What does SOS mean? Who invented the radio?

We often see a telegraph operator in war movies, "beep, beep" sending a telegram. Many people also know that SOS is a distress signal. So, do you know the principle of the telegraph? Who contributed to the invention of the wireless telegraph? Why do people use SOS as a distress signal?

1. Maxwell: The predictor of electromagnetic waves

As we said before, Faraday discovered the phenomenon of electromagnetic induction, generated electric current through magnetic field, and invented the generator. But why does magnetic field generate electric current? Faraday did not think clearly. Because Faraday's family was poor when he was young, he dropped out of elementary school after only two years. His great achievements were achieved by relying on his love for science and hard work. Therefore, Faraday was not very strong in mathematics. He always liked to express physical laws in an image-based way, but it was difficult for him to use mathematical language to explain his great discoveries.

At this time, another great figure, Maxwell, came on the scene.

Maxwell

Maxwell was 40 years younger than Faraday. When he just graduated from Cambridge University at the age of 23, he read Faraday's scientific papers. He was attracted by Faraday's profound thoughts and determined to use mathematics to make up for Faraday's shortcomings. A year later, he published his first paper on electromagnetism and had an in-depth discussion with Faraday.

Faraday was a great scientist and a man of high character. He was particularly concerned about young scholars. He said to Maxwell: "Don't just explain my ideas with mathematics, but be innovative." With the encouragement of the older generation of scientific masters, Maxwell finally succeeded in proposing the Maxwell equations and became the greatest physicist between Newton and Einstein.

Maxwell thought: the formation of electric current is due to the movement of electric charges, and only electric fields can drive electric charges. He keenly felt that the changing magnetic field did not directly generate electric current, but generated an electric field in the surrounding space. If there was a conductor near the electric field, electric current would be formed.

Maxwell further thought that since electricity and magnetism are closely related, and a changing magnetic field can generate an electric field, then a changing electric field should also generate a magnetic field. For example, if we use alternating current to connect a capacitor consisting of two metal plates, a changing electric field will be generated in the capacitor because the voltage of the alternating current changes repeatedly.

What is even more amazing is that if the magnetic field generated by the changing electric field is still changing, it will further generate an electric field. In this way, the oscillating electric and magnetic fields can excite each other and propagate far away, forming a wave-like substance named electromagnetic wave.

Maxwell calculated the speed of electromagnetic waves, which was exactly the same as the speed of light, so he boldly predicted that light is a kind of electromagnetic wave. Unfortunately, he did not personally confirm his prediction of electromagnetic waves. In 1879, Maxwell died of illness in Cambridge at the age of 48. In that year, Einstein, the greatest scientist of the 20th century, was born.

2. Hertz: Experimental confirmation of electromagnetic waves

The scientific baton was passed to German scientist Heinrich Rudolf Hertz.

Heinrich Rudolf Hertz

When Hertz was studying at the University of Berlin, he studied Maxwell's electromagnetic theory under the guidance of his mentor Helmholtz, and was determined to use experiments to confirm Maxwell's views. In 1888, Hertz designed a set of experimental equipment and carefully studied the wavelength, frequency and other information of this wave. He concluded that the speed of this wave is equal to the speed of light, which is completely consistent with Maxwell's prediction. So far, electromagnetic waves have been completely confirmed by people. Hertz's experiment not only confirmed Maxwell's electromagnetic theory, but also found a way for the development of radio, television and radar. The mobile phones that we can't live without today are transmitted through electromagnetic waves.

There are many advantages to using radio to transmit signals. For example, mechanical waves cannot propagate in a vacuum. If we shout in the universe, others cannot hear us. However, electromagnetic waves can be transmitted in a vacuum. Therefore, astronauts on the moon need to use radio communication even if they are very close. Radio signals are transmitted very quickly. If we shout a sentence from New York, even if it is transmitted unimpeded, it will take nine hours for people in Beijing to hear it. However, the transmission speed of radio is the speed of light, and it can be transmitted around the world in almost an instant. Moreover, electrical signals are easier to amplify and process information than mechanical signals. Since the day when electromagnetic waves were discovered, people have been studying how to use radio for communication.

3. The invention of wireless telegraphy

Before the discovery of electromagnetic waves, people had already used wired telegraphs. However, this method faced many problems such as laying wires and maintenance, so wireless telegraphs were put on the agenda by many scientists and businessmen. There are three scientists who contributed to the invention of wireless telegraphs: American-Serbian scientist Nikola Tesla, Italian scientist Marconi, and Russian scientist Popov.

In 1893, Nikola Tesla demonstrated radio communication for the first time in St. Louis, Missouri, and obtained a patent for radio technology in the United States in 1897. However, the U.S. Patent Office revoked his patent in 1904. This move is said to be because Tesla was too obsessed with his dream of transmitting electrical energy wirelessly for the benefit of mankind, and ignored the urgent need for wireless telegraphy by capitalists, such as Thomas Edison, Andrew Carnegie, and Morgan, so they cast an olive branch on a new scientist, the Italian Marconi.

In 1901, the radio message sent by Marconi successfully crossed the Atlantic Ocean from England to Newfoundland, Canada. In 1909, radio was used for the first time. A steamship was destroyed by a collision and sank to the bottom of the sea. Thanks to the radio, most of the crew were rescued. In the same year, Marconi won the Nobel Prize and became known to the world as the father of radio.

At almost the same time, Russian scientist Popov also invented a radio device - the radio. He also installed an antenna on the radio, which was the first antenna in human history. In 1896, Popov officially transmitted a message by radio at the annual meeting of the Russian Physical and Chemical Society. The content of the message was "Heinrich Hertz" to show respect for Hertz.

Different countries have different opinions on who invented radio first. Even in one country, opinions change repeatedly. For example, although the United States revoked Tesla's patent in 1904 and awarded it to Marconi, decades later in 1943, the U.S. Supreme Court revoked Marconi's patent and still ruled that Tesla was the inventor of radio. In any case, they are both great scientists who have provided unlimited convenience to our world.

4. Morse Code

The basic principle of wireless telegraphy is very simple. When the transmitter is powered on, a long or short electromagnetic pulse is generated. After the electromagnetic wave propagates to the receiving end, it is detected by the receiver. The initial radio signals were transmitted in the form of Morse code. This is because Morse code encodes English letters and numbers into two states: dots and lines. The encoding is simple and easy to transmit. We often see the telegraph operator in war movies pressing buttons "beep beep beep", which is the use of Morse code to send telegrams.

The familiar distress signal SOS itself has no meaning, but because it is very simple in Morse code, three dots, three lines, and three dots, the International Radiotelegraph Convention Organization has made it an international distress signal.

The telegraph operator first converted the information into Morse code, and then sent out long and short radio signals according to certain rules through a telegraph device similar to the one used in Hertz's experiment. The receiver used the same device to receive the signal, and then manually converted the signal code into text information. Obviously, this method of transmitting information is not very efficient, but 100 years ago, it was already the most advanced communication method. In the 20th century, to send a telegram, one had to queue up in the telegraph building, and the fee was charged by the number of words, so the content had to be written as simply as possible.

Until the end of the 20th century, some areas in my country were still using telegraphs for communication. After entering the 21st century, with the popularization of telephones, the Internet and other communication methods, telegraphs gradually withdrew from the field of civilian communications.

Today, Morse code and wireless telegraphy have become toys for some hobbyists, and some people feel very fashionable when using Morse code to communicate.

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Source: Mr. Li Yongle