In 1864, Maxwell proposed Maxwell's equations. He unified "electricity" and "magnetism".
He believes that the changing electric field will stimulate the magnetic field, the changing magnetic field will stimulate the electric field, this changing electric field and magnetic field constitute an electromagnetic field, in the form of transverse waves in space, that is, we now call electromagnetic waves In addition, Maxwell also found that the speed of light and the speed of electromagnetic waves are almost the same. So he predicted that light itself was an electromagnetic wave.
In 1886, Hertz wanted to experimentally test Maxwell's theory.
He designed an oscillating circuit that would cause an electric spark to periodically emit between two metal balls. According to Maxwell's theory, as long as there is an electric spark, there should be electromagnetic waves emitted, so in order to check whether there are electromagnetic waves, he designed a notched metal ring.
As a result, there was indeed a spark at the gap, which indicated that electromagnetic waves were indeed emitted. It proved Maxwell's theory, and Hertz's experiment became one of the most important scientific experiments in the history of physics.
<h1>Wireless communication</h1>
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 up a new world. Scientists began to think: is it possible to transmit information through electromagnetic waves, so that wireless communication can not be achieved?
Between 1890 and 1900, several inventors made different types of radio devices: Rocky, Tesla, Popov, and Marconi.
Among them, Rocky found inspiration from Hertz's experimental circuit from Hertz and made an electromagnetic wave receiver capable of receiving electromagnetic wave signals from 800 meters away.
The Russian physicist Popov also invented radio communication devices independently and gave a performance in March 1896. As for Tesla, he proposed the concept of radio communication and began to implement it, but at that time he was more enthusiastic about wireless power generation technology, and Tesla's investors found that Tesla invested in the concept of "radio communication" but used it for other projects. As a result, he refused to provide further financial support for Tesla.
None of the first three were able to replicate radio communications on a large scale. We need to know that in general, the first inventor is not known, but the people who made this invention popular are 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 made these inventions commercialized on a large scale. So history remembers their names, but not the names of the first inventors.
The person who achieved the large-scale promotion of radio communications was Marconi, and in this issue we mainly revolve around Marconi.
Marconi was born on April 25, 1874, in Bologna, Italy, home to one of the oldest universities in the world: the University of Bologna. Later, Marconi also became the pride of the University of Bologna.
At that time, Marconi's parents hired Marconi with a tutor named Augusto Rigi. He was a physicist and a pioneer in electromagnetism at the time. A private laboratory was established in Bologna.
Educated by Augusto Riggy, Marconi learned about electromagnetic theory. Augusto Rigi and Marconi have been in touch ever since. He continued to teach Marconi about the development of cutting-edge electromagnetic theory.
Marconi was particularly enthusiastic about inventing radio communication devices, and his ideas came from Hertz's experiments. For radio communication technology, the actual problem to be solved is: how to communicate over long distances.
Hertz's device can solve radio communications over short distances, while both Lodge and Popov can limit radio communication up to 1,000 meters. But 1,000 meters is simply too short to be enough. Marconi's solution to radio communications also focused on improving hertz experimental devices, especially at the sending and pick-up ends.
After repeated failures, Marconi's radio transmission distance slowly grew, in 1894, it could only transmit 3 meters, and by 1895 it exceeded 1000 meters. Marconi also made metal dust detectors, and installed antennas and bottom lines on both the transmitter and receivers, which really greatly improved efficiency, and by 1896, the transmission distance had exceeded 14 kilometers.
Later, he filed a patent application with the Italian Patent Office, which was unsuccessful. He went to England to apply for a fortune, and that was the year that the 22-year-old Marconi got his telegraph patent application numbered 12039 and attracted a lot of investment. Subsequently, Marconi began to improve the technology, using balloons and kites to increase the height of the antenna and improve the efficiency of transmitting and receiving signals.
By 1897, Marconi was able to achieve radio communications across the English Channel. And established the 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, obtained the support of the business group that had previously invested in Tesla, and obtained a patent to begin the large-scale development of radio communications in the United States.
In fact, he can achieve such an achievement is inseparable from his continuous improvement of technology, not only improving the detector, from the original metal shaving detector to the ore detector to receive radio waves, but also improving the antenna technology and so on.
That's why we now see that the antennas are all one, which is also called: vertically polarized antennas.
The early antennas were actually two metal rods protruding from the spark discharge device designed by Hertz when he was doing experiments.
The development of antennas
Secondly, the radios interfere with each other, and to solve this problem, Marconi introduced a resonant circuit.
Marconi also found that radio transmission at night was far better than during the day, and there was no obstacle to the length of the transmission, etc., but he did not know the specific reason at the time.
By 1906, Marconi was able to achieve radio communication for nearly 10,000 kilometers. Marconi's radio communications were used both in shipping and in the military, and many radio stations were spread across some countries.
In 1909, Marconi was awarded the Nobel Prize in Physics for his contributions to radio communications.
Since then, Marconi has continued to improve radiocommunication technology, including in 1912, when the world's largest means of transportation: the Titanic. The giant cruise ship was equipped with radio communications equipment provided by Marconi and telegraphers.
Before the invention of wireless telegraph, the voyage of the ship was actually a bet with nature, the voyage was lost, and in the slow voyage, the crew did not have any means of communication to communicate with the people on the mainland. Only when the ship returned to shore did it know it had arrived smoothly.
After the shipwreck, the telegrapher notified the nearby ships through radio communications to come to the rescue, which eventually saved 710 passengers.
The role of radiocommunication amazed the people of that era, especially after the shipwreck of the Titanic, the importance of radiocommunication became increasingly felt. The Times even made this comment:
We are grateful to Marconi for inventing the device, which enabled the Titanic to send the fastest distress signal. Before that, many ships sank without sending any signal of distress.
However, in Marconi's time, radio communications mainly relied on Morse code.
At that time, Marconi predicted that radio communication would develop towards a two-way future of communication, and later big brothers, mobile phones, and even the smart phones we use now actually confirmed his prediction.