "DeMagnett", for the first time reasonably explains the mysterious ability of the compass to point north and south, revealing that the earth itself is a large magnetic field.
The discovery of magnetism should be attributed to a sheep herding baby in Syria today, when he carried the bottom end of the iron-wrapped stick full of sheep, found that the stick poked some stones for nothing, poked some stones but pulled up hard.
In 1831, after Michael Faraday verified the "electromagnetic induction phenomenon", it was recognized that electricity and magnetism are one, and electricity produces magnetism, and magnetism can also produce electricity.
Cao Zexian said: "That is to say, without relying on batteries, let the water flow push a coil in the magnetic field, or tie a donkey to rotate there, you can continue to generate electricity." ”
That year, James Clark Maxwell was born with a historical mission, and the theory of electromagnetic fields he established unified electricity, magnetism, and optics. Radio technology for the benefit of mankind was developed on the basis of electromagnetic field theory.
With the original intention of "providing a mathematical basis" for Faraday's theory, Maxwell listed a system of quaternions that expressed the basic laws of electromagnetism, accurately depicted the characteristics of electromagnetic fields and the relationship between their interactions, and summarized the chaotic phenomena into a unified and complete theory. Since then, the British scientist Tate has simplified Maxwell's equations, which are not simple, and it has become what we see in textbooks.
In 1865, Maxwell predicted the existence of electromagnetic waves, deduced that electromagnetic waves travel at a speed equal to the speed of light, and concluded that light is a form of electromagnetic waves that reveals the connection between light phenomena and electromagnetic phenomena.
In 1887, the god-level genius Heinrich Rudolf Hertz did such an experiment, a wire of zinc metal at both ends of the zinc metal ball, press the switch, the metal ball snapped and fired, in the distance, the same device also ignited in the air.
"Running between the two sets of devices is an electromagnetic wave derived from Maxwell's equations." Cao Zexian said, "This simple circuit is the starting point of our modern physics, and it is a great device that affects our human beings." ”
In 1888, Hertz published experiments to verify the existence of electromagnetic waves. The electromagnetic theory, pioneered by Faraday and summarized by Maxwell, has thus achieved a decisive victory.
Hertz did not expect that his achievements would usher in a new era of radio electronics technology, as Cao Zexian said, "What kind of major results will be produced by scientific discoveries, many times there is a window paper, and someone will have to break it." ”
After the success of the experiment, Hertz's assistant once asked him: "Your experiment seems to have a great impact, what is its significance?" What else is there to use? ”
Hertz said: "Probably really useless. Proof that Maxwell was great is the significance of this experiment. ”
When galiermo Marconi, a young boy traveling in the Alps, heard the news of the results of this experiment, his heart giggled a little, and Marconi, who was only fourteen or fifteen years old at that time, realized the landing value of this experiment, electromagnetic waves can transmit information, and the switch that produces electric sparks is the prototype of the telegraph machine.
A few years later, Marconi proved that these invisible light waves could be used for radio communications, and radio came along with it.
Cao Zexian said: "The well-being of today's high-level communication technology to mankind depends on the step-by-step promotion of basic sciences such as physics and mathematics. ”
Source: Science and Technology Daily