He thinks that changing electric field will excite magnetic field, and changing magnetic field will excite electric field. This constantly changing electric and magnetic field constitutes an electromagnetic field, which propagates in space in the form of shear waves, which is what we now call electromagnetic waves. In addition, Maxwell also found that the speed of light and electromagnetic waves is almost the same. So he predicted that light itself is electromagnetic wave.
He designed an oscillating circuit, which can periodically generate electric sparks between two metal balls. According to Maxwell's theory, as long as there is an electric spark, there should be electromagnetic waves. So, in order to check whether there is electromagnetic wave, he designed a notched metal ring.
As a result, sparks did appear at the gap, indicating that electromagnetic waves did come out. This proves Maxwell's theory and Hertz's experiment has become one of the most important scientific experiments in the history of physics.
You know, light travels in a straight line in a vacuum, and light itself is an electromagnetic wave, so electromagnetic waves also have such properties. Hertz's discovery also opened a new world. Scientists began to think: can information be transmitted by electromagnetic waves, so as to realize wireless communication?
Between 1890 and 1900, several inventors made different types of radio devices, namely Loki, Tesla, popov and Marconi.
Rocky found inspiration according to Hertz's experimental circuit and made an electromagnetic wave receiver, which can receive electromagnetic wave signals 800 meters away.
Russian physicist popov also independently invented the radio communication device and gave a performance in March 1896. As for Tesla, he put forward the concept of radio communication and began to put it into practice, but at that time he was more keen on wireless power generation technology. Tesla's investors found that Tesla used the concept of "radio communication" for investment, but used it for other projects. Therefore, he refused to provide financial support for Tesla.
The first three failed to popularize radio communication on a large scale in the end. You know, the first inventor is generally unknown, but the person who popularized this invention is often immortal. Morse, who invented the telegraph, Bell, who invented the telephone, and Edison, who invented the electric light, were not the first inventors, but they commercialized these inventions on a large scale. Therefore, history remembered their names, but did not remember the names of the first inventors.
Marconi was the man who realized the large-scale popularization of radio communication. In this issue, we focus on Marconi.
Marconi was also particularly keen on inventing radio communication devices, and his ideas also came from Hertz's experiments. For radio communication technology, the problem to be solved is actually: how to carry out long-distance communication.
Hertz equipment can solve short-distance radio communication, while Loki and popov can limit radio communication to1000 m.. But 1000 meter is too short to be used at all. Marconi's solution to radio communication mainly focuses on improving the experimental device of Hertz, especially at the transmitter and receiver.
After many failures, Marconi's radio transmission distance gradually increased. 1894 can only transmit 3 meters, and 1895 exceeds 1000 meters. Marconi also made a metal dust detector, which installed an antenna and a bottom line on both the transmitter and the receiver, which really greatly improved the efficiency. At 1896, the transmission distance has exceeded14km.
Later, he submitted a patent application to the Italian Patent Office, and the result was unsuccessful. He went to England to apply for profit transfer. That is, in this year, Marconi, who was only 22 years old, got the telegraph patent application number 12039, which also attracted a lot of investment. Subsequently, Marconi began to improve the technology, increasing the height of the antenna through balloons and kites, and improving the efficiency of transmitting and receiving signals.
By 1897, Marconi had been able to achieve radio communication across the English Channel. And founded Marconi wireless telegraph company. At this time, he was only 23 years old.
By 1900, Marconi had achieved transatlantic radio communication. Subsequently, he began to seek development in the United States, won the support of the commercial group that had previously invested in Tesla, and obtained a patent to start large-scale development of radio communication in the United States.
In fact, this achievement is inseparable from his persistent improvement of technology. He not only improved the detector, but also improved the antenna technology from the original metal powder detector to the ore detector to receive radio waves.
This is why all the antennas we see now are integrated, also called vertically polarized antennas.
In fact, the early antenna was two metal rods extended from the spark discharge device designed by Hertz in the experiment.
Secondly, radios will interfere with each other. In order to solve this problem, Marconi introduced the resonant circuit.
Marconi also found that the effect of radio transmission at night is far better than that during the day, and there is no obstacle to the transmission length. But he didn't know the specific reason at that time.
In 1906, Marconi has been able to realize radio communication near 10000 km. Marconi's radio communication has been used in shipping and military, and there are many radio stations in some countries.
1909, Marconi won the Nobel Prize in Physics for his contribution to radio communication.
After that, Marconi constantly improved the radio communication technology, among which in 19 12, the world's largest means of transportation at that time: Titanic. This huge cruise ship is equipped with radio communication equipment and telegraph operators provided by Marconi Company.
Before the invention of wireless telegraph, the voyage of a ship was actually a bet with nature, and the crew lost contact during the voyage. During the slow voyage, the crew had no means of communication to communicate with people on the mainland. It was not until the ship returned to the shore that people knew that it had arrived smoothly.
Titanic sailed this time and never came back. After the shipwreck accident, the operator informed the nearby ships to come to the rescue by radio communication, and finally 7 10 passengers were rescued.
The role of radio communication amazed people of that era, especially after the sinking of Titanic, people felt the importance of radio communication more and more. The Times even published this comment:
However, in Marconi's time, radio communication mainly relied on Morse code.
At that time, Marconi predicted that radio communication would develop into two-way communication in the future. Later mobile phones, even the smart phones we use now, actually confirmed his prediction.